Verfahren zur Herstellung von Pyrazinderivaten

摘要

The invention comprises: (1) compounds of the general formula wherein X represents Br, OCH3 or OC2H5 and Y represents H or Br, but X is not Br when Y is H; (2) the preparation of the compounds in which Y = Br by treating 2-aminopyrazine with bromine in the presence of sodium acetate and acetic acid, and, if desired, treating the resulting 2-amino-3,5-dibromopyrazine (X = Y = Br) with an alkali metal methoxide or ethoxide; (3) the preparation of 2-amino-3-methoxypyrazine (X = OCH3, Y = H) by the following processes: (a) catalytic hydrogenation of 2-amino- 3-methoxy- 5-bromopyrazine (X = OCH3, Y = Br); (b) reaction of 2-amino-3-chloropyrazine with an alkali metal methoxide; or (c) treating 2-carbamido-3-methoxypyrazine with an alkali metal hypobromite; (4) the combination of (3)(c) with the preparation of the starting material by the action of hydrogen peroxide on 2-cyano-3-methoxypyrazine in the presence of alkali; (5) the combination of (4) with the preparation of the starting material by the action of an alkali metal methoxide on a 2-cyano3-halopyrazine; (6) the combination of (5) with the preparation of the starting material by the action of a phosphorus oxyhalide on 2-carbamido-3-hydroxypyrazine. According to the first Provisional Specification, X may represent any alkoxy group, and the sodium acetate in the bromination step may be replaced by other alkali or alkaline-earth metal salts of weak acids, e.g. sodium formate or calcium acetate.