Asymmetric reactions of axially chiral amides: use of removable ortho-substituents in radical cyclizations of o-iodoacrylanilides and N-allyl-N-o-iodoacrylamides

摘要

Radical cyclizations of enantiomerically enriched o-iodoacrylanilides and N-allyl-o-iodoanilides bearing a removable ortho-substituent such as trimethylsilyl or bromine provide oxindoles and indoles in good yields and with good to excellent levels of chirality transfer from the N-Ar axis to the new stereocenter. Transition state models for the chirality transfer are suggested. Chemoselectivity of the radical cyclization in favor of the iodine in the case of 2-iodo-6-bromo-N-allylacrylamides has been exploited for the synthesis of chiral pyrroloquinolinones by a one-pot sequence of 5-exo and 6-endo cyclizations. (C) 2004 Elsevier Ltd. All rights reserved.