21204-67-1Relevant articles and documents
Iron(II) N-heterocyclic carbene complexes in catalytic one-pot Wittig reactions: Mechanistic insights
Karaca, ?zden,Anneser, Markus R.,Kück, Jens W.,Lindhorst, Anja C.,Cokoja, Mirza,Kühn, Fritz E.
, p. 213 - 220 (2016)
An iron(II) N-heterocyclic carbene (NHC) complex is applied as catalyst for aldehyde olefination with ethyl diazoacetate (EDA) in the presence of triphenylphosphine. The reaction leads to high olefin yields with very good E-selectivities. The key step of the reaction is the catalytic in situ generation of a phosphorus ylide. Mechanistic studies reveal two possible pathways for the formation of the Wittig reagent with respect to the carbene source being the metal carbene (NHC)FeIV[dbnd]CH(CO2Et), and phosphazine, Ph3P[dbnd]N[sbnd]N[dbnd]CH(CO2Et). Based on the experimental observations a new mechanism for the transformation of phosphazine is proposed.
Catalytic Synthesis of 1 H-2-Benzoxocins: Cobalt(III)-Carbene Radical Approach to 8-Membered Heterocyclic Enol Ethers
De Bruin, Bas,De Zwart, Felix J.,Li, Zirui,Mathew, Simon,Wolzak, Lukas A.,Zhou, Minghui
supporting information, p. 20501 - 20512 (2021/12/03)
The metallo-radical activation of ortho-allylcarbonyl-aryl N-arylsulfonylhydrazones with the paramagnetic cobalt(II) porphyrin catalyst [CoII(TPP)] (TPP = tetraphenylporphyrin) provides an efficient and powerful method for the synthesis of novel 8-membered heterocyclic enol ethers. The synthetic protocol is versatile and practical and enables the synthesis of a wide range of unique 1H-2-benzoxocins in high yields. The catalytic cyclization reactions proceed with excellent chemoselectivities, have a high functional group tolerance, and provide several opportunities for the synthesis of new bioactive compounds. The reactions are shown to proceed via cobalt(III)-carbene radical intermediates, which are involved in intramolecular hydrogen transfer (HAT) from the allylic position to the carbene radical, followed by a near-barrierless radical rebound step in the coordination sphere of cobalt. The proposed mechanism is supported by experimental observations, density functional theory (DFT) calculations, and spin trapping experiments.
Catalytic asymmetric [3+2] cycloaddition of isomünchnones with methyleneindolinones
Feng, Xiaoming,Hu, Xinyue,Lin, Lili,Wang, Kaixuan,Xu, Chaoran,Zhou, Yuqiao
, p. 8917 - 8920 (2021/09/10)
An efficient enantioselective [3+2] cycloaddition of isomünchnones with methyleneindolinones that are generated by anin situintramolecular addition of the carbonyl group to rhodium carbenes is realized with a chiralN,N′-dioxide/Zn(ii) complex as a Lewis acid. A series of chiral oxa-bridged 3-spiropiperidines are obtained in high yields with excellent dr and excellent ee values.
Enantioselective Rauhut–Currier Reaction with β-Substituted Acrylamides Catalyzed by N-Heterocyclic Carbenes
Pitchumani, Venkatachalam,Breugst, Martin,Lupton, David W.
, p. 9413 - 9418 (2021/12/09)
β-Substituted acrylamides have low electrophilicity and are yet to be exploited in the enantioselective Rauhut–Currier reaction. By exploiting electron-withdrawing protection of the amide and moderate nucleophilicity N-heterocyclic carbenes, such substrates have been converted to enantioenriched quinolones. The reaction proceeds with complete diastereoselectivity, good yield, and modest enantioselectivity. Derivatizations are reported, as are computational studies, supporting decreased amide bond character with electron-withdrawing protection of the nitrogen.
