The Stereochemistry of Hydrogenation and Hydrogenolysis. XI. The Stereochemistry of the Reduction of 3-Methyl-4-chromanone

Abstract

Abstract 3-Methyl-4-chromanone (VIII) was reduced with a metal hydride complex, by the Meerwein-Ponndorf method and by catalytic hydrogenation. When VIII was reduced with a metal hydride complex and the Meerwein-Ponndorf method, trans-3-methyl-4-chromanol (IX) was produced as the main product. In the catalytic hydrogenation, VIII gave a cis-3-methyl-4-chromanol (X) as the main product over Raney nickel, but over the palladium catalyst the trnas isomer was larger than the cis isomer. These results indicate that, on Meerwein-Ponndorf and metal hydride reductions, the more stable product was formed as the main product; in the catalytic hydrogenation over the Raney nickel catalyst, VIII seems to be adsorbed mainly on the opposite side of the methyl group of the C-3 position and is hydrogenated to give the cis isomer, whereas, over the palladium catalyst, hydrogenation seems to proceed under the effect of “product development control over the catalyst” and the trans isomer is produced in a high yield.