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Design, Synthesis and Herbicidal Activity of Acyl Thiourea and Their Cyclization Products Containing Isoxazole Moiety

Author: WangMaoRong
Tutor: JiangLin
School: Shandong Agricultural University
Course: Applied Chemistry
Keywords: Acylthiourea 2H-1, 2,4 - thiadiazole and [2,3-a] pyrimidine Synthesis Crystal structure Herbicidal activity
CLC: TQ450.1
Type: Master's thesis
Year: 2011
Downloads: 57
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Abstract


Acetolactate synthase (ALS) inhibitors with high biological activity, broad spectrum herbicide, human and animal safety and other features, as weed control technology development in a major breakthrough. With ALS inhibitor resistance problem faced by more and more prominent as the target in ALS, looking ultra-efficient, low toxicity, broad spectrum weed control target compounds, chemical and pesticide industry has become one of the hotspots. Pyrimidine ring-containing acyl thiourea and its cyclization product 2H-1, 2,4 - thiadiazole and [2,3-a] pyrimidine compound is easy and the weed acetolactate synthase amino acid residues of the active center formation hydrogen bonding and hydrophobic interactions, the enzyme activity is reduced or lost, block the biosynthesis of branched chain amino acids. In this paper, a biologically active molecule design theory as a guide, designed and synthesized two series with ALS target compounds that target, and its herbicidal activity carried out in vivo screening, the main research contents and results are as follows: 1. Respectively, from 2,4 - two chlorobenzaldehyde 4 - trifluoromethylbenzaldehyde starting, oxime, chlorinated, into the ring, hydrolysis, chloride, isothiocyanate esterification, such as seven-step nucleophilic addition reactions, synthesized a series of structural novel isoxazole ring containing pyrimidinyl group thioureas: 16 kinds of N-(4,6 - disubstituted pyrimidin-2 - yl)-N'-[5 - methyl-3 - substituted phenyl isoxazole -4 - formyl] thiourea 4 a ~ 4 p , with Br2 as the oxidant, the above acylthiourea oxidative cyclization to give another series of novel fused heterocyclic derivatives: 16 kinds of 5,7 - substituted 2 - [5 - methyl-3 - (substituted phenyl isoxazol-4 - methyl imide]-2H-1, 2,4 - thiadiazole pyrazolo [2, 3-a] pyrimidine-5 a ~ 5 p . goal structure of the compound was confirmed by IR, 1H NMR and elemental analysis. 2 to monocots (barnyardgrass, crabgrass), dicots (small pigweed, rape) as test materials, fenoxaprop as control agents, the target compounds were evaluated indoor herbicidal activity. preliminary test showed that: 2 a series of target compounds have demonstrated some inhibitory activity and the root length of the stem length is greater than the inhibition inhibition inhibition of dicotyledons than for inhibition of monocots which, 5,7 - substituted-2 - [5 - methyl-3 - (4 - (trifluoromethyl) phenyl)-isoxazol-4 - methyl imide)]-2H-1, 2,4 - thiadiazole and [2,3-a] pyrimidine 5 a ~ 5 h inhibitory activity was higher, 100 mg / L concentration on rape root length inhibition rate of 75% or more, 5,7 - disubstituted -2 - [5 - methyl-3 - (2,4 - dichlorophenyl) isoxazol-4 - methyl imide]-2H-1, 2,4 - thiadiazole [2,3 - a] pyrimidine 5i ~ 5 p on rape root length inhibition rate 70% 75%, higher than the control drug. N-(4,6 - disubstituted pyrimidin-2 - yl)-N'-[5 - methyl-3 - (4 - (trifluoromethyl) phenyl)-isoxazol-4 - carbamoyl] thiourea 4 < sub> i ~ 4 p and N-(4,6 - disubstituted pyrimidin-2 - yl)-N'-[5 - methyl-3 - (2,4 - dichlorophenyl) isoxazol-4 - formyl] thiourea 4 a ~ 4h inhibitory activity is relatively good, at 100 mg / L concentration moderate herbicidal activity on rape root length inhibition rate at 55% 60%. 3 4i of target compounds were characterized by X-ray single crystal diffraction experiments, studies show that the compound belongs to triclinic, space group P-1, cell parameters: a = 7.351 (6) (?), B = 10 . 373 (10) (?), c = 14.120 (12) (?), α = 72.222 (14) °, β = 85.372 (15) °, γ = 85. 380 (14) °, V = 1020.1 (16 ) (?) 3, Z = 2, Dcalcd. = 1.418 g · cm -3 , μ = 0.211mm-l, F (000) = 448. Thiourea bridge on the pyrimidine ring nitrogen atoms and the nitrogen atom to intramolecular NH ... N hydrogen bonds formed as a stable six-membered ring. 4 preliminary study of target molecular structure and herbicidal activity relationship bioassay results showed that the benzene ring ortho to the position connected with electron withdrawing substituent, and the pyrimidine ring 4, 6 is a methyl group or a methoxy group such as for electron- , to improve the herbicidal activity of the compound is necessary.

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