Studies On The Synthesis And Bioactivity Of Substituted1,3-benzoxazin-2-ones

With the increazing requirement of food and environment improvement, thedeveloping low toxicity, novel structure, high safety, high selectivity and environmentfriendly "green" pesticides have become hot research. In recent years, heterocycliccompounds containing nitrogen and oxygen atom have received widely attention dueto their broad biological activity in the field of drug discovery. Because of theirfungicidal activity, herbicidal activity and pesticidal activity, benzoxazinones havebecome one of the hot research in the discovery of new pesticides.This paper mainly studied the synthesis and biological activity of a series ofsubstituted3,4-2H-1,3-benzoxazin-2-ones, including ten of3-(1,3,4-thiadiazolyl)-3,4-2H-1,3-benzoxazin-2-ones30a~30j, eleven of3-aryl-3,4-2H-1,3-benzoxazin-2-ones31a~31k, four of3-(methoxycarbonylmethyl)-3,4-2H-1,3-benzoxazin-2-ones32a~32d. All the structures of the target compoundswere characterized by IR,1H NMR and13C NMR. The structuer compound31k weredetermined by X-ray analysis.(1) A series of2-(substituted aminomethyl)phenols34a～34j，35a～35i，36a～36d were synthesized by “one-pot” procedure.①2（-1,3,4-Thiadiazolylaminomethyl）phenols34a~34j were prepared by reducing the intermediate Schiff bases withNaBH4. The intermediate Schiff bases were generated by reactions of5-methylsalicylals with2-amnio-1,3,4-thiadiazoles in anhydrous methanol withp-toluenesulfonic acid as catalyst.②2-(Arylaminomethyl)phenols35a~35e wereprepared by reducing the intermediate Schiff bases with NaBH4. The intermediateSchiff bases were generated by reactions of substituted salicylals with arylaminesunder solvent-free condition at100℃for3minutes. Compounds35f~35k wereprepared by reducing the intermediate Schiff bases with NaBH4. The intermediateSchiff bases were generated by reactions of hydroxyacetophenone with arylaminesunder microwave irradiation.③2-(Methoxycarbonylmethyl) phenols36a~36dwere prepared by reducing the intermediate Schiff bases with NaBH4withoutseparation. The intermediate Schiff bases were generated by reaction of substitutedsalicylals with methyl amino acid esters hydrochloride in anhydrous methanol usingtriethylamine as acid binding agent. All the structures of the compounds werecharacterized by IR,1H NMR and13C NMR.(2) Substituted3,4-2H-1,3-benzoxazin-2-ones were synthesized by the reactionsof2-(substituted aminomethyl)phenols with triphosgene in the presence of triethylamine.3-(1,3,4-Thiadiazolyl)-3,4-2H-1,3-benzoxazin-2-ones30a~30j wereprepared in refluxing toluene, but3-aryl-3,4-2H-1,3-benzoxazin-2-ones31a~31k and3-(methoxycarbonylmethyl)-3,4-2H-1,3-benzoxazin-2-ones32a~32d weresynthesized in tetrahydrofuran at60℃.(3) Two single crystals of compounds35h and31k were cultivated by slowlyevaporating the solvent, and their crystal structures were determined and analyzed byX-ray diffraction. The crystal structure shows that compound35h belongs tomonoclinic, P21/n space group; and compound31k to monoclinic, P21/c space group.(4) The fungicidal activity of all the target compounds30a~30j,31a~31i and32a~32d were evluated. Generally, the results demonstrated that all compounds haveshown certain to good activity against the tested strains. Compounds showed the bestactivity against rice blast fungus, the activity of compounds30f,31f,31g,32a,32d isof85.7%. Secondly, some compounds exhibited good activity against wheatgibberellic, the inhibition rate of compound30g,30h is84.6%. The compoundsshowed relatively good activity against rapeseed sclerotia with the inhibition rate ofcompound31c being72.7%. Some compounds exhibited certain activity againstPhytophthora capsici as shown by66.7%activity of compound30j.