Synthesis of Chiral Spirolactams via Sequential C−H Olefination/Asymmetric [4+1] Spirocyclization under a Simple Co<sup>II</sup>/Chiral Spiro Phosphoric Acid Binary System
Wen‐Kui Yuan, Bing‐Feng Shi
Abstract
Abstract An unprecedented enantioselective synthesis of spiro‐γ‐lactams via a sequential C−H olefination/asymmetric [4+1] spirocyclization under a simple Co II /chiral spiro phosphoric acid (SPA) binary system is reported. A range of biologically important spiro‐γ‐lactams are obtained with high levels of enantioselectivity (up to 98 % ee ). The concise, asymmetric synthesis of an aldose reductase inhibitor was successfully achieved. Notably, contrast to previous reports that relied on the use of cyclopentadienyl or its derivatives (achiral Cp*, Cp tBu , or chiral Cp x ) ligated Co III complexes requiring tedious steps to prepare, cheap and commercially available cobalt(II) acetate tetrahydrate was used as an efficient precatalyst.