Advancements in hydrochlorination of alkenes

• Daniel S. Müller

Beilstein J. Org. Chem. 2024, 20, 787–814, doi:10.3762/bjoc.20.72

• ex-situ as demonstrated very recently by De Borggraeve and co-workers (Figure 5A) [67]. In a first chamber (A) HCl (gas) was prepared from NaCl and H2SO4 which then was directed towards a second chamber (B) which contains the alkene under solvent-free conditions. The scope of this reaction (Figure 5B

HPW-Catalyzed environmentally benign approach to imidazo[1,2-a]pyridines

• Luan A. Martinho and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2024, 20, 628–637, doi:10.3762/bjoc.20.55

• much greener as compared to methanol, it was chosen as the solvent to study the reaction scope. The use of water or solvent-free conditions resulted in much lower reaction yields (Table 1, entries 14–16). Next, the scope of the reaction was investigated with a range of 2-aminopyridines/2-aminothiazoles

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

• and viability of these synthetic protocols, organic chemists have been opting towards the use of greener catalysts and solvents in drug development. Chemists dream to perform reactions under solvent-free conditions, which provide a greener approach towards organic transformations. Nowadays, the use of

• of strong acidic sites that are on the carbon-based solid acids enhance their catalytic ability, compared to traditional Lewis and protic acids [41][42][43]. The most common examples in literature for the reaction of the synthesis of BIMs under solvent-free conditions utilize either protic acids

• :0.05, under solvent-free conditions at 50 °C for 50 min, the product was obtained in 90% yield. To emphasize the role of DBDMH, when the reaction was performed without DBDMH, no product was observed. The generality of this protocol was also tested by employing various aromatic aldehydes, which formed

Catalytic multi-step domino and one-pot reactions

• Svetlana B. Tsogoeva

Beilstein J. Org. Chem. 2024, 20, 254–256, doi:10.3762/bjoc.20.25

• -aminopyrazoles with azlactones under solvent-free conditions, through subsequent elimination of a benzamide molecule in a superbasic medium, is described by the Fisyuk group [13]. A further facile one-pot process toward a new series of copper(II) benzo[f]chromeno[2,3-h]quinoxalinoporphyrin analogues is described

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• cyclization and sulfenylation promoted by AlCl3. Dialkyl disulfides 47 were also well tolerated in this Lewis acid-mediated sulfenylation reaction in solvent-free conditions at room temperature. In the same year, a three-component reaction between highly substituted cyclopropanes 49, sulfonamides 25 and N

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• 2010, Schnürch et al. utilized Fe(NO3)3 as the catalyst and TBHP (tert-butyl hydroperoxide) as the oxidant to realize the CDC of C(sp3)–H/C(sp2)–H bonds under solvent-free conditions (Scheme 21) [82]. However, the desired coupling products were obtained in low to moderate yields. The C–H oxidative

New one-pot synthesis of 4-arylpyrazolo[3,4-b]pyridin-6-ones based on 5-aminopyrazoles and azlactones

• Vladislav Yu. Shuvalov,
• Ekaterina Yu. Vlasova,
• Tatyana Yu. Zheleznova and
• Alexander S. Fisyuk

Beilstein J. Org. Chem. 2023, 19, 1155–1160, doi:10.3762/bjoc.19.83

• ) under solvent-free conditions, through subsequent elimination of a benzamide molecule in a superbasic medium (t-BuOK/DMSO). The fluorescent properties of the synthesized compounds were studied. 4-Arylpyrazolo[3,4-b]pyridin-6-ones luminesce in the region of 409–440 nm with a quantum yield of 0.09–0.23

• obtained under solvent-free conditions followed by the addition of t-BuOK in DMSO, the yield of pyrazolo[3,4-b]pyridin-6-one 4a was higher (73%, Table 1, entry 5) than when performing the reaction in a solvent (60%, Table 1, entry 6). Therefore, this procedure was used for the synthesis of compounds 4b–i

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

• -assisted reactions in water, solvent-free conditions and in other organic solvents. Clauson–Kaas reaction and its mechanism The Clauson–Kaas reaction refers to the synthesis of various N-substituted pyrroles via an acid-catalyzed reaction between aromatic or aliphatic primary amines and 2,5

• nanoorganocatalysts. Various solvent systems, such as aqueous conditions, different organic solvents, solvent-free conditions, ionic liquids, and DESs, have been reported in modified Clauson–Kaas reactions at room temperature, under thermal and microwave-assisted conditions. In the Clauson–Kaas reaction mechanism

• demonstrated the synthesis of polygonatine, an alkaloid natural product, using this protocol. (2) Reactions under solvent-free conditions In recent years, interest in organic reactions that do not use toxic organic solvents has increased due to environmental considerations. Ramesh et al. [71] in 2012 reported

Preparation of β-cyclodextrin-based dimers with selectively methylated rims and their use for solubilization of tetracene

