Exploring the In Situ Formation Mechanism of Polymeric Aluminum Chloride-Silica Gel Composites under Mechanical Grinding Conditions: As a High-Performance Nanocatalyst for the Synthesis of Xanthene and Pyrimidinone Compounds

The use of mechanical ball milling to facilitate the synthesis of organic compounds has attracted intense interest from organic chemists. Herein, we report a new process for the preparation of xanthene and pyrimidinone compounds by a onepot method using polymeric aluminum chloride (PAC), silica gel, and reaction raw materials under mechanical grinding conditions. During the grinding process, polymeric aluminum chloride and silica gel were reconstituted in situ to obtain a new composite catalyst (PAC-silica gel). This catalyst has good stability (six cycles) and wide applicability (22 substrates). The Al-O-Si active center formed by in situ grinding recombination was revealed to be the key to the effective catalytic performance of the PAC-silica gel composites by the comprehensive analysis of the catalytic materials before and after use. In addition, the mechanism of action of the catalyst was verified using density functional theory, and the synthetic pathway of the xanthene compound was reasonably speculated with the experimental data. Mechanical ball milling serves two purposes in this process: not only to induce the self-assembly of silica and PAC into new composites but also to act as a driving force for the catalytic reaction to take place. From a practical point of view, this one-pot catalytic method eliminates the need for a complex preparation process for catalytic materials. This is a successful example of the application of mechanochemistry in materials and organic synthesis, offering unlimited possibilities for the application of inorganic polymer materials in green synthesis and catalysis promoted by mechanochemistry.

Automated summary

This article reports a new method for the preparation of xanthene and pyrimidinone compounds by a one-pot method using polymeric aluminum chloride (PAC) and silica gel under mechanical grinding conditions. The reconstitution of PAC and silica gel during the grinding process leads to the formation of a new composite catalyst (PAC-silica gel), which exhibits good stability and wide applicability. The formation of the Al-O-Si active center through in situ grinding recombination is revealed to be the key to the effective catalytic performance of the PAC-silica gel composites. Mechanical ball milling serves as both a self-assembly inducer and a driving force for the catalytic reaction. This one-pot catalytic method eliminates the need for complex preparation processes for catalytic materials and shows the successful application of mechanochemistry in materials and organic synthesis.