Ni-Catalyzed Reductive Conjugate Addition

Silyl enol ethers are very useful synthetic intermediates, but unfortunately, their synthesis, normally by conjugate addition-silyl enol ether formation, requires the use of air and moisture unstable organometaUic reagents with the consequent problems of functional group incompatibihties, and 

SCHEME 3.32 Ni-catalyzed synthesis of aUylic and homoaUyhc O-silyl ethers by reductive coupling between aUcenes and aldehydes. 

SCHEME 3.34 Synthesis of 1,3-diketones by Ni-catalyzed redox coupling of enones, aldehydes, and aUcynes. 

The reductive aldol reaction employing trialkylboranes as reducing agents has been also developed by Montgomery et al. [62], who observed that the addition of aryl iodides is required to initiate the reaction. The corresponding aldol products were obtained in 60-91% yields and dr 86 14-96 4. 

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