Allylic Reactions of Benzocyclopropenes. Discrimination of halogen substituents in 1, 1‐Dihalogenobenzocyclopropenes

Reaction of 1, 1‐dichloro‐2, 5‐diphenylbenzocyclopropene ( 10a ) with 1 equiv. of silver fluoride yields 1‐chloro‐1‐fluoro‐2, 5‐diphenylbenzocyclopropene ( 10c ). Both 10a and 10c react with excess silver fluoride to give the difluoro compound 10b . Both 10b and 10c are also prepared via cyclo‐additions of 1, 2‐dichloro‐3, 3‐difluorocyclopropene ( 14 ) or 1, 2, 3‐flurocyclopropene ( 13 ) with diphenylbutadiene and subsequent aromatization with base. Similarly. 1‐chloro‐1‐fluorobenzocyclopropene ( 16 ) is accessible from butadiene and 13 .