Reactivities of Nitrenium Ion Intermediates and the Application to Organic Syntheses

近年来，人们对氮离子的化学性质进行了积极的研究，因为它不仅是某些致癌物的活性代谢物，而且是有机合成的重要中间体。芳基氮离子（ArN）^H或ArN^+-^- alcl_3)由芳基叠氮化物在三氟乙酸（TFA）、三氟甲烷磺酸（TFSA）或氯化铝存在下产生。单线态芳基氮离子能够引起分子间和分子内芳烃n的取代和烯烃的立体定向加成，而三态态氮离子只能引起氢的抽离。取代得到二芳胺、咔唑和9,10-二氢吖啶。烷基硫化物与苯基叠氮化物在TFA和TFSA存在下生成的苯基硝基离子反应，为烷基硫苯胺衍生物（即氨基苯基硫化物）的合成提供了一种新的方法。在TFA的存在下，1-（苯胺、氨基和烷基胺）吡啶盐的热分解或光解反应产生苯硝根离子、母硝根离子和烷基硝根离子。这些离子在单重态下也可以直接取代芳族的n。母体氮离子也在s -氨基苯基磺酸盐的光解反应中形成。< - b> -叠氮苯乙烯在TFA、二氟乙酸、三氯乙酸、二氯乙酸或氯乙酸存在下的反应，分别生成了新的化合物4-苯基1-5-卤代甲基异恶唑。相反，< α >-叠氮苯乙烯代替< β >-叠氮苯乙烯反应得到的不是异唑，而是苯乙酮亚胺。机理研究表明，该反应是通过乙烯基铵离子中间体进行的。

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.