title: Palladium-catalyzed direct arylation of 5-chloropyrazoles: a selective access to 4-aryl pyrazoles.
abstract: The use of a temporary protection by a chloro group at C5 of pyrazoles allows the synthesis of the 4-arylated pyrazoles, which were previously inaccessible by palladium-catalyzed direct arylation, with complete regioselectivity and in high yields using in most cases as little as 0.5-0.1 mol % Pd(OAc)(2) as the catalyst with electron-deficient aryl bromides. Moreover, from 5-chloro-1,3-dimethylpyrazole, sequential catalytic C4 arylation, dechlorination, catalytic C5 arylation reactions allowed the synthesis of a 4,5-diarylated pyrazole derivative.
authors: Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS-Université de Rennes Organométalliques: Matériaux et Catalyse, Campus de Beaulieu, 35042 Rennes, France.
authors: Tao
authors: T
authors: Yan
authors: Lu
authors: L
authors: Chen
authors: Christian
authors: C
authors: Bruneau
authors: Pierre H
authors: PH
authors: Dixneuf
authors: Henri
authors: H
authors: Doucet
mesh_terms: D002384:Catalysis; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D011720:Pyrazoles / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D009942:Organometallic Compounds; D011720:Pyrazoles; D010165:Palladium