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Search for "ultrasound irradiation" in Full Text gives 24 result(s) in Beilstein Journal of Organic Chemistry.
Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles
- Periklis X. Kolagkis,
- Eirini M. Galathri and
- Christoforos G. Kokotos
Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36
- bonding with polar species [114]. The nanoparticle of choice was CuO, which had already displayed several varied catalytic applications, so the P4VPy–CuO nanoparticles were synthesized through an ultrasound irradiation protocol and tested in the reaction between p-chlorobenzaldehyde and indole. An amount
Graphical Abstract
Scheme 1: Examples of BIMs used for their medicinal properties.
Scheme 2: Mechanisms for the synthesis of BIMs using protic or Lewis acids as catalysts.
Scheme 3: Synthesis of bis(indolyl)methanes using DBDMH.
Scheme 4: Competition experiments and synthesis of bis(indolyl)methanes using DBDMH.
Scheme 5: Proposed mechanism for formation of BIM of using DBDMH.
Scheme 6: Synthesis of bis(indolyl)methanes using I2.
Scheme 7: General reaction mechanism upon halogen bonding.
Scheme 8: Synthesis of bis(indolyl)methanes using I2, introduced by Ji.
Scheme 9: Synthesis of bis(indolyl)methanes using Br2 in CH3CN.
Scheme 10: Βidentate halogen-bond donors.
Scheme 11: Synthesis of bis(indolyl)methanes using bidentate halogen-bond donor 26.
Scheme 12: Proposed reaction mechanism.
Scheme 13: Synthesis of bis(indolyl)methanes using iodoalkyne as catalyst.
Scheme 14: Proposed reaction mechanism.
Scheme 15: Optimized reaction conditions used by Ramshini.
Scheme 16: Activation of the carbonyl group by HPA/TPI-Fe3O4.
Scheme 17: Synthesis of BIMs in the presence of nanoAg-Pt/SiO2-doped silicate.
Scheme 18: Mechanism of action proposed by Khalafi-Nezhad et al.
Scheme 19: Activation of the carbonyl group by the Cu–isatin Schiff base complex.
Scheme 20: Optimum reaction conditions published by Jain.
Scheme 21: Organocatalytic protocol utilizing nanoparticles introduced by Bankar.
Scheme 22: Activation of the carbonyl group by the AlCl3·6H2O-SDS-SiO2 complex.
Scheme 23: Optimal reaction conditions for the aforementioned nano-Fe3O4 based catalysts.
Scheme 24: Nanocatalytic protocol proposed by Kaur et al.
Scheme 25: Microwave approach introduced by Yuan.
Scheme 26: Microwave approach introduced by Zahran et al.
Scheme 27: Microwave irradiation protocol introduced by Bindu.
Scheme 28: Silica-supported microwave irradiation protocol.
Scheme 29: Proposed mechanism for formation of BIM by Nongkhlaw.
Scheme 30: Microwave-assisted synthesis of BIMs catalyzed by succinic acid.
Scheme 31: Proposed mechanism of action of MMO-4.
Scheme 32: Catalytic approach introduced by Muhammadpoor-Baltork et al.
Scheme 33: Reaction conditions used by Xiao-Ming.
Scheme 34: Ultrasonic irradiation-based protocol published by Saeednia.
Scheme 35: Pyruvic acid-mediated synthesis of BIMs proposed by Thopate.
Scheme 36: Synthesis of BIMs using [bmim]BF4 or [bmim]PF6 ionic liquids.
Scheme 37: Synthesis of BIMs utilizing In(OTf)3 in octylmethylimidazolium hexafluorophosphate as ionic liquid.
Scheme 38: FeCl3·6H2O-catalyzed synthesis of BIMs with use of ionic liquid.
Scheme 39: Synthesis of BIMs utilizing the [hmim]HSO4/EtOH catalytic system.
Scheme 40: Synthesis of BIMs utilizing acidic ionic liquid immobilized on silica gel (ILIS-SO2Cl).
Scheme 41: The [bmim][MeSO4]-catalyzed reaction of indole with various aldehydes.
Scheme 42: The role of [bmim][MeSO4] in catalyzing the reaction of indole with aldehydes.
Scheme 43: Synthesis of BIMs utilizing FeCl3-based ionic liquid ([BTBAC]Cl-FeCl3) as catalyst.
Scheme 44: Synthesis of BIMs using [Msim]Cl at room temperature.
Scheme 45: [Et3NH][H2PO4]-catalyzed synthesis of bis(indolyl)methanes.
Scheme 46: PILs-catalyzed synthesis of bis(indolyl)methanes.
Scheme 47: FSILs-mediated synthesis of bis(indolyl)methanes.
Scheme 48: Possible “release and catch” catalytic process.
Scheme 49: Synthesis of bis(indolyl)methanes by [DABCO-H][HSO4].
Scheme 50: Synthesis of bis(indolyl)methanes by [(THA)(SO4)].
Scheme 51: Synthesis of BBSI-Cl and BBSI-HSO4.
Scheme 52: Synthesis of BIMs in the presence of BBSI-Cl and BBSI-HSO4.
Scheme 53: Chemoselectivity of the present method.
Scheme 54: Synthesis of BIMs catalyzed by chitosan-supported ionic liquid.
Scheme 55: Proposed mechanism of action of CSIL.
Scheme 56: Optimization of the reaction in DESs.
Scheme 57: Synthesis of BIMs using ChCl/SnCl2 as DES.
Scheme 58: Synthesis of BIMs derivatives in presence of DES.
Scheme 59: BIMs synthesis in choline chloride/urea (CC/U).
Scheme 60: Flow chemistry-based synthesis of BIMs by Ley.
Scheme 61: Flow chemistry-based synthesis of BIMs proposed by Nam et al.
Scheme 62: Amino-catalyzed reaction of indole with propionaldehyde.
Scheme 63: Aminocatalytic synthesis of BIMs.
Scheme 64: Proposed mechanism for the aminocatalytic synthesis of BIMs.
Scheme 65: Enzymatic reaction of indole with aldehydes.
Scheme 66: Proposed mechanism for the synthesis of BIMs catalyzed by TLIM.
Scheme 67: Proposed reaction mechanism by Badsara.
Scheme 68: Mechanism proposed by D’Auria.
Scheme 69: Photoinduced thiourea catalysis.
Scheme 70: Proposed mechanism of photoacid activation.
Scheme 71: Proposed mechanism of action for CF3SO2Na.
Scheme 72: Proposed mechanism for the synthesis of BIMs by Mandawad.
Scheme 73: Proposed mechanism for the (a) acid generation and (b) synthesis of BIMs.
Scheme 74: a) Reaction conditions employed by Khaksar and b) activation of the carbonyl group by HFIP.
Scheme 75: Activation of the carbonyl group by the PPy@CH2Br through the formation of a halogen bond.
Scheme 76: Reaction conditions utilized by Mhaldar et al.
Scheme 77: a) Reaction conditions employed by López and b) activation of the carbonyl group by thiourea.
Scheme 78: Infrared irradiation approach introduced by Luna-Mora and his research group.
Scheme 79: Synthesis of BIMs with the use of the Fe–Zn BMOF.
Synthesis of 5-arylidenerhodanines in L-proline-based deep eutectic solvent
- Stéphanie Hesse
Beilstein J. Org. Chem. 2023, 19, 1537–1544, doi:10.3762/bjoc.19.110
- reaction of benzofuranone and aldehydes in good to excellent yields in a few minutes under ultrasound irradiation. Results and Discussion As a part of our ongoing research in DES chemistry, we were mainly interested in the conditions reported by Detsi [20], and attempted to apply them for rhodanine
Graphical Abstract
Figure 1: Examples of rhodanines and related five-membered heterocycles with interesting biological activitie...
Scheme 1: Synthesis of 5-benzylidenerhodanine derivatives. Conditions: areaction performed for 3 h at 60 °C. b...
Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach
- Dileep Kumar Singh and
- Rajesh Kumar
Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71
- amines 50 were reacted with 2,5-DMTHF (2) in 5 mol % Bi(NO3)3·5H2O in solvent-free conditions under ultrasound irradiation at room temperature. The main advantages of this procedure are its simple isolation process, excellent product yield without using expensive or sensitive solvents and reagents
Graphical Abstract
Figure 1: Various pyrrole containing molecules.
Scheme 1: Various synthestic protocols for the synthesis of pyrroles.
Figure 2: A tree-diagram showing various conventional and green protocols for Clauson-Kaas pyrrole synthesis.
Scheme 2: A general reaction of Clauson–Kaas pyrrole synthesis and proposed mechanism.
Scheme 3: AcOH-catalyzed synthesis of pyrroles 5 and 7.
Scheme 4: Synthesis of N-substituted pyrroles 9.
Scheme 5: P2O5-catalyzed synthesis of N-substituted pyrroles 11.
Scheme 6: p-Chloropyridine hydrochloride-catalyzed synthesis of pyrroles 13.
Scheme 7: TfOH-catalyzed synthesis of N-sulfonylpyrroles 15, N-sulfonylindole 16, N-sulfonylcarbazole 17.
Scheme 8: Scandium triflate-catalyzed synthesis of N-substituted pyrroles 19.
Scheme 9: MgI2 etherate-catalyzed synthesis and proposed mechanism of N-arylpyrrole derivatives 21.
Scheme 10: Nicotinamide catalyzed synthesis of pyrroles 23.
Scheme 11: ZrOCl2∙8H2O catalyzed synthesis and proposed mechanism of pyrrole derivatives 25.
Scheme 12: AcONa catalyzed synthesis of N-substituted pyrroles 27.
Scheme 13: Squaric acid-catalyzed synthesis and proposed mechanism of N-substituted pyrroles 29.
Figure 3: Reusability of catalyst γ-Fe2O3@SiO2-Sb-IL in six cycles.
Scheme 14: Magnetic nanoparticle-supported antimony catalyst used in the synthesis of N-substituted pyrroles 31...
Scheme 15: Iron(III) chloride-catalyzed synthesis of N-substituted pyrroles 33.
