Skeletal Rearrangements and the Structure of Products of Halosulfonamidation of Caryophyllene

Abstract

The reactions of β-caryophyllene with sulfonamides in acetonitrile in the presence of N-bromo- and N-iodosuccinimide have been studied. With NBS, only 3-amidino-6-bromo-1,1,7-trimethyldeca-hydro-3a,7-methanocyclopenta[8]annulenes were isolated. With NIS, some sulfonamides afford their isomeric iodine analogues, 1-amidino-9-iodo-4,4,8-trimethyltricyclo[6.3.1.02,5]dodecanes, also as single products, whereas other reagents give the mixtures of both types of the products. The yields vary from good to excellent, the structure of five products was proved by X-ray analysis. The proposed mechanism includes halogenation of the endocyclic C=C bond, subsequent intramolecular cyclization and either the solvent interception by the formed carbocation, or, prior to interception, the four-to-five-membered ring expansion. The experimentally observed stereo aqnd regioselectivity of the reaction is explained.