Catalytic Enantioselective Hosomi-Sakurai Conjugate Allylation of Cyclic Unsaturated Ketoesters

摘要

Despite impressive advances over the years,there are still important transformations that lack catalytic asymmetric variants.While Lewis acid catalyzed additions of allylsilanes to carbonyl compounds and acetals have been well studied using catalytic,as well as auxiliary-based methods to control absolute configuration,to the best of our knowledge,there are no effective methods for catalyzing the asymmetric 1,4-addition of allyltrimethylsilane to unsaturated carbonyl compounds.In that regard,we report herein a catalytic enantioselective conjugate addition of allyltrimethylsilane to various activated cyclic enones with selectivities surpassing 98% ee.The 1,4-addition of the air-and moisture-stable nucleophile to unsaturated carbonyl compounds proceeds to>95% conversion in the presence of Cu(OTf)2(10 mol%)with the commercially available di(tert-butyl)bis(oxazoline)(box)ligand(2).We show how these products can be functionalized to a variety of useful enantiomerically enriched systems.