Bégué Didier, Dargelos Alain, Braybrook Carl, Wentrup Curt
Institut des Sciences Analytiques et de Physicochimie pour l'Environnement et les Matériaux, UMR5254 , CNRS/Université de Pau et des Pays de l'Adour/E2S UPPA , 64000 , Pau , France.
Ian Wark Laboratory , CSIRO , Clayton , Victoria 3169 , Australia.
J Phys Chem A. 2019 Feb 21;123(7):1410-1422. doi: 10.1021/acs.jpca.8b11858. Epub 2019 Feb 11.
Phenylnitrene radical cations m/ z 91, CHN, 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 1 H- and 2 H-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-1 H-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 CHN, including 19, 24, the benzimidazole ion 38 and o-aminobenzonitrile ion 40, all of which can eliminate either HCN or HNC to yield the CHN 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.
在1-、2-和5-苯基四唑的质谱中观察到质荷比为91、CHN、8a的苯基亚硝基阳离子，尽管5-苯基四唑中不存在C-N键。在B3LYP/6-311G(d,p)理论水平上的计算表明，从1H-和2H-5-苯基四唑11和12最初形成C-苯基亚氨基氮烯13和/或苯甲腈亚胺自由基阳离子19之后，13会以较低的势垒异构化为苯基氰胺离子15。亚氨基氮烯离子13环化到苯环上，通过氮杂双环辛二烯亚胺16为苯基亚硝基离子8a和苯基碳二亚胺离子14提供了交替的、非常容易的途径。从14和15中消除HNC或HCN再次产生苯基亚硝基自由基阳离子8a。将苯基碳二亚胺离子14直接进行1,3-H迁移异构化为苯基氰胺离子15需要114 kcal/mol的非常高的活化能，并且该反应无需涉及。苯甲腈亚胺-3-苯基-1H-二氮杂环丙烷-苯基亚氨基氮烯-苯基碳二亚胺/苯基氰胺重排在热过程和光化学过程中有相似之处，但亚氨基氮烯13容易环化为氮杂双环辛二烯亚胺16是由正电荷促进的，这使得氮烯更具亲电性。此外，苯甲腈亚胺自由基阳离子19可以环化生成吲唑24，并且通过氢迁移、开环和闭环进行的一系列分子内重排允许许多组成CHN的离子相互转化，包括19、24、苯并咪唑离子38和邻氨基苯甲腈离子40，所有这些都可以消除HCN或HNC以产生苯基亚硝基的CHN离子8a和/或亚氨基环己二烯叉34。此外，苯甲腈亚胺19可以表现得像苄基碳正离子，进行新颖的环扩展生成环庚四烯二氮烯45。由2-苯基四唑1d衍生的N-苯基腈亚胺离子2d有效地裂解为苯基亚硝基离子8a，但也可能环化生成吲唑离子24。由1-苯基四唑5d衍生的N-苯基亚氨基氮烯59容易异构化为苯基氰胺离子15，从而生成苯基亚硝基自由基阳离子8a。
