Development of Novel Catalysts for Continuous Flow Synthesis

Currently, flow chemistry attracts much attention in academia and industry. We are interested in continuous flow synthesis with heterogeneous catalysts. To construct efficient flow reactors, preparation of active heterogeneous catalysts is one of the most important tasks. In general, heterogeneous catalysts have lower reactivity and selectivity compared with homogeneous catalysts. We designed active heterogeneous catalysts for continuous flow synthesis. Here, we describe development of polysilane-supported palladium/alumina hybrid catalysts and hydrogenation reactions under continuous flow conditions. These systems produced that the desired hydrogenation products in high yields with high selectivities without palladium leaching. We also developed PS-Pybox-calcium chloride catalyst system and applied it to asymmetric 1,4-addition reactions under continuous flow conditions. The substrate scope of these reactions is broad, and higher TON than batch systems has been attained. This is the first example using chiral calcium chloride as a catalyst in continuous flow synthesis.