Products and mechanism of some halogenation reactions of 1-sulfonyl-substituted tricyclo[4.1.0.02,7]heptanes

Abstract

Reactions of 1-methylsulfonyl- and 1-phenylsulfonyltricyclo[4.1.0.02,7]heptanes with iodine, dioxane dibromide, and dichloro-λ3-iodanylbenzene (under irradiation) gave products of stereoselective syn addition of halogen at the C1–C7 central bicyclobutane bond. 7-Methyl-1-phenylsulfonyltricyclo[4.1.0.02,7]-heptane reacted with dioxane dibromide in carbon tetrachloride to produce a mixture of 2-bromo- and 2,3-dibromo-1-methyl-exo-7-phenylsulfonylnorcaranes at a ratio of 1: 4 as a result of cleavage of the C1–C2 bicyclobutane bond. 7-Bromo- and 7-methoxycarbonyl-1-phenylsulfonyltricyclo[4.1.0.02,7]heptanes take up bromine exclusively at the C1–C7 central bond with strict syn stereoselectively. The regio- and stereoselectivity of the addition and their relations with the halogen nature were interpreted with account taken of structural specificities of intermediate 6-sulfonyl-substituted 6-norpinanyl radicals determined by ab initio quantumchemical calculations using 6-31G basis set.