Shi, Xinzhe published the artcileC-H Bond Arylation of Pyrazoles at the β-Position: General Conditions and Computational Elucidation for a High Regioselectivity, Recommanded Product: 1-Methylpyrazole, the publication is Chemistry – A European Journal (2021), 27(17), 5546-5554, database is CAplus and MEDLINE.
Direct arylation of most five-membered ring heterocycles are generally easily accessible and strongly favored at the α-position using classical palladium-catalysis. Conversely, regioselective functionalization of such heterocycles at the concurrent β-position remains currently very challenging. Herein, authors report general conditions for regioselective direct arylation at the β-position of pyrazoles, while C-H α-position is free. By using aryl bromides as the aryl source and a judicious choice of solvent, the arylation reaction of variously N-substituted pyrazoles simply proceeds via β-C-H bond functionalization. The β-regioselectivity is promoted by a ligand-free palladium catalyst and a simple base without oxidant or further additive, and tolerates a variety of substituents on the bromoarene. DFT calculations revealed that a protic solvent such as 2-ethoxyethan-1-ol significantly enhances the acidity of the proton at β-position of the pyrazoles and thus favors this direct β-C-H bond arylation. This selective pyrazoles β-C-H bond arylation was successfully applied for the straightforward building of π-extended poly(hetero)aromatic structures via further Pd-catalyzed combined α-C-H intermol. and intramol. C-H bond arylation in an overall highly atom-economical process.
Chemistry – A European Journal published new progress about 930-36-9. 930-36-9 belongs to pyrazoles-derivatives, auxiliary class Pyrazole, name is 1-Methylpyrazole, and the molecular formula is C18H23N3O4S, Recommanded Product: 1-Methylpyrazole.
Referemce:
https://en.wikipedia.org/wiki/Pyrazole,
Pyrazoles – an overview | ScienceDirect Topics