Catalytic Atroposelective Synthesis of C–N Axially Chiral Pyrazolyl Pyrroles via De Novo Construction of a Pyrrole Ring

The catalytic atroposelective synthesis of five-five-membered C-N axially chiral heterobiaryls featuring the de novo construction of a pyrrole ring was reported. This chiral phosphoric-acid-catalyzed asymmetric Paal-Knorr reaction of 5-aminopyrazoles with 1,4-diketones delivered C-N axially chiral pyrazolyl pyrroles in good yields (up to 96%) with excellent enantioselectivities (up to 97% ee). This work establishes an efficient strategy for constructing five-five-membered C-N axially chiral pyrazole scaffolds and enriches the family of C-N axially chiral molecules.