An Iterative Catalytic Route to Enantiopure Deoxypropionate Subunits: Asymmetric Conjugate Addition of Grignard Reagents to α,β-Unsaturated Thioesters.

This article presents information related to an iterative catalytic route to enantiopure deoxypropionate subunits. The occurrence of polydeoxypropionate chains in numerous biologically relevant compounds has stimulated the development of methods for their stereocontrolled synthesis. The poor results obtained in the 1,4 additions of the less reactive MeMgBr impeded the development of catalytic iterative methodology for 1,3-dimethyl arrays. The additions of MeMgBr proceed with equally high selectivity when the catalyst loading is reduced to only 1 mol %, providing the methylated 1,4-addition products with 92- 96% ee and isolated yields of 88-94%.