A Mild Selective Monobromination Reagent System for Alkoxybenzenes; N-Bromosuccinimide–Silica Gel

The monobromination of alkoxybenzenes with N-bromosuccinimide catalyzed by silica gel in carbon tetrachloride occurred preferentially at the para-position. m-t-Butylmethoxybenzene yielded 4-bromo-3-t-butyl-1-methoxybenzene with a selectivity of 74% even in the presence of a bulky substituent at the meta-position.