Bidentate Lewis Acids as Catalysts for the Activation of 1,2-Diazenes in Organic Synthesis

A new concept for the catalysis of the inverse-electron-demand Diels-Alder (IEDDA) reaction of 1,2-diazenes using bidentate Lewis acid was recently reported by our group. The general catalytic principle is based on the simultaneous coordination of the bidentate Lewis acid to the 1,2-diazene moiety, lowering the LUMO to facilitate the cycloaddition step. Extrusion of N-2 regenerates the catalyst and after elimination the aromatic product is obtained. In this account the development of this new catalytic principle is described and put into the general context of Lewis acid catalysis.