Dipartimento di Chimica Organica "A. Mangini", Università di Bologna, Viale del Risorgimento 4, Bologna I-40136, Italy.
Beilstein J Org Chem. 2010 Aug 9;6:713-25. doi: 10.3762/bjoc.6.84.
The reactions of group 13 metal trichlorides with aromatic azides were examined by CW EPR and pulsed ENDOR spectroscopies. Complex EPR spectra were obtained from reactions of aluminium, gallium and indium trichlorides with phenyl azides containing a variety of substituents. Analysis of the spectra showed that 4-methoxy-, 3-methoxy- and 2-methoxyphenyl azides all gave 'dimer' radical cations ArNHC₆H₄NH₂ and trimers ArNHC₆H₄NHC₆H₄NH₂ followed by polymers. 4-Azidobenzonitrile, with its electron-withdrawing substituent, did not react. In general the aromatic azides appeared to react most rapidly with AlCl₃ but this reagent tended to generate much polymer. InCl₃ was the least reactive group 13 halide. DFT computations of the radical cations provided corroborating evidence and suggested that the unpaired electrons were accommodated in extensive π-delocalised orbitals. A mechanism to account for the reductive conversion of aromatic azides to the corresponding anilines and thence to the dimers and trimers is proposed.
通过连续波电子顺磁共振（CW EPR）和脉冲电子顺磁共振（ENDOR）光谱研究了第 13 族金属三氯化物与芳族叠氮化物的反应。从三氯化铝、镓和铟与含有各种取代基的苯叠氮化物的反应中获得了复杂的 EPR 光谱。对光谱的分析表明，4-甲氧基-、3-甲氧基-和 2-甲氧基苯叠氮化物均生成“二聚体”自由基阳离子ArNHC₆H₄NH₂和三聚体ArNHC₆H₄NHC₆H₄NH₂，随后是聚合物。带有吸电子取代基的 4-叠氮苯甲腈没有反应。一般来说，芳族叠氮化物似乎与 AlCl₃反应最快，但该试剂往往会产生更多的聚合物。InCl₃是第 13 族卤化物中反应性最低的。自由基阳离子的密度泛函理论（DFT）计算提供了佐证，并表明未配对电子被容纳在广泛的π离域轨道中。提出了一种机制来解释芳族叠氮化物向相应苯胺的还原转化，然后是二聚体和三聚体的形成。
