Mechanism and scope of the cyanide-catalyzed cross silyl benzoin reaction
Mechanism and scope of the cyanide-catalyzed cross silyl benzoin reaction
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DOI：
10.1021/ja044086y
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发表时间：
2005-02-16
影响因子：
15
通讯作者：
Johnson, JS
中科院分区：
文献类型：
--
作者：
Xin, LH;Bausch, CC;Johnson, JS
In this work, cross silyl benzoin addition reactions between acylsilanes (1) and alclehydes (2) catalyzed by metal cyanides are described. Unsymmetrical aryl-, heteroaryl-, and alkyl-substituted benzoin adducts can be generated in moderate to excellent yields with complete regiocontrol using potassium cyanide and a phase transfer catalyst. From a screen of transition metal cyanide complexes, lanthanum tricyanide was identified as an improved second-gene ration catalyst for the cross silyl benzoin reaction. A study of the influence of water on the KCN-catalyzed cross silyl benzoin addition revealed more practical reaction conditions using unpurified solvent under ambient conditions. A sequential silyl benzoin addition/cyanation/ O-acylation reaction that resulted in two new C-C bonds was achieved in excellent yield. The mechanism of cross silyl benzoin addition is proposed in detail and is supported by crossover studies and a number of unambiguous experiments designed to ascertain the reversibility of key steps. No productive chemistry arises from cyanation of the more electrophilic aldehyde component. Formation of the carbon-carbon bond is shown to be the last irreversible step in the reaction.
