ABSTRACT
To direct the synthesis efforts of chemists in their search for a new herbicide, three approaches are possible. The first, and most likely to produce active compounds, is to use the structure of a known herbicide as a template. The second approach, often called the biorational method, derives from the knowledge of the structure of the target enzyme and or the detailed mechanism of the reaction involved. The third method is that of random screening of chemicals. This method, though lacking the sophistication of the second, has been highly successful and has resulted in many new compounds with diverse structures and mechanisms of action. The discovery of the imidazolinone herbicides started with a random screening test in which the phthalimide was found to have sufficient activity at 4 kg/ha to warrant the initiation of a synthesis program around this structure.
