A case of concerted formation of five and six member rings; solvolytic behavior of 1-aryl-1-chloro-4,8,13,17,21-pentamethyl-4,8,12,16,20-docosapentaenes

Chlorides 1 (1-aryl-1-chloro-4,8,13,17,21-pentamethyl-4,8,12,16,20-docosapentaenes) with various phenyl substituents were prepared, and solvolysis rates were measured in 80% (v/v) aqueous ethanol, and in 97% (w/w) aqueous 2,2,2-trifluoroethanol. Hammett ρ+ values obtained are -2.18, -2.13, resp., suggesting a concerted bicyclization in the rate determining step