Copper-Catalyzed [2 + 3] Cyclization of α‑Hydroxyl Ketones and Arylacetonitriles: Access to Multisubstituted Butenolides and Oxazoles

A copper-catalyzed
[2 + 3] formal cyclization reaction between
α-hydroxyl ketones and arylacetonitriles has been developed.
The reaction outcome was ultimately dependent on the structure of
the α-hydroxy ketones employed. Tertiary α-hydroxy ketones
gave 3,4,5,5-tetrasubstituted butenolides as the sole products, while
secondary α-hydroxy ketones furnished 2,4,5-trisubstituted oxazoles
selectively. This method has many advantages, such as the use of easily
available substrates, broad substrate scope, good functional tolerance,
and milder reaction conditions.