Extended pi-participation in biomimetic cyclization of squalene derivatives

Chlorides 4(1-aryl-1-chloro-5,9,14,18,22-pentamethyl-5,9,13,17,21-tricosapentaenes) with various phenyl substituents were prepared, and solvolysis rates were measured in aqueous ethanol (phi = 95% and 80%) and in aqueous 2,2,2-trifluoroethanol (omega = 97%). Hammett rho(+) values obtained are -1.86, -1.81 and -1.56, respectively, suggesting concerted cyclization of at least two double bonds in the rate determining step.