Scheme 16: Copper-catalyzed Clauson–Kaas synthesis and mechanism of pyrroles 35.
Scheme 17: β-CD-SO3H-catalyzed synthesis and proposed mechanism of pyrroles 37.
Figure 4: Recyclability of β-cyclodextrin-SO3H.
Scheme 18: Solvent-free and catalyst-free synthesis and plausible mechanism of N-substituted pyrroles 39.
Scheme 19: Nano-sulfated TiO2-catalyzed synthesis of N-substituted pyrroles 41.
Figure 5: Plausible mechanism for the formation of N-substituted pyrroles catalyzed by nano-sulfated TiO2 cat...
Scheme 20: Copper nitrate-catalyzed Clauson–Kaas synthesis and mechanism of N-substituted pyrroles 43.
Scheme 21: Synthesis of N-substituted pyrroles 45 by using Co catalyst Co/NGr-C@SiO2-L.
Scheme 22: Zinc-catalyzed synthesis of N-arylpyrroles 47.
Scheme 23: Silica sulfuric acid-catalyzed synthesis of pyrrole derivatives 49.
Scheme 24: Bismuth nitrate-catalyzed synthesis of pyrroles 51.
Scheme 25: L-(+)-tartaric acid-choline chloride-catalyzed Clauson–Kaas synthesis and plausible mechanism of py...
Scheme 26: Microwave-assisted synthesis of N-substituted pyrroles 55 in AcOH or water.
Scheme 27: Synthesis of pyrrole derivatives 57 using a nano-organocatalyst.
Figure 6: Nano-ferric supported glutathione organocatalyst.
Scheme 28: Microwave-assisted synthesis of N-substituted pyrroles 59 in water.
Scheme 29: Iodine-catalyzed synthesis and proposed mechanism of pyrroles 61.
Scheme 30: H3PW12O40/SiO2-catalyzed synthesis of N-substituted pyrroles 63.
Scheme 31: Fe3O4@-γ-Fe2O3-SO3H-catalyzed synthesis of pyrroles 65.
Scheme 32: Mn(NO3)2·4H2O-catalyzed synthesis and proposed mechanism of pyrroles 67.
Scheme 33: p-TsOH∙H2O-catalyzed (method 1) and MW-assisted (method 2) synthesis of N-sulfonylpyrroles 69.
Scheme 34: ([hmim][HSO4]-catalyzed Clauson–Kaas synthesis of pyrroles 71.
Scheme 35: Synthesis of N-substituted pyrroles 73 using K-10 montmorillonite catalyst.
Scheme 36: CeCl3∙7H2O-catalyzed Clauson–Kaas synthesis of pyrroles 75.
Scheme 37: Synthesis of N-substituted pyrroles 77 using Bi(NO3)3∙5H2O.
Scheme 38: Oxone-catalyzed synthesis and proposed mechanism of N-substituted pyrroles 79.
First example of organocatalysis by cathodic N-heterocyclic carbene generation and accumulation using a divided electrochemical flow cell
- Daniele Rocco,
- Ana A. Folgueiras-Amador,
- Richard C. D. Brown and
- Marta Feroci
Beilstein J. Org. Chem. 2022, 18, 979–990, doi:10.3762/bjoc.18.98
- was added to the catholyte and the mixture was left under ultrasound irradiation for 30 minutes. The solvent was removed under reduced pressure and the residue was purified by column chromatography on silica gel. The first experiment (Table 1, entry 1) was carried out using stainless steel as cathode
- to the catholyte. The mixture was left under ultrasound irradiation for 30 minutes. The solvent was removed under reduced pressure and the residue was purified by column chromatography on silica gel (petroleum ether/ethyl acetate 7:3), affording the corresponding pure 1a as an off-white solid. 1
Graphical Abstract
Scheme 1: Electrochemical generation of NHC.
Scheme 2: Transformation of electrochemically generated NHC into the corresponding thione by its reaction wit...
Scheme 3: Umpolung of the aldehyde carbonyl carbon atom. Formation of the Breslow intermediate using NHCs.
Figure 1: Schematic representation of a plane-parallel plate flow electrochemical reactor.
Figure 2: C/PVDF anode before (A) and after (B) the first experiment (Table 1, entry 1).
Scheme 4: Electrogenerated NHC-catalyzed self-annulation of cinnamaldehyde.
Scheme 5: Byproduct obtained from the reaction between methanol and the Breslow intermediate.
Figure 3: Expanded view of the electrochemical cell components: (a) Aluminium end plates; (b) insulating PTFE...
Menadione: a platform and a target to valuable compounds synthesis
- Acácio S. de Souza,
- Ruan Carlos B. Ribeiro,
- Dora C. S. Costa,
- Fernanda P. Pauli,
- David R. Pinho,
- Matheus G. de Moraes,
- Fernando de C. da Silva,
- Luana da S. M. Forezi and
- Vitor F. Ferreira
Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43
- ultrasound irradiation, obtaining quantitative yields when compared to the mechanical stirring procedure, thus demonstrating the best efficiency of the method [103]. In 2002, Arai and co-workers reported studies involving epoxidation reactions of menadione (10) using H2O2 as oxidant and a chiral salt derived
- a quantitative yield. Still about reduction reactions, Niemczyk and Van Arnum described a green methodology for reduction of menadione (10), during the pegylation of 14 to improving the solubility of the studied compounds [118]. The authors reduced 10 with sodium dithionite under ultrasound
- irradiation, generating the reduced adduct in 79% yield (Scheme 20). Depending on the type of solvent used, the yield may vary due to oxidation of the alcohol 14 back to 10 because of its low stability in solution. The pegylation strategy involved monomethoxypoly(ethyleneglycol)succinimide carbonate (mPEG-SC
Graphical Abstract
Figure 1: Natural bioactive naphthoquinones.
Figure 2: Chemical structures of vitamins K.
Figure 3: Redox cycle of menadione.
Scheme 1: Selected approaches for menadione synthesis using silver(I) as a catalyst.
Scheme 2: Methylation approaches for the preparation of menadione from 1,4-naphthoquinone using tert-butyl hy...
Scheme 3: Methylation approach of 1,4-naphthoquinone using i) rhodium complexes/methylboronic acid and ii) bi...
Scheme 4: Synthesis of menadione (10) from itaconic acid.
Scheme 5: Menadione synthesis via Diels–Alder reaction.
Scheme 6: Synthesis of menadione (10) using p-cresol as a synthetic precursor.
Scheme 7: Synthesis of menadione (10) via demethoxycarbonylating annulation of methyl methacrylate.
Scheme 8: Furan 34 used as a diene in a Diels–Alder reaction for the synthesis of menadione (10).
Scheme 9: o-Toluidine as a dienophile in a Diels–Alder reaction for the synthesis of menadione (10).
Scheme 10: Representation of electrochemical synthesis of menadione.
Figure 4: Reaction sites and reaction types of menadione as substrate.
Scheme 11: DBU-catalyzed epoxidation of menadione (10).
Scheme 12: Phase-transfer catalysis for the epoxidation of menadione.
Scheme 13: Menadione epoxidation using a hydroperoxide derived from (+)-norcamphor.
Scheme 14: Enantioselective Diels–Alder reaction for the synthesis of asymmetric quinone 50 catalyzed by a chi...
Scheme 15: Optimized reaction conditions for the synthesis of anthra[9,1-bc]pyranone.
Scheme 16: Synthesis of anthra[9,1-bc]furanone, anthra[9,1-bc]pyridine, and anthra[9,1-bc]pyrrole derivatives.
Scheme 17: Synthesis of derivatives employing protected trienes.
Scheme 18: Synthesis of cyclobutene derivatives of menadione.
Scheme 19: Menadione reduction reactions using sodium hydrosulfite.
Scheme 20: Green methodology for menadiol synthesis and pegylation.
Scheme 21: Menadione reduction by 5,6-O-isopropylidene-ʟ-ascorbic acid under UV light irradiation.
Scheme 22: Selected approaches of menadione hydroacetylation to diacetylated menadiol.
Scheme 23: Thiele–Winter reaction catalyzed by Bi(OTf)3.
Scheme 24: Carbonyl condensation of menadione using resorcinol and a hydrazone derivative.
Scheme 25: Condensation reaction of menadione with thiosemicarbazide.
Scheme 26: Condensation reaction of menadione with acylhydrazides.
Scheme 27: Menadione derivatives functionalized with organochalcogens.
Scheme 28: Synthesis of selenium-menadione conjugates derived from chloromethylated menadione 84.
Scheme 29: Menadione alkylation by the Kochi–Anderson method.
Scheme 30: Menadione alkylation by diacids.
Scheme 31: Menadione alkylation by heterocycles-substituted carboxylic acids.
Scheme 32: Menadione alkylation by bromoalkyl-substituted carboxylic acids.
Scheme 33: Menadione alkylation by complex carboxylic acids.
Scheme 34: Kochi–Anderson method variations for the menadione alkylation via oxidative decarboxylation of carb...
Scheme 35: Copper-catalyzed menadione alkylation via free radicals.
Scheme 36: Nickel-catalyzed menadione cyanoalkylation.
Scheme 37: Iron-catalyzed alkylation of menadione.
Scheme 38: Selected approaches to menadione alkylation.
Scheme 39: Menadione acylation by photo-Friedel–Crafts acylation reported by Waske and co-workers.
Scheme 40: Menadione acylation by Westwood procedure.
Scheme 41: Synthesis of 3-benzoylmenadione via metal-free TBAI/TBHP system.
Scheme 42: Michael-type addition of amines to menadione reported by Kallmayer.
Scheme 43: Synthesis of amino-menadione derivatives using polyalkylamines.
Scheme 44: Selected examples for the synthesis of different amino-substituted menadione derivatives.
Scheme 45: Selected examples of Michael-type addition of complex amines to menadione (10).
Scheme 46: Addition of different natural α-amino acids to menadione.
Scheme 47: Michael-type addition of amines to menadione using silica-supported perchloric acid.
