Syntheses of 4,5-Disubstituted Oxazoles via Regioselective C-4 Bromination

A scaleable and highly regioselective C-4 bromination of 5-substituted oxazoles is described. The use of DMF as solvent played a critical role in significantly improving the C-4/C-2 bromination ratio. The resulting 4-bromooxazoles were shown to be good Suzuki–Miyaura coupling partners with arylboronic acids. Furthermore, a simple and convenient method that employs triethylamine efficiently purged residual levels of palladium and iron to less than 10 ppm.