Catalytic, Enantioselective Sulfenylation of Ketone-Derived Enoxysilanes
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- 作者：Scott E. Denmark ; Sergio Rossi ; Matthew P. Webster ; Hao Wang
- 刊名：Journal of the American Chemical Society
- 出版年：2014
- 出版时间：September 17, 2014
- 年：2014
- 卷：136
- 期：37
- 页码：13016-13028
- 全文大小：824K
- ISSN：1520-5126
文摘
A catalytic, enantioselective, Lewis base-catalyzed 伪-sulfenylation of silyl enol ethers has been developed. To avoid acidic hydrolysis of the silyl enol ether substrates, a sulfenylating agent that did not require additional Br酶nsted acid activation, namely N-phenylthiosaccharin, was developed. Three classes of Lewis bases鈥攖ertiary amines, sulfides, and selenophosphoramides鈥攚ere identified as active catalysts for the 伪-sulfenylation reaction. Among a wide variety of chiral Lewis bases in all three classes, only chiral selenophosphoramides afforded 伪-phenylthio ketones in generally high yield and with good enantioselectivity. The selectivity of the reaction does not depend on the size of the silyl group but is highly sensitive to the double bond geometry and the bulk of the substituents on the double bond. The most selective substrates are those containing a geminal bulky substituent on the enoxysilane. Computational analysis revealed that the enantioselectivity arises from an intriguing interplay among sterically guided approach, distortion energy, and orbital interactions.