Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• acid catalyst for this transformation. At room temperature, the product of this environmentally friendly Strecker reaction is nitrile derivative 53 (R2 = CN, Scheme 15, method A), while at reflux carboxamide 53 (R2 = CONH2, Scheme 15, method A) is obtained. Notoriously, aromatic amines 2 did not work

Tuning the stability of alkoxyisopropyl protection groups

• Zehong Liang,
• Henna Koivikko,
• Mikko Oivanen and
• Petri Heinonen

Beilstein J. Org. Chem. 2019, 15, 746–751, doi:10.3762/bjoc.15.70

• ’-acetal-protected 2’-deoxythymidines were prepared using 7 equiv of the appropriate reagent 1a–e with the suitably protected thymidine 2 or 5 (Scheme 1) in the presence of p-toluenesulfonic acid as the acid catalyst. A suitable amount of the acid catalyst is 0.5 to 1 mol %, with which the reaction takes

• exception, as the electron-withdrawing trifluoroethyl group reduces the reactivity and the reaction time had to be increased to several hours. In addition, the yields of the protected products 3e and 6e also remained rather low, around 35%. If a larger amount than 1 mol % of the acid catalyst is used and

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• an acid catalyst (Scheme 14). Conditions which use p-toluenesulfonic acid in acetone [58] produced acetonide 29 in 49% yield after column chromatography. Conditions which employed concentrated sulfuric acid in acetonitrile [59][60] yielded the acetonide in 76–96% yield. Large excess of 2,2

Olefin metathesis catalysts embedded in β-barrel proteins: creating artificial metalloproteins for olefin metathesis

• Daniel F. Sauer,
• Johannes Schiffels,
• Takashi Hayashi,
• Ulrich Schwaneberg and
• Jun Okuda

Beilstein J. Org. Chem. 2018, 14, 2861–2871, doi:10.3762/bjoc.14.265

• ions such as Mg, Ca, Mn, Fe, Ni, Co, Cu, Zn etc. within a protein are abundant in nature [24]. As metalloenzymes, these metalloproteins are capable of catalyzing various important reactions in biosynthesis and key steps in cellular energy metabolism. The embedded metal ion mainly acts as a Lewis acid

• catalyst or redox catalyst. Various metalloenzymes have been applied in laboratory-scale reactions and a few metalloenzymes such as nitrile hydratase (cobalt(III) in the active site) for the production of acrylamide have found application in industry [25]. Notably, however, the reaction scope of natural

Synthesis of unnatural α-amino esters using ethyl nitroacetate and condensation or cycloaddition reactions

• Glwadys Gagnot,
• Vincent Hervin,
• Eloi P. Coutant,
• Sarah Desmons,
• Racha Baatallah,
• Victor Monnot and
• Yves L. Janin

Beilstein J. Org. Chem. 2018, 14, 2846–2852, doi:10.3762/bjoc.14.263

• -(trifluoromethyl)benzaldehyde (3j) and acetic anhydride using indium(III) chloride [15] as a Lewis acid catalyst [16] without any solvent at room temperature pointed out a complete conversion into acylal 7 overnight. A similar reaction using pivaloyl anhydride and either indium(III) chloride or tetrafluoroboric

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• trimethylsilylated phenyl-modified SBA-15 78. This white solid was reacted with ClSO3H to get SBA-15 functionalized with phenyl sulfonic acid groups (SBA-15-Ph-SO3H, 79, Scheme 14). The SBA-15-Ph-SO3H catalyst 79 is a hydrophobic nanoreactor solid acid catalyst that presents a series of advantages, such as

• intermediate IV. Finally, this intermediate is split by a nucleophilic attack of hydroxyl radicals to afford byproducts (including acetic acid, acetanilide, and formic acid) and desired product. The proposed mechanism was confirmed by EPR spectrum. The SSA catalyst is an inexpensive and reusable solid acid

• catalyst [63]. 4. Synthetic strategies of carbon-based materials and functionalized carbon-based materials containing sulfonic acid groups as a diverse class of catalysts and their uses in organic reactions Carbon-based materials containing sulfonic acid groups [33] have been used as novel, efficient, and

Microwave-assisted synthesis of biologically relevant steroidal 17-exo-pyrazol-5'-ones from a norpregnene precursor by a side-chain elongation/heterocyclization sequence

• Gergő Mótyán,
• László Mérai,
• Márton Attila Kiss,
• Zsuzsanna Schelz,
• Izabella Sinka,
• István Zupkó and
• Éva Frank

