Synthesis and functionalisation of 1H-pyrazolo[3,4-b]pyridines involving copper and palladium-promoted coupling reactions

Facile synthesis of 5-bromotropono[${c}$]-fused pyrazoles and isoxazole

“…39 Considering these results, we attempted to use the corresponding arylhydrazine hydrochloride as the reaction partner as shown in Scheme 2. To our delight, an improvement in terms of yields and reaction time was achieved, and the desired 1-aryl-5-bromo-3-methyltropono[c ]pyrazoles (10)(11)(12)(13)(14)(15) were obtained in satisfactory yields of 56%-77% after 12 h. The reaction results are summarized in the Table. As shown in the Table, all the desired products were obtained in satisfactory yields except for compounds 14 and 15 (entries 6 and 7). The products 14 and 15 were obtained in moderate yields of 60% and 52%, respectively, which we attributed to the strong electron-withdrawing effects of the CN and NO 2 groups, which rendered the condensation reaction unfavorable.…”

“…1,2 In particular, the important role of ring-fused pyrazoles in medicinal and pharmaceutical chemistry is indisputable and well reflected by a large number of recent publications, 3−6 including some excellent reviews. 7,8 Most fused pyrazole compounds reported in the literature comprise a common heterocyclic ring moiety, such as pyrazolopyrimidine, 9 pyrazolopyridine, 10 pyrazoloquinoline, 11 pyrazoloindol, 12 benzofuropyrazole, 13 benzopyranopyrazole, 14 and synthetic analogues thereof. In addition, as is well known, the ring-fused isoxazole skeleton is also an important structural unit that can be found in various bioactive compounds such as those with anti-HIV, 15 antifungal, 16 and nematicidal properties.…”

Palladium- and Copper-Catalyzed Aryl Halide Amination, Etherification and Thioetherification Reactions in the Synthesis of Aromatic Heterocycles

“…Guillaumet and co-workers reported an intermolecular copper-catalyzed amination method for the preparation of pyrazolopyridines (azaindazoles). 79 3-Cyano-2-chloropyridine was combined with a range of hydrazines using a copper(I) iodide/phenanthroline catalyst to deliver 3-amino-1H-azaindazoles in good yields (Scheme 29). The 3amino products were converted into the corresponding 3iodo derivatives by way of their diazonium salts, and were employed in a range of palladium-catalyzed coupling processes including Stille, Heck and Suzuki reactions.…”

Palladium‐catalyzed dehalogenation of 5‐halopyrazoles

“…Pyrazoles [1] and pyrazolones [2] are an important family of heterocyclic compounds because of their wide range of pharmacological properties [3–11]. In particular, modified pyrazoles [12–18], pyrazolones [19–21], and polypyrroles [22–27] are the component of various active materials. They are also key starting materials for the synthesis of commercial aryl/hetarylpyrazolone dye [28–30] and acting as the efficient ligand [31] for the construction of various organometallic catalysts especially with early transition metals and lanthanides.…”