Chromans

Chromans are a class of heterocyclic organic compounds defined by a benzene ring fused to a saturated six-member oxygen-containing ring, giving a dihydrobenzopyran scaffold. The core is often described as 2H-1-benzopyran or chroman. In this context, the pyran ring is saturated at positions 2 and 3, in contrast to the unsaturated chromenes.

Chromans are related to other benzopyran families. Chromenes are the unsaturated congeners with a double bond in the pyran ring, while fully saturated forms are commonly called chromanes or dihydrochromans. The term chromanol is used for ring systems bearing a hydroxy group on the chroman/chromene framework, as seen in some vitamin E derivatives; nonetheless, chroman chemistry shares much of the same core.

Chromans are encountered in natural products and are widely used as synthetic building blocks in medicinal and material chemistry. Their rigid bicyclic skeleton allows diverse substitution, giving compounds studied for antioxidant, antimicrobial, anti-inflammatory, and hormonal activities. The chroman core is also related to the head group of tocopherols (vitamin E), and many chroman derivatives are explored for pharmaceutical potential.

Chromans can be prepared by hydrogenation or cyclization approaches that incorporate a phenolic ring with a dihydropyran unit. They are typically less aromatic than chromenes, and substituents on the benzene ring influence lipophilicity and reactivity. As oxygen-containing heterocycles, they participate in standard reactions such as ring opening, oxidation, and functional-group interconversion, enabling further elaboration in synthetic sequences.