Direct <i>ortho</i>-Arylation of Pyridinecarboxylic Acids: Overcoming the Deactivating Effect of sp<sup>2</sup>-Nitrogen
作者:Adam J. S. Johnston、Kenneth B. Ling、David Sale、Nathalie Lebrasseur、Igor Larrosa
DOI:10.1021/acs.orglett.6b03085
日期:2016.12.2
Direct arylations of pyridines are challenging transformations due to the high Lewis basicity of the sp2-nitrogen. The use of carboxylates as directing groups is reported, facilitating the Pd-catalyzed C–H arylation of this difficult class of substrates. This methodology allows regioselective C3/C4 arylation, without the need to use solvent quantities of the pyridine, and using low-cost chloro- and
吡啶的直接芳基化由于sp 2-氮的高Lewis碱性而具有挑战性。据报道,使用羧酸盐作为导向基团,可促进此类难处理底物的Pd催化C–H芳基化。这种方法可以进行区域选择性的C3 / C4芳基化,而无需使用溶剂量的吡啶,并使用低成本的氯代和溴代芳烃作为偶联伙伴。此外,羧酸盐可通过一锅C-H芳基化反应/ Cu(I)介导的脱羧序列用作无痕量的引导基团,从而可进入无引导基团的吡啶联芳基。