1 research outputs found
Synthesis of 2‑Phenyl-4,5-Substituted Oxazoles by Copper-Catalyzed Intramolecular Cyclization of Functionalized Enamides
An efficient two-step synthesis of 2-phenyl-4,5-substituted
oxazoles
involving intramolecular copper-catalyzed cyclization of highly functionalized
novel β-(methylthio)Âenamides as the key step has been reported.
These enamides are obtained by nucleophilic ring-opening of newly
synthesized 4-[(methylthio)ÂheteroÂ(aryl)Âmethylene]-2-phenyl-5-oxazolone
precursors by alkoxides, amines, amino acid esters and aryl/alkyl
Grignard reagents, thus leading to the introduction of an ester, N-substituted
carboxamide or acyl functionalities at 4-position of the product oxazoles.
Synthesis of two naturally occurring 2,5-diaryloxazoles, i.e., texamine
and uguenenazole, via two-step hydrolysis–decarboxylation of
the corresponding 2,5-diaryloxazole-4-carboxylates has also been described.
Similarly, three of the serine-derived oxazole-4-carboxamides were
elaborated to novel trisubstituted 4,2′-bisoxazoles through
DAST/DBU-mediated cyclodehydration–dehydrohalogenation sequence.
The present protocol is complementary and an improvement to our previously
reported silver carbonate-induced cyclization of β-bisÂ(methylthio)Âenamides
to 2-phenyl-5-(methylthio)-4-substituted oxazoles