Process for the preparation of N-[2-[4-(aminosulfonyl) phenyl]ethyl]5-methylpyrazinecarboxamide

A process for the preparation of N-[2-[4-(aminosulfonyl)phenyl]ethyl]-5-methylpyrazine-carboxamide of the formula I:

• ##STR21## consisting of:
• i) treating 5-methylpyrazine-2-carboxylic acid of the formula VIII:
• ##STR22## with methanol under reflux to obtain 5-methylpyrazine-2-carboxylic acid methyl ester of the formula VIII A:
• ##STR23## ii) reacting 5-methylpyrazine-2-carboxylic acid methyl ester of the formula VIII A with 2-phenylethylamine of the formula II:
• ##STR24## at 100.degree. to 200.degree. C. to obtain 5-methylpyrazine 2-(2-phenylethyl) carboxamide of the formula IX:
• ##STR25## iii) chlorosulfonating the 5-methylpyrazine-2-(2-phenylethyl)carboxamide of the formula IX with chlorosulfonic acid at 0.degree.-45.degree. C. to obtain [N-[2-[4-(chlorosulfonyl)phenyl]ethyl]-5-methylpyrazine carboxamide] of the formula X:
• ##STR26## iv) and treating the [N-[2-[4-(chlorosulfonyl)phenyl]ethyl]-5-methyl purazinecarboxamide] of the formula X with ammonia to obtain N-[2-[4-(aminosulfonyl)phenyl]ethyl]-5-methylpyrazine carboxamide of the formula I.