可多重N-羟甲基化的Mannich反应机理研究

用MNDO法全优化了20多个Mannich反应中间体-N-羟甲基胺和亚甲胺碳正离子的平衡几何构型, 计算了它们的电子结构。根据N-羟甲基胺脱水反应的能量变化(△E)、亚甲胺碳正离子的净电荷(Q~C~+)和几何构型, 分类讨论比较了N-羟甲胺脱水的难易、亚甲胺碳正离子的稳定性以及对反应历程的影响。以脲素、甲醛和硝仿之间的mannich反应为例, 建议在可多重N-羟甲基化情形下Mannich反应的机理。此外还对硝基脲的N-羟甲基胺及其亚甲胺碳正离子进行了计算研究。

Study on mechanism of mannich reaction in a case of multiple N-Hydroxymethylation

The equilibrium geometries and electronic structures of >20 intermediates of the Mannich reaction, N-hydroxymethyl amines and methylene amine carbenium ions, have been optimized and calculated by the MNDO method. The feasibility of elimination of water, the stability of methylene amine carbenium ions, and the effect on the mechanism of the Mannich reaction are discussed. The mechanism of Mannich reactions of OC(NH2)2, HCHO, and HO(NO2)3 was suggested as a example of multiple N-hydroxymethylation. The N-hydroxymethyl amines and corresponding methylene amine carbenium ions for nitrourea have been also calculated and discussed.