Pyrans and chromenes are important classes of heterocycles because their core fragments are incorporated in a large variety of natural products and biologically active compounds. They are of considerable interest as they display a broad range of pharmaceutical proper- ties such as anti-tumor, 1 anti-cancer, 2 anti-microbial, 3 anti-fungal, 4 and anti-HIV charac- ter. 5 They are widely used as pigments, 6 in cosmetics and as potential biodegradable agrochemicals. 7 Because of the wide range of pharmacological activities and industrial applications, several methods for their preparation have been reported in the literature.
