Direct introduction of OH group to sp^2-carbon on platinum-loaded titanium oxide photocatalyst
Direct introduction of OH group to sp^2-carbon on platinum-loaded titanium oxide photocatalyst
复制标题
负载铂氧化钛光催化剂上sp^2-碳直接引入OH基团
DOI：
10.1007/s11244-014-0261-0
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
H. Yoshida
中科院分区：
文献类型：
--
作者：
H. Yuzawa;H. Yoshida
利用分子氧光催化氧化各种有机化合物作为一种有价值的合成路线已被广泛研究，但由于分子氧中的活性氧物种通常难以控制，其应用仍然受到限制。在这篇简短的综述中，我们描述了两种以H2O分子为羟基来源的光催化氧化反应，即芳环的光催化羟化反应和烯烃的光催化水合反应。在这两个反应中，光生活性氧物种攻击sp2-碳形成反应中间体。在芳环羟化反应中，在保持芳环共轭双键的同时，H原子从中间体上消除。在烯烃水合反应中，H基加到中间体上，形成双键饱和的醇类分子。在前一种情况下，活性氧物种的亲电性主要决定了生成的酚中羟基的取向。另一方面，在后一种情况下，中间自由基物种的热力学稳定性导致活性氧物种优先于末端的sp2-碳，这使得根据反Markovnikov规则提供醇的唯一区域选择性成为可能。
Photocatalytic oxidation of various organic compounds by using molecular oxygen has been broadly investigated as a valuable synthetic route, but the application has been still limited because the active oxygen species from the molecular oxygen are usually difficult to be controlled. In this short review, we describe two kinds of photocatalytic oxygenation with H2O molecule as a source of OH group; i.e., photocatalytic hydroxylation of aromatic ring and photocatalytic hydration of alkene, on Pt/TiO2photocatalyst. In both reactions, a photoformed active oxygen species attacks to the sp2-carbon to form a reaction intermediate. In the aromatic ring hydroxylation, the elimination of the H atom from the intermediate proceeds while the conjugate double bond of the aromatic ring maintains. In the alkene hydration, the addition of the H radical to the intermediate results in forming an alcohols molecule with the saturation of the double bond. In the former case, the electrophilic property of the active oxygen species predominantly determines the orientation of the OH group in the produced phenols. On the other hand, in the latter case, the thermodynamic stability of the intermediate radical species leads the active oxygen species preferentially to the terminal sp2-carbon, which makes it possible to provide the unique regioselectivity of alcohol according to the anti-Markovnikov rule.