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.