IMPROVED SYNTHESIS OF RACEMIC AND OPTICALLY-ACTIVE 4-HYDROXYCYCLOHEX-2-EN-1-ONE

A simple and inexpensive synthetic route which affords S-(-)-4-hydroxycyclohex-2-en-1-one (1a) with high stereoselectivity and moderate enantioselectivity is reported. A key step in this procedure involves baker's yeast promoted reduction of 1 alpha,4 alpha,4a alpha,6,7,8a alpha-hexahydro-1,4-methanonaphthalene-5,8-dione (3), which affords optically active 8-hydroxy-1 alpha,4 alpha,4a alpha,8 beta,8a alpha-tetrahydro-1,4-methanonaphthalen-5(1H)-one (4a, 80% de, 67% ee) in 32% yield. The absolute configuration of the 3,5-dinitrobenzoate ester of 4a (i. e., 5a) was established unequivocally via single crystal X-ray structural analysis.