Palladium-Catalyzed Chelation-Assisted Regioselective Oxidative Dehydrogenative Homocoupling/Ortho-Hydroxylation in N‑Phenylpyrazoles

A palladium-catalyzed
pyrazole-directed regioselective oxidative
C­(sp2)–H functionalization of the N-phenyl
ring in N-phenylpyrazoles to afford either a biaryl
bis-pyrazole (via dehydrogenative homocoupling) or N-(o-hydroxyphenyl)­pyrazole (via C–H oxygenation)
or their mixture is described. The substitutions on the N-phenyl ring and the pyrazole ring and the dilution of the reaction
medium with respect to the TFA/TFAA mixture (substrate concentration)
have a remarkable influence on the outcome of the reaction. It was
discovered that if the reactions were performed under highly dilute
conditions (ca. 10 times) then N-(o-hydroxyphenyl)­pyrazoles were the major or the sole products.

本数据集描述了一种钯催化下，针对N-苯基吡唑的N-苯基环区域选择性的C(sp2)-H氧化功能化反应。该反应旨在生成生物芳基双吡唑（通过脱氢偶联）或N-(邻羟基苯基)吡唑（通过C-H氧化）或其混合物。N-苯基环和吡唑环上的取代基以及反应介质（TFA/TFAA混合物）的稀释程度对反应结果具有显著影响。研究发现，在高度稀释条件下（约10倍）进行反应时，N-(邻羟基苯基)吡唑将成为主要产物或唯一产物。