2naphthylmethyl

2-Naphthylmethyl, commonly abbreviated Nap or 2-naphthylmethyl, is a protecting group used in organic synthesis. It is derived from 2-naphthol and is employed to mask alcohol and amino functionalities as Nap ethers or Nap carbamates.

The Nap group is installed by alkylation of the target oxygen or nitrogen with a 2-naphthylmethyl electrophile, typically 2-naphthylmethyl chloride or related reagents, in the presence of a base. The resulting Nap–O–R or Nap–NR′ bonds are relatively stable under many conditions, providing orthogonal protection in multi-step sequences.

Deprotection is usually achieved by oxidative cleavage, most commonly with DDQ, which cleaves the benzylic bond and releases the free alcohol or amine, generating 2-naphthaldehyde as a byproduct. Depending on the substrate, alternative methods such as ceric ammonium nitrate (CAN) or other oxidative or catalytic approaches may also be used, though conditions vary with the protected functionality.

Nap protection offers several advantages: it is bulky, providing effective steric shielding; it shows good stability to a range of acids and bases; and it can be removed selectively under mild oxidative conditions, often without disturbing other protecting groups. This makes the Nap group popular in complex molecule synthesis, including carbohydrate chemistry and the preparation of natural products, where orthogonal protection strategies are valuable.

See also: Nap protecting group; benzyl protecting group.