Scheme 48: Indolylnaphthoquinone or indolylnaphthalene-1,4-diol synthesis reported by Yadav et al.
Scheme 49: Indolylnaphthoquinone synthesis reported by Tanoue and co-workers.
Scheme 50: Indolylnaphthoquinone synthesis from menadione by Escobeto-González and co-workers.
Scheme 51: Synthesis of menadione analogues functionalized with thiols.
Scheme 52: Synthesis of menadione-derived symmetrical derivatives through reaction with dithiols.
Scheme 53: Mercaptoalkyl acids as nucleophiles in Michael-type addition reaction to menadione.
Scheme 54: Reactions of menadione (10) with cysteine derivatives for the synthesis of quinoproteins.
Scheme 55: Synthesis of menadione-glutathione conjugate 152 by Michael-type addition.
Ultrasound-assisted Strecker synthesis of novel 2-(hetero)aryl-2-(arylamino)acetonitrile derivatives
- Emese Gal,
- Luiza Gaina,
- Hermina Petkes,
- Alexandra Pop,
- Castelia Cristea,
- Gabriel Barta,
- Dan Cristian Vodnar and
- Luminiţa Silaghi-Dumitrescu
Beilstein J. Org. Chem. 2020, 16, 2929–2936, doi:10.3762/bjoc.16.242
- heterocyclic compounds, the use of ultrasound irradiation became a powerful tool by proving to be superior in terms of reaction rates, yields, and the purity of the products as compared to traditional convective heating methods [2]. Sonochemical syntheses can be successfully performed in homogeneous media
- chemistry protocol capable of inducing a more efficient energy input. Indeed, the reaction rate was significantly increased by applying the new protocol modified by means of an indirect ultrasound irradiation technique and high yields of the α-(arylamino)acetonitrile products were obtained after 30 minutes
- the ultrasound irradiation technique as a greener chemical protocol affording significantly enhanced reaction rates and higher crystallite size of the products, thus increasing the energy efficiency of the Strecker synthesis. An initial screening of the mutagenic potential of the newly synthetized α
Graphical Abstract
Scheme 1: Synthesis of α-amino-acetonitrile derivatives. Reaction conditions: Aldimine (1 equiv), TMSCN (1 eq...
Figure 1: Crystal structure of 2-phenothiazinyl-2-(p-tolylamino)acetonitrile 2a. a) ORTEP plot and b) crystal...
Figure 2: SEM images recorded at 200× for the raw reaction product 2b obtained through a) ultrasound-assisted...
Figure 3: SEM image recorded at 200× for the raw reaction product 2c obtained through a) ultrasound-assisted ...
Natural dolomitic limestone-catalyzed synthesis of benzimidazoles, dihydropyrimidinones, and highly substituted pyridines under ultrasound irradiation
- Kumar Godugu,
- Venkata Divya Sri Yadala,
- Mohammad Khaja Mohinuddin Pinjari,
- Trivikram Reddy Gundala,
- Lakshmi Reddy Sanapareddy and
- Chinna Gangi Reddy Nallagondu
Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156
- pyridines via C–N, C–C, and C–S bond formations in a mixture of ethanol and H2O under ultrasound irradiation. The catalyst is characterized by XRD, FTIR, Raman spectroscopy, SEM, and EDAX analysis. The main advantages of this methodology include the wide substrate scope, cleaner reaction profile, short
- : benzimidazoles; dihydropyrimidinones; highly substituted pyridines; natural dolomitic limestone; ultrasound irradiation; Introduction Nitrogen heterocycles are recognized as “privileged medicinal scaffolds” because these compounds are found in a wide variety of bioactive natural products and pharmaceuticals [1
- synthesis of 1-benzyl-2-phenyl-1H-benzo[d]imidazole (3a). At first, a control experiment was conducted by using model substrates, 1 and 2a, in H2O in the absence of catalyst under ultrasound irradiation for 60 min at 45–50 °C. It was found that the reaction did not proceed in the absence of a catalyst
Graphical Abstract
Figure 1: The benzimidazoles I–IV, dihydropyrimidinones/-thiones V–VIII, and 2-amino-4-aryl-3,5-dicarbonitril...
Scheme 1: NDL-catalyzed synthesis of i) 1,2-disubstituted benzimidazoles 3, ii) dihydropyrimidinones/-thiones ...
Figure 2: XRD pattern of the NDL catalyst.
Figure 3: FTIR spectrum of the NDL catalyst.
Figure 4: Raman spectrum of the NDL catalyst.
Figure 5: SEM images of the NDL catalyst.
Figure 6: EDAX analysis of the NDL catalyst.
Scheme 2: Unexpected formation of the bisimine I, 3h, from o-phenylenediamine (1) and salicylaldehyde (2h).
Figure 7: 1H NMR spectrum of 2,2'-((1E,1'E)-(1,2-phenylenebis(azanylylidene))bis (methanylylidene))diphenol (...
Figure 8: XRD pattern of a) the fresh NDL catalyst; b) the recovered NDL catalyst after the 7th cycle of the ...
Oxime radicals: generation, properties and application in organic synthesis
- Igor B. Krylov,
- Stanislav A. Paveliev,
- Alexander S. Budnikov and
- Alexander O. Terent’ev
Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107
Graphical Abstract
Figure 1: Imine-N-oxyl radicals (IV) discussed in the present review and other classes of N-oxyl radicals (I–...
Figure 2: The products of decomposition of iminoxyl radicals generated from oximes by oxidation with Ag2O.
Scheme 1: Generation of oxime radicals and study of the kinetics of their decay by photolysis of the solution...
Scheme 2: Synthesis of di-tert-butyliminoxyl radical and its decomposition products.
Scheme 3: The proposed reaction pathway of the decomposition of di-tert-butyliminoxyl radical (experimentally...
Scheme 4: Monomolecular decomposition of the tert-butyl(triethylmethyl)oxime radical.
Scheme 5: The synthesis and stability of the most stable dialkyl oxime radicals – di-tert-butyliminoxyl and d...
Scheme 6: The formation of iminoxyl radicals from β-diketones under the action of NO2.
Scheme 7: Synthesis of the diacetyliminoxyl radical.
Scheme 8: Examples of long-living oxime radicals with electron-withdrawing groups and the conditions for thei...
Figure 3: The electronic structure iminoxyl radicals and their geometry compared to the corresponding oximes.
Figure 4: Bond dissociation enthalpies (kcal/mol) of oximes and N,N-disubstituted hydroxylamines calculated o...
Scheme 9: Examples demonstrating the low reactivity of the di-tert-butyliminoxyl radical towards the substrat...
Scheme 10: The reactions of di-tert-butyliminoxyl radical with unsaturated hydrocarbons involving hydrogen ato...
Scheme 11: Possible mechanisms of reaction of di-tert-butyliminoxyl radical with alkenes.
Scheme 12: Products of the reaction between di-tert-butyliminoxyl radical and phenol derivatives.
Scheme 13: The reaction of di-tert-butyliminoxyl radical with amines.
Scheme 14: Reaction of di-tert-butyliminoxyl radicals with organolithium reagents.
Scheme 15: Cross-dehydrogenative C–O coupling of 1,3-dicarbonyl compounds with oximes under the action of mang...
Scheme 16: Cross-dehydrogenative C–O coupling of 1,3-dicarbonyl compounds with oximes under the action of Cu(BF...
Scheme 17: Oxidative C–O coupling of benzylmalononitrile (47) with 3-(hydroxyimino)pentane-2,4-dione (19).
Scheme 18: The proposed mechanism of the oxidative coupling of benzylmalononitrile (47) with diacetyl oxime (19...
Scheme 19: Oxidative C–O coupling of pyrazolones with oximes under the action of Fe(ClO4)3.
Scheme 20: The reaction of diacetyliminoxyl radical with pyrazolones.
Scheme 21: Oxidative C–O coupling of oximes with acetonitrile, ketones, and esters.
Scheme 22: Intramolecular cyclizations of oxime radicals to form substituted isoxazolines or cyclic nitrones.
Scheme 23: TEMPO-mediated oxidative cyclization of oximes with C–H bond cleavage.
Scheme 24: Proposed reaction mechanism of oxidative cyclization of oximes with C–H bond cleavage.
Scheme 25: Selectfluor/Bu4NI-mediated C–H oxidative cyclization of oximes.
Scheme 26: Oxidative cyclization of N-benzyl amidoximes to 1,2,4-oxadiazoles.
Scheme 27: The formation of quinazolinone 73a from 5-phenyl-4,5-dihydro-1,2,4-oxadiazole 74 under air.
Scheme 28: DDQ-mediated oxidative cyclization of thiohydroximic acids.
Scheme 29: Plausible mechanism of the oxidative cyclization of thiohydroximic acids.
Scheme 30: Silver-mediated oxidative cyclization of α-halogenated ketoximes and 1,3-dicarbonyl compounds.
Scheme 31: Possible pathway of one-pot oxidative cyclization of α-halogenated ketoximes and 1,3-dicarbonyl com...
Scheme 32: T(p-F)PPT-catalyzed oxidative cyclization of oximes with the formation of 1,2,4-oxadiazolines.
Scheme 33: Intramolecular cyclization of iminoxyl radicals involving multiple C=C and N=N bonds.
Scheme 34: Oxidative cyclization of β,γ- and γ,δ-unsaturated oximes employing the DEAD or TEMPO/DEAD system wi...
Scheme 35: Cobalt-catalyzed aerobic oxidative cyclization of β,γ-unsaturated oximes.
Scheme 36: Manganese-catalyzed aerobic oxidative cyclization of β,γ-unsaturated oximes.
Scheme 37: Visible light photocatalytic oxidative cyclization of β,γ-unsaturated oximes.
Scheme 38: TBAI/TBHP-mediated radical cascade cyclization of the β,γ-unsaturated oximes.
Scheme 39: TBAI/TBHP-mediated radical cascade cyclization of vinyl isocyanides with β,γ-unsaturated oximes.
Scheme 40: tert-Butylnitrite-mediated oxidative cyclization of unsaturated oximes with the introduction of an ...
