Expedient Metal-Free Synthesis of 1,3-Oxazinen-4-ones

1,3-Oxazinen-4-ones are medicinally important scaffolds which have traditionally been accessed using a hetero-Diels–Alder approach or more recently using a cobalt-catalyzed three-component cycloaddition. Herein we report a novel strategy to access this scaffold which allows for the rapid and high yielding synthesis of 1,3-oxazinen-4-ones under ambient temperature and pressures with improved substrate scope.