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Catalytic Asymmetric Intra- and Intermolecular Haloetherification of Enones: An Efficient Approach to (−)-Centrolobine

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posted on 12.10.2016, 00:00 by Pengfei Zhou, Yunfei Cai, Xia Zhong, Weiwei Luo, Tengfei Kang, Jun Li, Xiaohua Liu, Lili Lin, Xiaoming Feng
A catalytic asymmetric intra- and intermolecular haloetherification of electron-deficient alkenes (halogen = Cl, Br, I) has been realized by the use of chiral metal complexes of N,N′-dioxides. In the presence of a chiral Fe­(III) complex, a series of tetrahydropyran derivatives were obtained in good yields (up to 99% yield) with a high level of enantioselectivities (up to 97% ee). Promoted by a chiral Ce­(III) complex, chiral oxepane derivatives could be given in good results. Moreover, the intermolecular haloetherification of chalcones catalyzed by Sc­(III) complex using MeOH as nucleophile is demonstrated. This methodology also can be successfully applied to the synthesis of (−)-Centrolobine. Meanwhile, a reasonable reaction mechanism was proposed.