N-Heterocyclic Carbene-Mediated Oxidative Esterification of Aldehydes: Ester Formation and Mechanistic Studies
摘要:
An unexpected N-heterocyclic carbene-catalyzed esterification of alpha,beta-unsaturated aldehydes including aromatic aldehydes with reactive cinnamyl bromides in the presence of air oxygen or MnO2 as an oxidant is described. In the presence of oxygen, halogenated and electron-deficient aldehydes react smoothly to furnish esters in good yields. Great efforts have been made on mechanistic studies to deduce a plausible mechanism, based on the experimental results and isotopic labeling experiment.
Copper-Catalyzed Cross-Coupling of Thiols, Alcohols, and Oxygen for the Synthesis of Esters
作者:Seungyeon Lim、Miran Ji、Xi Wang、Chan Lee、Hye-Young Jang
DOI:10.1002/ejoc.201403311
日期:2015.1
Copper-catalyzed, one-pot, three-component coupling reactions using thiols, alcohols, and oxygen to form a variety of esters in good yields were studied. In the presence of easily oxidized benzylic and allylic alcohols, thiols were selectively oxidized to form thionoesters, which underwent facile S/O exchange to afford esters. Thiols may be used as an alternative benzoyl source under mild aerobic conditions
A ternary catalytic system comprising a chiral aldehyde, a transition metal, and a Lewis acid is rationally designed for the asymmetric α-allylic alkylation reaction of aza-aryl methylamines and π-allylmetal electrophiles. Structural diversity chiral amines bearing carbon–carbon double bonds and aza-heterocycles are produced in moderate to good yields with good to excellent enantioselectivities. These