SEQUENTIAL ALKOXY RADICAL FRAGMENTATION-TRANSANNULAR RADICAL CYCLIZATION-RADICAL RING EXPANSION REACTIONS - A NEW APPROACH TO BICYCLO[5.3.0]DECANONES AND TO BICYCLO[6.3.0]UNDECANONES

Treatment of the unsaturated decanols (7), (9) and (16) with iodosylbenzene diacetate-iodine leads to the formation of intermediate allyloxy radicals viz (1) which undergo fragmentation followed by transannular cyclisation of the resulting carbon centred radicals (2) leading to the bicyclo [5.3.0]decanones [(3), ''hydroazulenones''] (Scheme 1). When the iodomethylhydroazulenones (3) (R' = I) are treated with Bu3SnH-AIBN under high dilution, they undergo ring expansion to the isomeric bicyclo[6.3.0]undecanones (4).