Patent ID: 6548702
Filing Date: 2003-04-15
Classification: C07C

Abstract:
A process for the preparation of 2-methoxy-4-(N-t-butylaminocarbonyl)benzenesulfonyl chloride by sulfonating m-hydroxybenzoic acid, methylating the hydroxy group of the resulting sulfonic acid or its salt, transforming the carboxylic acid group and the sulfonic acid group to acid chloride groups and reacting the 4-chlorosulfonyl-3-methoxy-benzoyl chloride with t-butylamine, which comprises carrying out the sulfonation of the 3-hydroxy-benzoic acid of the formula II with 96% sulfuric acid, separating the resulting 3-hydroxy-4-sulfobenzoic acid of the formula III in the form of its salt of the general formula IV, wherein Z stands for alkali metal or ammonium group-, methylating the compound of the general formula IV in the presence of a phase transfer catalyst at a pH value of about 11.5, transforming the 3-methoxy-4-sulfobenzoic acid mono salt of the general formula V wherein the meaning of Z is as defined aboveâ€”to the acid chloride of the formula VI, and reacting the compound of the formula VI with t-butylamine used in equimolar amount or in a small excess, in the presence of an acid binding agent, in aprotic solvent, at low temperature.