ELECTROSYNTHESIS OF 5-CHLORO AND 5-AZIDO-4-PYRAZOLE CARBOXYLIC-ACID AT THE NICKEL-HYDROXIDE ELECTRODE

Pyrazole derivatives are valuable intermediates for drugs and agrochem icals.1-5) The literature seems to be almost devoid of suitable method s, form environmental point of view for the preparation of simple pyra zole carboxylic acid derivatives which could be prepared from aldehyde s with oxidizing agents such as NaClO4.6) These reagents are partially toxic and large scale conversions create waste disposal problems. A c lean oxidation technique Would be the indirect electrochemical oxidati on at the nickel hydroxide anode. Until recently there have been few e xamples of oxidation of heterocyclic aldehydes to the corresponding ac ids.7) We represent here an electrochemical method for oxidizing 5-chl oro-4-pyrazole carbaldehyde (1) and 5-azido-4-pyrazole carbaldehyde (2 ) to their corresponding acids (3 and 4) at a nickel hydroxide anode i n good yields (80-85%) (Scheme 1).