Synthesis and Antifungal Activity of 2-Aryl-1,2,4-triazolo[1,5-a]pyridine Derivatives

Synthesis of Pyrazolo[1,5-a]pyridinyl, Pyrazolo[1,5-a]quinolinyl, and Pyrazolo[5,1-a]isoquinolinyl Sulfonyl Fluorides via a [3 + 2] Annulation

A [3 + 2] cycloaddition reaction of N-aminopyridines, N-aminoquinolines, and N-aminoisoquinolines with 1-bromoethene-1-sulfonyl fluoride (BESF) was performed to obtain optimum yields of various useful pyrazolo[1,5-a]pyridinyl, pyrazolo[1,5-a]quinolinyl, and pyrazolo[5,1-a]isoquinolinyl sulfonyl fluorides (43-90% yield). The transformation process showed broad substrate specificity, mild reaction conditions, and operational simplicity. Therefore, the reaction has great applicable value in the field of medicinal chemistry and other disciplines.

2-Amino-4-methylpyridinium 2-(3-methylphenyl)acetate

In the title molecular salt, C6H9N2+·C9H9O2−, the cation is protonated at the pyridine N atom and the anion is deprotonated at the hydroxy O atom. The dihedral angle between the benzene and pyridine rings is 66.58 (10)°. In the molecular structure, a pair of N—H...O hydrogen bonds links the anion and cation, generating anR22(8) ring motif. These ring motifs are connected to adjacent anions and cationsviaintermolecular N—H...O hydrogen bonding, generating a bifurcatedR22(8) ring motif. C—H...O, C—H...π and π–π [centroid-to-centroid distances = 3.7053 (11) and 3.9547 (13) Å] interactions lead to the formation of a three-dimensional network.

Ethyl 8-(2,4-dichlorophenyl)-6-methyl-1,2,4-triazolo[1,5-a]pyridine-7-carboxylate

In the title compound, C₁₆H₁₃Cl₂N₃O₂, the carboxyl­ate group and the benzene ring attached to the central 1,2,4-triazolo[1,5-a]pyridine bicycle are twisted from its mean plane by 55.6 (1) and 72.6 (1)°, respectively. In the crystal, weak C—H⋯O inter­actions link the mol­ecules into zigzag chains propagating in [100].

Ethyl 6-methyl-8-phenyl-1,2,4-triazolo[1,5-a]pyridine-7-carboxylate

In title compound, C₁₆H₁₅N₃O₂, the 1,2,4-triazolo[1,5-a]pyridine ring system is almost planar (r.m.s. deviation = 0.0068 Å) and forms a dihedral angle of 61.4 (3)° with the phenyl ring. In the structure, centrosymmetrically related mol­ecules are linked into dimers by pairs of C—H⋯N hydrogen bonds.