Chair-boat interconversions in cyclic seven-membered amides and related structures
作者:Michał W. Majchrzak、Antoni Kotełko、Roman Guryn、Joseph B. Lambert、Stephen M. Wharry
DOI:10.1016/s0040-4020(01)92036-8
日期:1981.1
The transition state to ring reversal has been examined in a series of 7-membered rings related to caprolactam. The structural changes associated with introduction of Me groups, with alteration of the nature of the CN double bond, with ring fusion, or with introduction of a second, nonconjugated N atom perturb the transition state to ring reversal. From 1H and 13C NMR studies, we find that the lactam
在与己内酰胺相关的一系列7元环中,已经研究了向环反转的过渡状态。与引入Me基相关的结构变化,与CN双键性质的变化,与环的融合或与引入的第二个非共轭N原子的干扰使过渡态转变为环反转。从1 H和13 C NMR研究中,我们发现内酰胺键本身倾向于不同于环庚烯中存在的过渡态。除某些例外,观察到的壁垒与TS II一致,在TS II中,环的反转以环的C 5末端的运动开始;或与TS III一致,在TS III中,环的反转以C 3 -C 4的开始粘结扭转。结论与功能和空间变化引起的结构变化是一致的。