Scheme 41: Transformation of unsaturated oxime to oxyiminomethylisoxazoline via the confirmed dimeric nitroso ...
Scheme 42: tert-Butylnitrite-mediated oxidative cyclization of unsaturated oximes with the introduction of a n...
Scheme 43: Synthesis of cyano-substituted oxazolines from unsaturated oximes using the TBN/[RuCl2(p-cymene)]2 ...
Scheme 44: Synthesis of trifluoromethylthiolated isoxazolines from unsaturated oximes.
Scheme 45: Copper-сatalyzed oxidative cyclization of β,γ-unsaturated oximes with the introduction of an azido ...
Scheme 46: TBHP-mediated oxidative cascade cyclization of β,γ-unsaturated oximes and unsaturated N-arylamides.
Scheme 47: Copper-сatalyzed oxidative cyclization of unsaturated oximes with the introduction of an amino grou...
Scheme 48: TEMPO-mediated oxidative cyclization of unsaturated oximes followed by elimination.
Scheme 49: Oxidative cyclization of β,γ-unsaturated oximes with the introduction of a trifluoromethyl group.
Scheme 50: Oxidative cyclization of unsaturated oximes with the introduction of a nitrile group.
Scheme 51: Oxidative cyclization of β,γ-unsaturated oximes to isoxazolines with the introduction of a nitrile ...
Scheme 52: Oxidative cyclization of β,γ-unsaturated oximes to isoxazolines with the introduction of a sulfonyl...
Scheme 53: Oxidative cyclization of β,γ- and γ,δ-unsaturated oximes to isoxazolines with the introduction of a...
Scheme 54: Oxidative cyclization of β,γ-unsaturated oximes to isoxazolines with the introduction of a thiocyan...
Scheme 55: PhI(OAc)2-mediated oxidative cyclization of oximes with C–S and C–Se bond formation.
Scheme 56: PhI(OAc)2-mediated oxidative cyclization of unsaturated oximes accompanied by alkoxylation.
Scheme 57: PhI(OAc)2-mediated cyclization of unsaturated oximes to methylisoxazolines.
Scheme 58: Oxidative cyclization-alkynylation of unsaturated oximes.
Scheme 59: TEMPO-mediated oxidative cyclization of C-glycoside ketoximes to C-glycosylmethylisoxazoles.
Scheme 60: Silver-сatalyzed oxidative cyclization of β,γ-unsaturated oximes with formation of fluoroalkyl isox...
Scheme 61: Oxidative cyclization of β,γ-unsaturated oximes with the formation of haloalkyl isoxazolines.
Scheme 62: Cyclization of β,γ-unsaturated oximes into haloalkyl isoxazolines under the action of the halogenat...
Scheme 63: Synthesis of haloalkyl isoxazoles and cyclic nitrones via oxidative cyclization and 1,2-halogen shi...
Scheme 64: Electrochemical oxidative cyclization of diaryl oximes.
Scheme 65: Copper-сatalyzed cyclization and dioxygenation oximes containing a triple C≡C bond.
Scheme 66: Photoredox-catalyzed sulfonylation of β,γ-unsaturated oximes by sulfonyl hydrazides.
Scheme 67: Oxidative cyclization of β,γ-unsaturated oximes with introduction of sulfonate group.
Scheme 68: Ultrasound-promoted oxidative cyclization of β,γ-unsaturated oximes.
A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions
- Pezhman Shiri and
- Jasem Aboonajmi
Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52
- heterogeneous nanocatalyst in “click” reactions for the multicomponent synthesis of triazole products in water with ultrasound irradiation and 0.017 mol % catalyst loading. As such, a series of aryl/alkyl-substituted oxiranes was treated with sodium azide and nonactivated terminal alkynes, giving 1,2,3-triazole
Graphical Abstract
Scheme 1: Chemical structure of the catalysts 1a and 1b and their catalytic application in CuAAC reactions.
Scheme 2: Synthetic route to the catalyst 11 and its catalytic application in CuAAC reactions.
Scheme 3: Synthetic route of dendrons, illustrated using G2-AMP 23.
Scheme 4: The catalytic application of CuYAu–Gx-AAA–SBA-15 in a CuAAC reaction.
Scheme 5: Synthetic route to the catalyst 36.
Scheme 6: Application of the catalyst 36 in CuAAC reactions.
Scheme 7: The synthetic route to the catalyst 45 and catalytic application of 45 in “click” reactions.
Scheme 8: Synthetic route to the catalyst 48 and catalytic application of 48 in “click” reactions.
Scheme 9: Synthetic route to the catalyst 58 and catalytic application of 58 in “click” reactions.
Scheme 10: Synthetic route to the catalyst 64 and catalytic application of 64 in “click” reactions.
Scheme 11: Chemical structure of the catalyst 68 and catalytic application of 68 in “click” reactions.
Scheme 12: Chemical structure of the catalyst 69 and catalytic application of 69 in “click” reactions.
Scheme 13: Synthetic route to, and chemical structure of the catalyst 74.
Scheme 14: Application of the cayalyst 74 in “click” reactions.
Scheme 15: Synthetic route to, and chemical structure of the catalyst 78 and catalytic application of 78 in “c...
Scheme 16: Synthetic route to the catalyst 85.
Scheme 17: Application of the catalyst 85 in “click” reactions.
Scheme 18: Synthetic route to the catalyst 87 and catalytic application of 87 in “click” reactions.
Scheme 19: Chemical structure of the catalyst 88 and catalytic application of 88 in “click” reactions.
Scheme 20: Synthetic route to the catalyst 90 and catalytic application of 90 in “click” reactions.
Scheme 21: Synthetic route to the catalyst 96 and catalytic application of 96 in “click” reactions.
Scheme 22: Synthetic route to the catalyst 100 and catalytic application of 100 in “click” reactions.
Scheme 23: Synthetic route to the catalyst 102 and catalytic application of 23 in “click” reactions.
Scheme 24: Synthetic route to the catalysts 108–111.
Scheme 25: Catalytic application of 108–111 in “click” reactions.
Scheme 26: Synthetic route to the catalyst 121 and catalytic application of 121 in “click” reactions.
Scheme 27: Synthetic route to 125 and application of 125 in “click” reactions.
Scheme 28: Synthetic route to the catalyst 131 and catalytic application of 131 in “click” reactions.
Scheme 29: Synthetic route to the catalyst 136.
Scheme 30: Application of the catalyst 136 in “click” reactions.
Scheme 31: Synthetic route to the catalyst 141 and catalytic application of 141 in “click” reactions.
Scheme 32: Synthetic route to the catalyst 144 and catalytic application of 144 in “click” reactions.
Scheme 33: Synthetic route to the catalyst 149 and catalytic application of 149 in “click” reactions.
Scheme 34: Synthetic route to the catalyst 153 and catalytic application of 153 in “click” reactions.
Scheme 35: Synthetic route to the catalyst 155 and catalytic application of 155 in “click” reactions.
Scheme 36: Synthetic route to the catalyst 157 and catalytic application of 157 in “click” reactions.
Scheme 37: Synthetic route to the catalyst 162.
Scheme 38: Application of the catalyst 162 in “click” reactions.
Scheme 39: Synthetic route to the catalyst 167 and catalytic application of 167 in “click” reactions.
Scheme 40: Synthetic route to the catalyst 169 and catalytic application of 169 in “click” reactions.
Scheme 41: Synthetic route to the catalyst 172.
Scheme 42: Application of the catalyst 172 in “click” reactions.
Steroid diversification by multicomponent reactions
- Leslie Reguera,
- Cecilia I. Attorresi,
- Javier A. Ramírez and
- Daniel G. Rivera
Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121
- could be conducted under ultrasound irradiation using sodium ethoxide as catalyst, thus generating steroid ring A-fused 3,4-dihydropyrimidinones and 3,4-dihydropyrimidinthiones 44 in very good yields. Mohamed et al. [44] reported a 4CR for the synthesis of pyridopyrimidines fused to ring D of
Graphical Abstract
Figure 1: Structures of natural steroids of A) animal and B) plant origin.
Scheme 1: Synthesis of a steroidal β-lactam by Ugi reaction of a cholanic aldehyde [14].
Scheme 2: Synthetic route to steroidal 2,5-diketopiperazines based on a diastereoselective Ugi-4CR with an an...
Scheme 3: Multicomponent synthesis of a heterocycle–steroid hybrid using a ketosteroid as carbonyl component [18]....
Scheme 4: Synthesis of peptidomimetic–steroid hybrids using the Ugi-4CR with spirostanic amines and carboxyli...
Scheme 5: Synthesis of azasteroids using the Ugi-4CR with androstanic and pregnanic carboxylic acids [22].
Figure 2: Ugi-4CR-derived library of androstanic azasteroids with diverse substitution patterns at the phenyl...
Scheme 6: Synthesis of 4-azacholestanes by an intramolecular Ugi-4C-3R [26].
Scheme 7: Synthesis of amino acid–steroid hybrid by multiple Ugi-4CR using steroidal isocyanides [29].
Scheme 8: Synthesis of ecdysteroid derivatives by Ugi-4CR using a steroidal isocyanide [30].
Scheme 9: Stereoselective multicomponent synthesis of a steroid–tetrahydropyridine hybrid using a chiral bifu...
Scheme 10: Pd(II)-catalyzed three-component reaction with an alkynyl seco-cholestane [34].
Scheme 11: Multicomponent synthesis of steroid–thiazole hybrids from a steroidal ketone [36].
Scheme 12: Synthesis of cholanic pseudo-peptide derivatives by novel MCRs based on the reactivity of ynamide [37,38].
Scheme 13: Synthesis of steroid-fused pyrimidines and pyrimidones using the Biginelli-3CR [39,42,43].
Scheme 14: Synthesis of steroidal pyridopyrimidines by a reaction sequence comprising a 4CR followed by a post...
Scheme 15: Synthesis of steroid-fused pyrimidines by MCR of 2-hydroxymethylene-3-ketosteroids [46].
