Tandem transformations of cyclopentene alpha,alpha-dichlorocarboxamides into epoxy lactones induced by a gamma-hydroxyl group; a short synthesis of the Corey epoxy lactone and its enantiomer

摘要

The stable iminolactone 6 was obtained by NBS induced bromocyclization of carboxamide 4. Under treatment of 6 with DBU a tandem recyclization transformation occurred resulting in the formation of epoxyiminolactone 7. Bromo(iodo)cyclization of 4 in aqueous organic medium followed by treatment with base gave epoxylactone 9. Under the optimized conditions, Corey epoxylactone 1 and its enantiomer eat-1 were obtained from diastereomeric carboxamides 4 and 5 in an overall yield of 40%. (C) 2015 Elsevier Ltd. All rights reserved.