Transition-State Variation in the Nucleophilic Substitution Reactions of Aryl Bis(4-methoxyphenyl) Phosphates with Pyridines in Acetonitrile
作者:Hai Whang Lee、Arun Kanti Guha、Chang Kon Kim、Ikchoon Lee
DOI:10.1021/jo0162742
日期:2002.4.1
The kinetics and mechanism of the reactions of Z-aryl bis(4-methoxyphenyl) phosphates, (4-MeOC(6)H(4)O)(2)P(=O)OC(6)H(4)Z, with pyridines (XC(5)H(4)N) are investigated in acetonitrile at 55.0 degrees C. In the case of more basic phenolate leaving groups (Z = 4-Cl, 3-CN), the magnitudes of beta(X) (beta(nuc)) and beta(Z) (beta(lg)) indicate that mechanism changes from a concerted process (beta(X) =
Z-芳基双(4-甲氧基苯基)磷酸(4-MeOC(6)H(4)O)(2)P(= O)OC(6)H(4)Z的动力学和反应机理在55.0摄氏度下于乙腈中研究了具有吡啶(XC(5)H(4)N)的化合物。在更碱性的酚盐离去基团(Z = 4-Cl,3-CN)的情况下,β(X)的大小(beta(nuc))和beta(Z)(beta(lg))表示弱碱性机理从协调过程(beta(X)= 0.22-0.36,beta(Z)= -0.42到-0.56)变化吡啶(X = 3-Cl,4-CN)逐步形成具有速率限制的三角双锥体五坐标(TBP-5C)中间体(beta(X)= 0.09-0.14,beta(Z)= -0.08至-0.28)用于更碱性的吡啶(X = 4-NH(2),3-CH(3))。前者有一个较大的负交叉相互作用常数(rho(XZ)= -1.98),正有一个rho(XZ)(+0)支持该建议。97)。在碱性较低的酚盐离去基团(Z