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N-Heterocyclic carbene–palladium(II)-1-methylimidazole complex catalyzed Mizoroki–Heck reaction of aryl chlorides with styrenes  [cached]
Ting-Ting Gao,Ai-Ping Jin,Li-Xiong Shao
Beilstein Journal of Organic Chemistry , 2012, DOI: 10.3762/bjoc.8.222
Abstract: A well-defined N-heterocyclic carbene–palladium(II)-1-methylimidazole [NHC-Pd(II)-Im] complex 1 was found to be an effective catalyst for the Mizoroki–Heck reaction of a variety of aryl chlorides with styrenes. Both activated and deactivated aryl chlorides work well to give the corresponding coupling products in good to excellent yields by using tetrabutylammonium bromide (TBAB) as the ionic liquid.
Alkyne hydroarylation with Au N-heterocyclic carbene catalysts
Cristina Tubaro,Marco Baron,Andrea Biffis,Marino Basato
Beilstein Journal of Organic Chemistry , 2013, DOI: 10.3762/bjoc.9.29
Abstract: Mono- and dinuclear gold complexes with N-heterocyclic carbene (NHC) ligands have been employed as catalysts in the intermolecular hydroarylation of alkynes with simple unfunctionalised arenes. Both mono- and dinuclear gold(III) complexes were able to catalyze the reaction; however, the best results were obtained with the mononuclear gold(I) complex IPrAuCl. This complex, activated with one equivalent of silver tetrafluoroborate, exhibited under acidic conditions at room temperature much higher catalytic activity and selectivity compared to more commonly employed palladium(II) catalysts. Moreover, the complex was active, albeit to a minor extent, even under neutral conditions, and exhibited lower activity but higher selectivity compared to the previously published complex AuCl(PPh3). Preliminary results on intramolecular hydroarylations using this catalytic system indicate, however, that alkyne hydration by traces of water may become a serious competing reaction.
N-Heterocyclic carbene/Br nsted acid cooperative catalysis as a powerful tool in organic synthesis  [cached]
Rob De Vreese,Matthias D’hooghe
Beilstein Journal of Organic Chemistry , 2012, DOI: 10.3762/bjoc.8.43
Abstract: The interplay between metals and N-heterocyclic carbenes (NHCs) has provided a window of opportunities for the development of novel catalytic strategies within the past few years. The recent successful combination of Br nsted acids with NHCs has added a new dimension to the field of cooperative catalysis, enabling the stereoselective synthesis of functionalized pyrrolidin-2-ones as valuable scaffolds in heterocyclic chemistry. This Commentary will briefly highlight the concept of N-heterocyclic carbene/Br nsted acid cooperative catalysis as a new and powerful methodology in organic chemistry.
Nanofiber composites containing N-heterocyclic carbene complexes with antimicrobial activity
Elzatahry AA, Al-Enizi AM, Elsayed EA, Butorac RR, Al-Deyab SS, Wadaan MAM, Cowley AH
International Journal of Nanomedicine , 2012, DOI: http://dx.doi.org/10.2147/IJN.S31810
Abstract: nofiber composites containing N-heterocyclic carbene complexes with antimicrobial activity Rapid Communication (3134) Total Article Views Authors: Elzatahry AA, Al-Enizi AM, Elsayed EA, Butorac RR, Al-Deyab SS, Wadaan MAM, Cowley AH Published Date June 2012 Volume 2012:7 Pages 2829 - 2832 DOI: http://dx.doi.org/10.2147/IJN.S31810 Received: 15 March 2012 Accepted: 10 April 2012 Published: 07 June 2012 Ahmed A Elzatahry1,4, Abdullah M Al-Enizi1, Elsayed Ahmed Elsayed2,5, Rachel R Butorac3, Salem S Al-Deyab1, Mohammad AM Wadaan2, Alan H Cowley3 1Petrochemical Research Chair, Department of Chemistry, 2Chair of Advanced Proteomics & Cytomics Research, Faculty of Science, King Saud University, Riyadh, Kingdom of Saudi Arabia; 3Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX, USA; 4Institute of Advanced Technology and New Materials, City for Scientific Research and Technology Applications, New Borg Alrab, Alexandria, Egypt; 5Natural & Microbial Products Department, National Research Centre, Dokki, Cairo, Egypt Abstract: This report concerns nanofiber composites that incorporate N-heterocyclic carbenes and the use of such composites for testing antimicrobial and antifungal activities. The nanofiber composites were produced by electrospinning mixtures of the gold chloride or gold acetate complexes of a bis(imino)acenaphthene (BIAN)-supported NHC with aqueous solutions of polyvinyl alcohol (PVA). The products were characterized by scanning-electron microscopy, which revealed that nanofibers in the range of 250–300 nm had been produced. The biological activities of the nanofiber composites were tested against two Gram-positive bacteria, six Gram-negative bacteria, and two fungal strains. No activity was evident against the fungal strains. However, the gold chloride complex was found to be active against all the Gram-positive pathogens and one of the Gram-negative pathogens. It was also found that the activity of the produced nanofibers was localized and that no release of the bioactive compound from the nanofibers was evident. The demonstrated antimicrobial activities of these novel nanofiber composites render them potentially useful as wound dressings.
