WHAT IS DIFFERENT IN PHOTOCHEMICAL-REACTIONS OF PRIMARY AND SECONDARYALKYLCOBALOXIMES WITH AND WITHOUT RADICAL TRAPS

Photochemical cyclization and halogen abstraction reactions of seconda ry alkylcobaloximes 1b and 1d compared to their primary counterparts 1 a and 1c show an enhanced reactivity of secondary alkylcobaloximes: Th us, cyclohexylcobaloxime 1d reacts 13 times faster with CCl4 than n-he xylcobaloxime 1c, 6-hepten-2-yl-cobaloxime 1b rearranges 58 times fast er to its cyclopentylmethyl isomer 4b than 5-hexenylcobaloxime 1a. Alt hough free alkyl radicals are reactive intermediates in photolytic con versions of alkylcobaloximes 1 in organic solvents, the presence of Br CCl3 or bromobenzene in photoreactions of primary alkylcobaloximes 1a and 1c seems to cause a more efficient homolytic cleavage of the Co-C bond.