Carbazate, biphenyl-substituted

Serendipity in the traditional screening approaches is, up to now, one of the main resources for discovering acaricides with novel biochemical and physiological targets [2]. Based on the discovery that fungicidal phenylhydrazide compounds had some acaricidal activity, a synthesis program was initiated in Crompton Co. Research in 1990. From among several hundred carbazate derivatives synthesized and evaluated for acaricidal activity the methoxy-biphenyl-substituted carbazate (bifenazate. Fig. 30.2.1, Table 30.2.1) was selected for development [3]. 

After the discovery that ortho-biphenyl substituted hydrazide compounds [5] had acaricidal activity in the pesticide discovery screen (Table 30.2.3) several hundred - structurally diverse - biphenyl-substituted carbazate analogs were synthesized, and, in an optimization process using a bioassay with the two spotted spider mite (Tetranychus urticae Koch), isopropyl-2-(4-methoxy[l,l -biphenyl]-3-yl) hydrazine carboxylate (bifenazate) [3, 8] was identified as the most advantageous compound. 

In contrast to the ortho-biphenyl-substituted carbazates the isomeric alkyl-meta-biphenyl-carbazates are available in a multistep synthesis, allowing one to introduce different substituents, like alkoxy, alkylthio, alkylsulfonyl, to the pendant phenyl group (Scheme 30.2.1) [12] ... 

From these variations the structure-activity relationship for meta-substituted biphenyl carbazates can be summarized The introduction of a substituent para to the pendant phenyl group improves the activity compared with the unsubstituted ortho- or meta-biphenyl carbazates. The most active carbazates are those with a methoxy, ethoxy, y -fluoro-ethoxy substituent para to the phenyl moiety in the meta-biphenyl carbazates (Fig. 30.2.3). 

Scheme 30.2.1. Synthesis of meta-substituted biphenyl carbazates.

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See also in sourсe #XX -- [ ]

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