Reactions of lead(IV). Part XXIII. Reactions of lead tetrabenzoate with some benzenoid compounds, and comparison with those of dibenzoyl peroxide

Abstract

Lead tetrabenzoate effects, principally, the phenylation and benzoyloxylation of anisole by radical-chain processes which can give nearly quantitative yields; in contrast, benzene and nitrobenzene undergo only phenylation. It is argued that the anisole radical cation mediates in benzoyloxylation, and other characteristics of the chain reactions are discussed. Differences between lead tetrabenzoate and dibenzoyl peroxide as oxidants for benzenoid compounds have been explored; the chief differences are the much smaller capacity of the latter to oxidise by one-electron acceptance, and the fact that benzoyloxylation of anisole by the peroxide does not occur via formation of the anisole radical cation. Nonetheless, there is evidence that this radical cation can be formed from the adducts of the benzoyloxy-radical with anisole, and that this is an acid-catalysed reaction which competes with oxidation of the adducts to the benzoyloxyanisoles.