PHOTOBROMINATION OF SIDE-CHAIN METHYL-GROUPS ON ARENES WITH N-BROMOSUCCINIMIDE - CONVENIENT AND SELECTIVE SYNTHESES OF BIS(BROMOMETHYL)ARENES AND (BROMOMETHYL)METHYLARENES

Photobromination of side-chain methyl groups on arenes with N-bromosuccinimide (NBS) was investigated. Visible light irradiation in benzene solvent was extremely effective in increasing the selectivity of the reaction and the efficiency for product purification. The photobromination of 1,4-, 1,8-, 2,3-, and 2,6-dimethylnaphthalenes, 4,4'-dimethylbiphenyl, and p-xylene with 2.2 mol equivalents of NBS quantitatively afforded the corresponding bis(bromomethyl)arenes, respectively. The (bromomethyl)methylarenes were also obtained in good yields in the photobromination reactions of the above dimethylarenes with 1.1 mol equivalents of NBS.