Tableau du bureau des doctorants

The Laboratory of catalysis at the University of Liège has more than 30 years of expertise in macromolecular chemistry, organometallic synthesis and homogeneous catalysis. It is specialized in the application of transition metal complexes to promote reactions in fine organic synthesis and to control specific polymerization processes through molecular engineering. Its research activities cover all the steps involved in the development of a new homogeneous catalytic process in the laboratory, from the synthesis of ligands and organometallic complexes, to the characterization of discrete or macromolecular products, via the optimization of experimental conditions and the elucidation of reaction mechanisms.

The current research efforts of the Laboratory of catalysis are mainly focused on the development of new catalytic systems for carbon-carbon bond formation. In many cases, ruthenium-arene complexes are used as catalyst precursors because they are versatile and efficient promoters for various important organic transformations. This is due in part to the lability of the η6-arene ligand that can be easily removed upon thermal or photochemical activation to release highly active, coordinatively unsaturated species. In particular, three major types of reactions have been successfully investigated:

1. Olefin metathesis

During the 1990s, we demonstrated that [RuCl2(p-cymene)(PR3)] complexes bearing basic and bulky phosphine ligands, such as tricyclohexylphosphine (PCy3), were highly effective precatalysts for the ring-opening metathesis polymerization (ROMP) of strained and low-strain cyclic olefins [1]. Subsequently, we showed that [RuCl2(p-cymene)(NHC)] complexes, in which NHC is an N-heterocyclic carbene ligand, displayed a remarkable activity for initiating the ROMP of cyclooctene under visible light illumination [2]. Our latest advances in the field of olefin metathesis concern the development of bimetallic ruthenium-arene complexes bearing a range of polyunsaturated carbon-based fragments and either a phosphine or NHC ligand [3].

2. Atom transfer radical reactions

Another major contribution from our laboratory is the discovery that the [RuCl2(p-cymene)(PR3)] complexes were highly efficient at promoting the controlled atom transfer radical polymerization (ATRP) of vinyl monomers [4]. The range of ruthenium compounds suitable for initiating ATRP reactions was further expanded to [RuCl(Cp#)(PPh3)2] and [RuCl2(p-cymene)(NHC)] complexes, as well as the Grubbs ruthenium-benzylidene catalysts, under conventional or microwave heating conditions [5]. Our interest in transition metal-catalyzed radical polymerization led us to investigate also the related process of atom-transfer radical addition (ATRA) in the presence of ruthenium complexes [6]. More recently, we have demonstrated the feasibility of atom transfer radical cyclization (ATRC) in tandem with ring-closing metathesis using a common ruthenium catalyst precursor [7].

3. Coupling reactions

In addition to olefin metathesis and atom transfer radical reactions, we are also interested in various other coupling processes for organic synthesis. To achieve the catalytic synthesis of functionalized stilbene derivatives, such as resveratrol, a natural product known for its anti-inflammatory, antioxidant, and anticarcinogenic properties, we have already developed two strategies based either on ruthenium-catalyzed olefin cross-metathesis or palladium-catalyzed Heck and Suzuki-type coupling reactions [8]. We are also currently investigating the synthesis of vinyl esters through ruthenium-catalyzed addition of carboxylic acids to alkynes [9].

Key references

[1] a) "Ruthenium-Based Catalysts for the Ring-Opening Metathesis Polymerisation of Low-Strain Cyclic Olefins and of Functionalised Derivatives of Norbornene and Cyclooctene", A. W. Stumpf, E. Saive, A. Demonceau, A. F. Noels, Chem. Commun. 1995, 1127-1128 (doi: 10.1039/C39950001127); b) "Novel Ruthenium-Based Catalyst Systems for the ROMP of Low-Strain Cyclic Olefins", A. Demonceau, A. W. Stumpf, E. Saive, A. F. Noels, Macromolecules 1997, 30, 3127-3136 (doi: 10.1021/ma961040j).

[2] (a) "Visible Light Induced Ring-Opening Metathesis Polymerisation of Cyclooctene", L. Delaude, A. Demonceau, A. F. Noels, Chem. Commun. 2001, 986-987 (doi: 10.1039/b101699g); (b) "New In situ Generated Ruthenium Catalysts Bearing N-Heterocyclic Carbene Ligands for the Ring-Opening Metathesis Polymerization of Cyclooctene", L. Delaude, M. Szypa, A. Demonceau, A. F. Noels, Adv. Synth. Catal. 2002, 344, 749-756 (doi: 10.1002/1615-4169(200208)344:6/7%3C749::AID-ADSC749%3E3.0.CO;2-T).

