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
通过在吡唑的C5处使用氯原子进行的临时保护,可以合成4-芳基化的吡唑,后者以前无法通过钯催化的直接芳基化而获得,具有完全的区域选择性,并且在大多数情况下使用0.5即可高收率–0.1 mol%Pd(OAc)2作为具有缺电子的芳基溴化物的催化剂。此外,从5-氯-1,3-二甲基吡唑开始,通过顺序催化的C4芳基化,脱氯,催化的C5芳基化反应,可以合成4,5-二芳基吡唑衍生物。