Allyl alcohols carbomagnesiation

Normant and coworkers demonstrated that the intermolecular carbomagnesiation across acetylene (HC=CH) could be catalyzed by a copper salt . The treatment of w-heptylmag-nesium bromide with acetylene in the presence of a catalytic amount of CuBr (5 mol%) in EtgO at —20 °C followed by the reaction with C2H5CHO and quenching with H2O results in the formation of allylic alcohol 12 in 31% yield (Scheme 9) . The carbomagnesiation takes place in a yw-addition manner. 

A number of examples for the copper-catalyzed carbometallation151,300,300a or stannylmetallation61,61a of G-G double or triple bonds have been described in recent years. For example, reaction of ethynyl carbamate 346 with n-butylmagnesium bromide in the presence of 10 mol.% of copper(i)-iodide induced a smooth regio- and stereoselective carbomagnesiation to afford the vinylmagnesium intermediate 347 which can be trapped with benzaldehyde to the allyl alcohol 348 (Scheme 97).151... 

This carbomagnesiation can also be applied to allylic alcohols and ethers. In the case of the free alcohol, the reaction affords the. vyn-diol with 95 5 diasiercoscleciivity. 

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