Halo Substituent Effects on Intramolecular Cycloadditions Involving Furanyl Amides
作者:Albert Padwa、Kenneth R. Crawford、Christopher S. Straub、Susan N. Pieniazek、K. N. Houk
DOI:10.1021/jo0602322
日期:2006.7.1
Intramolecular Diels−Alder reactions involving a series of N-alkenyl-substituted furanyl amides were investigated. Stable functionalized oxanorbornenes were formed in high yield upon heating at 80−110 °C. The cycloaddition reactions include several bromo-substituted furanyl amides, and these systems were found to proceed at a much faster rate and in higher yield than without substitution. This effect
涉及一系列N的分子内Diels-Alder反应研究了-烯基取代的呋喃酰胺。在80-110°C加热时,高产率形成稳定的官能化氧杂降冰片烯。环加成反应包括几种溴取代的呋喃酰胺,与未取代的反应相比,发现这些系统以更快的速率和更高的收率进行反应。通过在呋喃环的3或5位掺入卤素可以观察到这种效果,并且这种效果很普遍。已经用量子力学计算研究了卤素取代的呋喃的环加成率增加的原因。这些反应的成功归因于反应放热的增加。这既降低了活化焓,又增加了逆向加成的障碍。呋喃上的卤素取代会增加反应物能量并稳定产品,