Synthesis of 2,5-Bis(hetero)aryl 4′-Substituted 4,5′-Bisoxazoles via Copper(I)-Catalyzed Domino Reactions of Activated Methylene Isocyanides with 2-Phenyl- and 2-(2-Thienyl)-4-[(aryl/heteroaryl)(methylthio)methylene]oxazol-5(4H)-ones

Abstract

An efficient straightforward synthesis of 2,5,4'-trisubstituted 4,5'-bisoxazoles via copper(I)-catalyzed domino reactions of 2-phenyl- and 2-(2-thienyl)-4-[(aryl/heteroaryl)methylene]-5-oxazolones with activated methylene isocyanides has been reported. The overall domino process comprised of formation of one C-C and two C-O bonds involves initial nucleophilic ring opening of oxazolones by cupriomethylene isocyanides followed by sequential construction of two oxazole rings in the presence of copper catalyst. The broad substrate scope and excellent functional group compatibility of the reaction has been demonstrated by employing a variety of heteroaryl- and aryl-substituted oxazolones and activated methylene isocyanides, yielding bisoxazoles with three potential points of diversity. A probable mechanism for this novel copper-catalyzed domino process has been proposed.