Antimicrobial Properties of Some Bis(Iminoacenaphthene (BIAN)-Supported N-Heterocyclic Carbene Complexes of Silver and Gold  [PDF]
Rachel R. Butorac,Salem S. Al-Deyab,Alan H. Cowley
Molecules , 2011, DOI: 10.3390/molecules16032285
Abstract: The AgCl, AgOAc, AuCl, and AuOAc complexes of the new bis(imino)acenaphthene(BIAN)-supported N-heterocyclic carbene ligand and the precursor imidazolium salt have been investigated with respect to their antimicrobial activities against Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Psudomonas aeruginosa. The most active antimicrobial is the precursor imidazolium salt, which has a minimum inhibitory concentration (MIC) value of
Gold(I) Complexes of N-Heterocyclic Carbene Ligands Containing Benzimidazole: Synthesis and Antimicrobial Activity  [PDF]
?lknur ?zdemir,Nazan Temelli,Selami Günal,Serpil Demir
Molecules , 2010, DOI: 10.3390/molecules15042203
Abstract: Gold(I) N-heterocyclic carbene (NHC) complexes were obtained in good yields from the corresponding silver complexes by treatment with [AuCl(PPh3)] following the commonly used silver carbene transfer route. The silver complexes were synthesized from the benzimidazolium halide salts by the in situ reactions with Ag2O in dichloromethane as a solvent at room temperature. All gold complexes have been characterized by 1H-NMR, 13C-NMR and IR spectroscopy and elemental analysis. Au-NHC complexes were evaluated for their in vitro antimicrobial activity against a variety of Gram-positive and Gram-negative bacteria and fungal species.
Expedient syntheses of the N-heterocyclic carbene precursor imidazolium salts IPr·HCl, IMes·HCl and IXy·HCl
Hintermann Lukas
Beilstein Journal of Organic Chemistry , 2007, DOI: 10.1186/1860-5397-3-22
Abstract: The 1,3-diaryl-imidazolium chlorides IPr·HCl (aryl = 2,6-diisopropylphenyl), IMes·HCl (aryl = 2,4,6-trimethylphenyl) and IXy·HCl (aryl = 2,6-dimethylphenyl), precursors to widely used N-heterocyclic carbene (NHC) ligands and catalysts, were prepared in high yields (81%, 69% and 89%, respectively) by the reaction of 1,4-diaryl-1, 4-diazabutadienes, paraformaldehyde and chlorotrimethylsilane in dilute ethyl acetate solution. A reaction mechanism involving a 1,5-dipolar electrocyclization is proposed.
N-Heterocyclic carbene-catalyzed direct cross-aza-benzoin reaction: Efficient synthesis of α-amino-β-keto esters
Takuya Uno,Yusuke Kobayashi,Yoshiji Takemoto
Beilstein Journal of Organic Chemistry , 2012, DOI: 10.3762/bjoc.8.169
Abstract: An efficient catalytic synthesis of α-amino-β-keto esters has been newly developed. Cross-coupling of various aldehydes with α-imino ester, catalyzed by N-heterocyclic carbene, leads chemoselectively to α-amino-β-keto esters in moderate to good yields with high atom efficiency. The reaction mechanism is discussed, and it is proposed that the α-amino-β-keto esters are formed under thermodynamic control.
Enolate chelating N-heterocyclic carbene complexes of Fe(II): Synthesis, structure and their catalytic activity for ring-opening polymerization of -caprolactone
YongSheng Wang,HongMei Sun,XuePing Tao,Qi Shen,Yong Zhang
Chinese Science Bulletin , 2007, DOI: 10.1007/s11434-007-0477-5
Abstract: The reaction of anhydrous FeBr2 with two equivalents of anionic N-heterocyclic carbene (NaL1 and NaL2), which are generated in situ by the reaction of the corresponding salt [4-R-C6H4COCH2{CH-(NCHCHNiPr)}Br] (R = OCH3, H2L1Br, 1; R = F, H2L2Br, 2) with two equivalents of NaN(SiMe3)2, affords bis-ligand Fe(II) complexes of L1 2Fe (3) and L2 2Fe (4) in high yield, respectively. Attempt to synthesize mono-ligand Fe(II) bromide by the 1:1 molar ratio of NaL to FeBr2 is unsuccessful, and the same complexes of 3 and 4 were obtained. Both 3 and 4 have been depicted by elemental analysis and X-ray structure determination. Preliminary studies show that both 3 and 4 can be used as single-component catalyst for the ring-opening polymerization of -caprolactone, and the catalytic activity of 3 is higher than that of 4.
Ionic Liquid-Mediated, Rapid N-Alkylation of Heterocyclic Compounds with Trialkyl Phosphites in the Presence of Dialkyl Acetylenedicarboxylates  [PDF]
Alireza Hassanabadi,Mohammad H. Mosslemin,Mohammad Anary-Abbasinejad,Azadeh Kalantarinejad,Mozhdeh Jerjisi Shirazi
Journal of Chemistry , 2012, DOI: 10.1155/2012/786024
Abstract: Ionic liquids such as 1,3-dialkylimidazolium bromides and make excellent solvents for N-alkylation of heterocyclic compounds such as saccharin and rhodanine with trialkyl phosphites in the presence of dialkyl acetylenedicarboxylates.
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