Small and medium-sized bridgehead bicyclic lactams: A systematic ab initio molecular orbital study
Small and medium-sized bridgehead bicyclic lactams: A systematic ab initio molecular orbital study
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DOI：
10.1021/ja960294h
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发表时间：
1996-09-11
影响因子：
15
通讯作者：
DuBois, TD
中科院分区：
文献类型：
--
作者：
Greenberg, A;Moore, DT;DuBois, TD
对从 2.2.2 到 4.3.3 系列的九种桥头双环内酰胺的从头算优化分子轨道计算表明，结构特性、共振能量、质子亲和力和核心轨道电离能的变化反映了反式环烯的类比。较小的内酰胺被计算为 N-质子化，较大的 O-质子化，并且预计“交叉”发生在 3.3.1 系统周围。根据共振能量，较大的桥头双环内酰胺可以被认为是超稳定的，因为 Schleyer 和同事定义了较大桥头烯烃的概念。这种超稳定性在内酰胺的亲核取代反应（例如水解）的动力学中应该是明显的，但在这些反应的热化学中并不明显。
Optimized ab initio molecular orbital calculations on nine bridgehead bicyclic lactams ranging from the 2.2.2 to the 4.3.3 series indicate variations in structural properties, resonance energies, proton affinities, and core orbital ionization energies that reflect the trans-cycloalkene analogy. The smaller lactams are calculated to be N-protonated, the larger O-protonated, and the ''crossover'' is predicted to occur around the 3.3.1 system. On the basis of resonance energies, larger bridgehead bicyclic lactams could be considered to be hyperstable as Schleyer and co-workers define the concept for larger bridgehead alkenes. This, hyperstability should be apparent in the kinetics of the nucleophilic substitution reactions of the lactams, such as hydrolysis, but not in the thermochemistry of these reactions.