The treatment of methyl-substituted 1-chloro-2-oxo-1-cyclohexanecarboxylic esters (7a–e) with anhydrous Na 2 CO 3 in refluxing xylene gave the corresponding methyl-substituted 1- cyclopentene-1-carboxylic esters (1a–e). Several intermediates important in the synthesis of natural products, such as 4, 4-dimethyl-1-cyclopentene-1-carbaldehyde (9), 5-methyl-1- cyclopentene-1-carbaldehyde (12), α-(3-methyl-1-cyclopentenyl) propionic acid (16), and ...