Combining Lewis acid and redox catalysis

A transition metal catalyst can be Lewis acidic to some extent, but it’s hard to imagine one with acidity comparable to classical inorganic Lewis acids such as AlCl₃ or FeCl₃. However, it’s easy to imagine the fun that could be had with a catalyst that is both redox active (capable of electron transfer) and highly Lewis acidic.

Given the apparent dearth of such molecules, organic chemists have focused on developing a multitude of dual catalytic reactions that use two distinct, yet chemically compatible, catalysts to mediate reactions that need activation on two fronts. As outstanding as these examples often are, when it comes down to it, they’re simply not that elegant – it’s a workaround.