Catalytic Organic Reactions on ZnO

The use of ZnO is a topic of continuing interest due to numerous applications in many areas of the chemical industry. In addition, with the development of industrialization, organic chemists have been confronted with a new challenge of finding novel methods in organic synthesis that can reduce and finally eliminate the impact of volatile organic solvents and hazardous toxic chemicals in the environment. Due to this, great efforts have been made by different research groups to achieve the goal of employing catalytic amounts of ZnO in organic transformations. Interesting results have been achieved, such as the use of catalytic amounts of ZnO alone or ZnO in combination with another metal ormetal oxide. In fact, ZnO as a heterogeneous catalyst can be easily separated from the reaction mixture and reused; it is generally not corrosive and does not produce problematic side products. Different classes of organic transformations have been studied and utilized using ZnO. Owing to the great interest in ZnO, reviews can be found on the properties and applications of ZnO, but to the best of our knowledge there is not a reported review on the application of ZnO as a catalyst in organic syntheses and transformations on which the author's group has also contributed significantly. Hence, the present review focuses on fine and specialty chemicals synthesis catalyzed by ZnO. It is out of the scope of this review to cover comprehensively all reactions that have ever been reported in the presence of mixed metals or metal oxides with ZnO.