Reaction of Aromatic N-Oxides with Dipolarophiles. X. : Role of Charge-Transfer Complexes in 1, 3-Dipolar Cycloaddition of Pyridine N-Oxides to Phenyl Isocyanate
Reaction of Aromatic N-Oxides with Dipolarophiles. X. : Role of Charge-Transfer Complexes in 1, 3-Dipolar Cycloaddition of Pyridine N-Oxides to Phenyl Isocyanate
复制标题
芳香族氮氧化物与亲偶极试剂的反应。
DOI：
10.1248/cpb.34.966
复制
发表时间：
1986
影响因子：
1.7
通讯作者：
T. Hisano
中科院分区：
文献类型：
--
作者：
K. Harano;Rie Kondo;M. Murase;Toshikazu Matsuoka;T. Hisano
在3-甲基吡啶n -氧化物与异氰酸苯酯的1,3 -偶极环加成反应中，光谱证据表明异氰酸苯酯与n -氧化物吡啶和芳香溶剂（如吡啶）均形成电荷转移配合物。结合电荷转移络合物的形成，研究了溶剂对其选择性的影响。在以3-甲基吡啶为溶剂的反应中，溶剂效应最为显著。3-甲基吡啶n -氧化物与异氰酸苯酯在几种溶剂中相互作用的平衡常数较大，表明反应混合物有利于络合物的形成。混合物的质子核磁共振（1H-NMR）谱显示，由于电荷转移络合作用，3-甲基吡啶n -氧化物的甲基信号发生了高场位移。在此基础上，讨论了配合物的结构和作用。
In the 1, 3-dipolar cycloaddition reaction of 3-methylpyridine N-oxide with phenyl isocyanate, spectroscopic evidence indicates that phenyl isocyanate forms charge-transfer complexes with both pyridine N-oxide and aromatic solvents such as pyridine. In connection with the charge-transfer complex formation, the solvent effect on the site selectivity was investigated. The most prominent solvent effect was observed in the reaction using 3-methylpyridine as a solvent. The equilibrium constants for the interaction of 3-methylpyridine N-oxide with phenyl isocyanate in several solvents were found to be quite large, indicating that the reaction mixtures favor complex formation. The proton nuclear magnetic resonance (1H-NMR) spectra of the mixtures show a high field shift of the methyl signal of 3-methylpyridine N-oxide due to charge-transfer complexation. Based on these results, the structure and role of the complexes are discussed.