AbstractPd‐catalyzed cross‐coupling reactions of chloropyrimidines with alkenylboronic acids readily proceed to give the corresponding alkenylpyrimidines in high to excellent yields. The coupling reaction of 2,4‐dichloropyrimidine or 2,4,6‐trichloropyrimidine with one equivalent of alkenylboronic acid occurred more easily on 4‐position than on 2‐position, which implied that the reaction is highly regioselective. The reaction is stereospecific since the configuration of C=C remained intact. The preliminary study on the cross‐coupling reactions of 2,4,6‐trichlorotriazine with one equivalent of arylboronic acids showed that the reactions afforded the monosubstituted triazines in moderate yields. The effect of steric hindrance of the substitutents on the reac