Radical Cascade Processes Leading to Fused- and Spiro-Bicyclic Ring Systems

The course of the reaction of 2-propargyl-2-(2-carboethoxyvinyl)cyclohexanone with tributyltin hydride and AIBN either neat or in benzene solution is discussed. The structure of the spirocyclic major product is shown to differ from that previously suggested and plausible reaction pathways are presented to account for the outcome.