| Nowadays, Chemical pesticides are coming into the new epoch of "high effectivity, low toxicity, no pollution". Protoporphyrinogen oxidase inhibiting herbicide is becoming a hot point of novel herbicide development because it inhibits the enzyme catalysing the synthesis of chlorophyl in plant cell, insures the different activity between plants and animals, and has the virtues of high effectivity, low toxicity and mezzo residue.The pesticide industry in China has been greatly developed since 1949. Now, there are more than 1000 manufacturing factories and almost 250 kinds of pesticides are produced. The total output of pesticides in China ranks the second in the world. However, the makeup of the pesticides in China is not so satisfactory. Insecticides occupy too large proportion and herbicides need to be greatly developed. At the same time, too many high toxicity or low activity products, which will be washed out, are still produced. Furthermore, the pesticide kinds made in China are almost those having been developed abroad previously. Chinese companies lack new product with its own intellectual property rights.Aimed at the problem discussed above, in the field of creating new protoporphyrinogen oxidase inhibiting herbicides with the structure of substituted phenyl isoxazoles and substituted phenyl pyrazoles, the following work is done in this paper.1) From 2-chloro-4-fluoro-phenol or 4-nitrotoluene, fifteen substituted phenyl isoxazole derivatives, which were not reported before, are prepared via methylation, acylation, condensation, ring closure reaction, alkylation and so on, with total yield 27%-59%. Their structures are confirmed by MS, NMR, IR and elemental analysis. Preliminary bioassay show that the substituted phenyl isoxazole derivatives have diffirent inhibiting activity to several tested weeds, and the diffirence between gramineous weeds and latifoliate weeds is small.2) From 2-chloro-4-fluoro-phenol or 4-nitrotoluene, thirty-two substituted phenyl pyrazole derivatives, which were not reported before, are prepared via methylation, acylation, condensation, ring closure reaction, alkylation, and so on with total yield 21 %-48%. Their structures are confirmed by MS, NMR, IR and element analysis. Preliminary bioassayshows that most substituted phenyl pyrazole derivatives exhibit high herbicidal activity to the tested latifoliate weeds (especially to Acalypha australis), while a little lower activity to tested gramineous weeds. However, some of them also show high activity to gramineous weeds. Among them, O-methyl-2-chloro-5-(4-chloro-l-methyl-5-trifluoromethyl-lH-pyrazol-3-yl)-4-fluorobenzaldehyde oxime (3-10a) is a compound having very high activity. In soil treatment, its inhibiting ratio to the tested latifoliate weeds is more than 90% at the dose of 15 g/hm2. Moreover, at the dose of 150 g/hm2, it can kill all tested weeds. Its activity is obviously higher than Fomesafen and Pentoxazone.3) Some substituted phenyl pyrazole derivatives' absorptions of 1H and 13C NMR are assigned through various two-dimensional NMR spectras (gCOSY, gHSQC, gHMBC et.al.). the coupling constants between I9F and 'H/13C are determined accurately. The study on NMR shows that the benzene ring and the pyrazole ring are almost in the same plane, while there is a hydrogen atom in the 4th position of the pyrazole ring; and the benzene ring and the pyrazole ring are in different planes, while there is a chlorine or bromine atom in the 4th position of the pyrazole ring. And the charge density is greatly influenced by the substituted groups in the 5th position of the benzene ring and the 4th position of the pyrazole ring.4) The effects of the substituted groups on the activity are discussed. The substituted phenyl pyrazole derivatives with a hydrogen atom in the 4th position of the pyrazole ring have lower activity, which can be greatly improved if the hydrogen atom is replaced by chlorine or bromine atom. The herbicidal activity of the substituted phenyl isoxazole derivatives with a chlorine atom in the 4...
|
PDF Full Text Request