Multicomponent Cascade Reaction by Metal-Free Aerobic Oxidation for Synthesis of Highly Functionalized 2‑Amino-4-coumarinyl-5-arylpyrroles

A novel approach has been constructed for the synthesis
of two
types of 2-amino-4-coumarinyl-5-arylpyrroles (ACAPs, 5 and 6) through a cascade reaction and a metal-free
catalyzed aerobic oxidation reaction of arylglyoxal monohydrates 1, 1,1-enediamines (EDAMs) 2 and 3, and 4-hydroxy-2H-chromen-2-ones 4 via multicomponent reactions to produce the target compounds with
good to excellent yields. Specifically, hydroxyl-substituted 2-amino-4-coumarinyl-5-arylpyrroles,
that is, 2-amino-4-coumarinyl-5-aryl-6-hydroxylpyrroles (ACAHPs) 6, were obtained by metal-free aerobic oxidation in 1,4-dioxane
at simple reflux for approximately 10 h. As a result, ACAHPs 6 have been produced without metal catalysts or traditional
oxidizing agents. This method represents a route to obtain the novel
ACAPs in an environmentally friendly, concise, rapid, and practical
manner with potential biological activity of the product.