A novel series of substituted 3-phenyl benzoylpyrazoles were prepared and tested as potential grass herbicides. The targeted materials were prepared by three newly developed synthetic routes, which allowed a comprehensive study of the SAR (structure-activity relationships) of this series. The best combination of grass weed activity (Avena fatua L, Setaria viridis (L) Beauv and Alopecurus myosuroides Huds) and wheat selectivity was obtained with an alkoxy group in the 4-position of the phenyl ring. Activity was further enhanced by the presence of tert-butyl on the pyrazole and a methyl group at the C-2 position of the benzoyl moiety. The alkoxy-substituted 3-phenylbenzoylpyrazoles are a novel class of herbicides with potential utility for control of important grass weeds in cereals.

This study assessed the toxicity and mode of action of a new experimental insecticide, LY219048 in insects and mammals. LY219048 produced rapid convulsions in mice and had LD50 values of 0.7 mg kg−1 and 4 mg kg−1 after intracerebral and intraperitoneal injection, respectively. In initial screens against insects, LY219048 showed low activity against the German cockroach (Blatella germanica L.). Lethality from dietary exposure required one to two weeks, even at concentrations as high as 10000 mg kg−1 (LC50 = 485 mg kg−1). In contrast, it had an LC50 value of 8.3 mg kg−1 against insecticide‐susceptible Drosophila melanogaster (Meig.) when synergized with piperonyl butoxide. Significant resistance to LY219048 (> 12‐fold) was detected in a cyclodiene‐resistant strain of D. melanogaster possessing an altered target site resistance mechanism. This finding suggested that LY219048 blocked the 4‐aminobutyric acid (GABA)‐gated chloride channel in a manner similar to that of the cyclodienes. In physiological studies in larval D. melanogaster central neurons, LY219048 antagonized the reduction of firing caused by 1 mM GABA. Dose‐response experiments showed that the ED50 for blocking inhibition under these conditions was c. 1 μ. Studies of 36CI uptake into bovine brain synaptosomes found that LY219048 was a potent antagonist. At 10 μ it completely blocked chloride flux stimulated by 50 μM GABA. LY219048 competitively displaced [3H]TBOB binding from bovine brain membranes, with an IC50 of 42 nM, which was comparable to values determined for TBPS (35 nM) and picrotoxinin (267 nM). There was little or no displacement (<25%) of [3H]flunitrazepam or [3H]muscimol binding by 10 μM LY219048. Taken together, these results provide strong evidence that this new chemical class of insecticide manifests its acute toxicity by blocking the GABA‐gated chloride channel.

The synthesis of a variety of 2-(haloethenyl)benzo[b]thiophenes from both substituted and unsubstituted benzo[b]thiophenes is described. Their corresponding 1,l-dioxides exhibited versatile reactivity via addition/conjugated elimination and direct substitution mechanisms with amine, thio, and alkoxy nucleophiles in good yield. 19 1) ZniHOAc 2) CH,CO,H 2) CH,CO,H ' \ c q c , CI cl 20, n=O 21. n=224 (Scheme 11). Substantial decomposition occurred in the reaction of chloral with thianaphthenyllithium; however, the thianaphthenylzinc reagent permitted the clean isolation of 19 in good yield. In contrast, the reaction of tribromoacetaldehyde with thianaphthenylzinc led to decomposition. Compound 24 was prepared by the in situ generation of tribromomethane anion" in DMSO and reaction with benzo[ b] thiophene-2-~arboxa1dehyde.l~ The intermediate trihaloethanols 19 and 24 were halogenated with either thionyl chloride or (diethy1amino)sulfur tri-(11) Atkins, P. J.; Gold, V.; Wassef, W. N. J. Chem. SOC., Chem. Commun. 1983, 283. cited in Chem. Abstr. 1962, 57, 4622d. (12) Mamaev, V. P.; Shkurko, 0. P. Zh. Obshch.Gajewski et al. 2-(Haloethenyl)benzo[b]thiophene 1,l-DioxidesScheme IV

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The benzoylpyrazoles belong to a class of herbicides that inhibit the enzyme 4-hydroxy-phenylpyruvate dioxygenase (HPPD). This mode of action is characterized by bleaching due to the disruption of plastoquinone and ?-tocopherol biosynthesis. Early studies indicated that the C(3) position of benzoylpyrazoles can accommodate a wide range of functionality. This paper describes synthetic efforts to improve cool season grass weed activity and wheat selectivity by incorporating cyclic moieties attached through nitrogen at this position. The aza substituents were generally installed by nucleophilic aromatic substitution, however, an efficient four-step method was developed for constructing substituted morpholino moieties directly on pre-formed benzoylpyrazoles. The structure–activity relationships revealed that certain piperidino moieties provided good activity on wild oat, while exhibiting selectivity toward wheat. They also showed that excellent levels of activity on wild oat and blackgrass can be achieved with morpholino substituents.