Elemental Chalcogen (Se, S) in PEG-400 to the Synthesis of Seleno- and Thioflavones from 2-Chlorophenyl Ethynyl Ketone and Nucleophilic Species of Chalcogen

An alternative green method was developed for the synthesis of thio- and selenoflavones by ring closure 2-chlorophenyl ethynyl ketone with NaHY (Y = S, Se). These nucleophilic chalcogen species were generated in situ using NaBH4 to reduce elemental presence polyethylene glycol-400 (PEG-400). The efficiency this reaction is strongly dependent on PEG-400 solvent, acting like a crown ether, complexing sodium atom species, making nucleophile more active. synthetic protocol proceeded efficiently at 100 °C under argon, range containing alkyl, aryl, or vinyl groups sulfur selenium chalcogen. By efficient simple approach, 18 chalcogenoflavones obtained good excellent yields after 2 h.