Optimization of the Lead Structure

All efforts to improve the herbicidal activity of BAY DAM 4493 by variation of the seven-membered ring were unsuccessful. Ring contraction to the five- and 

4) and ring enlargement (n = 5,6,7) up to the 11) significantly reduced the herbicidal potency 

Similar results were obtained upon the introduction of oxygen (Fig. 2.6.5) [9]. 

In contrast to this observation the introduction of monocyclic triazolinones dramatically enhanced the herbicidal activity. In a systematic manner hundreds of previously known and new intermediates were prepared and transformed into SACTs. Many new synthetic procedures have been developed. To date, derivatives of the type shown in Table 2.6.2 have been synthesized and published. 

The major breakthrough was the introduction of oxygen-bound residues, either on nitrogen and/or on carbon, (Fig. 2.6.6). 

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