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.
Thiomorpholine is a nitrogen- and sulfur-containing heterocyclic compound with the molecular formula C4H9NS. It can be considered a thio analog of morpholine. Thiomorpholines are comparable to other secondary amines in terms of nucleophilicity and N-alkylation or acylation with alkyl groups or acid halides.