Catalytic enantioselective Steglich rearrangements using chiral N-heterocyclic carbenes
摘要:
The evaluation of a range of enantiomerically pure NHCs, prepared in situ from imidazolinium or triazolium salt precatalysts, to promote the catalytic enantioselective Steglich rearrangement of oxazolyl carbonates to their C-carboxyazlactones, is reported. Modest levels of enantioselectivity (up to 66% ee) are observed using oxazolidinone derived NHCs. (C) 2011 Elsevier Ltd. All rights reserved.
pyridine nitrogen, which serves as the nucleophilic site in the asymmetric acyltransfer reaction, we discovered that chiral DMAP‐N‐oxides, in which the oxygen now acts as the nucleophilic site, are efficient acyltransfercatalysts. Our finding might open a new door for the development of chiral DMAP‐N‐oxides for asymmetric acyltransfer reactions.