Cascade reaction of 3-formylchromones: Highly selective synthesis of 4-oxo-3-(1H-pyrrol-3-yl)-4H-chromenes

Abstract

A novel method for the preparation of highly functionalized 4-oxo-3-(1H-pyrrol-3-yl)-4H-chromenes (OPCMs) from 3-formylchromones and α-isocyanoacetates via an unprecedented three-component [1 ​+ ​1 ​+ ​3] cycloaddition reaction in one pot was developed. The three-component cascade reaction was enabled by refluxing a mixture of the substrates in 1,4-dioxane in the presence of Ag2CO3 as a Lewis acid promoter. As a result, a series of functionalized pyrroles (OPCMs, 3), was prepared regioselectively and in high yields (80%–88%) through the formation of three bonds. This protocol can be used in the synthesis of OPCMs rather than through conventional, multi-step reactions and is suitable for both combinatorial and parallel syntheses of pyrroles.

Keywords

• 4-Oxo-3-(1H-pyrrol-3-yl)-4H-chromenes
• Three-component
• Cascade reaction
• [1 + 1 + 3] cycloaddition
• 3-Formylchromones