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

• used as organocatalyst in two classical umpolung reactions of cinnamaldehyde: its cyclodimerization and its oxidative esterification. Keywords: Breslow intermediate; cathodic reduction; flow electrochemistry; N-heterocyclic carbene; oxidative esterification; Introduction Ionic liquids (ILs) are well

• . Esterification of trans cinnamaldehyde Once the possibility of obtaining the Breslow intermediate was demonstrated, another typical reaction of N-heterocyclic carbenes was tested: the oxidative esterification of cinnamaldehyde in the presence of alcohols. To carry out these experiments three different alcohols

• of the electrogenerated carbene was used to promote dimerization and oxidative esterification reactions of cinnamaldehyde. Under the flow conditions investigated, a higher rate of NHC production was achieved, compared to previously reported batch reactions, which is an important consideration for

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• ][60]. They have been employed for a number of organic reactions viz., hydrosilylation of aldehydes and ketones, acetylation reactions, redox reactions, oxidative esterification, etc. [61][62][63]. Thus, in concern with increasing demand for sustainable development, a growing number of catalytic

Electron-transfer-initiated benzoin- and Stetter-like reactions in packed-bed reactors for process intensification

• Anna Zaghi,
• Daniele Ragno,
• Graziano Di Carmine,
• Carmela De Risi,
• Olga Bortolini,
• Pier Paolo Giovannini,
• Giancarlo Fantin and
• Alessandro Massi

Beilstein J. Org. Chem. 2016, 12, 2719–2730, doi:10.3762/bjoc.12.268

• homogeneous conditions and their subsequent utilization in transesterification and amidation processes by the reaction telescoping approach [12]. Similarly, the group of Brown reported on the oxidative esterification and amidation of aldehydes in undivided microfluidic electrolysis cells mediated by

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

• compounds to form C–C, C–N, C–O, C–Hal, C–P, and N–N bonds [10], the Bu4NI/t-BuOOH oxidative system [22], selective functionalization of molecules [23], the oxidative esterification and oxidative amidation of aldehydes [24], and the transition metal-catalyzed radical oxidative cross-couplings [13]. The

• coupling. These processes with aldehydes or primary alcohols as C-reagents giving esters are often referred to as oxidative esterification. 2.1 Transition metal salt-catalyzed reactions using compounds with C=C, C=O, and C–Hal bonds as oxidants One of the types of the oxidative esterification is based on

• are used as the solvents or are taken in a large excess relative to the CH-reagent. 2.3 Reactions catalyzed by N-heterocyclic carbenes N-heterocyclic nucleophilic carbenes 105 have found use for the oxidative esterification. Scheme 23 shows, in a simplified way, the proposed mechanism of this type of

Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules

• Thilo Focken and
• Stephen Hanessian

Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195

• in 28–64% ee [5]. In a similar fashion, Denmark’s oxazaphosphorinane cis-44a yielded keto esters 46a–c in high optical purities via conjugate addition to enones 41 followed by ozonolysis and oxidative esterification. Using diastereomer trans-44b on the other hand provided ketoesters 46a–c with only

Pd/C-catalyzed aerobic oxidative esterification of alcohols and aldehydes: a highly efficient microwave-assisted green protocol

• Marina Caporaso,
• Giancarlo Cravotto,
• Spyros Georgakopoulos,
• George Heropoulos,
• Katia Martina and
• Silvia Tagliapietra

Beilstein J. Org. Chem. 2014, 10, 1454–1461, doi:10.3762/bjoc.10.149

• metals. Homogeneous and heterogeneous Pd catalysts have been widely used in the selective oxidation of alcohols [36][37]. Most publications have focused on the conversion of alcohol to aldehydes or ketones [38][39]. Several examples of the heterogeneous oxidative esterification of alcohols in the

• versatility of these reactors in promoting reactions with gaseous reagents in a closed cavity [56]. In this present work, we report an efficient Pd/C-catalyzed aerobic oxidative esterification of aldehydes and alcohols in the presence of molecular oxygen in a closed MW reactor. The optimized procedure does

• was decided that the investigation be broadened to the readily accessible Pd/C. Gratifyingly, full substrate conversion to the desired ester was afforded without catalyst pre-sonication, even at 70 °C (Table 1, entries 9–11). For the sake of comparison, the oxidative esterification of benzylalcohol in

Synthesis of enantiomerically pure N-(2,3-dihydroxypropyl)arylamides via oxidative esterification

• Akula Raghunadh,
• Satish S More,
• T. Krishna Chaitanya,
• Yadla Sateesh Kumar,
• Suresh Babu Meruva,
• L. Vaikunta Rao and
• U. K. Syam Kumar

Beilstein J. Org. Chem. 2013, 9, 2129–2136, doi:10.3762/bjoc.9.250

• purity was observed. Keywords: N-(2,3-dihydroxypropyl)arylamide; nitrogen heterocyclic carbenes (NHC); oxidative esterification of aromatic aldehyde; Introduction Chiral structures with three carbons are an integral part of many biologically active compounds including alkaloids, pharmaceuticals and

• ][6] or (ii) catalytic oxidations with peroxides and chiral transition metal complexes [7][8][9]. The oxidative esterification of aldehydes involving oxidation followed by a C–O or C–N bond formation has received significant synthetic interest of late. Various transition metal complexes are employed

• to facilitate these reactions [10][11][12][13][14][15][16][17][18]. Herein we describe a highly enantioselective synthesis of (S) and (R)-N-(2,3-dihydroxypropyl)arylamides [19][20][21][22] in a two-step process in overall good yields by oxidative esterification of the corresponding aryl aldehydes

NHC-catalysed highly selective aerobic oxidation of nonactivated aldehydes

• Lennart Möhlmann,
• Stefan Ludwig and
• Siegfried Blechert

Beilstein J. Org. Chem. 2013, 9, 602–607, doi:10.3762/bjoc.9.65

• in [27][28].) The methodology could be extended to oxidative esterification by using alcohols as nucleophiles instead of water. However, this transformation is highly sensitive to moisture, which leads to the formation of acid as a side product. Even under dry conditions, with freshly distilled

• directly with the aldehyde to form two molecules of V. Based on our results we believe that pathway a is favoured for this reaction since b could only deliver a maximum of 50% of the oxidative esterification product in the presence of an alcohol as a nucleophile. In our experiments, however, yields up to