C2-Axis Chiral 10,10'-Bibenzoquinoline Ligands Specifically Partnered with AgOTf Enable Catalytic Enantioselective Cyclopropanations of Diazo Carbonates.

A new kind of (R)-10,10'-bibenzoquinoline (R-BBQ) ligands with C2-axis chirality and super-conjugated aromatic rings were rationally devised, and concisely and efficiently prepared in two steps by the classic Combes quinoline synthesis starting from the commercially available chiral (R)-1,1'-binaphthalene-2,2'-diamine (BINAM). Specifically partnered with AgOTf, the new chiral ligands effectively and enantioselectively catalyzed the cyclopropanations of diazo oxindoles and α-arylidene diazo succinimides with aromatic alkenes in good to excellent enantioselectivities (up to 98%ee) with moderate to excellent yields (up to 89% yield). Our protocol has disclosed the first example of silver-catalyzed highly enantioselective cyclopropanation of diazo carbonates. Compared with other noble metals and chiral ligands, this Ag(I)-BBQ partner is highly stable, cost-effective, facile, and easily available. An emission wavelength of 430 nm with strong intensity and thermally activated delayed fluorescence (TADF) emissions of typical ligand L1 were first observed, which demonstrated the new BBQ ligands may potentially serve as organic light-emitting materials.