Homolytic displacements at carbon. Part 3. Regiospecific syntheses of allyl sulphones in the reaction of allycobaloximes with organosulphonyl chlorides

Abstract

Toluene-p-, toluene-α-, methane-, and chloro-methanesulphonyl chlorides react thermally and photochemically with allyl-, 3-methylallyl-, 3,3-dimethylallyl-, and cinnamyl-cobaloximes to give the corresponding rearranged allyl tolyl, methyl, or chloromethyl sulphone and chlorocobaloxime(III). It is proposed that the mechanism involves a chain reaction in which the organosulphonyl radical and cobaloxime(II) species are the chain -propagating intermediates. Because of competing heterolytic reactions, the yields are higher in the photochemical than in the thermal reactions. Trichloromethanesulphonyl chloride reacts more rapidly, forming the trichloromethylsulphonyl radical which loses sulphur dioxide, so that it is the trichloromethyl radical which reacts with the allylcobaloxime to give the corresponding rearranged trichlorobutene. Dichloromethanesulphonyl chloride reacts similarly, but the dichloromethyl radical, formed by loss of sulphur dioxide, is rather unselective and gives a variety of products in its reaction with the allylcobaloxime.