Preparations of 4‐Substituted 3‐Carboxypyrazoles

The scopes of three synthetic methods reported for the preparation of an array of 3‐pyrazolecarboxylates featuring substituents on position 4 were investigated. The first one is based on the potassium permanganate oxidation of methylpyrazoles. The second starts with the condensation between DMF dimethylacetal and ethyl pyruvate and is followed by the addition of hydrazine hydrochloride. The last one makes use of the cycloaddition of diazomethane on acrylate esters followed by a bromine‐based oxidative rearrangement into 4‐substituted 3‐pyrazole esters.