Photochemical Arylation of Alkenols: Role of Intermediates and Synthetic Significance
作者:Stefano Protti、Daniele Dondi、Maurizio Fagnoni、Angelo Albini
DOI:10.1002/ejoc.200701177
日期:2008.5
the intermediacy of a phenonium ion from the addition of the primarily formed triplet phenyl cation to the alkenol double bond. Intramolecular addition of the OH group to form benzyl (aryl) tetrahydrofurans is favored inpolar protic solvents, where hydride shifts to form aryltetrahydropyrans also occur, whereas in ethyl acetate, intermolecular addition of the chloride anion to the phenonium ion takes
环醚的一锅串联合成是通过将光生苯基阳离子添加到羟基烯烃中获得的。因此,通过 4-氯-N,N-二甲基苯胺、-苯甲醚和-苯酚与β-羟基烯烃和2-苄基四氢呋喃与γ-羟基烯烃的辐照制备2-(或3-)苯基取代的四氢呋喃。使用非末端烯烃 [非对映异构 (E)-和 (Z)-3-己烯-1-醇] 反式-2-乙基-3-芳基四氢呋喃衍生物由两种异构体立体选择性地形成。光反应的输出取决于结构和溶剂,并且通过将主要形成的三线态苯基阳离子添加到烯醇双键的苯鎓离子的中介而合理化。OH基团的分子内加成形成苄基(芳基)四氢呋喃在极性质子溶剂中是有利的,其中氢化物转移形成芳基四氢吡喃也发生,而在乙酸乙酯中,氯阴离子与苯鎓离子发生分子间加成。上述反应的机制也在计算数据的基础上进行了讨论。 (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)