Balancing hydrogen-bond donors and acceptors in a family of bifunctional aromatic N-heterocycles

A series of bifunctional pyridine-aminopyrimidine/ariiinopyridine supramolecular reagents (SRs) have been synthesized through palladium-catalyzed cross-coupling reactions and characterized by single-crystal X-ray crystallography. 3-(2-Amino-4-methylpyrimidin-6-yI)pyridine 1, 4-(2-an-tino-4-methylpyfin-iidiri-6-yl)pyridine 2, and 4-methoxy-3-(2-amino-4-methylpyrimidin-6-yl)pyridine 3 were synthesized via Suzuki-Miyaura cross-coupling conditions in good yields, whereas 1-(2-aniino-4-methylpyrimidin-6-yl)-2-(3-methoxypyridin5-yl)ethyne 4, 1-(2-aminopyrid-5-yl)-2-(pyrid-3-yl)ethyne 5, and 1-(6-amino-3-pyridyl)-2-(4-{benzimidazol-1-yl}phenyl)ethyne 6 were synthesized through conventional Sonogashira cross-coupling conditions. The primary hydrogen-bonding motif in solid-state structures 1-5 is a self-complementary amino-pyrimidine N-H center dot center dot center dot N/N center dot center dot center dot H-N synthon, whereas adjacent molecules in the structure of 6 are connected via aminopyridine-benzimidazole N-H center dot center dot center dot N hydrogen bonds. Secondary anti-amino proton/pyridyl N-H center dot center dot center dot N hydrogen bonds exist in the structures of 1, 2, 4, and 5, thereby establishing a hierarchy of intermolecular interactions in structures with multiple hydrogen-bond donors and acceptors.