HOMOLYTIC DISPLACEMENT AT CARBON. V. FORMATION OF CYCLOPROPYLCARBINYLSULPHONES AND TRICHLOROETHYLCYCLOPROPANES FROM BUT-3-ENYL COBALOXIMES BY A NOVEL PROCESS INVOLVING HOMOLYTIC ATTACK AT THE δ-CARBON OF THE BUTENYL LIGAND

Article abstract of DOI:10.1016/S0022-328X(00)93390-4

But-3-enyl- and substituted but-3-enylcobaloximes react with bromotrichlormethane (or trichloromethanesulphonyl chloride) and with 4-toluenesulphonyl chloride thermally or photochemically to give good yields of β,β,β-trichloroethylcyclopropanes and cyclopropylcarbinyl(tolyl)sulphones, respectively.The reactions proceed by a chain mechanism in which a key step is a novel process in which homolytic attack of a trichloromethyl or 4-toluenesulphonyl radical at the δ-carbon of the butenyl ligand leads to synchronous or subsequent attack of the incipient γ-carbon radical on the α-carbon, causing cyclisation and displacement of cobaloxime(II).The other propagation step involves the reaction of the cobaloxime(II) with the bromotrichloromethane, trichloromethanesulphonyl chloride or 4-toluenesulphonyl chloride to give the reactive organic radical.