Rearrangement of five-membered heterocyclic enamines

Abstract

Addition of bromine to 1-methyl-2-benzilidenepyrrolidine (Ia) and subsequent treatment with sodium hydroxide afforded unstable 1-methyl-2-phenyl-3-piperidone (IVa) which was reduced with lithium aluminium hydride to an isolable mixture of diastereoisomeric 1-methyl-2-phenyl-3-piperidinols (Va). Analogous reaction with 1-methyl-2-ethylidenepyrrolidine (Ib) led to mixture of products containing, in addition to diastereoisomeric 1,2-dimethyl-3-piperidinols (Vb), also the substitution products 1-methyl-2-(1-hydroxyethyl)pyrrolidines VI and 1-methyl-2-ethyl-3-pyrrolidinols VII (as detected by mass spectrometry).