Beilstein J. Org. Chem. 2018, 14, 2589–2596, doi:10.3762/bjoc.14.236

• phenylhydrazine (5b) was completed within 7 h in refluxing EtOH in the presence of an acid catalyst. A reduction of the reaction time to 3 h could be achieved by changing the solvent to AcOH affording the desired product 6b in high yield (86%, Scheme 2). On the other hand, the reaction of 4 with methylhydrazine

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• acid catalyst for the asymmetric ring opening of cyclohexene oxide with alkyl- and arylthiols [37]. The optimal conditions were found to be 10 mol % of the catalyst relative to cyclohexene oxide, at room temperature, in dichloromethane as the solvent (Scheme 11). More polar solvents such as DMF

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

• Yuichi Yoshimura,
• Hideaki Wakamatsu,
• Yoshihiro Natori,
• Yukako Saito and
• Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

• donor of in the latter are carried out in the presence of an appropriate activator. As an activator of the glycosylation, a combination of a Lewis acid catalyst and a hypervalent iodine was developed for synthesizing 4’-thionucleosides, which could be applied for the synthesis of 4’-selenonucleosides as

• oxidative conditions. These were quite useful and the conceptually similar reactions were widely used for synthesizing nucleoside derivatives. Recently, a combination of a Lewis acid catalyst and hypervalent iodine was developed for synthesizing 4’-thionucleosides, which was based on a Pummerer-type

• alcohol 11. The most popular method to form a glycosyl bond between the sugar moiety and the base of a nucleoside is a Vorbrüggen reaction [15][16], in which a silylated base and sugar donor, e.g., 1-acetoxy sugar, are condensed by a Lewis acid catalyst. It was clear that this reaction could also be used

Synthesis of pyrazolopyrimidinones using a “one-pot” approach under microwave irradiation

• Mark Kelada,
• John M. D. Walsh,
• Robert W. Devine,
• Patrick McArdle and
• John C. Stephens

Beilstein J. Org. Chem. 2018, 14, 1222–1228, doi:10.3762/bjoc.14.104

• -ketonitrile in the presence of a hydrazine [1][2][3][4][19][20][21][22][23][24][25][26][27][28][29], with Rao et al. [31] and Bagley et al. [32] reporting microwave-assisted protocols, the former requiring an acid catalyst. In order to conduct a solvent screen we chose β-ketonitrile 1a as a model substrate

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• prepared by reacting α-tetralone (171) with ethyl orthoformate in the presence of an acid catalyst. Subsequent successive reactions are dihalocarbene addition to enolether 172, ring expansion of the adduct 173 to halocycloheptadienone 168, and dehydrohalogenation of 168 with lithium chloride. Later

An air-stable bisboron complex: a practical bidentate Lewis acid catalyst

• Longcheng Hong,
• Sebastian Ahles,
• Andreas H. Heindl,
• Gastelle Tiétcha,
• Andrey Petrov,
• Zhenpin Lu,
• Christian Logemann and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2018, 14, 618–625, doi:10.3762/bjoc.14.48

• -orbital of the boron atom. This may prevent the boron compound from decomposition as well as hydrolysis and provide a practical Lewis acid catalyst for organic reactions. To test the hypothesis, several Lewis bases were subjected to the coordination reaction with the bidentate bisboron catalyst, 5,10

• + Na]+ calcd for C18H18B2N2, 307.1548; found, 307.1561; IR (neat): 3124, 3041, 2965, 2918, 2829, 1581, 1468, 1425, 1310, 1286, 1276, 1153, 1113, 997, 950, 889, 754, 713, 610, 575. IEDDA reactions catalyzed by the air-stable bidentate Lewis acid catalyst B General procedure A for IEDDA reactions of

• phthalazine: In a Schlenk tube charged with a stirring bar, the air-stable bidentate Lewis acid catalyst B (5.00 mol %) and the stated solvent were added under N2. Then, the phthalazine (1.00 equiv), dienophile (2.00 equiv; for enamines, generated in situ from aldehyde and amine) were added subsequently. The

Synthesis and stability of strongly acidic benzamide derivatives

• Frederik Diness,
• Niels J. Bjerrum and
• Mikael Begtrup

Beilstein J. Org. Chem. 2018, 14, 523–530, doi:10.3762/bjoc.14.38

• p-toluenesulfonic acid (5) which is commonly used as a soluble organic acid catalyst in chemical reactions. Remarkably, neither the N-triflylbenzamides nor the N,N’-bis(triflyl)benzimidamides have been studied as Brønsted acid catalysts. Their chemical stability including compatibility with

Acid-catalyzed ring-opening reactions of a cyclopropanated 3-aza-2-oxabicyclo[2.2.1]hept-5-ene with alcohols

