Amberlyst-15® in PEG-400: Green Synthesis of 3-Benzoyl-5-Hydroxy Benzofuran and Naphtho[1,2-b]furan Derivatives at Room Temperature

Background: Oxygen heterocycles exhibit diverse biological and pharmacological activities. In particular, benzofurans are available in a wide number of natural products and have drawn considerable attention over the last few years due to their profound physiological and biological properties. The aim of this paper describes a green methodology to synthesize this potent molecule with high selectivity by using ionic resin in PEG at room temperature. Methods: The methodology is very simple and easily accessible at room temperature. It uses low catalyst loadings and is recycled subsequently. In addition, detailed experimental procedure for the selected compounds including the spectral data are provided. Results: Among the various ionic resins attempted, Amberlyst-15® in PEG-400 was the choice of selection for the synthesis of 3-benzoyl-5-hydroxy benzofuran and naphtho[1,2-b]furan derivatives at room temperature in an environmentally friendly method. This catalyst system resulted in excellent yields in short reaction times and high selectivity. Conclusion: We have developed a green highly efficient and environmentally friendly protocol for the facile synthesis of 3-benzoyl-5-hydroxy benzofuran and naphtho[1,2-b]furan derivatives at room temperature in high yields (>90-95%) using nontoxic and inexpensive ion exchange resin Amberlyst-15®. The notable advantages of the catalyst approach enables the reactions with high selectivity, short reactions time and excellent yields without generating any waste and was reused. Keywords: Amberlyst-15®, benzofurans and naphthofurans, green synthesis, intramolecular cyclization, michael addition.