Rearrangements and cyclizations in vinyl radicals. Unusual example of 1,4-radical translocation.

Vinyl radical 5 undergoes 5-exo cyclization onto the CC double bond in competition with the 5-exo cyclization onto the aryl ring. In addition, radical 5 exhibits an unusual 1,4-radical translocation/beta-fragmentation process. In contrast, radical 4 exclusively undergoes 5-exo cyclization onto the benzene ring. This latter reaction leads to spiro radical intermediates which can either give the 1,4-aryl migration products or can be trapped by 2-cyano-iso-propyl radicals. Copyright (C) 1996 Published by Elsevier Science Ltd