Reaction between aromatic aldehydes and 3–methyl-1-phenyl-2-pyrazoline-5-one catalyzed by nano-SiO2/HClO4 in water under reflux provided a simple and efficient route for the synthesis of 4-((5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)(aryl)methyl)-3-methyl-1-phenyl-1H-pyrazol-5-ol derivatives in high yields.

A novel one-flask synthetic method was developed in which 5-aminopyrazoles were reacted with N,N-substituted amides in the presence of PBr₃. Hexamethyldisilazane was then added to perform heterocyclization to produce the corresponding pyrazolo[3,4-d]pyrimidines in suitable yields. These one-flask reactions thus involved Vilsmeier amidination, imination reactions, and the sequential intermolecul...

The molecules of ethyl 4-(5-amino-3-methyl-1H-pyrazol-1-yl)benzoate, C13H15N3O2, are linked by two independent N-H...O hydrogen bonds into a chain of edge-fused and alternating R(4)2(8) and R(2)2(20) rings. A combination of N-H...N and N-H...O hydrogen bonds links the molecules of methyl 4-(5-amino-3-tert-butyl-1H-pyrazol-1-yl)benzoate, C15H19N3O2, into sheets of alternating R(2)2(20) and R(6)6...

The title compound, C(20)H(16)Cl(2)N(4)O, has two mol-ecules in the asymmetric unit. The two five-membered rings form a dihedral angle of 54.2 (3)° in one mol-ecule and 56.8 (3)° in the other independent mol-ecule. The amino group of the dihydro-pyrazolone unit of one mol-ecule acts as a hydrogen-bond donor to the carbonyl group of the dihydro-pyrazolone system of the other mol-ecule. The resul...