The homogeneous titanium- and dye-catalyzed as well as the heterogeneous semiconductor particle-catalyzed photohydroxymethylation of ketones by methanol were investigated in order to evaluate the most active photocatalyst system. Dialkoxytitanium dichlorides are the most efficient species for chemoselective hydroxymethylation of acetophenone as well as other aromatic and aliphatic ketones. Pinacol coupling is the dominant process for semiconductor catalysis and ketone reduction dominates the Ti(OiPr)4/methanol or isopropanol systems. Application of dilution effects on the TiO2 catalysis leads to an increase in hydroxymethylation at the expense of the pinacol coupling.
通过
甲醇进行的均相
钛和
染料催化以及非均相半导体颗粒催化的
酮类光羟甲基化反应进行了研究,以评估最活跃的光催化剂体系。二烷氧基
钛二
氯化物是对
苯乙酮以及其他芳香族和脂肪族
酮类进行
化学选择性羟甲基化的最有效物种。对于半导体催化来说,邻苯二醇偶联是主要过程,而
酮类还原主导着Ti(OiPr)
4/
甲醇或
异丙醇体系。在TiO
2催化中应用稀释效应会导致羟甲基化增加,而邻苯二醇偶联减少。