α-单取代环十二酮构象间相互转换的理论研究

在CVFF力场下,DMSO氛围中,通过分子动力学常温模拟研究α-单取代环十二酮的构象,常温优势构象为α-边外取代3333]-2-酮,环骨架为3333],羰基位于C2位置,取代基位于α-边外向位.动态分析带有不同取代基的α角顺取代和α-边外取代3333]-2-酮构象的相互转化的结果表明,它们的转换路径基本一致,转换能垒随着取代基体积的增大而升高.氯和溴取代环十二酮转换过程中最高能垒分别为43.9和44.3kJ/mol,相应的构象为α-边外取代31233]-2-酮;甲基、乙基和叔丁基取代环十二酮最高转换能垒达53.9kJ/mol,相应的构象为α-边外取代31233]-2-酮;存在活泼质子的氨基和羟基环十二酮转换能垒中最高能量构象为α-边外取代31323]-1-酮;苯硫基和苄基取代环十二酮除出现α-边外取代3333]-2-酮构象外,转换过程中还出现了较α-角顺取代3333]-2-酮构象更稳定的α-边外取代4233]-3-酮构象.

Theoretical Study on the Interconversion of α-Monosubstituted Cyclododecanone Conformations

Under the CVFF force field and in DMSO, the conformations of α-monosubstituted cyclododecanones were studied by molecular dynamics at room temperature. The results show that the ring skeleton of the preferred conformation is 3333], with the carbonyl group being present in the C2 position, which is consistent with the experimental results. The interconversion between α-corner-syn-3333]-2-one and α-side-exo-3333]-2-one was analyzed by using dynamics mimesis method. The calculated results show that their interconversion paths are consistent basically, the preferred conformation is α-side-exo-3333]-2-one and the interconversion energy barrier is increased along with the increase of the volume augmentation of the substituent groups. For α-chloro- and bromo-cyclododecanones, the maximum barriers are 43.9 and 44.3 kJ/mol, respectively, and the corresponding conformation is α-side-exo-31233]-2-one. For α-alkylcyclododecanones, the maximum barrier is as high as 53.9 kJ/mol, and the corresponding conformation is α-side-exo-31233]-2-one. While α-amino- and hydroxy-cyclododecacones, the conformation of the maximum energy is α-side-exo-31323]-1-one, and α-phenylthio- and benzyl-cyclododecanones, apart from {α-side-}exo-3333]-2-one conformation, the another stable conformation is α-side-exo-4233]-3-one instead of α-corner-syn-3333]-2-one.