Croat. Chem. Acta 69 (1996) 1347-1359.

Extended pi-Participation in Biomimetic Cyclization of Squalene Derivatives

Stanko Borcic, Kresimir Humski, Olga Kronja, and Ivica Malnar

Department of Chemistry, Faculty of Pharmacy and Biochemistry, University of Zagreb, Ante Kovacica 1, 10000 Zagreb, Croatia

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 (fi=95% and 80%) and in aqueous 2,2,2-trifluoroethanol (W=97%). Hammett ro⁺ 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.