Preparation of Axially Chiral 2,2'-Biimidazole Ligands through Remote Chirality Delivery and Their Application in Asymmetric Carbene Insertion into N-H of Carbazoles.

Axially chiral biimidazole ligands have been rarely synthesized and studied, in contrast to the significant achievements in the synthesis and application of central chiral imidazole ligands. Herein, a series of novel axially chiral 2,2'-biimidazole ligands were synthesized from the reaction of 2,2'-bis(bromomethyl)-1,1'-binaphthalene and 2,2'-biimidazole in one step through the strategy of remote chirality delivery. These ligands have been proven to be efficient for Cu- or Fe-catalyzed asymmetric insertion of α-aryl-α-diazoacetates into the N-H bond of carbazoles with up to 96% ee.