Base‐Promoted Direct Cascade Transformation of Chromones to Coumarins via Benzannulation and Transesterification

Abstract

A mild base-promoted reaction between 3-substituted chromones and β-keto esters for the easy access to various coumarins with structural diversity is described. This protocol provides highly functionalized 3-acyl-4-arylcoumar-ins in good-to-excellent yield via benzannulation and transesterification. A reaction mechanism containing Michael addition, 1,5-H shift and intramolecular transesterification is proposed.

Computer Aided Drug Design Methodologies with Natural Products in the Drug Research Against Alzheimer’s Disease

“…Coumarins are oxygenated heterocyclic lactones, called benzopyranones, which basically consist of a pyran ring attached to a benzene with the pyrone carbonyl specifically located in position 2, comprising an important class of secondary metabolites that are widely distributed in vegetables, as well as in fungi and bacteria [ 89 , 90 ] already thechromones are classified as coumarin isomers and are also oxygenated heterocyclic compounds that may come from natural or synthetic routes, and its structure consists of the fusion of a benzene ring with a pyran-4-one ring [ 91 , 92 ].…”

“…The xanthones, in turn, are also oxygenated heterocyclic compounds that can be of natural origin (present in plants, fungi, ferns, lichens) or synthetic; however, its basic structure is dibenzo-γ-pyro or, as it is known, 9H-xanten-9-one, formed in plants by the combination of the chiquimate and acetate pathways [ 93 , 94 ]. In view of their respective molecular architectures and easy modification, coumarins, chromones and xanthones have been the target of several studies, presenting numerous pharmacological properties [ 89 , 90 , 93 , 95 ].…”