Highly stereoselective H-D exchange of diastereotopic protons in 4′,1″-dimethyl-1,2,3,4-dibenzylcyclohepta-1,3-diene-6-one

The rates of base-catalyzed H-D exchange of the diastereotopic methylene protons adjacent to the carbonyl group in the title compound have been measured in methanol-O-d. Sodium methoxide as catalyst produced a rate ratio of 73:1. Reasons for the large increase in stereoselectivity over that encountered in the exchange of 4-tert-butylcyclohexanone are proposed.