Palladium(0) catalyzed alkenylation of 3′- or 4′-iodo- (or bromo-) benzocrown ethers are found to be a convenient procedure for the introduction of alkenyl groups (–CH=CH–R; R=Ph, COOEt and COOH). Iodination at 3′-position of benzocrown ethers could be achieved in good yield by the use of 4′-t-butyl derivatives.