Photothermal Side-Chain Bromination of Methyl-, Dimethyl-, and Trimethylbenzenes with N-Bromosuccinimide

Tri- and dibromination of methyl-, dimethyl-, and trimethylbenzenes with N-bromosuccinimide were accomplished by photothermal reaction with a tungsten lamp in carbon tetrachloride or benzene. (Dibromomethyl)arenes and (tribromomethyl) derivatives were produced depending upon a solvent used and a substituent on the benzene ring. In the bromination of methylbenzenes without a substituent on the ortho-position, (tribromomethyl)benzenes were formed. On the other hand, ortho-substituted methylbenzenes gave (dibromomethyl)benzenes. α,β-Dibromo-1,2-diarylstilbenes were formed via the debrominative carbon–carbon coupling reaction of (tribromomethyl) benzenes upon irradiation with a tungsten lamp.