Advancements in the Preparation of 4<i>H</i>‐Chromenes: An Overview

Abstract Functionalized 4 H ‐chromenes represent one class of the most important structural scaffolds in both synthetic and medicinal chemistry. They often appear in an arrange of biological natural products, pharmaceutical agents and drug candidates. The significance has stimulated the development of efficient methodologies for the synthesis of such compounds. In this review, a comprehensive discussion on different synthetic approaches to 4 H ‐chromenes has been presented with an emphasis on reaction features and mechanisms. Three main categories are outlined: 1) nucleophilic addition to 2 H ‐chromene derivatives, 2) 4 H ‐chromene ring formation involved cycloaddition or cyclization reactions, and 3) miscellaneous reactions. magnified image