Highermembered

Highermembered refers to cyclic structures in organic chemistry that contain seven or more atoms in the ring. This contrasts with the more common three-, four-, five-, and six-membered rings such as cyclopropane, cyclobutane, cyclopentane, and cyclohexane. Higher-membered rings can be saturated or unsaturated and may include heteroatoms (for example azepanes and oxocanes). The term is used in discussions of ring strain, conformational preferences, and macrocyclization.

Conformational behavior: As ring size increases beyond cyclohexane, angle strain generally decreases, and rings become more flexible. However, larger rings can adopt multiple low-energy conformations and can experience transannular strain if forced into bridged or fused systems. Substituents and heteroatoms influence puckering and stability.

Formation of higher-membered rings is often challenging due to entropic penalties. Common approaches include ring-closing metathesis to form medium to macrocyclic rings, intramolecular cyclizations, or templated strategies that preorganize the reacting groups. Macrocyclization typically requires dilute conditions and careful control of reaction geometry. Heteroatom-containing higher-membered rings (aza-, oxo-, thia- rings) are accessible by analogous strategies and often exhibit different reactivity.

These rings appear in natural products and pharmaceuticals, including azepanes and azocanes. Cycloheptane and cyclooctane are simple examples used as models for conformational studies. Macrocycles larger than about 12 atoms are important in medicinal chemistry due to their ability to bind challenging targets with defined shapes.

Research themes include understanding conformational landscapes, developing efficient methods for medium- and large-ring synthesis, and leveraging macrocyclic architectures in drug discovery and materials science.