2-Hydroxy-5-sulfobenzoic acid: an efficient organocatalyst for the three-component synthesis of 1-amidoalkyl-2-naphthols and 3,4-disubstituted isoxazol-5(4H)-ones

Abstract

2-Hydroxy-5-sulfobenzoic acid (2-HSBA) efficiently catalyzed the one-pot three-component synthesis of a wide variety of 1-amidoalkyl-2-naphthols and 3,4-disubstituted isoxazol-5(4H)-ones. The three-component process of substituted benzaldehydes, 2-naphthol, and amides (benzamide and acetamide) or urea occur using 10 mol% of 2-HSBA as an organocatalyst under solvent-free reaction conditions (SFRCs) at 100 °C. It was also found that the best results for the preparation of 3,4-disubstituted isoxazol-5(4H)-ones were achieved using 15 mol% of 2-HSBA under aqueous conditions at room temperature. The reactions are easy to do and were completed within 3–25 min (for amidoalkyl naphthols), and 70–120 min (for 3,4-disubstituted isoxazol-5(4H)-ones), while the expected products were obtained in 82–97 % yields. The catalyst can be recovered and reused several times in the template reactions. This procedure offers the advantages of convenience, simple operational procedure, cost-effectiveness, no use of hazardous organic solvents, and the commercial availability of the catalyst.