Dibromocarbene Addition to Michael Acceptors

Numerous examples of dibromocarbene addition to the carbon-carbon double bond of a,j3-unsaturated esters and ketones have been reported. It is of interest that with these substrates, simple quaternary alkylammonium salts (like BTEAC) are efficient phase transfer catalysts [14, 15]. Neither excess bromoform nor added alcohol are 

The observation that dibromocarbene adds to the a, 3-unsaturated double bond is consistent with this proposal [14]. Dibromocarbene is electrophilic and is expected to react with the more electron rich (isolated) carbon-carbon double bond rather than 

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