Axially Chiral Cyclic Phosphoric Acid Enabled Enantioselective Sequential Additions

Efficient axially chiral cyclic phosphoric acid catalyzed enantioselective sequential additions of 2-aryl-3H-indol-3-ones, aldehydes, and diethyl 2-aminomalonate have been developed, and a new type of nitrogen-containing heterocyclic compounds, 2,3-dihydro-1H-imidazo[1,5-c]indol-9(9aH)-one derivatives, were prepared in good yields and excellent ee values with a wide functional group tolerance, in which the reactivity and enantioselectivity of the substrates were enabled by our newly developed axially chiral cyclic phosphoric acid, (R)-CYC-9-CPA. Furthermore, the corresponding 1H-imidazo[1,5-a]indol-9(9aH)-ones were constructed through the easy oxidation of 2,3-dihydro-1H-imidazo[1,5-a]indol-9(9aH)-one derivatives.