Oxazole as an Electron-Deficient Diene in the Diels–Alder Reaction

Abstract

The Diels-Alder cycloaddition reaction of oxazole with ethylene is facilitated by addition of an alkyl group or Brønsted or Lewis acids to the oxazole nitrogen atom. The efficacy consists of stabilizing the transition state, lowering the activation barrier and the HOMO(dienophile)-LUMO(diene) gap, and increasing the reaction exothermicity.