H₃PW₁₂O₄₀ catalyzed new and multicomponent one-pot synthesis of 6-benzo[a]phenazin-5-ol derivatives of highly functionalized oxazoles via Robinson-Gabriel-type reaction

A facile and efficient procedure is developed for H3PW12O40 catalyzed new and one-pot synthesis of highly functionalized oxazoles linked to benzo[a]phenazin derivatives using phenylenediamine derivatives, 2-hydroxy-1,4-naphthoquinone, arylglyoxals and acetonitrile via a multicomponent tandem cyclization Robinson-Gabriel reaction in a very short time and easy workup without any byproduct. Acetonitrile served not only as a solvent but also as the substrate in the reaction.