Scheme 16: Synthesis of steroid-fused naphthoquinolines by the Kozlov–Wang MCR using ketosteroids [50,51].
Scheme 17: Conjugation of steroids to carbohydrates and peptides by the Ugi-4CR [62,63].
Scheme 18: Solid-phase multicomponent conjugation of peptides to steroids by the Ugi-4CR [64].
Scheme 19: Solid-phase multicomponent conjugation of peptides to steroids by the Petasis-3CR [68].
Scheme 20: Synthesis of steroidal macrobicycles (cages) by multiple multicomponent macrocyclizations based on ...
Scheme 21: One-pot synthesis of steroidal cages by double Ugi-4CR-based macrocyclizations [76].
Ammonium-tagged ruthenium-based catalysts for olefin metathesis in aqueous media under ultrasound and microwave irradiation
- Łukasz Gułajski,
- Andrzej Tracz,
- Katarzyna Urbaniak,
- Stefan J. Czarnocki,
- Michał Bieniek and
- Tomasz K. Olszewski
Beilstein J. Org. Chem. 2019, 15, 160–166, doi:10.3762/bjoc.15.16
- research on synthesis of catalysts for olefin metathesis and to expand the utility of ammonium-tagged ruthenium-based catalysts [69][70][71][72][73][74][75][76], herein we present the use of such catalysts for olefin metathesis in aqueous media promoted by microwave and ultrasound irradiation. Results and
- the RCM (Table 1, entries 1 and 2) both tested catalysts (1 mol %) under classical conditions exhibited similar activities with 4b being slightly less active (52 vs 48%, respectively). The reaction performed under ultrasound irradiation proved to be ca. 10% more productive with both catalysts compared
- catalysts (5 mol %) produced the desired product again with quite similar yields under classical conditions. However, the use of microwave or ultrasound irradiation promoted the undesired isomerisation of the C=C bond, thus lowering the yields of the desired product 9 (Table 1, entries 3 and 4). This result
Graphical Abstract
Figure 1: Structures of the Ru-based catalysts used in this study.
5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines
- Ranjana Aggarwal and
- Suresh Kumar
Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15
- -aminopyrazole 16 and 4-hydroxycoumarin (50) with isatin 54 under ultrasound irradiation in water (Scheme 11). Solvent and catalytic screening for the reaction have shown that water in presence of p-TSA at 60 °C on heating for 6 hours provide best results with excellent yields. Recently, Wang et al. [57] also
- reported a similar reaction of 5-aminopyrazole 16, arylaldehyde 47 with ethyl cyanoacetate (94) under ultrasound irradiation in presence of p-TSA in water for the synthesis of 3-methyl-6-oxo-4-aryl-4,5,6,7-tetrahydro-4H-pyrazolo[3,4-b]pyridine-5-carbonitrile derivatives 95 (Scheme 27). All the synthesized
Graphical Abstract
Figure 1: Selected examples of drugs with fused pyrazole rings.
Figure 2: Typical structures of some fused pyrazoloazines from 5-aminopyrazoles.
Scheme 1: Regiospecific synthesis of 4 and 6-trifluoromethyl-1H-pyrazolo[3,4-b]pyridines.
Scheme 2: Synthesis of pyrazolo[3,4-b]pyridine-6-carboxylates.
Scheme 3: Synthesis of 1,4,6-triaryl-1H-pyrazolo[3,4-b]pyridines with ionic liquid .
Scheme 4: Synthesis of coumarin-based isomeric tetracyclic pyrazolo[3,4-b]pyridines.
Scheme 5: Synthesis of 6-substituted pyrazolo[3,4-b]pyridines under Heck conditions.
Scheme 6: Microwave-assisted palladium-catalyzed synthesis of pyrazolo[3,4-b]pyridines.
Scheme 7: Acid-catalyzed synthesis of pyrazolo[3,4-b]pyridines via enaminones.
Scheme 8: Synthesis of pyrazolo[3,4-b]pyridines via aza-Diels–Alder reaction.
Scheme 9: Synthesis of macrocyclane fused pyrazolo[3,4-b]pyridine derivatives.
Scheme 10: Three-component synthesis of 4,7-dihydro-1H-pyrazolo[3,4-b]pyridine derivatives.
Scheme 11: Ultrasonicated synthesis of spiro[indoline-3,4'-pyrazolo[3,4-b]pyridine]-2,6'(1'H)-diones.
Scheme 12: Synthesis of spiro[indoline-3,4'-pyrazolo[3,4-b]pyridine] derivatives under conventional heating co...
Scheme 13: Nanoparticle-catalyzed synthesis of pyrazolo[3,4-b]pyridine-spiroindolinones.
Scheme 14: Microwave-assisted multicomponent synthesis of spiropyrazolo[3,4-b]pyridines.
Scheme 15: Unexpected synthesis of naphthoic acid-substituted pyrazolo[3,4-b]pyridines.
Scheme 16: Multicomponent synthesis of variously substituted pyrazolo[3,4-b]pyridine derivatives.
Scheme 17: Three-component synthesis of 4,7-dihydropyrazolo[3,4-b]pyridines and pyrazolo[3,4-b]pyridines.
Scheme 18: Synthesis of pyrazolo[3,4-b]pyridine-5-spirocycloalkanediones.
Scheme 19: Ultrasound-mediated three-component synthesis of pyrazolo[3,4-b]pyridines.
Scheme 20: Multicomponent synthesis of 4-aryl-3-methyl-1-phenyl-4,6,8,9-tetrahydropyrazolo [3,4-b]thiopyrano[4...
Scheme 21: Synthesis of 2,3-dihydrochromeno[4,3-d]pyrazolo[3,4-b]pyridine-1,6-diones.
Scheme 22: FeCl3-catalyzed synthesis of o-hydroxyphenylpyrazolo[3,4-b]pyridine derivatives.
Scheme 23: Ionic liquid-mediated synthesis of pyrazolo[3,4-b]pyridines.
Scheme 24: Microwave-assisted synthesis of pyrazolo[3,4-b]pyridines.
Scheme 25: Multicomponent synthesis of pyrazolo[3,4-b]pyridine-5-carbonitriles.
Scheme 26: Unusual domino synthesis of 4,7-dihydropyrazolo[3,4-b]pyridine-5-nitriles.
Scheme 27: Synthesis of 4,5,6,7-tetrahydro-4H-pyrazolo[3,4-b]pyridines under conventional heating and ultrasou...
Scheme 28: L-Proline-catalyzed synthesis of of pyrazolo[3,4-b]pyridine.
Scheme 29: Microwave-assisted synthesis of 5-aminoarylpyrazolo[3,4-b]pyridines.
Scheme 30: Microwave-assisted multi-component synthesis of pyrazolo[3,4-e]indolizines.
Scheme 31: Synthesis of fluoropropynyl and fluoroalkyl substituted pyrazolo[1,5-a]pyrimidine.
Scheme 32: Acid-catalyzed synthesis of pyrazolo[1,5-a]pyrimidine derivatives.
Scheme 33: Chemoselective and regiospecific synthesis of 2-(3-methylpyrazol-1’-yl)-5-methylpyrazolo[1,5-a]pyri...
Scheme 34: Regioselective synthesis of 7-trifluoromethylpyrazolo[1,5-a]pyrimidines.
Scheme 35: Microwave-assisted synthesis of 7-trifluoromethylpyrazolo[1,5-a]pyrimidine carboxylates.
Scheme 36: Microwave and ultrasound-assisted synthesis of 7-trifluoromethylpyrazolo[1,5-a]pyrimidines.
Scheme 37: Base-catalyzed unprecedented synthesis of pyrazolo[1,5-a]pyrimidines via C–C bond cleavage.
Scheme 38: Synthesis of aminobenzothiazole/piperazine linked pyrazolo[1,5-a]pyrimidines.
Scheme 39: Synthesis of aminoalkylpyrazolo[1,5-a]pyrimidine-7-amines.
Scheme 40: Synthesis of pyrazolo[1,5-a]pyrimidines from condensation of 5-aminopyrazole 126 and ethyl acetoace...
Scheme 41: Synthesis of 7-aminopyrazolo[1,5-a]pyrimidines.
Scheme 42: Unexpected synthesis of 7-aminopyrazolo[1,5-a]pyrimidines under solvent free and solvent-mediated c...
Scheme 43: Synthesis of N-(4-aminophenyl)-7-aryloxypyrazolo[1,5-a]pyrimidin-5-amines.
Scheme 44: Base-catalyzed synthesis of 5,7-diarylpyrazolo[1,5-a]pyrimidines.
Scheme 45: Synthesis of 6,7-dihydropyrazolo[1,5-a]pyrimidines in PEG-400.
Scheme 46: Synthesis of 7-heteroarylpyrazolo[1,5-a]pyrimidine-3-carboxamides.
Scheme 47: Synthesis of 7-heteroarylpyrazolo[1,5-a]pyrimidine derivatives under conventional heating and micro...
Scheme 48: Synthesis of N-aroylpyrazolo[1,5-a]pyrimidine-5-amines.
Scheme 49: Regioselective synthesis of ethyl pyrazolo[1,5-a]pyrimidine-7-carboxylate.
Scheme 50: Sodium methoxide-catalyzed synthesis of 3-cyano-6,7-diarylpyrazolo[1,5-a]pyrimidines.
Scheme 51: Synthesis of various pyrazolo[3,4-d]pyrimidine derivatives.
Scheme 52: Synthesis of hydrazinopyrazolo[3,4-d]pyrimidine derivatives.
Scheme 53: Synthesis of N-arylidinepyrazolo[3,4-d]pyrimidin-5-amines.
Scheme 54: Synthesis of pyrazolo[3,4-d]pyrimidinyl-4-amines.
Scheme 55: Iodine-catalyzed synthesis of pyrazolo[3,4-d]pyrimidinones.
Scheme 56: Synthesis of ethyl 6-amino-2H-pyrazolo[3,4-d]pyrimidine-4-carboxylate.
