Synthesis, X-ray structures, and catalytic applications of palladium(II) complexes bearing N-heterocyclic iminocarbene ligands

Asymmetric borylation of α,β-unsaturated esters catalyzed by novel ring expanded N-heterocyclic carbenes based on chiral 3,4-dihydro-quinazolinium compounds

A series of chiral 6-membered ring N-heterocyclic carbene (NHC) precursors based on 3,4-dihydro-quinazoline were synthesized with overall yields of 54-62%. NHCs generated from these precursors show excellent asymmetric catalytic properties for borylation of α,β-unsaturated esters with enantioselectivity of up to 93% with a catalyst content of only 1 mol%.

“Decarbonization” of an imino-N-heterocyclic carbene ligand via triple benzyl migration from hafnium

Binding of an imino-N-heterocyclic carbene to tetrabenzylhafnium triggers complete removal of the carbene carbon via three successive benzyl migrations.

Suzuki-Miyaura reactions catalyzed by C₂-symmetric Pd-multi-dentate N-heterocyclic carbene complexes

Suzuki-Miyaura coupling reactions are promoted by Pd complexes ligated with C₂-symmetric multi-dentate N-heterocyclic carbenes derived in situ from Pd(OAc)₂ and imidazolium salts. Good to excellent yields were obtained for aryl bromides as substrates. Turnover numbers of up to 10⁵ could be achieved with 5 × 10⁻⁴ mol% of Pd(OAc)₂/1 × 10⁻³ mol% NHC precatalyst in 24 h.