Microwave-Assisted Cerium(III)-Promoted Cyclization of Propargyl Amides to Polysubstituted Oxazole Derivatives

Functionalized polysubstituted oxazoles are an important class of five-membered N,O-heterocycles that occur widely in the structure of natural products and fine chemicals. They are also often used as building blocks in the synthesis ofheterocyclic molecules with more complex structures. Therefore, efficient synthetic protocols based on Lewis acid promoted reactions are desirable. In this context, we report that, under microwave irradiation, the CeCl3 center dot 7H(2)O/NaI/I-2 system is cap-able of promoting a 5-exo-dig cyclization of propargyl amides with good functional group tolerance. The microwave reactor also provides a more convenient and safer method for heating the reaction. This methodology represents a straightforward CeCl3 center dot 7H(2)O/NaI/I-2 promoted cyclization using microwave irradiation to accomplish the synthesis of polysubstituted oxazole derivatives.