Solid-Phase Synthesis of Piperidines by N-Acyliminium Ion Chemistry

An efficient solid-phase procedure for the synthesis of a number of 2-substituted piperidines is reported. Starting from solid-supported carbamate-tethered δ-amino acetals, 2-benzotriazolyl-substituted (Bt-substituted) piperidines were obtained by acid-induced ring-closure followed by trapping of the transient N-acyliminium ions with benzotriazole. These 2-Bt-substituted piperidines were then used as precursors for the successful introduction of several C-nucleophiles by N-acyliminium ion chemistry. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)