An electron paramagnetic resonance study of intermediates generated from aromatic aldiminesElectronic supplementary information (ESI) available: Gaussian98 or Jaguar optimised structures for precursor imines and imidoyl radicals together with their energies at all levels of theory. See http://www.rsc.org/suppdata/p2/b2/b201682f/
作者:Daniele Nanni、Patrizia Pareschi、John C. Walton
DOI:10.1039/b201682f
日期:2002.5.22
It was shown by EPR spectroscopy that N-aryl-imines undergo hydrogen atom abstraction by tert-butoxyl radicals to generate imidoyl radicals in competition with addition to the CN double bond to generate aminyl radicals. The latter were subsequently oxidised to nitroxides (aminoxyls) and also fragmented to release tert-butyl radicals and iminyl ethers. The main products identified were imines formed by combination of the imidoyl radicals with other radicals in the system. Thus, hydrogen abstraction is probably the most important homolytic pathway for the precursor imines. A similar reactivity pattern was found for N-tert-butyl-imines. DFT computations (B3LYP with a 6-31G* basis set) indicated that α-scissions of imidoyl radicals, ArNC˙R (R =
t-Bu or Me), to produce isonitriles, ArNC, were too endothermic to occur under the present experimental conditions. tert-Butoxyl radicals were
shown to add to 1-isocyano-4-chlorobenzene to generate N-arylimidoyl radicals that fragmented to afford 4-chloro-1-isocyanatobenzene.
EPR 光谱显示,N-芳基-亚胺通过叔丁氧自由基抽取氢原子生成亚胺酰自由基,与此同时,CN 双键加成生成氨基自由基。后者随后被氧化成亚硝基(aminoxyls),并破碎释放出叔丁基自由基和亚氨基醚。鉴定出的主要产物是咪酰基与系统中其他自由基结合形成的亚胺。因此,氢抽取可能是前体亚胺最重要的均聚途径。在 N-叔丁基亚胺中也发现了类似的反应模式。DFT 计算(采用 6-31G* 基集的 B3LYP)表明,在目前的实验条件下,亚胺酰基 ArNC˙R(R = t-Bu 或 Me)生成异腈 ArNC 的 α 裂解反应过于耗热。