THE SOLVENT-FREE SIDE-CHAIN OXIDATION OF 4-T-BUTYLTOLUENE VIA A PHOTOLYTICALLY ASSISTED HBR H2O2 SYSTEM/

A process has been developed for the oxidation of 4-t-butyltoluene to 4-t-butylbenzaldehyde via an indirect route involving the formation of either 4-t-butylbenzyl bromide or 4-t-butylbenzal bromide. The organi c bromides were formed using a photolytic HBr/H2O2 route in the absenc e of solvent. The bromination steps were found to be highly efficient in that all the substrate could be converted, consuming all the hydrog en peroxide at this stage of the reaction. Partial hydrolysis (up to 5 0%) of the benzyl bromide to the aldehyde was achieved employing the S ommelet route using hexamethylenetetramine. However, up to 58% aldehyd e yield could be afforded from the benzal bromide using a suitable pha se transfer agent and a small amount of co-solvent. In both cases, the extent of over-oxidation to 4-t-butylbenzoic acid was reduced by care ful control of the bromination step and eliminating dioxygen from the reactor. (C) 1998 SCI.