Asymmetric Michael addition of malonates to unsaturated ketones catalyzed by rare earth metal complexes bearing phenoxy functionalized chiral diphenylprolinolate ligands

• Published in: Tetrahedron: asymmetry 2016-10, Vol.27 (19), p.911-917
• Main Authors: Qian, Qinqin, Zhu, Wenguo, Lu, Chengrong, Zhao, Bei, Yao, Yingming
• Format: Article
• Language: English
• ISSN: 0957-4166; 1362-511X
• DOI: 10.1016/j.tetasy.2016.07.014

A simple, efficient catalytic asymmetric Michael addition of malonates to unsaturated ketones has been successfully developed. This process was promoted by rare earth metal complexes 1–4, which is bearing chiral phenoxy functionalized prolinol ligand at room temperature. The Sc complex 3 performed the best and the products reached up to 99% yield and 90% ee. [Display omitted] A simple, efficient catalytic asymmetric Michael addition of malonates to unsaturated ketones has been successfully developed. This process was promoted by rare earth metal complexes 1–4 bearing a chiral phenoxy functionalized prolinol ligand at room temperature [L1RE(L1H) (H2L1=(S)-2,4-di-tert-butyl-6-((2-(hydroxydiphenylmethyl)pyrrolidin-1-yl)methyl)phenol, RE=Yb 1, Y 2, Sc 3 and L2Sc(L2H) 4 (H2L2=(S)-2,4-di-dimethylbenzyl-6-((2-(hydroxydiphenylmethyl)-pyrrolidin-1-yl)methyl)phenol)]. Complex 3 was the best catalyst in the transformation and the products were obtained in up to 99% yield and with 90% ee. In addition, the molecular structures of the catalysts were well characterized, including X-ray determination of complex 3.