A cycloreversal reaction, leading to aroyl cations, is the major process in 2-aryl-4H-3,1-benzoxazin-4-ones under electron impact conditions. The ortho interaction of the methoxy and the nitro groups in the 2-phenyl moieties in these compounds present the most abundant ions at m/z 119 and 134, respectively, in their mass spectra as a result of the transfer of a hydrogen atom from the former and an oxygen atom from the latter to the imine nitrogen of the heterocycle. The ion structures and the mechanisms for the proposed fragmentations are based on high-resolution data, B/E and B2/E linked-scan spectra, collision-activated decomposition–B-/E linked-scan spectra and deuterium labelling.
在电子撞击条件下,2-芳基-4H-3,1-苯并恶嗪-4-酮的主要反应过程是环逆反应,从而产生芳基阳离子。这些化合物中 2-苯基中的甲氧基和硝基的正交作用分别在质谱的 m/z 119 和 134 处出现了最丰富的离子,这是因为前者的一个氢原子和后者的一个氧原子转移到了杂环的
亚胺氮上。所提出的离子结构和碎裂机制是基于高分辨率数据、B/E 和 B2/E 链接扫描光谱、碰撞激活分解-B-/E 链接扫描光谱和
氘标记。