Polyfluoro-heterocyclic compounds. Part VI. Nucleophilic substitution in tetrafluoro-4-nitropyridine
作者:R. D. Chambers、J. Hutchinson、W. K. R. Musgrave
DOI:10.1039/j39660000220
日期:——
5,6-tetrafluoro-4-nitrobenzene which gives exclusive replacement of fluorine ortho to the nitro-group. The pyridine-ring nitrogen is the greatest single factor in determining the orientation of nucleophilic attack. Competition experiments show relative reactivities to be in the order: pentafluoropyridine ≈ pentafluoronitrobenzene > tetrafluoro-4-nitropyridine. Fluorine-19 n.m.r. spectra of derivatives
四氟-4-硝基吡啶与氨和甲醇钠的反应会导致硝基的大量取代,这与2,3,5,6-四氟-4-硝基苯不同,后者是邻位氟被硝基完全取代的原因。吡啶环氮是决定亲核攻击方向的最大单一因素。竞争实验显示相对反应性依次为:五氟吡啶≈五氟硝基苯>四氟-4-硝基吡啶。已经检查了五氟吡啶衍生物的氟19 nmr光谱,但取代基甲氧基和氨基对化学位移的影响不一致,特别是在硝基存在下。