N-Acyliminium ions having a piperidine skeleton were attractive because the functionalized piperidines frequently show interesting biologically properties. The “indirect cation pool method” ¹⁾ is useful to prepare a solution of synthetically valuable N-acyliminium ions having a protecting group that is labile under acidic conditions, because organic cations can be generated and accumulated under neutral conditions. In this presentation we demonstrated utilities of highly enantiomerically enriched chiral N-Acyliminium ions bearing a piperidine skeleton, which are generated by the indirect cation pool method.

Almost enantiomerically pure chiral precursor 2 was prepared by using the enantioselective lithiation strategy using chiral diamine 1 (Scheme 1).²⁾ N-Acyliminium ion pool 3 was then irreversibly generated from 2 by the treatment of ArS(ArSSAr)⁺, which was generated by low temperature electrolysis (Scheme 2). The reaction of 3 with allylstannane gave trans isomer in high diastereomer and enantiomer ratios. In contrast, the coupling between 3 and allylmagnesium bromide afforded cis isomer in high stereoselectivity. As a result, we could selectively synthesized two

1) Suga, S.; Matsumoto, K.; Ueoka, K.; Yoshida, J. J. Am. Chem. Soc. 2006, 128, 7710-7711. Matsumoto, K.; Suga, S.; Yoshida, J. Org. Biomol. Chem. 2011, 9, 2586-2596.

2) Coldham, I.; O’Brien, P.; Patel, J. J.; Raimbault, S.; Sanderson, A. J.; Stead, D.; Whittaker, D. T. E. Tetrahedron: Asymmetry 2007, 18, 2113–2119.