Light-Induced Hetero-Diels−Alder Cycloaddition: A Facile and Selective Photoclick Reaction
作者:Selvanathan Arumugam、Vladimir V. Popik
DOI:10.1021/ja200356f
日期:2011.4.13
(k(D-A)∼ 4×10(4) M(-1) s(-1)) to electron-rich polarized olefins in an aqueous solution. The resulting photostable benzo[g]chromans are produced in high to quantitative yield. The unreacted oNQM is rapidly hydrated (k(H2O) ∼145 s(-1)) to regenerate the starting diol. This competition between hydration and cycloaddition makes oNQMs highly selective, since only vinyl ethers and enamines are reactive enough
2-Napthoquinone-3-methides (oNQMs) 由 3-(羟甲基)-2-naphthol 的有效光脱水 (Φ=0.2) 产生,经过简单的杂狄尔斯-阿尔德加成 (k(DA)∼ 4×10(4) M (-1) s(-1)) 到水溶液中的富电子极化烯烃。所得光稳定的苯并[g]色满以高到定量的产率生产。未反应的 oNQM 迅速水合(k(H2O) ∼145 s(-1))以再生起始二醇。水合和环加成之间的这种竞争使 oNQM 具有高度选择性,因为只有乙烯基醚和烯胺的反应性足以在水溶液中形成 Diels-Alder 加合物;与其他类型的烯烃没有观察到环加成反应。为了实现两个底物的光标记或光连接,一个用乙烯基醚部分衍生化,而 3-(羟甲基)-2-萘酚通过适当的接头连接到另一个。光诱导的 Diels-Alder “点击”策略允许形成永久或水解不稳定的连接。这种光点击反应 (k=4×10(4)