960116-25-0Relevant articles and documents
Manganese-Catalyzed C(sp2)-H Borylation of Furan and Thiophene Derivatives
Britton, Luke,Skrodzki, Maciej,Nichol, Gary S.,Dominey, Andrew P.,Pawlu?, Piotr,Docherty, Jamie H.,Thomas, Stephen P.
, p. 6857 - 6864 (2021/06/28)
Aryl boronic esters are bench-stable, platform building-blocks that can be accessed through metal-catalyzed aryl C(sp2)-H borylation reactions. C(sp2)-H bond functionalization reactions using rare- and precious-metal catalysts are well established, and while examples utilizing Earth-abundant alternatives have emerged, manganese catalysis remains lacking. The manganese-catalyzed C-H borylation of furan and thiophene derivatives is reported alongside an in situ activation method providing facile access to the active manganese hydride species. Mechanistic investigations showed that blue light irradiation directly affected catalysis by action at the metal center, that C(sp2)-H bond borylation occurs through a C-H metallation pathway, and that the reversible coordination of pinacolborane to the catalyst gave a manganese borohydride complex, which was as an off-cycle resting state.
Iridium-Catalyzed Silylation of Five-Membered Heteroarenes: High Sterically Derived Selectivity from a Pyridyl-Imidazoline Ligand
Hartwig, John F.,Karmel, Caleb,Kharitonova, Elena V.,Rubel, Camille Z.
supporting information, p. 6074 - 6081 (2020/02/25)
The steric effects of substituents on five-membered rings are less pronounced than those on six-membered rings because of the difference in bond angles. Thus, the regioselectivities of reactions of five-membered heteroarenes that occur with selectivities dictated by steric effects, such as the borylation of C?H bonds, have been poor in many cases. We report that the silylation of five-membered-ring heteroarenes occurs with high sterically derived regioselectivity when catalyzed by the combination of [Ir(cod)(OMe)]2 (cod=1,5-cyclooctadiene) and a phenanthroline ligand or a new pyridyl-imidazoline ligand that further increases the regioselectivity. The silylation reactions with these catalysts produce high yields of heteroarylsilanes from functionalization at the most sterically accessible C?H bonds of these rings under conditions that the borylation of C?H bonds with previously reported catalysts formed mixtures of products or products that are unstable. The heteroarylsilane products undergo cross-coupling reactions and substitution reactions with ipso selectivity to generate heteroarenes that bear halogen, aryl, and perfluoroalkyl substituents.
