The possible minimum energy paths (MEP) for the [3 + 3] cyclodimerization (33CD) of thiophosgene S‐imides under formation of tetrachlorodithiadiazinanes are determined with density functional theory (DFT) calculations. Application of the natural bond orbital (NBO) method in combination with electron localization function (ELF) analysis corroborates the experimental observation of the unexpected head‐to‐head 33CD of thiophosgene S‐(N‐arylimides) to form the corresponding 2,3‐diaryl‐5,5,6,6‐tetrachloro‐1,4,2,3‐dithiadiazinanes instead of the isomeric 2,5‐diaryl‐3,3,6,6‐tetrachloro‐1,4,2,5‐dithiadiazinanes. Based on complete active space self‐consistent field (CASSCF) results, delocalized diradicals are postulated as intermediates for the stepwise pseudoradical type formation of the obtained 2,3‐diaryl‐5,5,6,6‐tetrachloro‐1,4,2,3‐dithiadiazinanes, whereby non‐covalent interactions play an important role.

中文翻译：

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DFT研究通过头对头[3 + 3]硫代羰基S-酰亚胺的二聚反应形成1,4,2,3-二硫二氮杂二酮的机理

通过密度泛函理论（DFT）计算确定了硫光气S-酰亚胺在[3 + 3]环二聚（33CD）形成下的可能的最小能量路径（MEP）。自然键轨道（NBO）方法与电子定位功能（ELF）分析相结合的应用证实了硫光气S‐（N-芳基酰亚胺）形成相应的2,3-二芳基-5,5,6,6-四氯-1,4,2,3-二硫二氮杂酮，而不是异构的2,5-二芳基-3,3,6,6-四氯-1,4,2,5-二硫二氮杂。根据完整的活动空间自洽场（CASSCF）结果，假定局域化的双基自由基是获得的2,3-二芳基-5,5,5,6,6-四氯-1,4,2的逐步伪自由基型形成的中间体，3-二噻二嗪，其中非共价相互作用起重要作用。