Amine-Catalyzed Asymmetric (3 + 3) Annulations of β′-Acetoxy Allenoates: Enantioselective Synthesis of 4H‑Pyrans

The asymmetric (3 + 3) annulations of β′-acetoxy allenoates with either 3-oxo-nitriles or pyrazolones have been realized by using 6′-deoxy-6′-[(l)-N,N-(2,2′-oxidiethyl)-valine amido]­quinine (6h) as the catalyst. The three functions of catalyst 6h, including Lewis base (quinuclidine N), H-bond donor (amide NH), and Brønsted base (morpholine N), cooperatively take crucial roles on the chemo- and enantioselectivity, allowing for the construction of 4H-pyran and 4H-pyrano­[2,3-c]­pyrazole in high yields and enantioselectivity.