Various N-(1-aryl-1-alkenyl)-2-chloroacetamides bearing alkoxymethyl or alkylthiomethyl group on amide nitrogen were synthesized by a one-step hydroamidation of 2-aza-1,3-pentadienes. Some N-(1-aryl-1-alkenyl)-2-chloroacetamides were found to have high herbicidal activities against upland farm weeds.