Method for alkylation of phenylacetonitrile

The present invention relates to a method for alkylation of phenylacetonitrile by reaction with halogenated derivatives. The reaction of phenylacetonitrile with a XRX derivative of the type or RX wherein R denotes an alkyl containing from 2 to 5 carbon atoms group and X is halogen, is carried out in a heterogeneous basic medium consisting of soda aqueous and dimethybulfoxyde. The method is particularly applicable to obtaining phenyl-1-cyclopentanecarboxylic acid by alkylation of phenylacetonitrile by the dibromo-1,4 butane followed by hydrolysis of 1-phenyl cyclopentane carbonitrile.