An Efficient Synthetic Access to Substituted Thiazolyl-pyrazolyl-chromene-2-ones from Dehydroacetic Acid and Coumarin Derivatives by a Multicomponent Approach

Two new series of pyran-or coumarin-substituted thiazolyl-pyrazole-chromen-2-one derivatives 10a-10d and 11a-11d were efficiently synthesized under environmentally friendly reaction conditions through a convenient one-pot multicomponent reaction of a heterocyclic bromoacetyl derivative 3 or 4 with thiosemicarbazide and a substituted 3-(acetoacetyl)coumarin derivative 5a-5d in anhydrous ethanol. The reaction proceeds through Hantzsch thiazole and Knorr pyrazole syntheses in refluxing ethanol. The key features of this approach are its operational simplicity, the quick access to the desired products, and the good to excellent yields. The structures of the newly synthesized compounds were established by IR spectroscopy, H-1, C-13, and 2D NMR spectroscopy, and mass spectrometry.