Terminal-Selective sp ³ C–H Borylation of Carbonyl Derivatives by a Di(pyridyl)arylmethane-Ligated Iridium Catalyst

High Resolution Image Download MS PowerPoint Slide An iridium catalyst based on a 2,2’-dipyridylarylmethane ligand shows high activity at low catalyst loading for terminal sp 3 C–H borylation of aliphatic carbonyl derivatives under conditions where the substrate is the limiting reagent. The site selectivity of the process is not directed by the functional group but, instead, by a preference for borylation of unhindered methyl groups over methylene or α-branched methyl groups. The active catalyst species are formed in situ from commercial precatalysts and a hydrosilane activator, with structural evidence provided by an isolable complex bearing a κ 3 -metalated ligand. The resulting alkylboronate esters are versatile reagents and are amenable to Pd-catalyzed B -alkyl Suzuki cross-coupling.