One-pot, fluoride-promoted wittig reaction

A one-pot, fluoride-promoted Wittig reaction was developed. The reactions of ethyl -bromoacetate with aliphatic, aromatic, and heteroaromatic aldehydes in the presence of tri-n-butylphosphine and tetrabutylammonium fluoride produced ,-unsaturated esters in good to excellent yields and E-stereoselectivity. Under the same conditions, reactions of ethyl -bromopropionate, -bromo acetonitrile, and -bromoacetophenone with aliphatic and aromatic aldehydes in the presence of tri-n-butylphosphine and tetrabutylammonium fluoride produced the expected ,-unsaturated derivatives in good E-stereoselectivity. The protocol was extended to semistabilized ylides and applied to the synthesis of some combretastatin analogs.