Syntheses, Thermal Reactivities, and Computational Studies of Aryl-Fused Quinoxalenediynes: Effect of Extended Benzannelation on Bergman Cyclization Energetics
作者:John D. Spence、Andro C. Rios、Megan A. Frost、Claire M. McCutcheon、Christopher D. Cox、Sonia Chavez、Ramiro Fernandez、Benjamin F. Gherman
DOI:10.1021/jo302009c
日期:2012.11.16
2-diethynylbenzene. Strong exotherms indicative of enediyne cyclization were observed by differential scanning calorimetry, while solution cyclizations in the presence of 1,4-cyclohexadiene confirmed C1–C6 Bergman cyclization. To provide further insight into Bergman cyclization energetics, computational studies were performed to compare changes in the cyclization enthalpy barrier, reaction enthalpy, and barrier
通过亚胺缩合策略合成了一系列[ b ]稠合的6,7-二乙炔基喹喔啉衍生物,以研究延长的苯甲酰化对烯二炔热反应性的影响。相对于1,2-二乙炔基苯,高共轭喹喔啉二炔的吸收和发射光谱发生红移约100-200 nm。通过差示扫描量热法观察到指示烯二炔环化的强烈放热,而在1,4-环己二烯存在下的溶液环化证实了C 1 –C 6Bergman环化。为了进一步了解Bergman环化能,我们进行了计算研究,以比较环化焓屏障,反应焓和Retro-Bergman开环屏障的变化。苯甲酰化从1,2-二乙炔基苯延伸至2,3-二乙炔基萘或6,7-二乙炔基喹喔啉对环化屏障的影响极小。相比之下,线性延伸的苯甲酰化反应增加了环化的焓,从而减少了对后伯格曼开环的障碍。另外,发现延长的苯甲酰化的取向对环化吸热性具有显着影响。特别是,与6相比,5,6-二乙炔基喹喔啉的环化焓降低了6.9 kcal / mol。