Homolytic displacement at carbon: X. Toluenesulphonyl iodide as a source of toluenesulphonyl radicals for the formation of allyl-, benzyl-, cyclopropylcarbinyl-, spirocyclopropylcycloalkyl-, bicyclo[1.0.3]alkyl-, and bicyclo[1.0.4]Alkyl-4-tolylsulphones from organocobaloximes

Abstract

4-Toluenesulphonyl iodide reacts thermally at ⩽ 40°C with a wide range of alkenyl- and benzyl-cobaloximes to give good yields of the organo-4-tolylsulphone. Allylcobaloximes yield predominantly, and in some cases exclusively, the rearranged allylsulphone; alicyclic but-3-enylcobaloximes yield the corresponding cyclopropyl- carbinylsulphone; cycloalkenylethylcobaloximes yield the spiro-1,1-cyclopropyl- cycloalkylsulphone; and cycloalk-2-enylmethylcobaloximes yield the bicyclo- [1.0. N] alkylsulphone. Spiro- and bicyclo-alkyl compounds are also formed with other free radical precursors. The reactions are believed to take place through a chain mechanism in which cobaloxime(II), present adventitiously or formed by partial homolysis of the substrate, abstracts iodine from the toluenesulphonyl iodide to give the toluenesulphonyl radical, which attacks the organic ligand of the cobaloxime, preferably at the terminal olefinic carbon, thereby displacing cobaloxime(II) and giving the observed organic product.