Structural Characterization of Two Polymorphs of 1-(4-Methylpyridin-2-yl)thiourea and Two Derived 2-Aminothiazoles

摘要

Two polymorphic forms of 1-(4-methylpyridin-2-yl)thiourea (1) and the crystal and molecular structures of the 2-aminothiazolesN-(4-methylpyridin-2-yl)-4-(pyridin-2-yl)thiazol-2-amine (2) andN-(4-methylpyridin-2-yl)-4-(pyrazin-2-yl)thiazol-2-amine (3), derived from1and the respective alpha-bromoketone via the Hantzsch reaction, are described. Both polymorphic forms 1 alpha (space group P2(1)/c, Z = 4) and 1 beta (space group P2(1)/n, Z = 8) crystallize in the monoclinic system but exhibit distinctly different intermolecular hydrogen bonding patterns. Compound 2 (orthorhombic, space group Pca2(1), Z = 8) forms polymeric N-HMIDLINE HORIZONTAL ELLIPSISN hydrogen-bonded zigzag tapes in the polar crystal structure, with a significant twisting between the thiazole and pyridine rings. In contrast, the crystal structure of3(monoclinic, space group P2(1)/c, Z = 4) features nearly planar centrosymmetric N-H center dot center dot center dot N hydrogen-bonded dimers, which are laterally joined through long C-H center dot center dot center dot N contacts, affording a pi center dot center dot center dot pi stacked layered structure.