Recent Advances in the Synthesis of Heterocycles via Diels-Alder Reactions on Chromone Cores.

Chromones are versatile substrates for the synthesis of heterocycles via Diels-Alder reactions and can participate in both classical Diels-Alder and hetero-Diels-Alder (HDA) reactions, acting as both dienes and dienophiles. This review covers the reports of the past decade where chromones play a key role as intermediates for the synthesis of a wide range of heterocycles, including xanthones, dihydroxanthones, and various fused systems like indoloquinolizines and spiro-[chromeno-[2,3-b]-pyridine-3,4-pyrazole], among others, demonstrating the rich structural diversity that can be accessed from chromone scaffolds. Also discussed are the reaction mechanisms, the dual functionality of chromones as both dienes and dienophiles, factors influencing regio- and stereoselectivity, and various catalytic strategies.