Catalyst‐ and Solvent‐Free Synthesis of Pentacyclic‐dione Derivatives from 4‐Hydroxythiocoumarin and Aldehyde Using Pseudo‐Three‐Component Reaction

Abstract

AbstractThe synthesis of hitherto unreported pentacyclic‐dione derivatives having three heteroatoms in the ring is reported from 4‐hydroxythiocoumarins and aryl (hetero)/alkyl aldehydes under solvent‐ and catalyst‐free conditions through pseudo‐three‐component reaction. The reaction proceeds through Knoevenagel condensation of 4‐hydroxythiocoumarin with aldehyde followed by Michael addition with another molecule of 4‐hydroxythiocoumarin with the elimination of hydrogen sulfide to furnish the final product. The salient features of this protocol are mild reaction conditions, good yield, broad substrate scope, no need for catalyst or solvent or chromatographic separation, and high atom economy.