Additive-Free Commercial Alumina Catalyzes the Halogen Exchange Reaction of Long Alkyl Halides in Batch and in Flow Processes.

The synthesis of alkyl halides can be performed by simply halide exchange reactions between two different alkyl halides, catalyzed by aluminosilicates. Here, we show that commercially available alumina shows a superior catalytic activity for the halogen exchange reaction between long alkyl halides (more than 6 carbons), including fluorides, in either batch or flow modes. The catalytic activity of the solid alumina is modulated by alkaline countercations on the surface, and sodium-supported alumina shows the optimal performance for the iodo-bromo and iodo-fluoro exchange under inflow reaction conditions, after >24 h reaction time, without any external additive.