ATTEMPTS AT VINYL RADICAL CARBONYLATION THROUGH CYCLIZATION ONTO CARBONYL AND CYANO GROUPS

Sulfanylvinyl radicals 4-6, 16, produced From toluenesulfanyl radical addition to alkynes 1-3, 15, gave only products arising from cyclizati on onto the thiophenyl ring and H-abstraction. No products were obtain ed deriving from possible 5-membered cyclization onto the esteric or t hioesteric carbonyl group. Similar results were obtained from toluenes ulfanyl radical addition to alkynyl nitriles 20 and 24, which did not provided any evidence for 5- or 6-membered vinyl radical cyclization o nto the aliphatic cyano group, In contrast, both toluenesulfanyl- and benzenesulfanyl- vinyl radicals 32 and 37a smoothly cyclize onto the a romatic cyano group leading to ketones 35 and 39. This protocol repres ents a novel indirect radical carbonylation and provides a useful synt hetic approach to indenones, (C) 1998 Elsevier Science Ltd. All rights reserved.