The Preparation of 1H-Pyrazole-1-carboxylic Acid, 1, 1-Dimethylethyl Esters from Dilithiated C(α), N-Hydrazones of Hydrazinecarboxylic Acid, 1, 1-Dimethylethyl Ester

Abstract

C(α), N-Hydrazones of hydrazinecarboxylic acid, 1, 1-dimethylethyl ester [C(α), N-carbo-t-butoxyhydrazones] were metalated with excess lithium diisopropylamide, and the dianion-type intermediates were condensed with select aromatic esters followed by acid cyclization to substituted 1H-pyrazole-1-carboxylic acid, 1, 1-dimethylethyl esters (N-carbo-t-butoxypyrazoles).