2naphthyl

2-naphthyl is the aryl substituent derived from naphthalene by removing a hydrogen from the 2-position of the fused ring system. The 2-naphthyl group is a C10H7 moiety that is used as a synthetic building block in organic chemistry, attached to a parent molecule at the 2-position of naphthalene.

Nomenclature and structure: It is one of the two common mononaphthyl regioisomers, the other being 1-naphthyl. The 2-naphthyl substituent is generated by functionalization at the C-2 position of naphthalene and is distinct from the 1-naphthyl isomer in terms of its site of attachment and subsequent reactivity in many reactions.

Preparation and methods of introduction: The 2-naphthyl group can be installed through several general strategies. Regioselective lithiation or directed metalation at the 2-position of naphthalene derivatives followed by quenching with an electrophile is one route. Cross-coupling approaches use 2-naphthyl halides or triflates with partners such as boron, silicon, or zinc reagents in Suzuki–Miyaura, Negishi, or related couplings. Other methods include transformations from prefunctionalized naphthalene precursors that direct substitution to the 2-position. These methods enable construction of biaryl systems and other complex architectures bearing a 2-naphthyl unit.

Applications: The 2-naphthyl group serves as a versatile aryl fragment in organic synthesis, enabling formation of biaryls and polycyclic architectures. It appears in dyes, ligands for metal complexes, and various pharmaceutical and agrochemical scaffolds where specific regioselectivity and steric properties of the naphthyl core are advantageous.

Safety: As with many polycyclic aromatic hydrocarbons and aryl halides, handling should follow standard laboratory safety practices. Naphthalene and its derivatives can be irritants and may pose health risks with prolonged exposure; work in a well-ventilated area and use appropriate protective equipment.