Reaction of benzylideneacetone with hydrogen sulphide and ammonia; heterocyclic analogues of bicyclo[3,3,1]nonane

Abstract

The title reaction has been reinvestigated. The basic products of the reaction are shown to be two stereoisomers of 1,5-dimethyl-3,7-diphenyl-9-aza-2,6-dithiabicyclo[3,3,1]nonane, (IX) and (X), rather than bis-(α-mercapto-α-methylcinnamyl)amine (II), and their conformations are discussed. Oxidation of these compounds gives bis-(2-acetyl-1-phenylethyl) disulphide (XIII). The neutral product of the reaction is now shown to be 5-acetyl-2,6-diphenyl-4-hydroxy-4-methyltetrahydrothiopyran (XVII); R¹= Me, R²= OH). The stereochemistry of this compound is defined, and its 4-epimer is synthesised. As an intermediate, bis-(2-acetyl-1-phenylethyl)sulphide(XVIII) was prepared. Dibenzylideneacetone, when treated with hydrogen sulphide and ammonia, is shown to give a dispirotrithiolan (XX), via tetrahydro-1-thiopyrone (XIX) intermediates.