Endo Y, Shudo K
Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.
Yakugaku Zasshi. 1994 Aug;114(8):565-76. doi: 10.1248/yakushi1947.114.8_565.
The acid-catalyzed reaction of N-acyl- and N-sulfonylhydroxylamines with benzene proceeded smoothly to give C-C products; 2- and 4-hydroxybiphenyls. The reaction and the thermolysis of N-aryloxypyridinium salts involve common intermediates. The results of product analysis, the orientation of the reaction, effects of substituents on the nitrogen atom and on the phenyl ring suggested a mechanism involving a phenoxenium ion. The positive charge of the phenoxenium ion localized not on the oxygen atom but on the ortho and para carbons of the benzene ring. C-O product: diphenylethers are formed when the heterolysis of the N-O bonds is slow and the aromatic solvent has high nucleophilicity, suggesting an SN2-like reaction on the oxygen atom. The phenoxenium ions are also concerned with a rearrangement of O-arylhydroxylamine to 2-aminophenol. An ion-molecule pair involving phenoxenium ion and ammonia as an intermediate of the intramolecular ortho rearrangement.
N-酰基和N-磺酰基羟胺与苯的酸催化反应顺利进行，生成碳-碳产物；2-和4-羟基联苯。N-芳氧基吡啶鎓盐的反应和热解涉及共同的中间体。产物分析结果、反应的取向、氮原子和苯环上取代基的影响表明了一种涉及苯氧鎓离子的机理。苯氧鎓离子的正电荷并不定域在氧原子上，而是在苯环的邻位和对位碳原子上。碳-氧产物：当N-O键的异裂缓慢且芳族溶剂具有高亲核性时，会形成二苯醚，这表明在氧原子上发生了类似SN2的反应。苯氧鎓离子也与O-芳基羟胺重排为2-氨基苯酚有关。涉及苯氧鎓离子和氨的离子-分子对作为分子内邻位重排的中间体。