[3] (a) "Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes: Synthesis, Characterization, and Catalytic Studies", X. Sauvage, Y. Borguet, G. Zaragoza, A. Demonceau, L. Delaude, Adv. Synth. Catal. 2009, 351, 441-455 (doi: 10.1002/adsc.200800664); (b) "Homobimetallic Ruthenium-Arene Complexes Bearing Vinylidene Ligands: Synthesis, Characterization, and Catalytic Application in Olefin Metathesis", Y. Borguet, X. Sauvage, G. Zaragoza, A. Demonceau, L. Delaude, Organometallics 2010, 29, 6675-6686 (doi: 10.1021/om1006177).

[4] (a) "Highly Efficient Ruthenium-Based Catalytic Systems for the Controlled Free-Radical Polymerisation of Vinyl Monomers", F. Simal, A. Demonceau, A. F. Noels, Angew. Chem., Int. Ed. Engl. 1999, 38, 538-540 (doi: 10.1002/(SICI)1521-3773(19990215)38:4<538::aid-anie538>3.0.CO;2-W); (b) "Evaluation of Ruthenium-Based Complexes for the Controlled Radical Polymerization of Vinyl Monomers", F. Simal, D. Jan, L. Delaude, A. Demonceau, M.-R. Spirlet, A. F. Noels, Can. J. Chem. 2001, 79, 529-535 (doi: 10.1139/cjc-79-5-6-529).

[5] (a) "Tuning of Ruthenium N-Heterocyclic Carbene Catalysts for ATRP", L. Delaude, S. Delfosse, A. Richel, A. Demonceau, A. F. Noels, Chem. Commun. 2003, 1526-1527 (doi: 10.1039/b301733h); (b) "Single-Mode Microwave-Assisted Atom Transfer Radical Polymerization Catalyzed by [RuCl2(p-cymene)(PCy3)]", S. Delfosse, Y. Borguet, L. Delaude, A. Demonceau, Macromol. Rapid Commun. 2007, 28, 492-503 (doi: 10.1002/marc.200600790).

[6] (a) "Electrochemistry as a Correlation Tool with the Catalytic Activities in [RuCl2(p-cymene)(PAr3)]-catalysed Kharasch Additions", A. Richel, A. Demonceau, A. F. Noels, Tetrahedron Lett. 2006, 48, 20772081 (doi: 10.1016/j.tetlet.2006.01.138); (b) "Microwave-Enhanced Ruthenium-Catalysed Atom Transfer Radical Additions", Y. Borguet, A. Richel, S. Delfosse, A. Leclerc, L. Delaude, A. Demonceau, Tetrahedron Lett. 2007, 48, 6334-6338 (doi: 10.1016/j.tetlet.2007.07.029).

[7] "Tandem Catalysis of Ring-Closing Metathesis/Atom Transfer Radical Reactions with Homobimetallic Ruthenium-Arene Complexes", Y. Borguet, X. Sauvage, G. Zaragoza, A. Demonceau, L. Delaude, Beilstein J. Org. Chem. 2010, 6, 1167-1173 (doi: 10.3762/bjoc.6.133).

[8] (a) "Catalytic Methods for the Synthesis of Stilbenes With an Emphasis on Their Phytoalexins", K. Ferré-Filmon, L. Delaude, A. Demonceau, A. F. Noels, Coord. Chem. Rev. 2004, 248, 2323-2336 (doi: 10.1016/j.ccr.2004.02.011); (b) "Stereoselective Synthesis of (E)-Hydroxystilbenoids by Ruthenium-Catalyzed Cross-Metathesis", K. Ferré-Filmon, L. Delaude, A. Demonceau, A. F. Noels, Eur. J. Org. Chem. 2005, 3319-3325 (doi: 10.1002/ejoc.200500068).

[9] "Microwave-Assisted Synthesis of Vinyl Esters through Ruthenium-Catalyzed Addition of Carboxylic Acids to Alkynes", F. Nicks, L. Libert, L. Delaude, A. Demonceau, Aust. J. Chem. 2009, 62, 227-231 (doi: 10.1071/CH08480).

See also the list our recent publications.