1003017-86-4

Upstream product

• 45860-18-2 1,3,5-tribromo-2-nitroso-benzene 
• 141556-42-5 [1,3-bis(2,4,6-trimethylphenyl)imidazol]-2-ylidene 
• 865-47-4 potassium tert-butylate 
• 12775-96-1 copper 
• 141556-45-8 1,3-bis(mesityl)imidazolium chloride 
• 56222-36-7 N,N'-bis(2,4,6-trimethylphenyl)ethanediimine 
• 1394238-38-0 2-benzylidene-1,3-dimesityl-2,3-dihydro-1H-imidazole 
• 1354689-39-6 1,3-dimesitylimidazol-2-ylidene-NNO 

Relevant academic research and scientific papers

On the involvement of a spiroepoxide intermediate in N-heterocyclic carbene (NHC)-catalyzed benzoin condensations - An approach by oxygenation of deoxy-breslow intermediates

The involvement of a spiroepoxide, an isomer of the Breslow intermediate, in the catalytic cycle of the N-heterocyclic carbene (NHC)-catalyzed benzoin condensation was suggested by S. Gronert in 2007, based on calculations. To test this hypothesis, enediamines were generated in situ from (in part 13C-labeled) N-heterocyclic carbenes, benzyl bromide and base, and subsequently treated with various single-oxygen atom oxidants. Clean oxidation occurred with a triazolylidene-derived enediamine and an N-sulfonyloxaziridine as oxidant, but NMR monitoring gave no hint to the accumulation of a spiroepoxide. Instead, oxidative cleavage of the enediamine to the free carbene and benzaldehyde was observed, with subsequent oxidation of the carbene to a urea. Presumably, electrophilic oxygenation of the enediamine occurs at the exocyclic methylene carbon atom and affords a zwitterion - identical to the primary carbene-aldehyde adduct of the benzoin cycle - which undergoes retro-cleavage to carbene and aldehyde. However, the occurrence of a spiroepoxide as transient intermediate of the oxidative C=C bond cleavage cannot rigorously be excluded.

Electrochemical flow-reactor for expedient synthesis of copper-N-heterocyclic carbene complexes

An electrochemical flow-cell for highly efficient and selective generation of CuI-N-heterocyclic carbene complexes under neutral and ambient conditions is reported. The feasibility of the flow-cell is demonstrated through the electrochemical sy

Deoxygenation of nitrosoarene by N-heterocyclic carbene (NHC): an elusive Breslow-type intermediate bridging carbene and nitrene

N-Heterocyclic carbene (NHC) activates and deoxygenates nitrosoarene (ArNO) to afford arylnitrene (ArN), thereby portraying a fundamental route connecting two 6e?species. A combination of spectroscopic and computational studies suggests that th

Revealing the unusual role of bases in activation/deactivation of catalytic systems: O-NHC coupling in M/NHC catalysis

Numerous reactions are catalyzed by complexes of metals (M) with N-heterocyclic carbene (NHC) ligands, typically in the presence of oxygen bases, which significantly shape the performance. It is generally accepted that bases are required for either substrate activation (exemplified by transmetallation in the Suzuki cross-coupling), or HX capture (e.g. in a variety of C-C and C-heteroatom couplings, the Heck reaction, C-H functionalization, heterocyclizations, etc.). This study gives insights into the behavior of M(ii)/NHC (M = Pd, Pt, Ni) complexes in solution under the action of bases conventionally engaged in catalysis (KOH, NaOH, t-BuOK, Cs2CO3, K2CO3, etc.). A previously unaddressed transformation of M(ii)/NHC complexes under conditions of typical base-mediated M/NHC catalyzed reactions is disclosed. Pd(ii) and Pt(ii) complexes widely used in catalysis react with the bases to give M(0) species and 2(5)-oxo-substituted azoles via an O-NHC coupling mechanism. Ni(NHC)2X2 complexes hydrolyze in the presence of aqueous potassium hydroxide, and undergo the same O-NHC coupling to give azolones and metallic nickel under the action of t-BuOK under anhydrous conditions. The study reveals a new role of NHC ligands as intramolecular reducing agents for the transformation of M(ii) into ligandless M(0) species. This demonstrates that the disclosed base-mediated O-NHC coupling reaction is integrated into the catalytic M/NHC systems and can define the mechanism of catalysis (molecular M/NHC vs. NHC-free cocktail-type catalysis). A proposed mechanism of the revealed transformation includes NHC-OR reductive elimination, as implied by a series of mechanistic studies including 18O labeling experiments.

Oxygen-atom insertion of NHCecopper complex: The source of oxygen from N, N-dimethylformamide

An unprecedented protocol for oxygen-atom insertion reaction of NHCecopper complexes has been developed by employing N,N-dimethylformamide as the oxygen source, which allows the preparation of imidazolinones from carbene complexes and decodes one of the m

Adducts of nitrous oxide and N-heterocyclic carbenes: Syntheses, structures, and reactivity

N-Heterocyclic carbenes (NHCs) react at ambient conditions with nitrous oxide to give covalent adducts. In the crystal, all compounds show a bent N 2O group connected via the N-atom to the former carbene carbon atom. Most adducts are stable at room temperature, but heating induces decomposition into the corresponding ureas. Kinetic experiments show that the thermal stability of the NHC-N2O adducts depends on steric as well as electronic effects. The coordination of N2O to NHCs weakens the N-N bond substantially, and facile N-N bond rupture was observed in reactions with acid or acetyl chloride. On the other hand, reaction with tritylium tetrafluoroborate resulted in a covalent modification of the terminal O-atom, and cleavage of the C-N2O bond was observed in a reaction with thionyl chloride. The coordination chemistry of IMes-N2O (IMes = 1,3-dimesitylimidazol-2-ylidene) was explored in reactions with the complexes CuOTf, Fe(OTf)2, PhSnCl3, CuCl2, and Zn(C 6F5)2. Structural analyses show that IMes-N2O is able to act as a N-donor, as an O-donor, or as a chelating N,O-donor. The different coordination modes go along with pronounced electronic changes as evidenced by a bond length analysis.

Covalent capture of nitrous oxide by N-heterocyclic carbenes

A good catch: N-Heterocyclic carbenes (NHCs) form stable adducts with nitrous oxide (N2O) under mild reaction conditions. The adducts display unique reactivity as evidenced by an alkylation reaction which leads to a rupture of the N-N bond.