Syntheses And Herbicidal Activity Of Pyrazolyl Benzoxazole Derivatives

Inhancement of mankind's environmental concept had imparted the development of novel pesticides a new theme featured "super high effectivity, low toxicity, no pollution". Protoporphyrinogen oxidase inhibitor herbicide is becoming a hot point of novel herbicide development because it inhibits the enzyme catalysing the synthesis of chlorophyl in plant cell, allows good toxicity selectivity between plants and animals, and is characterized by high effectivity, low toxicity and moderate residue.Since China's reform and open up, the pesticide industry in China has greatly been developed. There are more than 2000 manufacturing factories and almost 300 kinds of pesticides are produced. In 2007, the total amount of pesticide production output ranks the first worldwide. However, the makeup of pesticide products in China is not so rational. Insecticides take too large proportion while the development of herbicides are far behind the level of the world, among which two much high toxicity and low activity products, to be phased out, are still prevailing in the market. Furthermore, the pesticides produced in china are numerously imitation of those previously developed in lack of independent intellectual property rights.Aimed at the problem discussed above, in the field of creating new protoporphyrinogen oxidase inhibitor herbicide with an essential structure of substituted pyrazolyl benzoxazoles, the following work is accomplished in this paper.Using 4-fluorophenol as starting material, via a serial of reactions included chloridation, acylation, condensation, ring closure, methylation, nitration, and so on, 21 substituted pyrazolyl benzoxazole derivatives are prepared. All the structures are confirmed by H~1 NMR, MS and element analysis, and are never reported in any literature. Preliminary bioassay shows that most substituted pyrazolyl benzoxazole derivatives exhibit high herbicidal activity to the tested gramineous weeds and latifoliate weeds.