• Katrina Tait,
• Alysia Horvath,
• Nicolas Blanchard and
• William Tam

Beilstein J. Org. Chem. 2017, 13, 2888–2894, doi:10.3762/bjoc.13.281

• -oxabicyclo[2.2.1]alkenes reductively cleave the N–O bond (a) (Scheme 4), therefore, no examples cleaving the C–O bond have been reported in the literature. In this paper, we aim to explore the use of an acid catalyst with an alcohol nucleophile on the ring-opening of cyclopropanated 3-aza-2-oxabicyclic

• A variety of different acid catalysts was screened and the results are summarized in Table 1. In the presence of a Lewis acid catalyst (Table 1, entries 1–3), the reaction did not proceed as seen with FeCl3 (Table 1, entry 1) or produced ring-opened product 26 in low yields (Table 1, entries 2 and 3

Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides

• Irwan Iskandar Roslan,
• Kian-Hong Ng,
• Gaik-Khuan Chuah and
• Stephan Jaenicke

Beilstein J. Org. Chem. 2017, 13, 2739–2750, doi:10.3762/bjoc.13.270

• and amides have been developed, controlled by the reagents employed. With the Brønsted base KOt-Bu and CBrCl3 as radical initiator, benzo[d]imidazo[2,1-b]thiazoles are synthesized via attack at the α-carbon and keto carbon of the β-ketoester moiety. In contrast, switching to the Lewis acid catalyst

• ][21][22]. Interestingly, by replacing the radical initiator and Brønsted base system with a Lewis acid catalyst, benzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones were formed instead (Scheme 1b). This highlights the versatility of β-ketoesters where the regioselectivity of the reaction is directed by the

Novel approach to hydroxy-group-containing porous organic polymers from bisphenol A

• Tao Wang,
• Yan-Chao Zhao,
• Li-Min Zhang,
• Yi Cui,
• Chang-Shan Zhang and
• Bao-Hang Han

Beilstein J. Org. Chem. 2017, 13, 2131–2137, doi:10.3762/bjoc.13.211

• the stretching vibration of methyl groups shows quantitative changes between BPA and PPOPs, suggesting the degradation of BPA in o-dichlorobenzene and it is reported that the cleavage of methylene can be catalyzed under acidic or basic conditions [29][30]. p-Toluenesulfonic acid acted as an acid

• catalyst in this contribution and will promote the cleavage of BPA at high temperature. The broad absorption bands located at ca. 3500 cm−1 is attributed to the characteristic stretching vibration of hydroxy groups, which is consistent with the literature data [25]. The absorption peak at 1705 cm−1

New bio-nanocomposites based on iron oxides and polysaccharides applied to oxidation and alkylation reactions

• Daily Rodríguez-Padrón,
• Alina M. Balu,
• Antonio A. Romero and
• Rafael Luque

Beilstein J. Org. Chem. 2017, 13, 1982–1993, doi:10.3762/bjoc.13.194

• . The quantity of probe molecule adsorbed by the solid acid catalyst can subsequently be easily quantified. In order to distinguish between Lewis and Brønsted acidity, it was assumed that all DMPY selectively titrates Brønsted sites (methyl groups hinder coordination of nitrogen atoms with Lewis acid

New tricks of well-known aminoazoles in isocyanide-based multicomponent reactions and antibacterial activity of the compounds synthesized

• Maryna V. Murlykina,
• Maryna N. Kornet,
• Sergey M. Desenko,
• Svetlana V. Shishkina,
• Oleg V. Shishkin,
• Aleksander A. Brazhko,
• Vladimir I. Musatov,
• Erik V. Van der Eycken and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2017, 13, 1050–1063, doi:10.3762/bjoc.13.104

• -binucleophile, acid – catalyst). Literature data indicate [14][25][59][97][98][99][100][101] that 5-aminopyrazoles bearing in the fourth position electron-withdrawing substituents like carboxamide, carboxylate or a carbonitrile group, posses chemical properties being different from other 5-aminopyrazoles but

cis-Diastereoselective synthesis of chroman-fused tetralins as B-ring-modified analogues of brazilin

• Dimpee Gogoi,
• Runjun Devi,
• Pallab Pahari,
• Bipul Sarma and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2016, 12, 2816–2822, doi:10.3762/bjoc.12.280

• Friedel–Crafts cyclization (Scheme 2, upper panel) and the products are relevant in the field of natural product-like molecules, because the synthesized molecules are close analogs of a natural product (brazilin). Moreover, the use of TsOH·H2O as an easily-accesible Brønsted acid catalyst with low loading

