Diversely Substituted Imidazo[1,2-a]pyrazine-8-oxo-3-carbaldehydes: An Iodine-Mediated Cyclization/Oxidation Approach

A mild and efficient iodine-mediated intramolecular heteroannulation approach for the construction of the imidazo[1,2-a]pyrazinone core has been developed. Under ambient conditions, this metal-free protocol allows easy access to densely functionalized imidazo[1,2-a]pyrazinone-3-carbaldehydes or (aminomethyl)imidazo[1,2-a]pyrazinones from substrates containing terminal alkynes by cyclization and subsequent oxidation or amination. Further diversification may be introduced by using substrates containing an internal alkyne and/or Suzuki coupling after cyclization to generate polysubstituted (dihydro)imidazo[1,2-a]pyrazinones.