Phenylnitrene Radical Cation and Its Isomers from Tetrazoles, Nitrile Imines, Indazole, and Benzimidazole,The Journal of Physical Chemistry A

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Phenylnitrene Radical Cation and Its Isomers from Tetrazoles, Nitrile Imines, Indazole, and Benzimidazole
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2019-01-28 00:00:00 , DOI: 10.1021/acs.jpca.8b11858
Didier Bégué ₁ , Alain Dargelos ₁ , Carl Braybrook ₂ , Curt Wentrup ₃

Affiliation

Phenylnitrene radical cations m/z 91, C₆H₅N, 8a^•+ are observed in the mass spectra of 1-, 2-, and 5-phenyltetrazoles, even though no C–N bond is present in 5-phenyltetrazole. Calculations at the B3LYP/6-311G(d,p) level of theory indicate that initial formation of the C-phenylimidoylnitrene 13^•+ and/or benzonitrile imine radical cation 19^•+ from 1H- and 2H-5-phenyltetrazoles 11 and 12 is followed by isomerizations of 13^•+ to the phenylcyanamide ion 15^•+ over a low barrier. A cyclization of imidoylnitrene ion 13^•+ onto the benzene ring offers alternate, very facile routes to the phenylnitrene ion 8a^•+ and the phenylcarbodiimide ion 14^•+ via the azabicyclooctadienimine 16^•+. Eliminations of HNC or HCN from 14^•+ and 15^•+ again yield the phenylnitrene radical cation 8a^•+. A direct 1,3-H shift isomerizing phenylcarbodiimide ion 14^•+ to the phenylcyanamide ion 15^•+ requires a very high activation energy of 114 kcal/mol, and this reaction needs not be involved. The benzonitrile imine −3-phenyl-1H-diazirine–phenylimidoylnitrene–phenylcarbodiimide/phenylcyanamide rearrangement has parallels in thermal and photochemical processes, but the facile cyclization of imidoylnitrene 13^•+ to azabicyclooctadienimine 16^•+ is facilitated by the positive charge making the nitrene more electrophilic. Furthermore, the benzonitrile imine radical cation 19^•+ can cyclize to indazole 24^•+, and a series of intramolecular rearrangements via hydrogen shifts, ring-openings and ring closures allow the interconversion of numerous ions of composition C₇H₆N₂^•+, including 19^•+, 24^•+, the benzimidazole ion 38^•+ and o-aminobenzonitrile ion 40^•+, all of which can eliminate either HCN or HNC to yield the C₆H₅N^•+ ions of phenylnitrene, 8a^•+, and/or iminocyclohexadienylidene, 34^•+. Moreover, benzonitrile imine 19^•+ can behave like a benzylic carbenium ion, undergoing a novel ring expansion to cycloheptatetraenyldiazene 45^•+. The N-phenylnitrile imine ion 2d^•+ derived from 2-phenyltetrazole 1d cleaves efficiently to the phenylnitrene ion 8a^•+ but may also cyclize to the indazole ion 24^•+. The N-phenylimidoylnitrene 59^•+ derived from 1-phenyltetrazole 5d undergoes facile isomerization to the phenylcyanamide ion 15^•+ and hence phenylnitrene radical cation 8a^•+.

中文翻译：

苯并四氮唑，腈，亚胺，吲唑和苯并咪唑的亚硝基自由基阳离子及其异构体

在1-苯基，2-苯基和5-苯基四唑的质谱图中观察到苯基亚硝基自由基阳离子m / z 91，C ₆ H ₅ N，8a ^•+，即使在5-苯基四唑中不存在C–N键也是如此。在B3LYP / 6-311G（d，p）的理论水平上的计算表明，C-苯基亚酰亚胺基亚硝酸根13 ^•+和/或苯甲腈亚胺自由基阳离子19 ^•+的初始形成是由1 H-和2 H -5-苯基四唑11形成的。和12之后是13 ^•+异构化为苯基氰酰胺离子15 ^•+在较低的壁垒上。imidoylnitrene离子的环化13 ^•+到苯环上提供备用，很容易路由到phenylnitrene离子8A ^•+和phenylcarbodiimide离子14 ^•+经由azabicyclooctadienimine 16 ^•+。从14 ^•+和15 ^•+中消除HNC或HCN再次产生了亚苯基亚苯基阳离子8a ^•+。直接1,3-H移位将苯基碳二亚胺离子14 ^•+异构化为苯基氰酰胺离子15 ^•+需要114 kcal / mol的非常高的活化能，并且该反应不需要参与。苯甲腈亚胺−3-苯基-1 H-二嗪啉-苯基亚酰胺基亚硝基-苯基碳二亚胺/苯基氰酰胺的重排在热和光化学过程中具有相似性，但由于正电荷使亚硝基亚胺13 ^•+容易环化成氮杂双环辛二亚胺16 ^•+。更亲电的。此外，苄腈亚胺自由基阳离子19 ^•+可以环化为吲唑24 ^•+，以及通过氢转移，开环和闭环进行的一系列分子内重排，使许多组成为C ₇ H ₆ N ₂^•+的离子相互转换，包括19 ^•+，24 ^•+，苯并咪唑离子38 ^•+和邻氨基苯甲腈离子40 ^•+都可以消除HCN或HNC从而生成苯基亚硝酸8a ^•+和/或亚氨基环己二烯基34 ^•+的C ₆ H ₅ N ^•+离子。此外，苄腈亚胺19 ^•+的行为类似于苄基碳正离子，经历了新的扩环反应，形成环庚二烯基二氮烯45 ^•+。衍生自2-苯基四唑1d的N-苯基腈亚胺离子2d ^•+可以有效裂解为亚苯基苯基离子8a ^•+，但也可以环化为吲唑离子24 ^•+。衍生自1-苯基四唑5d的N-苯基亚氨基基氮烯59 ^•+易于异构化为苯基氰酰胺离子15 ^•+，从而苯基亚硝基自由基阳离子8a ^•+。

更新日期：2019-01-28

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