Mefenacet

The liquid-liquid partition procedure described above can be substituted by using a Chem Elut column. After concentrating the extract derived from Section 2.2 to 20 mL, the concentrate is applied to a Chem Elut column and charged at room temperature for 5-10 min. Naproanilide, propanil and mefenacet are eluted with 80 mL of n-hexane when using the Chem Elut column. The recoveries are in the range 96-110% (personal data). 

Clomeprop Clomeprop Diflufenican Inabenflde Mefenacet Flutoranil Mepronil Multi-analysis... 

Analyte Clomeprop Metabolite (derivative) Diflufenican Inabenfide Mefenacet Flutoranil Mepronil ... 

Using multi-analytical methods, most of the anilides, including naproanilide, propanil and mefenacet, show recoveries of >70% from 0.5mgkg fortified tomato. According to the official analytical method of the Ministry of Environment, Japan, the recovery of clomeprop fortified at 0.4mgkg in brown rice is >90% (personal data). 

Garrido et al. developed an electrochemical procedure for the determination of mefenacet residues in rice crops. Qptimization of parameters such as pH, frequency and electrochemical electrode surface treatment is necessary to obtain accurate analytical data. 

An SPE method has been developed to replace the classical LLP method. Water sample is extracted with an SPE column such as Cig and styrene-divinylbenzene copolymer (PS-2) cartridges, which consist of a reversed bonded-phase silica sorbent, provided as an extraction tool. This is a simple and rapid method, and applied to the determination of residual amounts of naproanilide, propanil, mefenacet, etc. This system determines the residual amounts of most of the pesticides and has been successfully applied to determination of pesticides in water. 

Ministry of Environment, The Official Analytical Methods of the Ministry of Environment, Japan, Ministry of Environment, Tokyo, mefenacet (1993), clomeprop (1996), naproanriide (2000) (in Japanese). 

M. Ueji, H. Kobayashi, and K. Nakamura, Analytical Methods for Pesticide Residues, Soft Science, Tokyo, p. 313 (inabenfide), p. 356 (mefenacet), p. 381 (naproanilide) (2001) (in Japanese). 

The rice herbicides cinmethylin (Figure 2.23), mefenacet (Figure 2.24) and daimuron and methyldymron (Figure 2.25) also interfere with meristematic activity in susceptible species. 

Mecoprop phenoxy carboxylic acid Mefenacet heterocyclic nitrogen, benzothiazole, amide... 

Rabon tretachlorvinphos Racer flurochloridone Racumin coumatetralyl Radapon dalapon-sodium Radar propiconazole Ramik diphacinone Ramrod propachlor Rancho mefenacet Randox allidochlor Rangado dimethylvinphos Ratak brodifacoum/difenacoum... 

The selected herbicides flufenacet and mefenacet from the class of oxyacetamides and fentrazamide from tetrazolinones are introduced here. 

The first compound of the heteroaryloxyacetamide class (simplified as oxyacetamides) launched in 1986 was mefenacet (FOE 1976 Fig. 8.1), as a paddy rice herbicide. Whereas FOE 1976 was synthesized at Bayer (now Bayer CropScience), its good performance was investigated by biologists of Nihon Tokushu Nouyaku Seizou K.K. (now Bayer CropScience K.K.) through primary, secondary and field trial tests. 

Continuous study of oxyacetamide chemistry shifted research from the paddy herbicide to an upland herbicide with increasing water solubility that is suitable for such upland use. To this end, benzanellated analogues such as the benzothia-zole moiety of mefenacet were changed to simple five-membered heterocycles that contain at least one nitrogen atom to increase water solubility, and sulfur or oxygen atom to decrease lipophilicity, for instance thiazoles, thiadiazoles, oxazoles and oxadiazoles (Fig. 8.2). Consequently, many patent applications of the new class of heteroxyacetamide herbicides were disclosed [17, 18]. 

Figures 8.3 and 8.4 show the synthetic pathways for mefenacet [19] and flu-fenacet [20], respectively. The new key intermediates to produce flufenacet are acetoxyacetamide derivative 3, derived from acetoxyacetylchloride (2) and N-isopropyl-4-fluoroaniline (1), and 2-methylsulfonyl-5-trifluoromethyl-l,3,4-thiadiazole (5), derived from trifluoroacetic acid.

In summary, to date, two heteroxyacetamide class compounds have been launched on the market, i.e., mefenacet and flufenacet. 

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