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.
of highly enantioenriched tetrasubstituted alkene architectures from isatin-based Morita-Baylis-Hillman carbonates and allylic derivatives, under the cooperative catalysis of a tertiary amine and a chiral iridium complex. The success of the switchable construction of the tetrasubstituted alkene motif relies on the diastereodivergent 1,3-oxo-allylation reaction between N-allylic ylides and chiral π-allyliridium
Synthesis of Enantioenriched Bromohydrins via Divergent Reactions of Racemic Intermediates from Anchimeric Oxygen Borrowing
作者:Yi-Ming Cao、Dieter Lentz、Mathias Christmann
DOI:10.1021/jacs.8b06432
日期:2018.8.29
catalyzed bromocyclization/regiodivergent reaction of racemic intermediates sequence, which is enabled by anchimeric oxygen borrowing. Different types of alkenes are applicable, and both enantiomers of the bromohydrin products were obtained in generally excellent yields and enantioselectivities. In addition, an example of enantioconvergentsynthesisfrom the two isomeric products is presented.