C2 Symmetric chiral N-heterocyclic carbene catalyst for asymmetric intramolecular Stetter reaction

The asymmetric intramolecular Stetter reaction of ω-formyl α,β-unsaturated carbonyl compounds was catalyzed by a C2 symmetric chiral carbene, generated from (4S,5S)-diphenyl-1,3-bis(mesitylmethyl)-4,5-dihydro-1H-imidazolium tetrafluoroborate, to afford 2-substituted cyclopentanones in good enantioselectivity of up to 80%.