Synthesis, structure, and tautomerism of 3a,7-dimethyl-4,6-diphenyl-2-ethynyl-7a-hydroxyperhydropyrrolo[3,2-c]pyridine

Isomeric [with respect to the fusion of the piperidine and pyrrolidine rings, as well as with respect to the mutual orientation of the substituents attached to the C(2) and C(3a) carbon atoms] 3a, 7-dimethyl-4,6-diphenyl2-ethynyl-7a-hydroxyperhydropyrrolo[3,2-c]pyridines were isolated for the first time in the reaction of 3,5-dimethyl-2,6-diphenyl-4-piperidinone oxime with acetylene under the conditions of the Trofimov reaction under pressure. It was established that, in solutions, the isomers of this compound with an axial-equatorial fusion of the rings exist in the form of ring-chain tautomers. © 1993 Plenum Publishing Corporation.