Cobalt-Catalyzed CH Bond Functionalizations with Aryl and Alkyl Chlorides

Inexpensive cobalt catalysts derived from N-heterocylic carbenes (NHC) allowed efficient catalytic CH bond arylations on heteroaryl-substituted arenes with widely available aryl chlorides, which set the stage for the preparation of sterically hindered tri-ortho-substituted biaryls. Likewise, challenging direct alkylations with -hydrogen-containing primary and even secondary alkyl chlorides proceeded on pyridyl- and pyrimidyl-substituted arenes and heteroarenes.The cobaltcatalyzed C-H bond functionalizations occurred efficiently at ambient reaction temperature with excellent levels of site-selectivities and ample scope. Mechanistic studies highlighted that electron-deficient aryl chlorides reacted preferentially, while the arenes kinetic C-H bond acidity was found to largely govern their reactivity.