Scheme 57: Synthesis of 4-substituted-(3,6-dihydropyran-4-yl)-1H-pyrazolo[3,4-d]pyrimidines.
Scheme 58: Synthesis of 1-(2,4-dichlorophenyl)pyrazolo[3,4-d]pyrimidin-4-yl carboxamides.
Scheme 59: Synthesis of 5-(1,3,4-thidiazol-2-yl)pyrazolo[3,4-d]pyrimidine.
Scheme 60: One pot POCl3-catalyzed synthesis of 1-arylpyrazolo[3,4-d]pyrimidin-4-ones.
Scheme 61: Synthesis of 4-amino-N1,C3-dialkylpyrazolo[3,4-d]pyrimidines under Suzuki conditions.
Scheme 62: Microwave-assisted synthesis of pyrazolo[3,4-b]pyrazines.
Scheme 63: Synthesis and derivatization of pyrazolo[3,4-b]pyrazine-5-carbonitriles.
Scheme 64: Synthesis of 2-thioxo-pyrazolo[1,5-a][1,3,5]triazin-4-ones.
Scheme 65: Synthesis of 2,3-dihydropyrazolo[1,5-a][1,3,5]triazin-4(1H)-one.
Scheme 66: Synthesis of pyrazolo[1,5-a][1,3,5]triazine-8-carboxylic acid ethyl ester.
Scheme 67: Microwave-assisted synthesis of 4,7-dihetarylpyrazolo[1,5-a][1,3,5]triazines.
Scheme 68: Alternative synthetic route to 4,7-diheteroarylpyrazolo[1,5-a][1,3,5]triazines.
Scheme 69: Synthesis of 4-aryl-2-ethylthio-7-methylpyrazolo[1,5-a][1,3,5]triazines.
Scheme 70: Microwave-assisted synthesis of 4-aminopyrazolo[1,5-a][1,3,5]triazine.
Scheme 71: Synthesis of pyrazolo[3,4-d][1,2,3]triazines from pyrazol-5-yl diazonium salts.
Scheme 72: Synthesis of 2,5-dihydropyrazolo[3,4-e][1,2,4]triazines.
Scheme 73: Synthesis of pyrazolo[5,1-c][1,2,4]triazines via diazopyrazolylenaminones.
Scheme 74: Synthesis of pyrazolo[5,1-c][1,2,4]triazines in presence of sodium acetate.
Scheme 75: Synthesis of various 7-diazopyrazolo[5,1-c][1,2,4]triazine derivatives.
Scheme 76: One pot synthesis of pyrazolo[5,1-c][1,2,4]triazines.
Scheme 77: Synthesis of 4-amino-3,7,8-trinitropyrazolo-[5,1-c][1,2,4]triazines.
Scheme 78: Synthesis of tricyclic pyrazolo[5,1-c][1,2,4]triazines by azocoupling reaction.
Halogen-containing thiazole orange analogues – new fluorogenic DNA stains
- Aleksey A. Vasilev,
- Meglena I. Kandinska,
- Stanimir S. Stoyanov,
- Stanislava B. Yordanova,
- David Sucunza,
- Juan J. Vaquero,
- Obis D. Castaño,
- Stanislav Baluschev and
- Silvia E. Angelova
Beilstein J. Org. Chem. 2017, 13, 2902–2914, doi:10.3762/bjoc.13.283
- TO-7Cl. The condensation of 2-methylbenzothiazolium salt 2a and 4,7-dichloroquinolinium methyl sulfate 4a was conducted in water, methanol or ethanol by stirring the reaction mixture at room temperature or by ultrasound irradiation for not more than 40 minutes. Prolonged sonication causes heating of
- the samples in the ultrasonic bath and this makes external cooling difficult. In addition, the ultrasound irradiation promotes side reactions and thus leads to slightly lower reaction yields when compared to the room temperature conditions. It is well known that water is one of the most useful green
Graphical Abstract
Scheme 1: Chemical structures of TO and SYBR Green I – commercial monomethine fluorescent dsDNA binders.
Scheme 2: Synthesis of the monofluoro-substituted dye TO-1F. Reagents, conditions and yields: (i) sodium meth...
Scheme 3: Synthesis of new halogen-containing analogues of TO. Reagents, conditions and yields: (i) DMS, 100 ...
Figure 1: Absorption spectra of the studied compounds in MeOH (c = 1 × 10−5 M).
Figure 2: Absorption spectra of dye 5b (c = 5 × 10−7 M) in TE buffer, in the absence and presence of dsDNA (c...
Figure 3: Fluorescence spectra of dye 5a (c = 5 × 10–7 M) in TE buffer and in the presence of increasing conc...
Figure 4: Photostability of dyes TO-7Cl and 5a–d in acetonitrile in the concentration range of 1 × 10−5 M.
Figure 5: B3LYP optimized structures.
Figure 6: Graphical representation of the frontier orbitals (isodensity plot, isovalue = 0.02 a.u.).
Figure 7: Simulated TDPBE0 spectra in methanol.
Figure 8: Electron density (isovalue = 0.002) mapped with electrostatic potential (color scheme: green for ne...
Synthesis, effect of substituents on the regiochemistry and equilibrium studies of tetrazolo[1,5-a]pyrimidine/2-azidopyrimidines
- Elisandra Scapin,
- Paulo R. S. Salbego,
- Caroline R. Bender,
- Alexandre R. Meyer,
- Anderson B. Pagliari,
- Tainára Orlando,
- Geórgia C. Zimmer,
- Clarissa P. Frizzo,
- Helio G. Bonacorso,
- Nilo Zanatta and
- Marcos A. P. Martins
Beilstein J. Org. Chem. 2017, 13, 2396–2407, doi:10.3762/bjoc.13.237
- using ultrasound irradiation promoted shorter reaction times, high regioselectivity, and excellent yields, when compared with conventional thermal heating [30]. Presently, we demonstrate an eco-friendly synthesis of 5- and 7-substituted tetrazolo[1,5-a]pyrimidine isomers, in good to excellent yields
Graphical Abstract
Figure 1: Hydrogen coupling constants (3JH-H) of (a) H6–H7 for 3a and (b) H5–H6 for 5h.
Figure 2: LUMO coefficients for (a) β-enaminones 1a,h, and their (b) conjugated acids.
Figure 3:
(a) 1H and (b) 13C NMR spectra demonstrating the 3d![[Graphic 9]](/bjoc/content/inline/1860-5397-13-237-i9.svg?max-width=637&scale=1.18182)
4d equilibrium in DMSO-d6 at 25 °C.
Figure 4: ORTEP® [45] plot of 7a with thermal ellipsoids drawn at 50% probability level.
Figure 5: Tetrazolo[1,5-a]pyrimidine observed in solution (CDCl3 and DMSO-d6) and 2-azidopyrimidine observed ...
Figure 6: ORTEP® [45] plot of 8i with thermal ellipsoids drawn at 50% probability level.
Figure 7: Representation of the possible equilibrium existing between 6i, 7i, and 8i.
Solvent-free copper-catalyzed click chemistry for the synthesis of N-heterocyclic hybrids based on quinoline and 1,2,3-triazole
- Martina Tireli,
- Silvija Maračić,
- Stipe Lukin,
- Marina Juribašić Kulcsár,
- Dijana Žilić,
- Mario Cetina,
- Ivan Halasz,
- Silvana Raić-Malić and
- Krunoslav Užarević
Beilstein J. Org. Chem. 2017, 13, 2352–2363, doi:10.3762/bjoc.13.232
- , there is a persistent incentive to find greener alternatives, which would reduce time and energy requirements as well as waste generated by these reactions. Among other non-conventional approaches such as microwave and ultrasound irradiation [7][12][13], mechanochemistry has emerged as a viable approach
Graphical Abstract
Scheme 1: Synthetic procedures for preparation of p-halogen-substituted and non-substituted phenyl-1,2,3-tria...
Figure 1: Experimental Raman spectra of the alkyne 4 and triazole products 5–8. Bands attributed to the vibra...
Figure 2: In situ Raman monitoring of a) mechanochemical formation of triazole 5 using copper(II) acetate mon...
Figure 3: a) In situ Raman monitoring for mechanochemical synthesis of 5 using brass balls and PMMA reaction ...
Figure 4: ESR spectra of samples obtained after milling by methods 2a (black), 2b (red) and 2c (blue). The in...
Figure 5: X-ray structure of the triazole compounds. (a) Molecular structure of 5, with the atom-numbering sc...
Solvent-free sonochemistry: Sonochemical organic synthesis in the absence of a liquid medium
- Deborah E. Crawford
Beilstein J. Org. Chem. 2017, 13, 1850–1856, doi:10.3762/bjoc.13.179
- success of both of these reactions by ultrasound irradiation in the absence of solvent creates potential for organic synthesis to be carried out by applying a milder form of mechanical energy, i.e., sound waves. As a result, it may be possible that reactions which are particularly sensitive to intense
Graphical Abstract
Figure 1: Typical laboratory employed planetary ball mill and ultrasonic bath.
Scheme 1: Reaction between o-vanillin and 1,2-phenylenediamine by ultrasonic irradiation for 60 minutes.
Figure 2: o-Vanillin in its flake form and 1,2-phenylenediamine in its bead form.
Figure 3: Clear separation of the reagents observed, with orange coated beads of 1,2-phenylenediamine residin...
Figure 4: Chemical structures of the products obtained from the reaction between o-vanillin and 1,2-phenylene...
Figure 5: Reaction mixture before and after ultrasonic irradiation for 60 minutes.
Figure 6: 1H NMR spectrum of diimine 1 in CDCl3/EtOD.
Scheme 2: Aldol reaction between ninhydrin and dimedone to form 2.
Figure 7: 1H NMR spectrum of 1,3-indandione 2 in DMSO-d6.
