1benzopyran

1-benzopyran, commonly referred to as chromene, is a bicyclic aromatic heterocycle composed of a benzene ring fused to a pyran ring containing an oxygen atom. This fusion yields the benzopyran core that is a foundational motif in the benzopyran family of compounds.

In nomenclature, 1-benzopyran and 2-benzopyran are the two principal isomers of benzopyran, differing by the position of the fusion between the rings and the location of the oxygen in the pyran ring. The 1-benzopyran isomer is often called chromene in common usage.

Natural occurrence and significance: The 1-benzopyran skeleton appears in many natural products, notably chromenes and flavonoids. The core structure contributes to color in pigments and to various biological activities. Chromene-containing compounds have been studied for antimicrobial, anticancer, anti-inflammatory properties; however, activity is highly dependent on substituents.

Synthesis and reactions: 1-benzopyran cores can be prepared via acid-catalyzed cyclization of o-hydroxychalcones or via intramolecular cyclizations of suitably substituted enones. The fused ring system behaves as an aromatic heterocycle, undergoing typical electrophilic substitution on the benzene portion and various functionalizations at the pyran ring.

See also: Chromene; Benzopyran; Flavonoids.