An Efficient Preparation of 2-Methyl-1-Cyclopentene-1-Carboxylic Acid, a Versatile Synthetic Building Block

A practical three-step procedure for the preparation of 2-methyl-1-cyclopentene-1-carboxylic acid is detailed. This process relies on the reaction of commercially available 2-carboethoxycyclopentanone with nitromethane in the presence of equimolecular amounts of piperidine, followed by denitration of the derived allylic nitro compound by treatment with 5% Pd/C in the presence of ammonium formate and final hydrolysis of the ester moiety. Keywords: Dieckmann's ester, carboxylic acids, allylic nitro compounds, Pd-catalyzed denitration