The digital code driven autonomous synthesis of ibuprofen automated in a 3D-printer-based robot

• Philip J. Kitson,
• Stefan Glatzel and
• Leroy Cronin

Beilstein J. Org. Chem. 2016, 12, 2776–2783, doi:10.3762/bjoc.12.276

• (triflic) acid (CF3SO3H) as the Lewis acid catalyst to yield 4-isobutylpropiophenone (2). Once this is complete a solution of di(acetoxy)phenyl iodide (PhI(OAc)2) and trimethyl orthoformate (TMOF) in methanol (MeOH) is added to the reaction mixture in order to induce a 1,2-aryl migration to produce the

Selective synthesis of thioethers in the presence of a transition-metal-free solid Lewis acid

• Federica Santoro,
• Matteo Mariani,
• Federica Zaccheria,
• Rinaldo Psaro and
• Nicoletta Ravasio

Beilstein J. Org. Chem. 2016, 12, 2627–2635, doi:10.3762/bjoc.12.259

• the green chemistry point of view would be the direct substitution of alcohols (that are also available at low cost) with thiols. In this case the only byproduct will be water. However, due to the lack of a good leaving group the use of an acid catalyst is mandatory. Both Brønsted and Lewis acids can

• of thioethers 3a–p synthesized. Product distribution during reaction of 5b and 2a over a solid acid catalyst. Product distribution during reaction of 1c and 2e. Recyclability test of SiAl 0.6 catalyst in the reaction of 1a and 2a. Racemization of (R)-1-phenylethanol during the reaction with

Diels–Alder reactions in confined spaces: the influence of catalyst structure and the nature of active sites for the retro-Diels–Alder reaction

• Ángel Cantín,
• M. Victoria Gomez and
• Antonio de la Hoz

Beilstein J. Org. Chem. 2016, 12, 2181–2188, doi:10.3762/bjoc.12.208

• ] (see Figure 2a, b) that owing to the retro-DA reaction the selectivity of the endo-endo isomer decreases from 85% to 65% as we previously reported. [30] Considering the interesting application of beta zeolites as Lewis acid catalyst for Diels–Alder reactions in different fields, i.e., the formation of

Silica-supported sulfonic acids as recyclable catalyst for esterification of levulinic acid with stoichiometric amounts of alcohols

• Raimondo Maggi,
• N. Raveendran Shiju,
• Veronica Santacroce,
• Giovanni Maestri,
• Franca Bigi and
• Gadi Rothenberg

Beilstein J. Org. Chem. 2016, 12, 2173–2180, doi:10.3762/bjoc.12.207

• chromatography on silica gel (eluent = hexane/ethyl acetate) and characterised by multinuclear NMR. Anchoring methodologies: a) impregnation; b) covalent binding. Activity of the supported sulfonic acid catalyst within the first six cycles. Reaction conditions: 1 mol % cat., acid:alcohol ratio = 1:1, solvent

Solvent-free synthesis of novel para-menthane-3,8-diol ester derivatives from citronellal using a polymer-supported scandium triflate catalyst

• Lubabalo Mafu,
• Ben Zeelie and
• Paul Watts

Beilstein J. Org. Chem. 2016, 12, 2046–2054, doi:10.3762/bjoc.12.193

• variety of applications. The synthesis method involves the acylation of 3 with various acid anhydrides. The synthesis method also employs a polymer-supported scandium triflate as a water resistant and environmentally friendly acid catalyst. Results and Discussion Synthesis para-menthane-3,8-diol from

• (140 g, 0.0076 mol of a 0.3% (v/v)) solution at a temperature of 100 °C. After 4 hour of stirring the aqueous phase was separated from the organic oil phase. The organic phase was neutralised with 50 mL of 2.5% (v/v) sodium hydrogen carbonate (NaHCO3) solution to remove the remains of sulphuric acid

• catalyst and dried (MgSO4). The product was recrystallized from n-hexane at −18 °C for 24 hours. p-Menthane-3,8-diol (3) was obtained as white crystals (96%). 1H NMR (400 MHz, CDCl3, ppm) δ 0.80–0.96 (m, 3H), 0.89–0.90 (m, 1H), 0.99–1.03 (m, 2H), 1.11–1.19 (m, 3H), 1.33 (s, 3H), 1.66–1.68 (m, 2H), 1.72

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• , the mechanism of this reaction is still not fully understood. The nature of the acid catalyst [220] and the type of O–O-bond cleavage in the Criegee intermediate [221] were found to play an important role in this reaction. Probably the hydrogen bonds in Baeyer–Villiger reactions play an important role