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Iridium-Catalyzed Asymmetric Hydrogenation of β,γ-Unsaturated γ‑Lactams: Scope and Mechanistic Studies

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posted on 2017-02-17, 19:21 authored by Qianjia Yuan, Delong Liu, Wanbin Zhang
An efficient asymmetric hydrogenation of β,γ-unsaturated γ-lactams using an iridium–phosphoramidite complex is reported. The chiral γ-lactams were obtained in excellent yields and enantioselectivities (up to 99% yield and 99% ee). The mechanistic studies indicated that the reduced products were obtained via the hydrogenation of the N-acyliminium cations, generated from β,γ-unsaturated γ-lactams, which was verified by 1H NMR analysis. The reaction was carried out at a reduced catalyst loading of 0.1 mol %, and the reduced products can be transformed to two potential bioactive compounds. A new route is provided for the synthesis of chiral γ-lactams.