• Konstantin Lebedinskiy,
• Volodymyr Lobaz and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2022, 18, 1596–1606, doi:10.3762/bjoc.18.170

• methylated primary rim based on the remarkable methylation ability of methyl tosylate with relatively mild bases at solvent-free conditions has been developed. It has been proved that using Lewis acid in the phosphine imide reactions with CDs can increase the reactivity of some low-reactive compounds, giving

Lewis acid-catalyzed Pudovik reaction–phospha-Brook rearrangement sequence to access phosphoric esters

• Jin Yang,
• Dang-Wei Qian and
• Shang-Dong Yang

Beilstein J. Org. Chem. 2022, 18, 1188–1194, doi:10.3762/bjoc.18.123

• catalyst through a similar transformation under solvent-free conditions [44]. Recently, Zhang’s group disclosed a cesium carbonate-catalyzed Pudovik reaction–phospha-Brook rearrangement sequence and extended the phosphorus source from phosphate to phosphonate [45]. Despite of these important advancements

Synthesis of odorants in flow and their applications in perfumery

• Merlin Kleoff,
• Paul Kiler and
• Philipp Heretsch

Beilstein J. Org. Chem. 2022, 18, 754–768, doi:10.3762/bjoc.18.76

• ) to (+)-nootkatone (8) under catalyst and solvent-free conditions in a segmented flow. Enzyme-catalyzed acetylation of isoamyl alcohol (9) in a biphasic n-heptane/water mixture utilizing a CorningTM Low Flow reactor. Esterification of alcohols by transesterification, catalyzed by immobilized

Complementarity of solution and solid state mechanochemical reaction conditions demonstrated by 1,2-debromination of tricyclic imides

• Petar Štrbac and
• Davor Margetić

Beilstein J. Org. Chem. 2022, 18, 746–753, doi:10.3762/bjoc.18.75

• conditions (temperature) and the inability to control the elimination process [17]. The objective of this work was to establish whether the 1,2-debromination with the Zn/Ag couple could be carried out under solvent-free conditions in a ball mill and whether the tedious Zn/Ag couple preparation procedure [18

Mechanochemical halogenation of unsymmetrically substituted azobenzenes

• Dajana Barišić,
• Mario Pajić,
• Ivan Halasz,
• Darko Babić and
• Manda Ćurić

Beilstein J. Org. Chem. 2022, 18, 680–687, doi:10.3762/bjoc.18.69

• protocol for the ortho-halogenation of acetanilide with NXS (X = Cl, Br, I) using Pd(OAc)2 as precatalyst in the presence of p-toluenesulfonic acid (TsOH) as an additive under solvent-free conditions [49]. Recently, Mal and Bera reported the utilization of NXS (X = Br, Cl) as bifunctional reagents for the

DDQ in mechanochemical C–N coupling reactions

• Shyamal Kanti Bera,
• Rosalin Bhanja and
• Prasenjit Mal

Beilstein J. Org. Chem. 2022, 18, 639–646, doi:10.3762/bjoc.18.64

• mechanochemistry [5][6] mainly focuses on conducting synthetic transformations in solid-state or solvent-free conditions. Mechanochemistry is one of the emerging avenues in chemistry that can make the world more sustainable by following the “Twelve Principles of Green Chemistry” [2]. Mechanochemistry is one of the

• known, but limited reports are available for reactions carried out under solvent-free conditions [28][29]. However, improving environmentally benign methods [30][31] of C–N bond synthesis is of enormous significance [32][33][34]. In comparison to the metal-mediated C–N coupling reactions [35], the

• benzaldehyde under the solvent-free conditions (Table S1, Supporting Information File 1). Notably, the use of 1.0 equiv of DDQ as oxidant, afforded the product 2-phenylquinazolin-4(3H)-one (5a) in 98% yield within 1 h. However, when reducing the amount of DDQ to 0.5 equiv the of product 5a decreased to 48%. On

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

Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions

• Surendran Amrutha,
• Sankaran Radhika and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 262–285, doi:10.3762/bjoc.18.31

• dendrimers were grown on graphene nanosheets for catalyzing the reaction using highly active Pd-Co bimetallic nanoparticles under copper and solvent-free conditions at room temperature. K2CO3 was found to be the suitable base which provided a relatively good yield (Scheme 28) [41]. The graphite sheets could

New advances in asymmetric organocatalysis

• Radovan Šebesta

Beilstein J. Org. Chem. 2022, 18, 240–242, doi:10.3762/bjoc.18.28

• nitromethane to β-silyl α,β-unsaturated carbonyl compounds catalyzed by bifunctional squaramide catalysts are effective under solvent-free conditions [26]. Zhai and Du demonstrated that asymmetric [3 + 2] annulation reactions of 2-isothiocyanato-1-indanones with barbiturate-based olefins are efficiently

