Stereochemistry of hexachlorocyclopentadiene [4+2]-cycloaddition to 2-substituted 4,7-dihydro-1,3-dioxepins
作者:Roman S. Pavelyev、Ruzalia M. Vafina、Olga A. Lodochnikova、Albina S. Galiullina、Ekaterina I. Romanova、Konstantin V. Balakin、Yurii G. Shtyrlin
DOI:10.1016/j.tetlet.2016.07.023
日期:2016.8
Experimental investigation of hexachlorocyclopentadiene [4+2]-cycloaddition to 2-substituted 4,7-dihydro-1,3-dioxepins revealed an atypical stereochemical effect. Clear experimental evidence was obtained that more bulky C2 substituents favour the thermodynamically and sterically less favourable endo-isomers. The possible reasons for such behaviour are secondary interactions of the highest occupied
六氯环戊二烯[4 + 2]-环加成2-取代的4,7-二氢-1,3-二氧杂环丁烷的实验研究显示出非典型的立体化学作用。获得明确的实验证据,即更大的C 2取代基有利于热力学和空间上较不利的内异构体。发生这种行为的可能原因是内态跃迁状态下最高占据轨道和最低未占据轨道的二次相互作用。环加成,非对映异构溶剂化和进攻性二烯试剂与乙缩醛氧的配位。反应立体选择性还取决于溶剂性质和反应温度。我们还发现,微波辐射显着影响[4 + 2]-环加成的收率和立体化学,尽管其潜在影响的性质仍不清楚。