1,3-Benzothiazole-2-carbohydrazide → 3-Benzothiazol-2-yl-5,6-dihydro-8H-[1,2,4]triazolo[4,3-a]pyrazine-7-carboxylic acid benzyl ester

Participants

Reaction Steps

A mixture of 5-ethoxy-3,6-dihydro-2H-pyrazine-1-carboxylic acid benzyl ester (prepared according to the method of Example 259, Step A, 490 mg, 1.87 mmol) and benzothiazole-2-carboxylic acid hydrazide (360 mg, 1.87 mmol; J. Org. Chem. 1958, 23, 1344) in n-butanol (2 mL) was stirred at reflux overnight, cooled to room temperature, concentrated, and purified by flash column chromatography (1% methanol/chloroform) to give 580 mg of the title compound of Example 259, Step B (contaminated with an equimolar amount of benzothiazole-2-carboxylic acid hydrazide which was removed in the subsequent step) as a yellow solid.

Provenance & Evidence