Control of diastereoselectivity in the cyclization of dipropenyl ketone to 2,6-dimethyl-1-heterocyclo-hexan-4-one

摘要: 1. The stereodirectivity of the cyclization hepta-2,5-dien-4-one and isomeric dienones to 1-heterocyclohexan-4-ones with amines or H2S is governed by concentration ammonium salt in mixture. 2. Increasing RNH3+X− results preferential formation meso-form product. In “weakly acidic” media, racemic form (R,R S,S) predominates. 3. A convenient method for preparation 2,6-dimethylthiopyran-4-one from appropriate Na2S described.