Department of Chemistry, 1102 Natural Sciences II, University of California, Irvine, California 92697-2025, USA.
J Org Chem. 2013 Apr 19;78(8):4090-8. doi: 10.1021/jo4004025. Epub 2013 Mar 11.
Quantum mechanical calculations have been used to investigate type 2 intramolecular N-acylnitroso Diels-Alder reactions. Experimentally observed regioselectivities and diastereoselectivities of these reactions have been reproduced using B3LYP/6-31+G(d) DFT calculations. The factors that govern selectivity (i.e., tether length, tether substitution and diene substitution) were systematically investigated. Tethers less than 6 carbon atoms lead to 1,3-regioisomers due to conformational restrictions. Substituents on the tether lead to diastereoselective outcomes dictated by transannular interactions in the transition states. The modest diastereoselectivity of diene-substituted substrates is rationalized as arising from reduction of eclipsing interactions in the flattened diene transition states. This method should prove valuable for planning syntheses involving type 2 intramolecular Diels-Alder reactions.
量子力学计算已被用于研究 2 型分子内 N-酰基硝酮 Diels-Alder 反应。使用 B3LYP/6-31+G(d)DFT 计算重现了这些反应的实验观察到的区域选择性和立体选择性。系统研究了控制选择性的因素（即，连接体长度、连接体取代和二烯取代）。由于构象限制，小于 6 个碳原子的连接体导致 1,3-区域异构体。连接体上的取代基导致由过渡态中环烷相互作用决定的立体选择性结果。二烯取代底物的适度立体选择性可以合理地解释为在扁平化的二烯过渡态中减少了重叠相互作用。该方法对于规划涉及 2 型分子内 Diels-Alder 反应的合成应该是有价值的。
