Pyrimidine, also known as 1,3-diazobenzene, is a heterocyclic compound with the chemical formula C4H4N2. Pyrimidine is formed by substituting 2 nitrogen atoms for 2 carbons in the meta-position of benzene. It is a diazine and retains its aromaticity. Derivatives of pyrimidine widely exist in organic macromolecular nucleic acids, and many drugs also contain pyrimidine rings. In nucleic acids, three nucleobases are pyrimidine derivatives: cytosine, thymine and uracil. There are a variety of pyrimidine-containing drugs on the market, most of which are kinase inhibitors.
Benzothiophene is an aromatic organic compound with the molecular formula C8H6S and a naphthalene-like odor. Benzothiophenes are used in research as a starting material for the synthesis of larger, often biologically active structures. It exists in medicinal chemical structures such as raloxifene, zileuton, and sertaconazole, and can also be found in BTCP. It is also used to make dyes such as thioindigo.