Potassium Carbonate–Mediated Efficient and Convenient Synthesis of 3-Methyl-1-phenylchromeno[4,3-c]pyrazol-4(1H)-ones

Abstract

Unprecedented cyclization was observed during N-sulfonylation of 3-[1-(phenylhydrazono)-ethyl]-chromen-2-one in pyridine, affording 3-methyl-1-phenylchromeno[4,3-c]pyrazol-4(1H)-ones. To avoid use of noxious pyridine, reaction was tried in different basic conditions and the best results were obtained with potassium carbonate in acetone. A wide range of substrates bearing either electron-donating or electron-withdrawing substituents on phenylhydrazine ring were compatible with the developed methodology. Rapid access of starting material, 3-acetylcoumarin, excellent yields of products, and use of environmentally benign base and solvent for the cyclization make this strategy an efficient and convenient method for synthesis of 3-methyl-1-phenylchromeno[4,3-c]pyrazol-4(1H)-ones.

GRAPHICAL ABSTRACT

Keywords:

• Acetone
• 3-methyl-1-phenylchromeno[4,3-c]pyrazol-4(1H)-ones
• potassium carbonate

Notes

^a The reactions were carried out with 2a (0.72 mmol) and base (0.72 mmol) at 50 °C for 24 h.

^b 2 equiv were used.

^c Desired products were not formed.

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