Enantioselective N‑Heterocyclic Carbene-Catalyzed Synthesis of Spirocyclic Oxindole-benzofuroazepinones

Herein,
we report an enantioselective synthesis of azepinones via
the N-heterocyclic carbene (NHC) catalyzed [3+4]
annulation reaction of isatin-derived enals and aurone-derived azadienes.
The corresponding spirocyclic oxindole-benzofuroazepinones were obtained
in good yields, with excellent diastereo- and enantioselectivities.
The resulted azepinones were evaluated for their in vitro cytotoxic
activities against six human tumor cell lines, with two compounds
showing significant inhibitory activity comparable with that of cisplatin.