A new method for the preparation of N-acyliminium salts 3a-ab by reaction of nitrilium salts 1 with non-enolizable alkyl and aryl ketones 2 is described. Ketones without electron-releasing substituents react only with N-arylnitrilium salts 1. An X-ray structural analysis was carried out for the N-acyliminium salt 3j. From variable temperature NMR spectroscopy intramolecular conformational changes (essentially rotation around the iminium C=N double bond, coupled to rotation about the amide C-N single bond) of few compounds 3 were determined. The observed barriers to hindered rotation are compared with barriers calculated by the AM1 method.
描述了一种通过
氰镎盐1与非烯醇化烷基和芳基酮2反应制备N-
酰亚胺正离子3a-ab的新方法。不含电子释放取代基的酮仅与N-芳基
氰镎盐1反应。对N-
酰亚胺正离子3j进行了X射线结构分析。通过变温核磁共振光谱,确定了少数化合物3的分子内构象变化(主要是围绕
亚胺C=N双键的旋转,与酰胺C-N单键的旋转耦合)。实验观察到的旋转能垒与
AM1方法计算的能垒进行了比较。