An efficient synthesis of a variety of 2,5-diaryloxazole derivatives via a rhodium-catalyzed annulation of triazoles and aldehydes is achieved. Various oxazole derivatives could be obtained in good to excellent yields. A concise synthesis of antimycobaterial natural products balsoxin and texamine has been achieved using this method.
Ligandless Microwave-Assisted Pd/Cu-Catalyzed Direct Arylation of Oxazoles
作者:François Besselièvre、Florence Mahuteau-Betzer、David S. Grierson、Sandrine Piguel
DOI:10.1021/jo7027135
日期:2008.4.1
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.
C-H Bond Activation: A Versatile Protocol for the Direct Arylation and Alkenylation of Oxazoles
The versatile palladium complex Pd(PPh3)4 catalyses both direct arylation and alkenylation of oxazoles efficiently. The method is regioselective and stereospecific with respect to bromoalkenes and tolerates a wide range of functional groups.