In the presence of sodium hydroxide, 5-alkylcyclohexanedione-3-carboxylate is prepared by the condensation and cyclization of the corresponding enone with diacetylacetonate. After hydrolysis and decarboxylation, it reacts with propionyl chloride to produce 3-propionyloxy-5-alkylcyclohexenone. The product was dissolved in methylene chloride and isomerized in the presence of aluminum trichloride to give 2-propionyl-3-hydroxy-5-alkylcyclohexanone. Finally, reacted with H2NOCH2CH=CHCl to synthesize clethodim.