vic-Iodothiocyanates and iodoisothiocyanates. Part 1. Preparation and isomerization

Abstract

Treatment of alkenes with iodine(I) thiocyanate gives high yields of vic-iodothiocyanates and vic-iodoisothiocyanates. The ratio of the adducts varies with the reagents used, the conditions employed, and the nature of the alkene. The products are consistent with the intermediacy of an iodonium ion for cyclohexene and 5α-androst-2-ene and an open or asymmetric cation for α-arylalkenes. The rate of addition is accelerated by phase-transfer catalysts, especially in the case of 5α-androst-2-ene. The iodothiocyanate is the kinetically formed product which may be rearranged to the thermodynamically more stable iodoisothiocyanate by boron trifluoride–ether, either in situ or separately, thereby providing a simple route to the latter derivatives.