The condensation reaction of 2-mercapto-3-methoxybenzaldehyde with 3-aminopyridine afforded an unexpectedN-alkylated [1,5]dithiocine instead of theN-salicylideneaniline. The proposed mechanism for this condensation involves a strong intramolecular hydrogen bond between the thiol and the amine groups, leading to a second condensation. The corresponding product,i.e.4,10-dimethoxy-13-(pyridin-3-yl)-6H,12H-6,12-epiminodibenzo[b,f][1,5]dithiocine methanol 0.463-solvate, C21H18N2O2S2·0.463CH3OH, was characterized by single-crystal X-ray diffraction analysis. The supramolecular structure shows π–π stacking and S...S interactions in the crystal packing. Within the asymmetric unit, two geometries of the N atom are observed. Although a planar geometry should be expected, a pyramidal one is observed due to the crystal packing. The presence of the two geometries was further supported by density functional theory (DFT) calculations that show an electronic energy difference of less than 2 kJ mol−1between the two conformers.
2-巯基-3-甲氧基苯甲醛与 3- 氨基吡啶发生缩合反应,意外地生成了 N-烷基化的 [1,5]dithiocine 而不是 N-水杨酰苯胺。所提出的缩合机理涉及硫醇和胺基团之间的强分子内氢键,从而导致第二次缩合。相应的产物,即 4,10-二甲氧基-13-(吡啶-3-基)-6H,12H-6,12-表二亚氨基二苯并[b,f][1,5]二硫代甲醇 0.463-溶液(C21H18N2O2S2-0.463CH3OH),通过单晶 X 射线衍射分析进行了表征。该超分子结构在晶体堆积中显示出 π-π 堆积和 S...S 相互作用。在不对称单元中,可以观察到 N 原子的两种几何形状。虽然应该是平面几何,但由于晶体堆积的原因,观察到的是金字塔几何。密度泛函理论(DFT)计算进一步证实了这两种几何形状的存在,计算显示这两种构象之间的电子能量差小于 2 kJ mol-1。