Solvent-free synthesis of enantioenriched β-silyl nitroalkanes under organocatalytic conditions

• Akhil K. Dubey and
• Raghunath Chowdhury

Beilstein J. Org. Chem. 2021, 17, 2642–2649, doi:10.3762/bjoc.17.177

• -unsaturated carbonyl compounds catalyzed by bifunctional squaramide catalysts has been developed. This methodology offers both enantiomers of β-silyl nitroalkanes in good to excellent yields (up to 92%) and enantioselectivities (up to 97.5% ee) under solvent-free conditions at room temperature. Control

• organosilanes [29][37][38], we present herein an organocatalyzed conjugate addition reaction of nitromethane to β-silyl enones to afford chiral β-silyl nitroalkanes (Scheme 1). Notably, the developed method was not only carried out under solvent-free conditions at room temperature but was found to be tolerant

• solvent-free conditions, and was complete within 24 h without affecting the enantioselectivity of product 3a (Table 1, entry 10). Reducing the loading of nitromethane (2) to 5 equivalents, a slight drop in yield (82%) of product 3a was observed whereas the enantioselectivity (97% ee) remained the same

N-Sulfinylpyrrolidine-containing ureas and thioureas as bifunctional organocatalysts

• Viera Poláčková,
• Dominika Krištofíková,
• Boglárka Némethová,
• Renata Górová,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2021, 17, 2629–2641, doi:10.3762/bjoc.17.176

• Michael additions of aldehydes to nitroalkenes both under solvent-free conditions and in solution. The N-sulfinylurea catalyst was more efficient than the corresponding thiourea. For some substrates, enantioselectivities reached 98% ee. The stereogenic center on the sulfur did not have a considerable

• have evaluated the suitability of these catalysts under solvent-free conditions. With the help of DFT calculations, we elucidated the mode of action of these catalysts. Results and Discussion Synthesis of catalysts We have started the synthesis of the catalysts from Boc-protected (S)-prolinol (1), from

• ). Michael additions under solvent-free reaction conditions To evaluate the applicability of the new catalysts C1 and C2, we decided to test them in the Michael addition under solvent-free conditions. Ball-milling experiments were conducted in a mixer mill, in which the milling vessels perform radial

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• -disubstituted-anthracenes from bis(dihexyloxyphenyl)arylmethanes or diveratrylmethanes and aromatic acylals [44]. In the first step, reaction between aromatic aldehydes 49 and acetic anhydride (50) promoted by Bi(OTf)3 under solvent-free conditions afforded aromatic acylals 51 (Scheme 11). In the next two steps

• -free conditions (Scheme 43) [79]. The authors used various heteroaromatic aldehydes and substituted aromatic aldehydes containing electron-donating and electron-withdrawing substituents, to obtain the ortho adducts 188 in variable yields (14–74%). The use of pyridine-3-carbaldehyde and 2,4,5

• -workers [77] provided better results. In a related approach, Estévez-Braun and co-workers synthesized dibenzo[a,h]anthracene-12,13-diones 188 from 2-hydroxy-1,4-naphthoquinone (186), β-naphthol (181), and aromatic aldehydes 187 through a multicomponent reaction that used InCl3 as catalyst under solvent

Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

• Susanne M. Fischer,
• Simon Renner,
• A. Daniel Boese and
• Christian Slugovc

Beilstein J. Org. Chem. 2021, 17, 1689–1697, doi:10.3762/bjoc.17.117

• triphenylphosphine (TPP) in catalyzing oxa-Michael additions. A matrix consisting of three differently strong Michael acceptors and four alcohols of varying acidity was used to assess the activity of the three catalysts. All test reactions were performed with 1 mol % catalyst loading, under solvent-free conditions

• highlight that solvent-free conditions are particularly effective and allow for reducing the catalyst loading by the factor of 10, thereby obtaining a higher share of 3dia and full conversion towards 3dic. Interestingly, the catalytic activity of TPP in reactions with 3 as the Michael acceptor is only

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• reductive elimination occurs in the presence of base to achieve the desired product 119 (Scheme 36) [59]. Direct arylation of disubstituted triazoles 123 with aryl halides 124 using a Pd/C catalyst under solvent-free conditions to give fully decorated triazoles 125 was reported by Farinola et al. Different

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• under solvent-free conditions was carried out, using sodium carbonate as base promoter. The resulting dimethyl 2-(1-aminoalkyl)malonates 50 were obtained in moderate to good yields as single diastereoisomers in all cases except for aromatic aldimines. Compounds 50 could be easily transformed

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• cyclization reaction of allyl bromide (228) with a carbonyl compound promoted by BBIMBr/SnBr2 complex under solvent-free conditions has been explored [97]. The mechanism of the reaction was shown to include a Barbier reaction of allyl bromide with an aldehyde in the presence of SnBr3 and a quaternary ammonium