Regio- and stereo-controlled copper organometallic addition to a piperidinyl aziridine: synthesis of trans 3-amino-4-alkyl-piperidines

3,4-Piperidinyl aziridine N-phosphonate underwent ring opening in Grignard addition catalyzed by a copper reagent to yield trans 3-amino-4-alkyl-piperidines. The nucleophilic addition occurred trans to the aziridine group and regioselectively at C-4 position of the piperidine ring. The high regioselectivity was rationalized by steric argument based on conformational analysis.