Reactivities of Nitrenium Ion Intermediates and the Application to Organic Syntheses

近年来，硝离子的化学研究一直很活跃，因为它们不仅是某些致癌物质的活性代谢物，而且是有机合成的重要中间体。芳基氮化物在三氟乙酸(TFA)、三氟甲磺酸(TFSA)或三氯化铝的存在下产生芳基氮离子(Arn.^H或Arn^+-^-AlCl3)。单重态的芳基氮离子能够引起分子间和分子内的芳香族N-取代以及与烯烃的立体加成反应，而三重态的氮离子只导致氢的抽提。取代反应得到二芳胺、咔唑和9，10-二氢吖啶。在TFA和TFSA存在下，烷基硫化物与由苯基叠氮化物生成的苯基镍离子发生反应，得到了一种合成烷基硫代苯胺衍生物(即氨基苯硫醚)的新方法。在TFA存在下，1-(苯氨基、氨基和烷基氨基)-吡啶盐热分解或光解生成苯基镍离子、母体镍离子和烷基镍离子。这些离子还允许在单重态下发生直接芳香族N-取代。S-氨基苯基硫酸盐的光解也生成了母体离子。-lt；β-叠氮苯乙烯在TFA、二氟乙酸、三氯乙酸、二氯乙酸或氯乙酸的存在下分别反应生成了新的化合物4-苯基-5-卤甲基异恶唑。相反，-lt；α&gt；-叠氮苯乙烯代替-lt；β&gt；-叠氮苯乙烯反应生成的不是异氮唑，而是苯乙酮亚胺。机理研究表明，反应是通过乙烯基硝离子中间体进行的。

The chemistry of nitrenium ions has been actively investigated in recent years since they are not only reactive metabolites of some carcinogens but also important intermediates for organic syntheses.Arylnitrenium ions (ArN.^H or ArN^+-^-AlCl_3) are generated from aryl azides in the presence of trifluoroacetic acid (TFA), trifluoromethanesulfonic acid (TFSA), or aluminium chloride. The singlet arylnitrenium ions are capable of bringing about inter- and intra-molecular aromatic N-substitutions and stereospecific additions to olefins, whereas the triplet nitrenium ions lead only to hydrogen abstraction. The substitutions afforded diarylamines, carbazoles, and 9,10-dihydroacridine. The reaction of alkyl sulfides with phrnylnitrenium ion generated from phenyl azide in the presence of both TFA and TFSA gave a new synthetic method for alkyl thioaniline dirivatives (i.e. aminophenyl sulfides).Phenylnitrenium ion, parent nitrenium ion, and alkylnitrenium ions are generated in the thermolysis or photolysis of 1-(phenylamino, amino, and alkylamino)-pyridinium salts in the presence of TFA. Direct aromatic N-substitutions are also allowed to occur by these ions in singlet states. The parent nitrenium ion is also formed in the photolysis of S-aminophenylsulfonium salts.The reaction of <beta>-azidostyrene in the presence of TFA, difluoroacetic acid, trichloroacetic acid, dichloroacetic acid, or chloroacetic acid produced a novel compound 4-pheny1-5-halomethylisoxazole, respectively. On the contrary, the reaction of <alpha>-azidostyrene instead of <beta>-azidostyrene did not give isozazole but acetophenone imide. Mechanistic study suggests that the reactions proceed via vinylnitrenium ion intermediates.