A process for forming 4-ketocyclopentene and substituted 4-ketocyclopentene compounds starting from the corresponding 1-carbohydroxarbyloxy-2-keto-4-hydroxy-5-cyclopentene by reduction followed by decarboxylation. The ketone may thereafter be converted to a cyclopentadiene compound by reducing the ketone to form an alcohol, replacing the hydroxyl functionality of the alcohol under substitution conditions with a leaving group, and deprotonating the resulting product under base induced elimination conditions to form the cyclopentadiene compound. Alternatively functionalized cyclopentadienyl compounds can be produced without isolation of an unsubstituted cyclopentadienyl compound by combining the elimination and deprotonation steps with a replacement step in a single unit operation.