A catalytic, enantioselective, Lewis base-catalyzed α-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 Brønsted acid activation, namely N-phenylthiosaccharin, was developed. Three classes of Lewis bases-tertiary amines, sulfides, and selenophosphoramides-were identified as active catalysts for the α-sulfenylation reaction. Among a wide variety of chiral Lewis bases in all three classes, only chiral selenophosphoramides afforded α-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.

Catalytic, Enantioselective Sulfenylation of Ketone-Derived Enoxysilanes / S..E. Denmark, S. Rossi, M..P. Webster, H. Wang. - In: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. - ISSN 0002-7863. - 136:37(2014 Sep 17), pp. 13016-13028. [10.1021/ja506133z]

Catalytic, Enantioselective Sulfenylation of Ketone-Derived Enoxysilanes

S. Rossi;
2014

Abstract

A catalytic, enantioselective, Lewis base-catalyzed α-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 Brønsted acid activation, namely N-phenylthiosaccharin, was developed. Three classes of Lewis bases-tertiary amines, sulfides, and selenophosphoramides-were identified as active catalysts for the α-sulfenylation reaction. Among a wide variety of chiral Lewis bases in all three classes, only chiral selenophosphoramides afforded α-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.
Catalysis; Ethers; Ketones; Lewis Bases; Silanes; Stereoisomerism; Sulfamerazine; Catalysis; Chemistry (all); Biochemistry; Colloid and Surface Chemistry
Settore CHIM/06 - Chimica Organica
17-set-2014
Article (author)
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/532839
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