Pd(OAc)₂ promoted bis‐N‐heterocyclic carbene‐catalyzed oxidative transformation of aldehydes

Abstract

The bis‐N‐heterocyclic carbene‐catalyzed (bis‐NHC‐catalyzed) oxidative transformation of aldehydes was successfully studied in water under air. The reaction rate increased through the use of Pd(OAc)2 as an additive. Notably, the catalytic system exhibited good tolerance toward aliphatic and aromatic aldehydes bearing halide and alkyl functional groups. In addition, gram‐scale reaction was also tested in this study. The use of water and operational simplicity make this methodology environmentally benign and cost‐effective.

Aerobic Oxidative N‐Heterocyclic Carbene Catalysis

“…3.2 Oxidation using metal redox active catalyst Gois, 2010 [63] Ester 20 mol% Fe(TfO) 2, Air 20 24 90 Gois, 2011 [64] Ester 20 mol% Fe(TfO) 2 , Air 20 24 90 Cheng, 2011 [65] Ester 5 mol% Pd(OAc) 2 , Air 5 24 100 Pan, 2012 [66] Ester 5 mol% [RuCl 2 (p-cymene)] 2 , Air 10 24 130 Studer, 2013 [67] Ester 5 mol% Ru(bpz) 3 (PF 6 ) 2 , Air 2,5 1-16 rt Huang, 2018 [32] Ester 10% RuCl 3, O 2 10 24 rt Huang, 2018 [32] Chiral lactone via (3 + 3) 10% RuCl 3 , O 2 10 24 rt Huang, 2018 [32] Chiral lactone via (4 + 2) 10% RuCl 3 , O 2 10 24 rt Lee, 2020 [68] Carboxylic acids 1 mol% Pd(OAc) 2 , HCO 2 H 1 24 80…”

“…Inspired by Fu and co-workers protocol from 2013 (Scheme 16), Lee and co-workers (2020) performed a bis-NHC 99 catalyzed aerial oxidation of aryl aldehydes 58 to carboxylic acids 59 (Scheme 25). [68] Fu and co-workers reported long reaction times (2-3 days) and high catalyst loading (5 mol%). Lee and co-workers were able to show that by adding 1 mol% Pd(OAc) 2 as an additive in combination with oxygen the reaction time could be decreased to 24 hours and the NHC catalyst loading to 1 mol %.…”