Rapid, quantitative, solvent-free synthesis of medium-ring diaza heterocycles from diketene–acetone adduct and diamines

The synthesis of medium-ring heterocycles remains a challenge largely due to unfavorable energetic factors. We are reporting syntheses of 7–9-member diaza heterocycles that go to completion in 5 min, require no solvents, and are quantitative with the only byproducts being acetone and water. The reaction products could be isolated in pure form by simply placing the mixture under vacuum. The reaction sequence possesses many of the hallmarks of a click reaction.