twoaryl

Twoaryl, sometimes written two-aryl or diaryl, is a chemical descriptor used to indicate that a molecule contains two aryl groups. An aryl group is an aromatic ring or ring fragment derived from benzene by removal of one hydrogen, with phenyl as the typical example. The two aryl units may be attached to the same atom, or connected through a linker, producing motifs such as biaryl frameworks, diaryl ethers, and diaryl ketones. Although two-aryl is used in some contexts, diaryl is the more common term in systematic nomenclature. The simplest example is biphenyl, two phenyl rings joined by a single carbon–carbon bond.

In synthesis, two-aryl motifs are most often created by forming a bond between two aryl fragments, typically via cross-coupling reactions such as Suzuki-Miyaura, Negishi, Kumada, or Stille couplings, usually catalyzed by palladium or nickel. Other approaches include Ullmann-type couplings for Ar–O–Ar or Ar–N–Ar linkages and directed metallation strategies. The choice of method depends on the desired linkage, substitution pattern, and considerations of steric and electronic effects.

Two-aryl structures are widespread in chemistry and related fields. Biaryl compounds often exhibit restricted rotation and distinctive electronic properties, making them important in organic electronics and materials science. Diaryl motifs are common in dyes, pharmaceuticals, and ligands for homogeneous catalysis, where the planarity and conjugation of the aryl rings influence performance and selectivity.