Syntheses of sterically shielded stable carbenes of the 1,2,4-triazole series and their corresponding palladium complexes: efficient catalysts for chloroarene hydrodechlorination.

The new sterically shielded 1,3,4-trisubstituted 1,2,4-triazol-5-ylidenes 8b–d were synthesized by a three step method starting from 2-phenyl-1,3,4-oxadiazole. The syntheses of palladium complexes 9a–d and 10a–d (including the sterically shielded derivatives 9c,d and 10a–d) were carried out via the reactions of the stable carbenes 8a–d with palladium halogenide salts in THF or toluene solution. Complexes 9c,d and 10a–d were found to be excellent catalysts for the reductive dechlorination (hydrodechlorination) of p-dichlorobenzene. The structures of 8c, 9a,b, and 10a were determined by single-crystal X-ray diffraction.

[1]  A. Růžička,et al.  Amino Group Functionalized N-Heterocyclic 1,2,4-Triazole-Derived Carbenes: Structural Diversity of Rhodium(I) Complexes , 2013 .

[2]  Y. Mitoma,et al.  Direct and complete cleansing of transformer oil contaminated by PCBs , 2013 .

[3]  K. Scheidt,et al.  A continuum of progress: applications of N-hetereocyclic carbene catalysis in total synthesis. , 2012, Angewandte Chemie.

[4]  Zu-Jin Lin,et al.  Facile synthesis of palladium nanoparticles encapsulated in amine-functionalized mesoporous metal–organic frameworks and catalytic for dehalogenation of aryl chlorides , 2012 .

[5]  Rui Liu,et al.  Tunable protic ionic liquids as solvent-catalysts for improved synthesis of multiply substituted 1,2,4-triazoles from oxadiazoles and organoamines , 2012 .

[6]  A. V. Kiselev,et al.  Heterocyclic carbene complexes of nickel, palladium, and copper(I) as effective catalysts for the reduction of ketones* , 2012, Chemistry of Heterocyclic Compounds.

[7]  G. Bertrand,et al.  A Brief Survey of our Contribution to Stable Carbene Chemistry. , 2011, Organometallics.

[8]  R. Delaune,et al.  Environmental Applications of Nanoscale and Microscale Reactive Metal Particles , 2011 .

[9]  Shi-Yong Lin,et al.  Hydrodehalogenation of Aryl Chlorides and Aryl Bromides Using a Microwave-Assisted, Copper-Catalyzed Concurrent Tandem Catalysis Methodology , 2011 .

[10]  S. Merino,et al.  Synthesis and characterization of metallodendritic palladium-biscarbene complexes derived from 1,1'-methylenebis(1,2,4-triazole). , 2011, Dalton transactions.

[11]  W. Kirmse.  The beginnings of N-heterocyclic carbenes. , 2010, Angewandte Chemie.

[12]  M. Fuchter.  N-heterocyclic carbene mediated activation of tetravalent silicon compounds: a critical evaluation. , 2010, Chemistry.

[13]  A. Jacobi von Wangelin,et al.  Practical iron-catalyzed dehalogenation of aryl halides. , 2010, Chemical communications.

[14]  M. Page,et al.  Ni(I) and Ni(II) ring-expanded N-heterocyclic carbene complexes: C-H activation, indole elimination and catalytic hydrodehalogenation. , 2010, Chemical communications.

[15]  P. Ghosh,et al.  A comparison between nickel and palladium precatalysts of 1,2,4-triazole based N-heterocyclic carbenes in hydroamination of activated olefins. , 2010, Dalton transactions.

[16]  C. Cazin,et al.  Highly efficient catalytic hydrodehalogenation of polychlorinated biphenyls (PCBs). , 2009, Chemical communications.

[17]  M. Fagnoni,et al.  Eco-friendly hydrodehalogenation of electron-rich aryl chlorides and fluorides by photochemical reaction , 2009 .

[18]  Y. Mitoma,et al.  Metallic Ca-Rh/C-methanol, a high-performing system for the hydrodechlorination/ring reduction of mono- and poly chlorinated aromatic substrates. , 2009, Environmental Science and Technology.

[19]  Gregor Reeske,et al.  Copper(I) halide complexes of the new 4,4′-bridged heteroaromatic biscarbenes of the 1,2,4-triazole series , 2008 .

[20]  G. Rayenko,et al.  Reaction of 1-tert-butyl-3,4-diphenyl-1,2,4-triazol-5-ylidenes with a malonic ester. , 2008, Organic & biomolecular chemistry.

[21]  G. Sheldrick.  A short history of SHELX. , 2008, Acta crystallographica. Section A, Foundations of crystallography.

[22]  D. Enders,et al.  Organocatalysis by N-heterocyclic carbenes. , 2007, Chemical reviews.

[23]  A. Cowley,et al.  Stable carbenes. Synthesis and properties of benzimidazol-2-ylidenes , 2006 .

[24]  S. Nolan,et al.  Suzuki-Miyaura, alpha-ketone arylation and dehalogenation reactions catalyzed by a versatile N-heterocyclic carbene-palladacycle complex. , 2006, The Journal of organic chemistry.

[25]  S. Nolan,et al.  Cross-coupling and dehalogenation reactions catalyzed by (N-heterocyclic carbene)Pd(allyl)Cl complexes. , 2004, The Journal of organic chemistry.

[26]  S. Mohapatra,et al.  Selective reduction of alkenes, α,β-unsaturated carbonyl compounds, nitroarenes, nitroso compounds, N,N-hydrogenolysis of azo and hydrazo functions as well as simultaneous hydrodehalogenation and reduction of substituted aryl halides over PdMCM-41 catalyst under transfer hydrogen conditions , 2004 .

[27]  Ying Cheng,et al.  Heterocycles derived from heteroatom-substituted carbenes. , 2004, Chemical reviews.

[28]  Xiaobo Fan,et al.  Approach to highly efficient dechlorination of PCDDs, PCDFs, and coplanar PCBs using metallic calcium in ethanol under atmospheric pressure at room temperature. , 2004, Environmental science & technology.

[29]  G. Rayenko,et al.  Synthesis of 1,2,4-triazol-5-ylidenes and their interaction with acetonitrile and chalcogens. , 2003, The Journal of organic chemistry.

[30]  R. Schneider,et al.  Catalytic Carbon‐Fluorine Bond Activation with Monocoordinated Nickel‐Carbene Complexes: Reduction of Fluoroarenes , 2003 .

[31]  S. Nolan,et al.  Catalytic Dehalogenation of Aryl Halides Mediated by a Palladium/Imidazolium Salt System , 2001 .

[32]  D. Enders,et al.  Chemical Reactions of the Stable Carbene 1,3,4-Triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene , 1996 .

[33]  D. Enders,et al.  Preparation, Structure, and Reactivity of 1,3,4-Triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene, a New Stable Carbene† , 1995 .

[34]  S. V. Tsukerman,et al.  Synthesis of unsaturated diketones and δ2-pyrazoline derivatives from terephthalaldehyde , 1971 .