GAMMA-OXYGENATED-ALPHA,BETA-UNSATURATED SULFONES IN RADICAL CYCLIZATIONS AND CASCADE PROCESSES

A wide variety of radical precursors having the structure of gamma-oxy genated-alpha,beta-unsaturated sulfone (substrates 1-4) have been prep ared. Both 5-hexenyl and 6-heptenyl radicals, generated by reaction of substrates 1-4 with Bu3SnH/AIBN, underwent an efficient cyclization v ia intramolecular addition to the vinyl sulfone moiety. By introductio n of a double bond joined to the oxygen at gamma-position, a cascade p rocess based on two sequential radical cyclizations took place, afford ing highly substituted 2-oxa[3.3.0] or 9-oxa[4.3.0] bicyclic compounds . (C) 1998 Elsevier Science Ltd. All rights reserved.