Efficient Access to Original 6-Substituted 5-Nitro-2,3-dihydro­imidazo[2,1-b]oxazoles

Abstract

A one-pot sequential intramolecular cyclization and Suzuki–Miyaura or Sonogashira reaction under microwave irradiation are reported in the 5-nitro-2,3-dihydroimidazo[2,1-b]oxazole series. The intramolecular cyclization of 1-(2,4-dibromo-5-nitro-1H-imidazol-1-yl)propan-2-ol between the hydroxyethyl group and the bromine atom at the 2-position is carried out first, followed by optimization and generalization of the Suzuki–Miyaura and Sonogashira cross-coupling reactions of the bromine atom at the 4-position. The various boronic acids and alkynyl derivatives used to perform these palladium-catalyzed cross-coupling reactions allowed to substitute the 6-position of 5-nitro-2,3-dihydroimidazo[2,1-b]oxazole compounds.