Ye, Mengchun et al. published their research in Chemical Science in 2013 | CAS: 63725-52-0

6-Chloro-1-methylpyrazolo[5,4-b]pyridine (cas: 63725-52-0) belongs to pyrazole derivatives. Pyrazole is a weak base, with pKb 11.5 (pKa of the conjugated acid 2.49 at 25 °C).Pyrazole used as a ligand to prepare organometallic compounds. The presence of both electronegative nitrogen atoms in the pyrazole ring reduces the electron density of the C3- and C5-positions leaving electron density of C4-position unaltered. Thus the C4-position is vulnerable to electrophilic attack. The C3 electrophilic-position may undergo deprotonation in the presence of a strong base leading to ring opening.Name: 6-Chloro-1-methylpyrazolo[5,4-b]pyridine

A robust protocol for Pd(ii)-catalyzed C-3 arylation of (1H) indazoles and pyrazoles: total synthesis of nigellidine hydrobromide was written by Ye, Mengchun;Edmunds, Andrew J. F.;Morris, James A.;Sale, David;Zhang, Yejia;Yu, Jin-Quan. And the article was included in Chemical Science in 2013.Name: 6-Chloro-1-methylpyrazolo[5,4-b]pyridine This article mentions the following:

C3-arylated indazole and pyrazoles are privileged structural motifs in agrochems. and pharmaceuticals. C-3 C-H arylation of (1H) indazole and pyrazole was a significant challenge due to the poor reactivity of the C-3 position. Herein, the authors report a practical Pd(ii)/Phen catalyst and conditions for the direct C-3 arylation of indazole and pyrazole with ArI or ArBr without using Ag additives as halide scavengers. The use of toluene, chlorobenzene, trifluoromethylbenzene and mesitylene as the solvent is crucial for the selectivity and reactivity. The authors further demonstrate the robustness of this protocol through the first total synthesis of nigellidine hydrobromide as well as the expedient preparation of heterocycles structurally related to pesticides and drug mols. In the experiment, the researchers used many compounds, for example, 6-Chloro-1-methylpyrazolo[5,4-b]pyridine (cas: 63725-52-0Name: 6-Chloro-1-methylpyrazolo[5,4-b]pyridine).

6-Chloro-1-methylpyrazolo[5,4-b]pyridine (cas: 63725-52-0) belongs to pyrazole derivatives. Pyrazole is a weak base, with pKb 11.5 (pKa of the conjugated acid 2.49 at 25 °C).Pyrazole used as a ligand to prepare organometallic compounds. The presence of both electronegative nitrogen atoms in the pyrazole ring reduces the electron density of the C3- and C5-positions leaving electron density of C4-position unaltered. Thus the C4-position is vulnerable to electrophilic attack. The C3 electrophilic-position may undergo deprotonation in the presence of a strong base leading to ring opening.Name: 6-Chloro-1-methylpyrazolo[5,4-b]pyridine

Referemce:
Pyrazole – Wikipedia,
Pyrazoles – an overview | ScienceDirect Topics