Saucy-Marbet Claisen rearrangement

A catalytic asymmetric Saucy-Marbet Claisen rearrangement of propargyl ethers to -substituted allenyl carbonyls has been reported (Scheme 4). ... 

Since its discovery in 1912, the Claisen rearrangement of allyl vinyl ethers (1 - 2 equation 1) has become one of the most powerful tools for stereoselective carbon-carbon bond formation. Much of its current popularity is due to the subsequent development of a series of new variants of this 3,3-sigma-tropic rearrangement. In 1940, Carroll reported the base-catalyzed rearrangement of -keto esters and allylic alcohols to alkenic ketones (3 4 5 equation 2). Twenty years later. Saucy and Marbet dem-... 

The allyl vinyl ethers are usually prepared in situ, but it is also possible to isolate the primarily formed mixed acetals or allyl vinyl ethers155-1 57. With low-boiling vinyl ethers the reaction is carried out in a sealed tube with an excess of the vinyl ether. For a tandem Claisen-rearrangc-ment-ene cyclization involving the Saucy-Marbet reaction cf. ref 158. The generation of isopropenyl ethers from esters is described in ref 159. For a related Claisen rearrangement by the reaction of 2-methoxybutadiene with ends and phenols see ref 160. 

The reaction, which is in fact practised industrially, is the Saucy-Marbet reaction, where 2- methoxypropene, obtained by thermolysis of 2,2-dimethoxypro-pane, is converted into 2-methylbut-3-en-2-ol. The intermediate, which is not isolated, undergoes a sigmatropic rearrangement (Claisen rearrangement) to give 6-methylhept-5-en-2-one. 

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