Dynamic Stereochemistry of N-Acyl-9-triptycylamine derivatives.

研究了n -9-三甲环乙酰胺(1)及其n -甲基、n -乙基、n -苄基和n -苯基衍生物的动态立体化学性质。这些化合物是由9-三甲酰基胺烷基化和乙酰化合成的。对所有化合物进行了x射线晶体分析，发现除母体化合物外，所有化合物的氮原子都有明显的锥体化。对于n -乙基化合物，Z-和e -异构体在单晶中存在，而其他化合物在晶体中采用Z-构型。在溶液中，1和n -苯基化合物几乎完全作为酰胺键的Z-异构体存在，而其他化合物则以Z-和e -异构体的平衡混合物存在。在任何化合物中，平衡常数（Z/E）随溶剂极性的增加而增加。用动态核磁共振光谱法研究了酰胺键的旋转。旋转势垒也随着溶剂极性的增加而增加。在低温下，n -乙基和n -苄基化合物的亚甲基质子不相等，表明溶液中氮原子具有锥体性。对Tp-N键的立体位变进行了测量和讨论。

Dynamic stereochemistry of N-9-triptycylacetamide (1) and its N-methyl-, N-ethyl-, N-benzyl-, and N-phenyl derivatives was studied. These compounds were synthesized by alkylation of 9-triptycylamine followed by acetylation. X-Ray crystallographic analysis of all the compounds were made, and revealed that the nitrogen atom is significantly pyramidalized in any compound except for the parent one 1. For the N-ethyl compound, both Z- and E-isomers exist in a single crystal, while the other compounds adopt Z-configuration in crystal. In solution, 1 and the N-phenyl compound exist almost exclusively as the Z-isomer as for the amide bond, while the other compounds exist as an equilibrium mixture of Z- and E-isomers. The equilibrium constant (Z/E) tends to increase with the solvent polarity in any compound. Rotation of the amide bond was studied by dynamic NMR spectroscopy. The barrier to rotation also tends to increase with the solvent polarity. At low temperatures, the methylene protons of the N-ethyl and N-benzyl compounds are nonequivalent to each other, indicating the pyramidality of the nitrogen atom in solution. Stereomutation of the Tp-N bond was measured and discussed.