C2轴对称樟脑磺酰胺基醇配体催化环己烯乙炔对酮的不对称加成反应

应用C2轴对称的樟脑磺酰胺基醇配体和Cu(OTf)2催化带官能团的环己烯乙炔对酮的不对称加成反应. 芳香酮、脂肪酮和杂环酮都适用于此体系, 并且在室温下最高e.e.值约为89%, 其中脂肪酮首次被应用于此反应, 极大地扩展了底物的范围. 研究结果表明, 脂肪酮的立体位阻对反应的对映选择性起着至关重要的作用.

Asymmetric Addition of 1-Ethynylcyclohexene to Ketones Catalyzed by a Chiral C2-Camphorsulfonamide Ligand

Addition of terminal alkynes to carbonyls is considered as an effective route for the synthesis of chiral propargyl alcohols and has gained a considerable significance in recent years.For possible further transformations of the alkene group,such as epoxidation,hydroxylation,ozonolysis,addition of carbenes,the asymmetric addition of 1-ethynylcyclohexene to ketones should have more potential applications than phenyla-cetylene for the synthesis of complex bioactive natural products.In this paper,the development of good enan-tioselective catalysts involving Cu(OTf)2 and chiral C2-camphorsulfonamide for the alkynylation of ketones including aromatic,heteroaromatic and aliphatic ketones was described.The reaction proceeded under mild conditions(toluene,room temperature) with the available catalyst.The reactions of aliphatic ketones could be completed in less than 12 h to give the products in good yields and enantioselectivities.The best enantioselectivity(up to 89% e.e.) was obtained in the alkynylation of 3-methylbutan-2-one.Moreover,the hindrance of the aliphatic ketones played a critical role in the control of the enantioselectivities of the corresponding pro-ducts.