Ultrasound-promoted organocatalytic enamine–azide [3 + 2] cycloaddition reactions for the synthesis of ((arylselanyl)phenyl-1H-1,2,3-triazol-4-yl)ketones
- Gabriel P. Costa,
- Natália Seus,
- Juliano A. Roehrs,
- Raquel G. Jacob,
- Ricardo F. Schumacher,
- Thiago Barcellos,
- Rafael Luque and
- Diego Alves
Beilstein J. Org. Chem. 2017, 13, 694–702, doi:10.3762/bjoc.13.68
- DMSO using Et2NH (1 mol %) was also performed under ultrasound irradiation. The reaction performed under ultrasound irradiation with 20% of the amplitude for 20 minutes (followed by TLC until the total consumption of the starting materials) yielded product 3a in 92% (conditions B, Scheme 2). Inspired
- by results described under conditions B, we performed additional experiments using ultrasound irradiation with Et2NH as organocatalyst (Table 1). Initially, substrates 1a and 2a were reacted in DMSO under ultrasound irradiation for 20 min using different amplitudes (Table 1, entries 1–4). We observed
- (Scheme 3) after 5 minutes reaction under ultrasound irradiation (40% of amplitude) at room temperature. Comparing these results with already published ones under conventional conditions, our methodology using ultrasound irradiation affords the products in 5 minutes and in comparable yields while the
Graphical Abstract
Figure 1: Biologically relevant selanyl-1,2,3-triazoles.
Scheme 1: General scheme of the reaction.
Scheme 2: Comparative study of the conventional conditions and ultrasound irradiation. Conditions A: Reaction...
Scheme 3: Reaction of 2-azidophenyl phenyl selenide 1a with activated ketones 2f–k.
From betaines to anionic N-heterocyclic carbenes. Borane, gold, rhodium, and nickel complexes starting from an imidazoliumphenolate and its carbene tautomer
- Ming Liu,
- Jan C. Namyslo,
- Martin Nieger,
- Mika Polamo and
- Andreas Schmidt
Beilstein J. Org. Chem. 2016, 12, 2673–2681, doi:10.3762/bjoc.12.264
- bis(3-butyl-1-(2-phenolate)-1H-imidazolium-2-yl)gold (10): A solution of 0.066 g (0.10 mmol) of bis(3-butyl-1-(2-hydroxyphenyl)-1H-imidazolium-2-yl)gold chloride (9) and 0.014 g (0.10 mmol) of K2CO3 in 5 mL of methanol was stirred for 30 minutes under ultrasound irradiation. After concentrating the
Graphical Abstract
Figure 1: Examples of anionic N-heterocyclic carbenes.
Scheme 1: A postulated mesomeric betaine – NHC equilibrium (6A/6B) and formation of an anionic NHC 7. Formati...
Figure 2: Molecular drawing of one of the two crystallographic independent molecules of borane adduct 8 (disp...
Figure 3: Molecular drawing of the cation of the gold complex 9 (displacement parameters are drawn at 50% pro...
Scheme 2: The anionic NHC 7 forms a rhodium complex and a nickel complex. d) [RhCl(COD)]2, toluene, rt to ref...
Figure 4: Molecular drawing of rhodium complex 11 (minor disorder parts omitted for clarity, displacement par...
Figure 5: Molecular drawing of the dimeric nickel complex 12 (displacement parameters are drawn at 50% probab...
Cross-dehydrogenative coupling for the intermolecular C–O bond formation
- Igor B. Krylov,
- Vera A. Vil’ and
- Alexander O. Terent’ev
Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13
Graphical Abstract
Scheme 1: Cross-dehydrogenative coupling.
Scheme 2: Cross-dehydrogenative C–O coupling.
Scheme 3: Regioselective ortho-acetoxylation of meta-substituted arylpyridines and N-arylamides.
Scheme 4: ortho-Acyloxylation and alkoxylation of arenes directed by pyrimidine, benzoxazole, benzimidazole a...
Scheme 5: Cu(OAc)2/AgOTf/O2 oxidative system in the ortho-alkoxylation of arenes.
Scheme 6: Pd(OAc)2/persulfate oxidative system in the ortho-alkoxylation and acetoxylation of arenes with nit...
Scheme 7: ortho-Acetoxylation and methoxylation of O-methyl aryl oximes, N-phenylpyrrolidin-2-one, and (3-ben...
Scheme 8: Ruthenium-catalyzed ortho-acyloxylation of acetanilides.
Scheme 9: Acetoxylation and alkoxylation of arenes with amide directing group using Pd(OAc)2/PhI(OAc)2 oxidat...
Scheme 10: Alkoxylation of azoarenes, 2-aryloxypyridines, picolinamides, and N-(1-methyl-1-(pyridin-2-yl)ethyl...
Scheme 11: Acetoxylation of compounds containing picolinamide and quinoline-8-amine moieties using the Pd(OAc)2...
Scheme 12: (CuOH)2CO3 catalyzed oxidative ortho-etherification using air as oxidant.
Scheme 13: Copper-catalyzed aerobic alkoxylation and aryloxylation of arenes containing pyridine-N-oxide moiet...
Scheme 14: Cobalt-catalyzed aerobic alkoxylation of arenes and alkenes containing pyridine N-oxide moiety.
Scheme 15: Non-symmetric double-fold C–H ortho-acyloxylation.
Scheme 16: N-nitroso directed ortho-alkoxylation of arenes.
Scheme 17: Selective alkoxylation and acetoxylation of alkyl groups.
Scheme 18: Acetoxylation of 2-alkylpyridines and related compounds.
Scheme 19: Acyloxylation and alkoxylation of alkyl fragments of substrates containing amide or sulfoximine dir...
Scheme 20: Palladium-catalyzed double sp3 C–H alkoxylation of N-(quinolin-8-yl)amides for the synthesis of sym...
Scheme 21: Copper-catalyzed acyloxylation of methyl groups of N-(quinolin-8-yl)amides.
Scheme 22: One-pot acylation and sp3 C–H acetoxylation of oximes.
Scheme 23: Possible mechanism of oxidative esterification catalyzed by N-heterocyclic nucleophilic carbene.
Scheme 24: Oxidative esterification employing stoichiometric amounts of aldehydes and alcohols.
Scheme 25: Selective oxidative coupling of aldehydes with alcohols in the presence of amines.
Scheme 26: Iodine mediated oxidative esterification.
Scheme 27: Oxidative C–O coupling of benzyl alcohols with methylarenes under the action of Bu4NI/t-BuOOH syste...
Scheme 28: Oxidative coupling of methyl- and ethylarenes with aromatic aldehydes under the action of Bu4NI/t-B...
Scheme 29: Cross-dehydrogenative C–O coupling of aldehydes with t-BuOOH in the presence of Bu4NI.
Scheme 30: Bu4NI-catalyzed α-acyloxylation reaction of ethers and ketones with aldehydes and t-BuOOH.
Scheme 31: Oxidative coupling of aldehydes with N-hydroxyimides and hexafluoroisopropanol.
Scheme 32: Oxidative coupling of alcohols with N-hydroxyimides.
Scheme 33: Oxidative coupling of aldehydes and primary alcohols with N-hydroxyimides using (diacetoxyiodo)benz...
Scheme 34: Proposed mechanism of the oxidative coupling of aldehydes and N-hydroxysuccinimide under action of ...
Scheme 35: Oxidative coupling of aldehydes with pivalic acid (172).
Scheme 36: Oxidative C–O coupling of aldehydes with alkylarenes using the Cu(OAc)2/t-BuOOH system.
Scheme 37: Copper-catalyzed acyloxylation of C(sp3)-H bond adjacent to oxygen in ethers using benzyl alcohols.
Scheme 38: Oxidative C–O coupling of aromatic aldehydes with cycloalkanes.
Scheme 39: Ruthenium catalyzed cross-dehydrogenative coupling of primary and secondary alcohols.
Scheme 40: Cross-dehydrogenative C–O coupling reactions of β-dicarbonyl compounds with sulfonic acids, acetic ...
Scheme 41: Acyloxylation of ketones, aldehydes and β-dicarbonyl compounds using carboxylic acids and Bu4NI/t-B...
Scheme 42: Acyloxylation of ketones using Bu4NI/t-BuOOH system.
Scheme 43: Cross-dehydrogenative C–O coupling of β-dicarbonyl compounds and their heteroanalogues with N-hydro...
Scheme 44: Cross-dehydrogenative C–O coupling of β-dicarbonyl compounds and their heteroanalogues with t-BuOOH....
Scheme 45: Oxidative C–O coupling of 2,6-dialkylphenyl-β-keto esters and thioesters with tert-butyl hydroxycar...
Scheme 46: α’-Acyloxylation of α,β-unsaturated ketones using KMnO4.
Scheme 47: Possible mechanisms of the acetoxylation at the allylic position of alkenes by Pd(OAc)2.
Scheme 48: Products of the oxidation of terminal alkenes by Pd(II)/AcOH/oxidant system.
Scheme 49: Acyloxylation of terminal alkenes with carboxylic acids.
Scheme 50: Synthesis of linear E-allyl esters by cross-dehydrogenative coupling of terminal alkenes wih carbox...
Scheme 51: Pd(OAc)2-catalyzed acetoxylation of Z-vinyl(triethylsilanes).
Scheme 52: α’-Acetoxylation of α-acetoxyalkenes with copper(II) chloride in acetic acid.
Scheme 53: Oxidative acyloxylation at the allylic position of alkenes and at the benzylic position of alkylare...
Scheme 54: Copper-catalyzed alkoxylation of methylheterocyclic compounds using di-tert-butylperoxide as oxidan...
Scheme 55: Oxidative C–O coupling of methylarenes with β-dicarbonyl compounds or phenols.
Scheme 56: Copper-catalyzed esterification of methylbenzenes with cyclic ethers and cycloalkanes.
Scheme 57: Oxidative C–O coupling of carboxylic acids with toluene catalyzed by Pd(OAc)2.
Scheme 58: Oxidative acyloxylation at the allylic position of alkenes with carboxylic acids using the Bu4NI/t-...
Scheme 59: Cross-dehydrogenative C–O coupling of carboxylic acids with alkylarenes using the Bu4NI/t-BuOOH sys...
Scheme 60: Oxidative C–O cross-coupling of methylarenes with ethyl or isopropylarenes.
