Reaction of 5-aminopyrazoles with β-dimethylaminopropiophenones. Synthesis of new pyrazolo[3,4-b]pyridines

"On-Water" Facile Synthesis of Novel Pyrazolo[3,4-b]pyridinones Possessing Anti-influenza Virus Activity

A facile and versatile "on-water" protocol for the synthesis of pyrazolo[3,4-b]pyridinones was developed by the unprecedented construction of two rings and five new bonds in one-pot. It was proved that water was an important promoter of the reaction and PEG2000 was found to improve the reaction in terms of yield. 32 Derivatives were newly synthesized and most of them were prepared in an hour. The scope and limitation indicated that electron withdrawing groups substituted on synthons, substituted benzoyl acetonitriles or aryl aldehydes, were helpful to construct the pyrazolo[3,4-b]pyridinones. The reaction media PEG2000/H₂O was successfully recycled and reused at least 5 times without any obvious decrease in yield. The anti-influenza activities of the derivatives were evaluated and the screening results highlighted two derivatives, which exhibited strong inhibitory activity against H5N1 pseudovirus. These positive bioassay results implied that the library of potential anti-influenza virus agent candidates could be rapidly prepared in an eco-friendly manner, and provided a new insight into drug discovery for medicinal chemists.

An easy synthetic access to new pyrazole spiro derivatives from 3-amino-1-phenyl-2-pyrazolin-5-one

Pyrazole and pyrazolone moieties have shown important biological activities.

A hydrogen-bonded dimer in 6-(4-bromophenyl)-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazolo[3,4-b]pyridine and a chain of rings built from N-H...N and C-H...pi(pyridine) hydrogen bonds in 3-(4-nitrophenyl)-4-phenyl-1H-pyrazolo[3,4-b]pyridine

In 6-(4-bromophenyl)-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazolo[3,4-b]pyridine, C(19)H(16)BrN(3), the reduced pyridine ring adopts a conformation that is close to a screw-boat form. Molecules are linked by pairs of symmetry-related C-H...pi(arene) hydrogen bonds into cyclic centrosymmetric dimers. Molecules of 3-(4-nitrophenyl)-4-phenyl-1H-pyrazolo[3,4-b]pyridine, C(18)H(12)N(4)O(2), are linked into centrosymmetric R(2)(2)(8) dimers by pairs of symmetry-related N-H...N hydrogen bonds, and these dimers are linked by pairs of C-H...pi(pyridine) hydrogen bonds to form a chain of edge-fused rings, or a molecular ladder, along [100]. The molecular aggregation in this compound is completed by two weak C-H...O hydrogen bonds, one of which links the chains along [100] into sheets.