5-Methyl-2-pyrazinecarboxylic acid → 2-Pyrazinecarboxylic acid, 5-methyl-, methyl ester

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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° to 200° 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°-45° 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.

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