Mukaiyama-Michael reaction
The Mukaiyama-Michael reaction , also called Mukaiyama-Michael addition , is a name reaction in organic chemistry and was first published in 1974 by the Japanese chemist Teruaki Mukaiyama . Enol silanes are added to α, β-unsaturated carbonyl compounds.
The reaction is closely related to the Mukaiyama aldol reaction and the Michael addition .
Overview reaction
The Mukaiyama-Michael reaction can be carried out with a large number of different enol silanes and α, β-unsaturated carbonyl compounds. A Lewis acid is used as the catalyst.
In addition to the variant shown with methyl groups, any other alkyl and aryl radicals can be used. Studies have shown that instead of silylated enols, silyl acetals can also be used.
mechanism
Mechanistically speaking, the Mukaiyama-Michael reaction is the counterpart of the base-catalyzed Michael addition. A possible mechanism could look like this:
In this mechanism, the complex formation around the Lewis acid used, in this case TiCl 4, plays an important role. In the actual reaction step, the double formation of the carbonyl compound 1 attacks the silicon atom of the trimethylsilyl group. The keto form of the enol silane used is then formed. This keto form forms a new carbon-carbon bond. The process described takes place in concert. After the catalyst has been split off, a mixture of the syn and anti diastereomers of intermediate 2 is formed . After work-up, i.e. hydrolysis, the product 3 is obtained , also as a mixture of syn and anti diastereomers.
application
Due to the good regio- and stereoselectivity of the Mukaiyama-Michael reaction, it has numerous applications in modern synthetic chemistry. It is used, for example, for the synthesis of γ-butenolides.
Individual evidence
- ↑ a b Koichi Narasaka, Kenso Soai, Teruaki Mukaiyama: The new michael reaction . In: Chemistry Letters . tape 3 , no. 10 , October 5, 1974, p. 1223-1224 , doi : 10.1246 / cl.1974.1223 .
- ↑ a b c d Zerong Wang: Comprehensive Organic Name Reactions and Reagents . 3 volumes. John Wiley & Sons, New Jersey 2009, ISBN 978-0-471-70450-8 , pp. 1996–1999 , doi : 10.1002 / anie.201000292 .
- ↑ Sean P. Brown, Nicole C. Goodwin, David WC MacMillan: The First Enantioselective Organocatalytic Mukaiyama - Michael Reaction. A Direct Method for the Synthesis of Enriched γ-Butenolide Architecture . In: Journal of the American Chemical Society . tape 125 , no. 5 , February 1, 2003, p. 1192-1194 , doi : 10.1021 / ja029095q , PMID 12553821 .