ol7b00658_si_002.cif (124.44 kB)

Enantioselective Synthesis of 4H‑Pyran via Amine-Catalyzed Formal (3 + 3) Annulation of δ‑Acetoxy Allenoate

Download (124.44 kB)
posted on 27.03.2017, 13:49 by Weiping Zhou, Chunjie Ni, Jiangfei Chen, Dong Wang, Xiaofeng Tong
The formal (3 + 3) annulations of δ-acetoxy allenoates and 1C,3O-bisnucleophiles are reported with the use of 6′-deoxy-6′-perfluoro­benzamido-quinine (4g) as a catalyst, which provide rapid access to 4H-pyrans with excellent enantioselectivity. The reaction features a wide reaction scope and mild reaction conditions. The crucial roles of amide NH of 4g as a H-bond donor have also been elucidated, which not only activates allenoate to facilitate formation of cationic intermediate A but also enhances the electrophilicity of its δ-position for nucleophilic 1,6-addition.