Palladium-Catalyzed Direct Arylation of 5-Chloropyrazoles: A Selective Access to 4-Aryl Pyrazoles
作者:Tao Yan、Lu Chen、Christian Bruneau、Pierre H. Dixneuf、Henri Doucet
DOI:10.1021/jo301047v
日期:2012.9.7
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