A Class of C2 and Pseudo C2 Symmetric Ketone Catalysts for Asymmetric Epoxidation. Conformational Effect on Catalysis
摘要:
A class of C-2 and pseudo C-2 symmetric ketones with one fused ring at each side of the carbonyl group have been prepared from quinic acid and found to be effective catalysts for the asymmetric epoxidation of a variety of olefins. Electron deficient olefins such as enones can be efficiently epoxidized. Encouragingly good enantioselectivity is also obtained for the epoxidation of styrenes. The studies show that the ketone conformation plays an important role in the reactivity and selectivity of the catalyst.
A Powerful New Strategy for Diversity-Oriented Synthesis of Pyrroles from Donor−Acceptor Cyclopropanes and Nitriles
作者:Ming Yu、Brian L. Pagenkopf
DOI:10.1021/ol036180+
日期:2003.12.1
Lewisacid activated donor-acceptor cyclopropanes react with aliphatic, aromatic, and alpha,beta-unsaturated nitriles in a novel cascade [3 + 2] dipolarcycloaddition, dehydration, and tautomerization sequence to afford pyrroles in moderate to excellent overall yield. This cost-effective and regiospecific method is ideally suited for the preparation of combinatorial libraries. [reaction: see text]