Thiopyrimidines represent one of the most active classes of compounds, possessing a wide spectrum of biological activities. Herein, we report the synthesis of 2-(heptylthio)pyrimidine-4,6-diamine (HPDA) via S-alkylation. The structure of HPDA was elucidated using ¹H and ¹³C nuclear magnetic resonance (NMR), heteronuclear multiple bond correlation (HMBC), high resolution mass (HRMS), and infrared (IR) spectroscopies.

The title compound, C₁₃H₁₆N₄S (DAMP-DMB), was synthesized through the reaction of 2,4-dimethylbenzyl chloride with diaminopyrimidine-thiol. Single-crystal X-ray diffraction analysis confirmed that the compound crystallizes in the monoclinic crystal system, space group P2₁/c. The asymmetric unit contains a single molecular entity. Structural examination revealed the presence of a dimeric arrangement consolidated by N—H...N hydrogen-bonding interactions. Additionally, Hirshfeld surface analysis indicated that H...H, N...H, C...H, and S...H contacts account for 98.9% of the total intermolecular interactions to the Hirshfeld surface.

2,5-Dimethylbenzyl 2-{(4,6-diaminopyrimidin-2-yl)thio}acetate was prepared by an alkylation reaction between the sodium salt of 4,6-diamino-2-mercaptopyrimidine and chloroacetic acid. The structure was unambiguously elucidated based on high-resolution mass spectrometry (HRMS) as well as spectroscopies such as infrared (IR) and nuclear magnetic resonance (NMR).