Efficient synthesis of bis(indolyl)methanes, bispyrazoles and biscoumarins using 4-sulfophthalic acid

Abstract

4-Sulfophthalic acid (4-H3SPA) solution 50 wt% in H2O has been effectively catalyzed the synthesis of a series of biologically relevant bis(indolyl)methanes by the electrophilic substitution of indole derivatives on aldehyde compounds and 4,4′-(arylmethylene)-bis(3-methyl-1-phenyl-1H-pyrazol-5-ol)s by condensing 5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one with various aldehydes under aqua conditions at room temperature. 3,3′-(Arylmethylene)-bis-4-hydroxycoumarins have also been synthesized in the presence of 0.1 mL (0.262 mmol) of 4-H3SPA solution 50 wt% in H2O at 80 °C. The procedure is simple and the expected bis-heterocyclic compounds were isolated in good to excellent yields. The present protocol provides the benefits of convenience, mild reaction conditions, eco-friendliness, and no use of hazardous organic solvents.