| abstract |
The invention relates to 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-methoxy-benzoic acid of general formula (II) with 96% sulfuric acid, separating the resulting 3-hydroxy-4-sulfobenzoic acid of general formula (III) in the form of its salt of general formula (IV), wherein Z stands for alkali metal or ammonium group, methylating the compound of 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 general formula (V), wherein the meaning of Z is as defined above, to the acid chloride of general formula (VI), and reacting the compound of general 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. |