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

A simple and inexpensive synthetic route which affords S-(-)-4-hydroxy cyclohex-2-en-1-one (1a) with high stereoselectivity and moderate enan tioselectivity is reported. A key step in this procedure involves bake r'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 opticall y 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. Th e absolute configuration of the 3,5-dinitrobenzoate ester of 4a (i. e. , 5a) was established unequivocally via single crystal X-ray structura l analysis.