Synthesis of 3-aminopyrrolidines and piperidines from endocyclic enamine derivatives

Reactions of endocyclic enecarbamates to form functionalized 3-aminopyrrolidines and piperidines are described. Iodoamination of N-acyl-2-pyrrolines followed by aziridination in methanol is an effective route to N-acyl-3-amino-2-methoxypyrrolidines. Azidomethoxylation of endocyclic carbamates by ceric ammonium nitrate (CAN) in the presence of NaN3 and methanol gives 3-azido-2-methoxypiperidines and pyrrolidines. Formation and trapping of the N-acyliminium ions derived from these substrates under Lewis acidic conditions was also explored for the stereoselective preparation of 2-alkyl pyrrolidine and piperidine derivatives.