Planar Chiral Phosphoric Acids with Biphenylene-Tethered Paracyclophane Scaffolds: Synthesis, Characterization, and Catalytic Screening

Phosphoric acids with planar chiral
paracyclophane scaffolds have
been prepared in optically pure form starting from 1,8-dibromobiphenylene,
by means of a chiral phosphorodiamidate as the phosphorylating agent.
Structural characterization and configurational assignment have been
performed by X-ray diffraction studies. The acids promote the organocatalytic
enantioselective H-transfer reduction of α-arylquinolines with
up to 90% enantiomeric excess.