Synthesis of 2-oxazolones
A palladium-catalyzed coupling of N-alkynyl tert-butyloxycarbamates with aryl halides and related electrophiles via an oxidative addition followed by oxypalladation/reductive elimination provides a convenient access to diversely substituted oxazolones in satisfactory yields and shows good functional group compatibility.
Z. Lu, W. Cui, S. Xia, Y. Bai, F. Luo, G. Zhu, J. Org. Chem., 2012, 77, 9871-9877.
A mild, rapid, and efficient Pd(PPh3)4-catalyzed intramolecular cyclization of N-alkynyl alkyloxycarbamates with CuCl2 or CuBr2 provides 4-halo-oxazolones with good functional group tolerance. 4-halo-oxazolones can serve as precursors for Pd-catalyzed cross-coupling reactions.
H. Huang, G. He, G. Zhu, X. Zhu, S. Qiu, H. Zhu, J. Org. Chem., 2015, 80, 3480-3487.
General and efficient methods allow the synthesis of 2-oxazolones and α-aminoketones from β,β-dibromoenamides depending on the choice of R groups and the reaction conditions. On the basis of mechanistic studies, both reactions proceed via an intermolecular Suzuki-Miyaura C-C coupling and an intramolecular C-O coupling.
D. I. Chai, L. Hoffmeister, M. Lautens, Org. Lett., 2011, 13, 106-109.