Ligandless Microwave-Assisted Pd/Cu-Catalyzed Direct Arylation of Oxazoles

An efficient microwave-assisted palladium/copper co-mediated direct arylation of oxazoles with aryl bromides under ligandless conditions has been developed. The method is functional group tolerant and provides rapid access to medicinally relevant compounds in good yields. Coupled to the van Leusen oxazole ring synthesis, this methodology is illustrated by an expedient two-step synthesis of the four 2,5-diaryloxazole alkaloids texamine, texaline, balsoxin, and O-Me-halfordinol from commercially available starting materials.