N-Heterocyclic Carbene Catalysed Oxidative Coupling of Aldehydes with Alcohols/Thiols and One-Pot Oxidation/Esterification of Allylic Alcohols

• Published in: European journal of organic chemistry Vol. 2013; no. 35; pp. 7881 - 7885
• Main Authors: Ji, Miran, Wang, Xi, Lim, Yu Na, Kang, Ye-Won, Jang, Hye-Young
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.12.2013; WILEY‐VCH Verlag; Wiley; Wiley Subscription Services, Inc
• Subjects: Aldehydes; Carbenes; Chemistry; Chemistry, Organic; Dehydrogenation; Esters; Oxidation; Physical Sciences; Reaction mechanisms; Science & Technology; Synthetic methods; Thioesters; Thioesters; ESTERIFICATION; NHC; AMIDATION; Esters; CARBONYL-COMPOUNDS; AROMATIC-ALDEHYDES; Carbenes; Dehydrogenation; AEROBIC OXIDATION; Oxidation; Synthetic methods; ARYL; Reaction mechanisms; EFFICIENT; TRANSITION-METAL-FREE
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201301337

A versatile carbene‐catalysed oxidation protocol involving N‐heterocyclic carbene catalysts and 2,2,6,6‐tetramethylpiperidine N‐oxyl (TEMPO) is described for the synthesis of esters, cinnamic acids, and thioesters. A wide range of esters, thioesters, and cinnamic acids were obtained by metal‐free coupling of aldehydes with aliphatic, allylic and aromatic alcohols, benzyl mercaptan, and water. In addition to the oxidative coupling of aldehydes with nucleophiles, dehydrogenation of saturated aldehydes and oxidation of allylic alcohols were found under our oxidative coupling conditions. Unlike other TEMPO‐mediated oxidative esterification reactions, this reaction does not proceed through a TEMPO ester intermediate to form esters and thioesters. N‐Heterocyclic carbene complexes catalyse various oxidative coupling reactions in the presence of TEMPO. A variety of α,β‐unsaturated and saturated esters, and aromatic esters and thioesters were synthesised.