An Efficient Solvent-Free Synthesis of Spirooxindole-quinazolinediones using TiO2/SiO2 Nanocomposite Catalyst

In the last decade, spirooxindoles has been identified as an important class of nitrogen containing heterocycles, which display wide range of biological properties such asantimalarial, antituberculosis, and growth hormone secretagogue [1]. Nanostructured metal oxides based their high physical and chemical abilities promote numerous organic transformations [2]. Nano titanium dioxide (TiO2 NPs) is considered very close to an ideal of these highly efficient nanocatalysts due to its unique properties such as being non-toxic, inexpensive, moisture stable and reusable catalyst [3]. In addition, TiO2 NPs over silica shells (TiO2-SiO2 nanocomposite) with improved the catalytic efficiency of TiO2 NPs by an increase in the specific surface area, has been thought to be a new efficient catalyst. In the present study, I designed a new simple One-Pot three-component reaction of 1H-indole-2,3-diones (isatins) 1, dimedone (2) and urea (3) to afford spiro[4.3 ]oxindole-3,4,7,8-tetrahydro-7,7- dimethylquinazoline-2,5-(1H,6H)-diones 4, which was catalyzed by TiO2/SiO2 nanocomposite, under solvent-free conditions. This method in addition to its simplicity of operation has the advantages of high yields, easy work-up with avoidance of using harmful organic solvents, and recyclability of the catalyst.