Pyrimidine

Pyrimidine is a heterocyclic aromatic compound consisting of a six-member ring with two nitrogen atoms at positions 1 and 3, a 1,3-diazine. Its molecular formula is C4H4N2. The ring is planar and aromatic, and it serves as the parent structure for the pyrimidine family of compounds. The electron-withdrawing nitrogens make the ring relatively electron-poor, which contributes to pyrimidine being a weaker base than pyridine and influences the typical sites of electrophilic substitution.

In biology, the pyrimidine ring is a core component of the nucleobases cytosine, thymine, and uracil, which form DNA and RNA. Substituted pyrimidines are widespread in medicinal chemistry; a notable example is 5-fluorouracil, a pyrimidine analog used in cancer therapy. Beyond biology, pyrimidine derivatives are common building blocks in pharmaceuticals, agrochemicals, and materials science.

Synthesis and derivatives: A variety of methods exist to prepare pyrimidines, including cyclization of β-dicarbonyl precursors with amidines and related condensation routes that assemble the ring and introduce substituents. The parent ring is used to furnish numerous substituted pyrimidines for research and industry, reflecting its importance as a versatile heterocyclic scaffold.

See also: nucleobases, diazines.