REACTIONS OF ESTERS WITH PHOSPHORUS YLIDES .3. DIRECT CONVERSION INTO BRANCHED OLEFINS

Aromatic and aliphatic esters can be directly converted into the corresponding isopropenyl compounds by reaction with methylenetriphenylphosphorane. In the case of aliphatic esters “salt-free” conditions are required to effect selective conversions. Reaction with other n-alkylidenetriphenylphosphoranes likewise affords the corresponding branched olefins as mixtures of E and Z isomers. a-Branched or stabilized phosphoranes do not react in this way. The reaction has also been extended to ylides containing (protected) functional groups. Examples are presented in which esters are reacted with ethoxycarbonyl-, carboxylate-, and ethylenedioxy-substituted phosphoranes and thereby converted into branched olefins containing these functional groups twice. The influence of ester structure and reaction conditions upon yield and product distribution is discussed. © 1979, American Chemical Society. All rights reserved.