Cyclizations of ω-Allenyl Radicals

Article abstract of DOI:10.1021/jo00186a009

Allenyl halides of structure (CH3)2C=C=CH(CH2)nX with n=3-6 have been prepared and reacted with n-Bu3SnH to generate the corresponding radicals for examination of the cyclization reactions of these reactive intermediates.The observed hydrocarbon products indicate that cyclization occurs for the n=3,4, and 5 radicals but not for the n=6 species.The n=3 radical isomerizes very efficiently by intramolecular addition to the sp carbon of the allene group.The n=5 intermediate reacts relatively slowly by attack at the near sp² carbon.Both cyclization modes are observed for the n=4 species.The details of these radical cyclizations are discussed.