Synthesis of alkanesulphonyl chlorides from alkylcobaloximes and trichloromethanesulphonyl chloride

Abstract

Alkyl- and substituted alkylcobaloximes react photochemically with trichloromethanesulphonyl chloride to give high yields of alkanesulphonyl chlorides. erythro-2-Phenyl[1-2H1,2-2H1]ethylcobaloxime gives an equimolar mixture of erythro- and threo-2-phenyl[1-2H1,2-2H1]ethanesulphonyl chloride and diastereoisomerically pure 1-phenyl [1-2H1] propan-2-ylcobaloxime gives a 1 : 1 mixture of diastereoisomers of 1-phenyl [1-2H1]propane-2-sulphonyl chloride. The reaction is believed to proceed through a non-chain process initiated by photolysis of the carbon–cobalt bond. The product alkanesulphonyl chloride is then formed, either by a direct attack of the alkyl radical on the sulphur of trichloromethanesulphonyl chloride, or through capture of the alkyl radical by sulphur dioxide and halogen abstraction by the so-formed alkanesulphonyl radical from trichloromethanesulphonyl chloride. The latter process seems the more likely. No evidence could be obtained for an intermolecular homolytic attack of trichloromethyl radicals on the saturated alkyl ligand.