Extended π-participation in biomimetic cyclization of squalene derivatives

Abstract

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 Op = 95% and 80%) and in aqueous 2,2,2-trifluoroethanol (w = 97%). Hammett p+ 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