Synthesis of Dihydrojasmone and cis-Jasmone

Abstract

2-Ethoxycarbonyl-4-methoxycarbonyl-3-methyl-2-cyclopentenone (1), prepared readily from methyl acetoacetate, may be utilized for facile preparations of dihydro- and cis-jasmone. Compound 1 reacted with pentyl iodide and 1-bromo-2-pentyne in the presence of sodium hydride to give 2-ethoxycarbonyl-4-methoxycarbonyl-3-methyl-2-pentyl-3-cyclopentenone (2) and 2-ethoxycarbonyl-4-methoxycarbonyl-3-methyl-2-(2-pentynyl)-3-cyclopentenone (3), respectively. Decarbalkoxylations of compounds 2 and 3 afforded dihydrojasmone (4) and dehydrojasmone (5), respectively. Catalytic hydrogenation of dehydrojasmone (5) over a Pd-CaCO₃ catalyst gave cis-jasmone (6).