Long-chain phenols. Part 16. A novel synthesis of homologous orsellinic acids and their methyl ethers

Abstract

By the novel reaction of 3,5-dimethoxyfluorobenzene with n-alkyl-lithium compounds, followed by carbonation, homologous orsellinic acid dimethyl ethers (6-alkyl-2,4-dimethoxybenzoic acids) have been obtained. The reactions proceeded best with the homologues of methyl-lithium. These reactions are considered to occur by way of 3,5-dimethoxybenzyne. 2,4-Dimethoxyfluorobenzene did not form an aryne but gave 3-fluoro-2,6-dimethoxybenzoic acid instead. Decomposition with water of alkyl-lithium reaction mixtures from 3,5-dimethoxyfluorobenzene yielded 5-n-alkylresorcinol dimethyl ethers. Demethylation of 6-alkyl-2,4-dimethoxybenzoic acids with boron trichloride proceeded partially and selectively to give the 6-alkyl-2-hydroxy-4-methoxybenzoic acids, and completely with aluminium chloride to give the homologous orsellinic acids. Boron tribromide was less effective, but readily gave the 5-alkyl resorcinols from the corresponding dimethyl ethers.