Mechanistic analysis of the reaction between elemental sulfur or selenium and 1,3-dialkylimidazolium acetate ionic liquids, in the absence of an external base or solvent, affords evidence for the equilibrium presence of carbene species in these ionic liquids. It demonstrates the potential to control, through anion selection, the concentration of carbene in stable ionic liquids.

A carbene-catalyzed highly regioselective and enantioselective 1,4-addition reaction between isothioureas enals has been achieved under oxidative conditions.

The nature of the active species which lead to the formation of the initiator carbene in photocatalytic metathesis reaction was investigated. The solid phase produced during irradiation was found to involve the active species while the soluble species showed no catalytic activity. The structure of the active solid was analyzed by ESCA, FT IR, NMR and chemical analysis methods and defined as a t...

The iridium(Ir) (triNHC = tri-N-heterocyclic carbene)-catalyzed transfer hydrogenation of glycerol carbonate (GC) is described in the absence additional hydride sources. reduction provides a sustainable route to produce industrially-valuable formate and lactate with high turnover numbers (TONs). bimetallic Ir(I) involving triNHC carbene ligands exhibits TONs, reaction mechanism, including Ir(tr...

The benzannulation reaction of Fischer carbene complexes is investigated under conditions where the reaction of the carbene complex is occurring in the presence of two different alkynes. A series of competition experiments are examined where the effects of various structural factors are explored by pitting 10 different carbene complexes with 11 different alkynes. Terminal alkynes will react sel...

The first examples of reactions of Fischer carbene complexes with triynes are reported. The regioselectivity of the reaction of the two different alkyne functions in the symmetrical triyne depends on the nature of the substituent of the triyne. Bis-silyl-substituted triynes react at the central alkyne unit, whereas bis-aryl- and bis-alkyl-substituted triynes react at the end alkyne unit. The re...

A study on the mechanism of the asymmetric intramolecular Stetter reaction is reported. This investigation includes the determination of the rate law, kinetic isotope effects, and competition experiments. The reaction was found to be first order in aldehyde and azolium catalyst or free carbene. A primary kinetic isotope effect was found for the proton of the aldehyde. Taken together with a seri...

[reaction: see text]. A novel convergent approach to fully functionalized ring C allocolchicinoids is developed which is based on the benzannulation reaction of Fischer carbene complexes with alkynes. The efficacy of this strategy was established with the conversion of bromide 1a (R1 = Me, R2 = H) to the biaryl phenol 3a (R = Me, R(L) = Pr, R(S) = H) via the carbene complex 2a. Bromide 1b (R1 =...

The diastereoselective synthesis of cis-2-amino-3-hydroxyindanones was realized by the N-heterocyclic carbene-catalyzed [4 + 1] annulation of phthalaldehyde and imines, which may involve a tandem aza-benzoin reaction and aldol reaction.

Pd-catalyzed reaction of N-tosylhydrazones with benzyl halides affords di- and trisubstituted olefins in high yields with excellent stereoselectivity. This coupling reaction is supposed to proceed through a migratory insertion of Pd carbene species.