Compounds of the chloroacetamide family are major pre- emergence herbicides for control of seedling grass in corn and soybean crops, and are among the most widely used her- bicides in the world.1,2) For example, the thiophene derivative dimethenamid [2-chloro-N-(2,4-dimethyl -3-thienyl)-N-(2- methoxy-1-methylethyl)acetamide] (1) is used for control of annual grasses and certain broadleaf weeds, primarily in corn and soybeans and also in peanuts.3—7) In ...