Palladium-Catalyzed Direct Alkenylation of 2‑Oxazolones: An Entry to 3,4,5-Trisubstituted 2‑Oxazolones

Described herein is a novel method
for the synthesis of 3,4,5-trisubstituted
2-oxazolones featuring the first Pd-catalyzed dehydrogenative alkenylation
of 2-oxazolones, which is realized by employing 10 mol % of Pd­(OAc)2 as the catalyst and the use of readily available Cu­(OAc)2 as the oxidant. A wide range of functional groups, such as
F, Cl, Br, OMe, ester, ketone, amide, alkyl, and aryl substituents,
are found to be compatible under the reaction conditions. The utilization
of the C–H functionalization strategy provides a straightforward,
convenient, and highly atom-economical approach for the construction
of 3,4,5-trisubstituted 2-oxazolones. It is worth noting that the
4-alkenyl 2-oxazolones can be smoothly converted into naphtho­[1,2-d]­oxazol-2-ones via a photochemical transformation.