Tests for herbicidal activity

Figure 9.28 Synthesis of the primary SP amide/ester library L17 tested for herbicidal activity and structure of the hit 9.69 derived from its screening.

As a preliminary bioassay, some alkali metal salts of (9-aIkyl 1-(substituted phenoxyacetoxy)aUtylphosphonic acids IIA-IIE were tested for herbicidal activity on barnyard grass (Echinochloa crusgalli) and cabbage type rape (Brassica napus) by the Petri dish method. For further herbicidal activity evaluation, most of... 

In a preliminary bioassay, sodium [1-(substituted phenoxyacetoxy)aLkyl]meth-ylphosphinates IIIH, were tested for herbicidal activity against barnyard grass (E. crusgalli) and cabbage type rape (B. napus) by Petri dish method. The results are listed in Table 4.22. 

The synthesis and testing of heterocyclic compounds for herbicidal activity has been of continuous interest in our laboratories. As one phase of this program, a search of the literature indicated only a relatively few 2-aryl-l,2,4-triazin-3-ones (1, n-0) and 2-aryl-1,2,4-triazepin-3-ones (2) had been reported, and of those, none appeared to have been examined for herbicidal properties. A synthesis program was therefore initiated in order to access their potential as weed control agents. 

In the research laboratories of the Bayer AG the attention of Westphal and his coworkers was turned to this new group of compounds. Owing to their similarity to nucleic acids a series of 1,2,4-triazinone compounds were synthesised and tested for biological activity. This led to the recognition of the herbicidal activity of the group (Westphal et al.. 1966). 

To test the necessity of at least one ring nitrogen for herbicidal activity, we also evaluated the 2,6-dicyanoaniline 46, which, curiously, is also available from acetylacetone and malononitrile, in diis case in a 1 to 2 ratio, upon heating in aqueous alkah Q5). 

The herbicidal activity and corp selectivity of IG-21 (code number for development HWS) were further examined at 1,200-50 g ai/ha. IG-21 was tested for postemergence activity against a range of plant species including purslane (Portulaca oleracea), slender amaranth (Amaranthus ascendens), goosefoot (Chenopodium album), spiny amaranth Amaranthus spinosus), sugarbeet Beta vulgaris), maize Zea mays) and rice Oryza sativa). Results are shown in Table 2.50. 

Thirteen cyclic phosphonates IVD were prepared to test their herbicidal activity. In series IVD, when the phosphorus-containing six-member ring and furyl group as were kept, further examination was focused on the effect of substituent Yj,. As a preliminary bioassay, the cyclic phosphonates IVD were tested for inhibitory effect... 

This test is intended for use in developing data on the inhibitory activity of chemicals for herbicidal activity pre-evaluating. This section prescribes the test procedures and conditions using seeds of plants to develop data on plant stem/root inhibitory effect of chemicals. 

Early studies carried out by Angelov et al. [102] established the herbicidal activity of 4-iodo-2,5-dihydro-l,2-oxaphosphole-2-oxide derivatives 91. Some of the tested compounds showed promising properties for further application as herbicides in farming. 

Since the acetoxy and methoxy synthetic derivatives exhibited herbicidal activity, we were curious whether this also occurred with other esters and ether derivatives of 1 and its isomer, 3,7-dimethyl-6-hydroxy-8-methoxyisochroman (4). We reasoned that 3,7-dimethyl-6,8-dimethoxyisochroman (3) represents a logical precursor for the systematic preparation of the desired ester and ether analogs of isochromans 1 and 4. To test this conjecture, we needed both an efficient synthesis of bis-ether 3 and a practical way to demethylate the C(6) or C(8) ethers selectively. 

June Compound G-27692 (simazine) was found to be two to four times more herbicidally active than the first selected lead compound, G-25804 (chlorazine). The selectivity for corn of G-27692 was confirmed in new tests with outstanding results. The selection of simazine as the new com herbicide was a decisive step towards the first marketable triazine herbicide. 

Dichlorophenol has a large-scale use in pharmaceutical and herbicide synthesis, but is classed as a priority recalcitrant environmental pollutant conversion to 2-chlorophenol, which can be recycled, is therefore a desirable reaction. Ni/Si02, Au/SiC>2 and NiAu/SiC>2 have been prepared from diaminoethane complexes and tested for this reaction their activities rising in the sequence... 

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