| Autor: |
Linghu X; Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290, USA., Bausch CC, Johnson JS |
| Jazyk: |
angličtina |
| Zdroj: |
Journal of the American Chemical Society [J Am Chem Soc] 2005 Feb 16; Vol. 127 (6), pp. 1833-40. |
| DOI: |
10.1021/ja044086y |
| Abstrakt: |
In this work, cross silyl benzoin addition reactions between acylsilanes (1) and aldehydes (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-generation 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. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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