Direct C-H Arylation of Heteroarenes with Aryl Chlorides by Using an Abnormal N-Heterocyclic-Carbene-Palladium Catalyst
作者:Jasimuddin Ahmed、Samaresh Chandra Sau、Sreejyothi P、Pradip Kumar Hota、Pavan K. Vardhanapu、Gonela Vijaykumar、Swadhin K. Mandal
DOI:10.1002/ejoc.201601218
日期:2017.2.3
Herein, we report a versatilecatalyticsystem for the direct C–H arylation of heteroarenes with activated arylchloride substrates. The catalyst works successfully for a variety of heteroarenes and arylchloride coupling partners under very low catalyst-loading conditions. We have successfully performed the direct C–H arylations of 1-methylpyrrole, 1-methylindole, furan, thiophene, furfural, and N-benzyl-1
Palladium-Catalyzed Cross-Coupling of Five-Membered Heterocyclic Silanolates
作者:Scott E. Denmark、John D. Baird、Christopher S. Regens
DOI:10.1021/jo7023784
日期:2008.2.1
The preparation of pi-rich 2-aryl heterocycles by palladium-catalyzed cross-coupling of sodium heteroarylsilanolates with aryl iodides, bromides, and chlorides is described. The cross-coupling process was developed through extensive optimization of the following key variables: (1) identification of stable, isolable alkali metal silanolates, (2) identification of conditions for preformation and isolation of silanolate salts, (3) judicious choice in the palladium catalyst/ligand combination, and (4) selection of the protecting group on the nitrogen of indole. It was found that the alkali metal silanolates, either isolated or formed in situ, offered a significant rate enhancement and broader substrate scope over the use of silanols activated by Bronsted bases such as NaOt-Bu. In addition, the optimized conditions for the cross-coupling of 2-indolylsilanolates were readily applied to the cross-coupling of 2-pyrrolyl-, 2-furyl-, and 2-thienylsilanolates.