Mechanism of the solvolysis of allylic diphenyl phosphates in phenol

Abstract

The alkylation of phenol by solvolysis of allylic diphenyl phosphates in phenol is shown to be a carbonium ion process, and to be autocatalysed by diphenyl hydrogen phosphate. The products obtained in these solvolyses have been compared with those obtained from the alkylation of phenol by diphenyl hydrogen phosphate and olefins, under comparable conditions. These studies have shown that alkylation on carbon is favoured with more stable carbonium ions, such as tertiary or 3,3-dimethylallyl, while alkylation on oxygen is favoured with secondary carbonium ions. The acid-catalysed rearrangement, to 2-methylcoumaran, of the initial alkylated products of the solvolysis of allyl diphenyl phosphate has been shown to be largely intramolecular.