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KMID : 0903519960390010070
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Journal of the Korean Society of Agricultural Chemistry and Biotechnology
1996 Volume.39 No. 1 p.70 ~ p.76
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Smile Rearrangement of Herbicidal Flazasulfuron
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성낙도/Sung, Nack Do
김대황/김용집/이광재/Kim, Dae Whang/Kim, Yong Jip/Lee, Gwang Jae
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Abstract
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A series of the herbicidal pyridylsulfonyl areas, none substitutent. 1-(4,6-dimethoxypyrimidine-2-yl)-3-(2-pyridylsulfonyl) urea, 3 and 3-trifluoromethyl substitutent, 1-(4,6-ctimethoxypyrimidine-2-yl)-3-(3-trifluoromethyl-2-pyridylsulfonyl) urea, 5(Flazasulfuron) were syntbesizied and the rate of hydrolysis of their has been studied in 25%(v/v) aqueous dioxane at 45℃. From the results of solvent effect(m≪, n≪3 & ｜m｜≪｜ℓ｜), thermodynamic parameter (△S=0.54∼-2.19e.u. & △H=0.025 Kcal.mol.^(-1)), hydrolysis product analysis, pK_a constant(3: 4.9 & 5: lit.4.6) and the rate equation, a marked difference in the kinetics of the reaction of 3 and 5(Flazasulfuron) was observed. It may be concluded that the hydrolysis of 5 proceeds through the A-S_N2Ar reaction via conjugate acid(5H^+) below pH 7.0, whereas, above pH 9.0, the hydrolysis proceeds through irreversibly (E₁)_(anion) and reversibly (E₁CB)_R mechanism via conjugate base(CB), respectively. But in case of 5, A-S_N2Ar, (E₁)anion and (E₁CB)_R mechanism involved Smile rearrangement. The mate of rearrangement of 5 to a 3-trifluoromethyl-2-pyridylpyrimidinyl urea(PPU) in acid and 3-trifluoromethyl-2-pyridyl-4.6-dimethoxypyridinyl amine (PPA) in base was increased about 3.5 times by the introduction of trifluoromethyl group in the 3-position on the 2-pyridyl ring. From the basis of these findings, a possible mechanism for the hydrolysis of 5 was proposed and discussed.
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KEYWORD
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