Regioselective hydroxylation of phenols by simultaneous photochemical generation of phenol cation-radical and hydroxyl radical
作者:Daniel Collado、Ezequiel Perez-Inestrosa、Rafael Suau、Juan T. Lopez Navarrete
DOI:10.1016/j.tet.2006.01.003
日期:2006.3
Substituted phenols having pendant isoquinoline N-oxide were synthesized and their photochemical and luminiscent properties studied. Photolysis in an acid medium was found to yield the related photohydroxylation products, in a regioselective process, in addition to the isoquinoline deoxygenated precursor. Photoinduced electron transfer from the donor phenols to the protonated form of the first excited
合成了具有N-氧化异喹啉侧基的取代酚,并研究了它们的光化学和发光特性。除了在异喹啉脱氧的前体之外,在区域选择性过程中,发现在酸性介质中的光解还产生相关的光羟基化产物。从供体苯酚到侧链异喹啉N的第一激发单重态(S 1)的质子化形式的光诱导电子转移充当受体的氧化物会导致红移发射电荷转移(CT)状态,实际上是自由基/阳离子-自由基对。N–OH键的均相还原会还原芳香族异喹啉核,并产生一个羟基自由基,该自由基可与酚阳离子自由基中所需的环碳偶合,从而在由酚阳离子的自旋密度控制的区域选择性过程中产生光羟基化产物激进的。这些光羟基化过程可有效地与酚阳离子自由基中去质子化的趋势进行竞争。光羟基化过程本身及其区域选择性不包括质子偶联的电子转移机理或连续的电子转移/去质子化反应。相比之下,