Enantioselective synthesis of 2-amino-4H-chromene derivatives with antifungal activities on phytopathogenic fungi

Abstract

An enantioselective cascade allylation/cyclization reaction of 1-(methylthio)-2-nitroenamines with 2-(1-hydroxyallyl)phenols was accomplished by using a chiral Ir(I) catalyst. A broad range of 2-amino-3-nitro-4H-chromene derivatives were obtained in moderate to high yields (55–99%) with moderate to excellent enantioselectivities (50–99% ee). Meanwhile, enantioenriched 2-amino-3-cyano-4H-chromene derivatives could be readily synthesized by using malononitrile in this cascade reaction. The antifungal activities of 2-amino-4H-chromene derivatives were investigated against four species of phytopathogenic fungi and a novel antifungal lead compound with good antifungal activity against Rhizoctonia solani (EC₅₀ = 17.43 mg L⁻¹) was found.