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.
Organocatalyzed [2+2] Cycloaddition Reactions between Quinone Imine Ketals and Allenoates
Liu, Teng,He, Chixian,Wang, Fan,Shen, Xiang,Li, Yongqin,Lang, Man,Li, Guijun,Huang, Chao,Cheng, Feixiang
, p. 518 - 526 (2020/10/12)
A new cycloaddition reaction of quinone imine ketals (QIKs), which could be utilized to the construction of functionalized azaspirocyclics under mild conditions, is described. This transformation involved a [2+2] cycloaddition reaction between QIKs and allenoates catalyzed by DABCO, and then treatment with 1 N HCl in one-pot. The strategy could provide a practical route to access azetidine-fused spirohexadienones in good to excellent yields and with high E -selectivity.
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.
supporting information, 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.
Substituted dienes prepared from betulinic acid – Synthesis, cytotoxicity, mechanism of action, and pharmacological parameters
Frydrych, Ivo,Urban, Milan,?arek, Jan,Benická, Sandra,D?ubák, Petr,Gurská, Soňa,Hajdúch, Marián,Kotulová, Jana,Li?ková, Barbora,Olejníková, Denisa,Pokorny, Jan
, (2021/07/28)
A set of new substituted dienes were synthesized from betulinic acid by its oxidation to 30-oxobetulinic acid followed by the Wittig reaction. Cytotoxicity of all compounds was tested in vitro in eight cancer cell lines and two noncancer fibroblasts. Almost all dienes were more cytotoxic than betulinic acid. Compounds 4.22, 4.30, 4.33, 4.39 had IC50 below 5 μmol/L; 4.22 and 4.39 were selected for studies of the mechanism of action. Cell cycle analysis revealed an increase in the number of apoptotic cells at 5 × IC50 concentration, where activation of irreversible changes leading to cell death can be expected. Both 4.22 and 4.39 led to the accumulation of cells in the G0/G1 phase with partial inhibition of DNA/RNA synthesis at 1 × IC50 and almost complete inhibition at 5 × IC50. Interestingly, compound 4.39 at 5 × IC50 caused the accumulation of cells in the S phase. Higher concentrations of tested drugs probably inhibit more off-targets than lower concentrations. Mechanisms disrupting cellular metabolism can induce the accumulation of cells in the S phase. Both compounds 4.22 and 4.39 trigger selective apoptosis in cancer cells via intrinsic pathway, which we have demonstrated by changes in the expression of the crucial apoptosis-related protein. Pharmacological parameters of derivative 4.22 were superior to 4.39, therefore 4.22 was the finally selected candidate for the development of anticancer drug.
TREATMENT OF DISORDERS ASSOCIATED WITH OXIDATIVE STRESS AND COMPOUNDS FOR SAME
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Page/Page column 51-52, (2021/09/17)
The present invention relates to the treatment of disorders associated with oxidative stress including neuropathic pain and small synthetically derived compounds for treating such disorders.
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.
Enantioselective Allenoate-Claisen Rearrangement Using Chiral Phosphate Catalysts
Ellwart, Mario,Gensch, Tobias,Han, Seo-Jung,Lin, Hsin-Hui,Miró, Javier,Sigman, Matthew S.,Toste, F. Dean
supporting information, p. 6390 - 6399 (2020/04/27)
Herein we report the first highly enantioselective allenoate-Claisen rearrangement using doubly axially chiral phosphate sodium salts as catalysts. This synthetic method provides access to β-amino acid derivatives with vicinal stereocenters in up to 95percent ee. We also investigated the mechanism of enantioinduction by transition state (TS) computations with DFT as well as statistical modeling of the relationship between selectivity and the molecular features of both the catalyst and substrate. The mutual interactions of charge-separated regions in both the zwitterionic intermediate generated by reaction of an amine to the allenoate and the Na+-salt of the chiral phosphate leads to an orientation of the TS in the catalytic pocket that maximizes favorable noncovalent interactions. Crucial arene-arene interactions at the periphery of the catalyst lead to a differentiation of the TS diastereomers. These interactions were interrogated using DFT calculations and validated through statistical modeling of parameters describing noncovalent interactions.
Phosphine-catalyzed dearomative [3+2] annulation of 3-nitroindoles and allenoates
Liu, Kui,Wang, Gang,Cheng, Shao-Jie,Jiang, Wen-Feng,He, Cheng,Ye, Zhi-Shi
supporting information, p. 1885 - 1890 (2019/06/21)
The efficient phosphine-catalyzed dearomative [3+2] annulation of 3-nitroindoles with allenoates has been successfully developed, providing a facile access to cyclopenta[b]indolines with good to excellent yields and high diastereoselectivities. This strategy features mild reaction conditions, high functional group tolerance, and scalability. Additionally, the 2-nitrobenzofuran and 2-nitrobenzothiophene were good dearomative [3+2] annulation partners.
Heavier Carbonyl Olefination: The Sila-Wittig Reaction
Reiter, Dominik,Frisch, Philipp,Szilvási, Tibor,Inoue, Shigeyoshi
supporting information, p. 16991 - 16996 (2019/10/16)
The Wittig reaction is one of the most versatile tools in the repertoire of organic chemists. Thus, a broad variety of carbonyl compounds can be converted to tailor-made alkenes with phosphorus ylides under mild conditions. However, no comparable reaction has been reported for silanones, the silicon congeners of ketones. Here, we demonstrate for the first time the successful application of the Wittig olefination to iminosilylsilanone 1. The selective formation of a series of silenes (R2Sia? CR2) via the sila-Wittig reaction revealed an unprecedented approach to otherwise elusive compounds. In addition, the highly reactive and zwitterionic nature of 1 was also susceptible to nucleophilic attacks and cycloaddition reactions by and with the phosphorus ylides. Our results therefore make another important contribution to discovering the differences and similarities between carbon and silicon.