Scheme 61: Phosphorylation of benzyl C–H bonds using the Bu4NI/t-BuOOH oxidative system.
Scheme 62: Selective C–H acetoxylation of 2,3-disubstituted indoles.
Scheme 63: Acetoxylation of benzylic position of alkylarenes using DDQ as oxidant.
Scheme 64: C–H acyloxylation of diarylmethanes, 3-phenyl-2-propen-1-yl acetate and dimethoxyarene using DDQ.
Scheme 65: Cross-dehydrogenative C–O coupling of 1,3-diarylpropylenes and 1,3-diarylpropynes with alcohols.
Scheme 66: One-pot azidation and C–H acyloxylation of 3-chloro-1-arylpropynes.
Scheme 67: Cross-dehydrogenative C–O coupling of 1,3-diarylpropylenes, (E)-1-phenyl-2-isopropylethylene and is...
Scheme 68: Cross-dehydrogenative C–O coupling of alkylarenes and related compounds with N-hydroxyphthalimide.
Scheme 69: Acetoxylation at the benzylic position of alkylarenes mediated by N-hydroxyphthalimide.
Scheme 70: C–O coupling of methylarenes with aromatic carboxylic acids employing the NaBrO3/NaHSO3 system.
Scheme 71: tert-Butyl peroxidation of allyl, propargyl and benzyl ethers catalyzed by Fe(acac)3.
Scheme 72: Cross-dehydrogenative C–O coupling of ethers with carboxylic acids mediated by Bu4NI/t-BuOOH system....
Scheme 73: Oxidative acyloxylation of dimethylamides and dioxane with 2-aryl-2-oxoacetic acids accompanied by ...
Scheme 74: tert-Butyl peroxidation of N-benzylamides and N-allylbenzamide using the Bu4NI/t-BuOOH system.
Scheme 75: Cross-dehydrogenative C–O coupling of aromatic carboxylic acids with ethers using Fe(acac)3 as cata...
Scheme 76: Cross-dehydrogenative C–O coupling of cyclic ethers with 2-hydroxybenzaldehydes using iron carbonyl...
Scheme 77: Cross-dehydrogenative C–O coupling of ethers with β-dicarbonyl compounds and phenols using copper c...
Scheme 78: Cross-dehydrogenative C–O coupling of 2-hydroxybenzaldehyde with dioxane catalyzed by Cu2(BPDC)2(BP...
Scheme 79: Ruthenium chloride-catalyzed acyloxylation of β-lactams.
Scheme 80: Ruthenium-catalyzed tert-butyl peroxydation amides and acetoxylation of β-lactams.
Scheme 81: PhI(OAc)2-mediated α,β-diacetoxylation of tertiary amines.
Scheme 82: Electrochemical oxidative methoxylation of tertiary amines.
Scheme 83: Cross-dehydrogenative C–O coupling of ketene dithioacetals with carboxylic acids in the presence of...
Scheme 84: Cross-dehydrogenative C–O coupling of enamides with carboxylic acids using iodosobenzene as oxidant....
Scheme 85: Oxidative alkoxylation, acetoxylation, and tosyloxylation of acylanilides using PhI(O(O)CCF3)2 in t...
Scheme 86: Proposed mechanism of the oxidative C–O coupling of actetanilide with O-nucleophiles in the presenc...
Scheme 87: Three-component coupling of aldehydes, anilines and alcohols involving oxidative intermolecular C–O...
Scheme 88: Oxidative coupling of phenols with alcohols.
Scheme 89: 2-Acyloxylation of quinoline N-oxides with arylaldehydes in the presence of the CuOTf/t-BuOOH syste...
Scheme 90: Cross-dehydrogenative C–O coupling of azoles with primary alcohols.
Scheme 91: Oxidation of dipyrroles to dipyrrins and subsequent oxidative alkoxylation in the presence of Na3Co...
Scheme 92: Oxidative dehydrogenative carboxylation of alkanes and cycloalkanes to allylic esters.
Scheme 93: Pd-catalyzed acetoxylation of benzene.
An efficient access to the synthesis of novel 12-phenylbenzo[6,7]oxepino[3,4-b]quinolin-13(6H)-one derivatives
- Wentao Gao,
- Guihai Lin,
- Yang Li,
- Xiyue Tao,
- Rui Liu and
- Lianjie Sun
Beilstein J. Org. Chem. 2012, 8, 1849–1857, doi:10.3762/bjoc.8.213
- hydrochloric acid. Subsequently, we reported a similar reaction under ultrasound irradiation conditions by using KHSO4 as catalyst [36]. Although the two methodologies are elegant and impressive, our attempts to follow both routes to synthesize 2 were frustrated by very low yields. In this regard, Bose et al
Graphical Abstract
Scheme 1: Synthesis of ethyl 2-(chloromethyl)-4-phenylquinoline-3-carboxylate (2).
Scheme 2: Synthesis of 2-(phenoxymethyl)-4-phenylquinoline-3-carboxylic acid derivatives 3a–l.
Scheme 3: Synthesis of 12-phenylbenzo[6,7]oxepino[3,4-b]quinolin-13(6H)-ones 4a–h.
Scheme 4: Cyclization and de-tert-butylation reaction of 3l by using PPA.
Regioselectivity in the multicomponent reaction of 5-aminopyrazoles, cyclic 1,3-diketones and dimethylformamide dimethylacetal under controlled microwave heating
- Kamal Usef Sadek,
- Ramadan Ahmed Mekheimer,
- Tahany Mahmoud Mohamed,
- Moustafa Sherief Moustafa and
- Mohamed Hilmy Elnagdi
Beilstein J. Org. Chem. 2012, 8, 18–24, doi:10.3762/bjoc.8.3
- ., either kinetic or thermodynamic [11][12][13]. It has been reported that the use of microwave or ultrasound irradiation provides an additional parameter for synthetic selectivity [14][15][16][17]. Results and Discussion The multicomponent reaction of 5-aminopyrazoles, dimedone and aromatic aldehydes was
Graphical Abstract
Scheme 1: Microwave-assisted synthesis of 4 and 6.
Figure 1: ORTEP diagram of compound 6a.
Figure 2: ORTEP diagram of compound 5.
Figure 3: ORTEP diagram of compound 6e.
Figure 4: ORTEP diagram of compound 6g.
Scheme 2: A proposed mechanism to account for the formation of products 6. The factors that determine the nat...
First synthesis of 2-(benzofuran-2-yl)-6,7-methylene dioxyquinoline-3-carboxylic acid derivatives
- Wentao Gao,
- Jia Liu,
- Yun Jiang and
- Yang Li
Beilstein J. Org. Chem. 2011, 7, 210–217, doi:10.3762/bjoc.7.28
- ethyl 4-chloro-3-oxobutanoate using KHSO4 as catalyst under ultrasound irradiation conditions. The targeted compounds 3a–h were obtained in good yields of 52–82% and their structures were established based on spectral data and elemental analyses. Keywords: benzofuran; Friedländer condensation
- carried out under ultrasound irradiation conditions at 80 °C using KHSO4 as catalyst in 80% EtOH as solvent. The resulting product 5 was obtained in good yield (74%) after purification by a flash chromatography on silica gel (eluent: petroleum ether/ethyl acetate = 5:1). The next step involves the
Graphical Abstract
Figure 1: Structures of compounds 1, 2 and 3.
Scheme 1: Synthesis of ethyl 2-chloromethyl-6,7-methylenedioxyquinoline-3-carboxylate (5).
Scheme 2: One-pot synthesis of the targeted compounds 3a–g.
Scheme 3: Possible mechanistic pathway of formation of 2-(benzofuran-2-yl)-6,7-methylenedioxyquinoline-3-carb...
An improved synthesis of 1,3,5-triaryl- 2-pyrazolines in acetic acid aqueous solution under ultrasound irradiation
- Ji-Tai Li,
- Xiao-Hui Zhang and
- Zhi-Ping Lin
Beilstein J. Org. Chem. 2007, 3, No. 13, doi:10.1186/1860-5397-3-13
- used in organic synthesis in the last three decades. A large number of organic reactions can be carried out in higher yields, shorter reaction time or milder conditions under ultrasound irradiation. Results Preparation of a series of 1,3,5-triaryl-2-pyrazolines through the reaction of chalcones and
- phenylhydrazine hydrochloride was carried out in 83–96% yield within 1.5–2 h in sodium acetate-acetic acid aqueous solution under ultrasound irradiation. Conclusion We have described a practical and convenient procedure for the synthesis of 1,3,5-triaryl-2-pyrazolines in sodium acetate-acetic acid aqueous
- solution at room temperature under ultrasound irradiation. Background Pyrazoline derivatives have been found to possess a broad spectrum of biological activities such as tranquillizing, muscle relaxant, psychoanaleptic, anticonvulsant, antihypertensive, and antidepressant activities. [1][2][3][4][5][6
Graphical Abstract
Scheme 1: Synthesis of 1,3,5-triaryl-2-pyrazolines.
Scheme 2: The mechanism of 1,3,5-triarylpyrazoline formation.
Photosonochemical catalytic ring opening of α-epoxyketones
- Hamid R. Memarian and
- Ali Saffar-Teluri
Beilstein J. Org. Chem. 2007, 3, No. 2, doi:10.1186/1860-5397-3-2
- -f, the ratios of diastereomeric photoproducts have not been changed too much using ultrasound irradiation. In order to explain the results obtained, we have compared the results of the semi-empirical PM3 calculations on the complexes of 1a-f + 2 in the ground state with those of α-epoxyketones 1a-f
Graphical Abstract
Scheme 1: Ultrasound-assisted photocatalytic ring opening of α-epoxyketones.
Scheme 2: Possible intermediates involved in the ring opening of α-epoxyketones.
Scheme 3: Possible formation of a complex involved in reaction in acetone.
Scheme 4: Interaction of oxygen lone pair of carbonyl group with carbocation center.
Figure 1: The semi-empirical PM3 calculations for interaction of 1a with NBTPT.
