Kauffmann olefination

Under a Kauffmann olefination refers developed by Thomas Kauffmann reaction for converting a ketone or an aldehyde into a methylene group. The reaction is related to the Tebbe reaction, the Wittig reaction or the Lombardo reagent.

Preparation of the reagent

The reagent for the Kauffmann olefination is prepared in situ from various molybdenum or tungsten chlorides by reaction with methyllithium at low temperature ( -78 ° C).

The olefination reagent is formed when warming up of the reaction mixture. It was shown by NMR studies have shown that it is the reactive species is not a Schrock carbene ( such as the Tebbe reagent) is.

Mechanism

Mechanistic studies have shown that it is in the olefination process a sequence of cycloaddition and Cycloeleminierungsschritten.

Area of ​​application

The Kauffmann olefination has found a long time virtually no attention in the literature. However, recently, it has been found to be very mild and non-basic olefination an application in natural product synthesis. In this work, a combination of the Olefinierungsschritt and an olefin metathesis has been developed. It is noteworthy that the inorganic reaction products of the Kauffmann olefination not decompose the metathesis catalyst.