In perkin reaction we take aliphatic aldehydes the base readily reacts with aipha hydrogen and give major of the aldol product.

the perkin reaction

yes synthesis of phenanthrene is an exceptional case of perkin reaction.here acetate ion is added to aromatic aldehydes though acetic anhydrides usually work it out

Gibson Dyson has written:

'Perkin's reaction' -- subject(s): Accessible book

Start with the aromatic aldehyde and acid anhydride. Salt of an Carboxylic acid is used to abstract a proton from the alpha carbon of acid anhydride. The carbanion generated would attack the electrophillic centre of aldehyde. This centre is carbonyl carbon. There after an stablised anion is formed. Further hydrolysis gives the required Cinnamic acid.