Improved process for preparing benzenesulfonate salts

Claim 1

A process for preparing benzenesulfonate salts of the formula (I) RCO₂PhSO₃M      (I) where: R is C₁-C₂₀ linear alkyl; C₁-C₁₅ alkyl substituted by N(R₁)COR₂, CONR₁R₂, CO₂R₃, OR₃ or SO₂R₃; OR₃; CH=CHCO₂R₃; phenyl substituted by CO₂R₃; CH(OR₃)₂; CH(SO₂R₃)₂; C(R₄)(R₅)Cl; C(R₇)₂OC(O)R₆; or CH₂OR₈; R₁ is H or C₁-C₁₀ alkyl, aryl or alkaryl; R₂ is C₁-C₁₄ alkyl, aryl or alkaryl; R₃ is C₁-C₂₀ alkyl, alkenyl, alkynyl or alkaryl, optionally alkoxylated with one or more ethyleneoxy or propyleneoxy groups or mixtures thereof; R₄ is C₄-C₁₄ alkyl or alkenyl; R₅ is H, methyl or ethyl; R₆ is C₁-C₂₀ linear or branched alkyl, alkylethoxyalkylated, cycloalkyl, aryl or substituted aryl; R₇ are independently H, C₁-C₂₀ alkyl, aryl, C₁-C₂₀ alkylaryl and substituted aryl; R₈ is aryl optionally substituted by C₁-C₅ alkyl; and M is selected from an alkali metal or an alkaline earth metal by reacting an acid chloride or chloroformate of the formula (II) RCOCl      (II) with a phenol sulfonic acid of the formula (III) HOPhSO₃M      (III) in an inert aprotic solvent having a boiling point above 100°C, the improvement comprising reacting said acid chloride with said phenol sulfonic acid in the presence of from 0.1 to 10 mole percent of a phase transfer catalyst selected from quaternary ammonium and quaternary phosphonium salts based on the amount of phenol sulfonic acid present in the reaction.