Vitamin B1-catalyzed aerobic oxidative esterification of aromatic aldehydes with alcohols

Abstract

An aerobic oxidative esterification of aryl aldehydes with alcohols has been developed by employing vitamin B1 as a cost-effective, metal-free, and eco-friendly NHC catalyst.

Aerobic Oxidative N‐Heterocyclic Carbene Catalysis

“…By continuing to explore the potential of this approach, we can look forward to more sustainable, efficient, and cleaner chemical reactions in the years to come. Oxidation with stoichiometric amount Kharasch oxidant Studer, 2010 [40] α,β-unsaturated ester 100 mol% DPQ 2 2-6 rt 3.1 Oxidation of the Breslow intermediate using air Chen & Chang, 2006 [50] 1,2-aminoalcohol Air 20 24 50 Hazra, 2009 [51] Ester Air 15 2-3 64 Liu, 2011 [53] α, β-unsaturated ester Air 20 48 70 Youn, 2011 [55] Phthalide, Isocoumarin Air 10 2-24 80 Anand, 2012 [56] Ester Air 10 2-48 rt Blechert, 2013 [86] Carboxylic acid Air 2 2-64 rt Fu, 2013 [57] Carboxylic acid Air 5 36-120 60 Zhong, 2016 [58] Dihydropyranone Air 20 12-20 rt Bortolini, 2017 [35] Carboxylic acid Air 100 16 55 Nakajima, 2018 [60] Furoic acid Air 7 4 40 Xu, 2021 [61] Ester Air 20 12-24 60-80 Connon, 2013 [62] Ester Air 15 12 45…”

“…In 2021, Xu and co-workers used vitamin B1 4 as a pre-NHC catalyst to perform the esterification of aryl aldehydes 58. [61] Aerial oxygen was used as a terminal oxidant (Scheme 20). The reactions were performed at elevated temperatures (60-80 °C) and the reaction times between 12 to 24 h. The esters 76 are obtained with moderate to excellent yields.…”

“…In 2021, Xu and co‐workers used vitamin B1 4 as a pre‐NHC catalyst to perform the esterification of aryl aldehydes 58 [61] . Aerial oxygen was used as a terminal oxidant (Scheme 20).…”

Oxidative N‐Heterocyclic Carbene Catalysis

“…Acyl azolium intermediates for 1,2‐addition reactions with O ‐ or S ‐nucleophiles were catalytically formed by means of oxygen used as such or in combination with ETMs. Thus, aerobic oxidative esterification of aryl aldehydes with benzylic, heterocyclic, alkyl, and allyl alcohols was attained with vitamin B1 (thiamine, VB1 ) to furnish a range of ester derivatives in yields of 18–72 % (Scheme 25), an equally effective outcome being observed in a model scale‐up experiment (10 mmol of 4‐nitrobenzaldehyde, 61 % yield) [45] . On the strength of control experiment, the aldehyde‐to‐acyl azolium route has been confirmed, then followed by O ‐acylation of the alcohol counterpart.…”

Threefold reactivity of a COF-embedded rhenium catalyst: reductive etherification, oxidative esterification or transfer hydrogenation

“…Furthermore, the utility and scalability of such methods is hindered by the need for high temperature and pressure, 33 co-catalysts, [34][35][36] or stoichiometric oxidizing agents. 37,38 Notably, metal-free methods for the oxidative esterification of aldehydes [39][40][41] remain limited by stoichiometric oxidants.…”