Copper-Catalyzed C-H Activation for the Synthesis of Benzoxazoles

Significance

An efficient method for the synthesis of functionalized benzoxazoles is reported utilizing copper catalysis under high temperature aerobic conditions. The reactions proceeded with poor to high yields, depending on the nature and position of the phenyl substituent. Generally, para-substituted acetanilides gave higher yields of products than those with meta or ortho substituents. The reaction failed when X = EWG and afforded poor yields or no reaction when R^¹ = alkyl. In contrast, when X = coordinating group such as amide or carbamate, the reaction proceeded very well with fairly high yields and good regioselectivity (seven-substituted benzoxazole products). The substrate scope was reasonably well studied and mechanistic considerations were also included in the paper.