Lewis Acid-Catalyzed Benzannulation of Vinyloxiranes with 3‑Formylchromones or 1,4-Quinones for Diversely Functionalized 2‑Hydroxybenzophenones, 1,4-Naphthoquinones, and Anthraquinones

A facile and convenient protocol for the regioselective
construction
of functionalized 2-hydroxybenzophenones is described. This protocol
involves the Sc(OTf)3/BF3·OEt2-catalyzed benzannulation of 2-vinyloxirans with 3-formylchromone,
which involves cascade in situ diene formation, [4 + 2] cycloaddition,
elimination, and ring-opening strategies. Moreover, it provides an
expedited synthetic pathway to access biologically intriguing 1,4-naphthoquinones
and anthraquinones including vitamin K3 and tectoquinone. The synthesized
compounds also hold potential for use as UV filters and show promise
as chemosensors for Cu2+ and Mg2+ ions.