使用PdCl(C 3 H 5)(dppb)/ KOAc催化剂,钯催化吡唑与芳基卤化物的直接芳基化反应显示出吡唑的C4和C5 C H键具有相似的反应性,而C3 C H键几乎不具有反应性,并一步一步即可获得各种4,5-二芳基吡唑类化合物。该C H键官能化反应容许芳基溴化物上的各种取代基,例如硝基,氰基,甲酰基,丙酰基,酯,氯,氟或三氟甲基。
Selective Palladium‐Catalyzed Direct CH Arylation of Unsubstituted
<i>N</i>
‐Protected Pyrazoles
作者:Esa T. T. Kumpulainen、Antti Pohjakallio
DOI:10.1002/adsc.201301139
日期:2014.5.5
selective C‐5 arylation of N‐dimethylaminosulfamoyl‐protected pyrazole with aryl bromides is catalyzed by 2–5 mol% palladium in the presence of triphenylphosphine ligand and carboxylic acid additive. Selectivities up to 45:1 (C‐5:C‐4) can be achieved by running the reaction in non‐polar solvents. A thorough study of scope and limitations shows good general tolerance of aryl bromide substitution. However