0000000001225691
AUTHOR
Henri Doucet
showing 15 related works from this author
C-H Bond Arylation of Pyrazoles at the β-Position: General Conditions and Computational Elucidation for a High Regioselectivity
2021
International audience; Direct arylation of most five-membered ring heterocycles are generally easily accessible and strongly favored at the α-position using classical palladium-catalysis. Conversely, regioselective functionalization of such heterocycles at the concurrent β-position remains currently very challenging. Herein, we report general conditions for regioselective direct arylation at the β-position of pyrazoles, while C-H α-position is free. By using aryl bromides as the aryl source and a judicious choice of solvent, the arylation reaction of variously N-substituted pyrazoles simply proceeds via β-C-H bond functionalization. The β-regioselectivity is promoted by a ligand-free palla…
Direct arylation of heteroaromatic compounds with congested, functionalised aryl bromides at low palladium/triphosphane catalyst loading.
2011
International audience; A new ferrocenyl triphosphane ligand associated to palladium was found to be an efficient catalyst for the direct coupling of highly congested, functionalised aryl bromides with a variety of heteroarenes. These coupling reactions can generally be performed by using a low-loading (0.1-0.5 mol%) of the catalyst. The present protocol tolerates important and useful functional groups, which allows for further elaboration into more sophisticated heterocyclic molecules. The straightforward arylation of heteroaromatic compounds with congested ortho-substituted aryl bromides may permit further convergent syntheses of diverse ligands, biologically active molecules and molecula…
Use of a bulky phosphine of weak σ-donicity with palladium as a versatile and highly-active catalytic system: allylation and arylation coupling react…
2005
Abstract Carbon–carbon(sp2–sp2 and sp1–sp2) and carbon–nitrogen (nucleophilic allylation) coupling processes are promoted by a catalytic system containing [PdCl(η3–C3H5)]2 with the new ferrocenyl bis(difurylphosphine) 1,1′-bis[di(5-methyl-2-furyl)phosphino]ferrocene, Fc[P(FuMe)2]2. Starting from aryl bromides or allylic acetates this versatile catalyst system may be used at low palladium loadings (10−1–10−4 mol%) in some Heck, Suzuki, Sonogashira and allylic amination reactions to give cross-coupled products in excellent yield. Remarkably high activity is obtained in allylic substitution reactions, providing a significant impetus for the development of bulky phosphines possessing weak σ-don…
Palladium-Catalyzed Direct Arylation of Heteroaromatics with Activated Aryl Chlorides Using a Sterically Relieved Ferrocenyl-Diphosphane
2012
International audience; The palladium-catalyzed direct arylations at C3 or C4 positions of heteroaromatics are known to be more challenging than at C2 or C5 positions. Aryl chlorides are also challenging substrates for direct arylation of heteroaromatics. We observed that in the presence of a palladium-catalyst combining only 0.5 mol % of Pd(OAc)2 with the sterically relieved new ferrocenyl diphosphane Sylphos, the direct arylation at C3 or C4 of oxazoles, a benzofuran, an indole, and a pyrazole was found to proceed in moderate to high yields using a variety of electron deficient aryl chlorides. Turnover numbers up to 176 have been obtained with this catalyst. Assessment of the electron-don…
Palladium-based catalytic systems for the synthesis of conjugated enynes by Sonogashira reactions and related alkynylations
2007
Conjugated alkynes are recurring building blocks in natural products, a wide range of industrial intermediates, pharmaceuticals and agrochemicals, and molecular materials for optics and electronics. The palladium-catalyzed cross-coupling between sp(2)-hybridized carbon atoms of aryl, heteroaryl, and vinyl halides with sp-hybridized carbon atoms of terminal acetylenes is one of the most important developments in the field of alkyne chemistry over the past 50 years. The seminal work of the 1970s has initiated an intense search for more general and reliable reaction conditions. The interest in the catalytic activation of demanding substrates, the need to minimize the consumption of depletive r…
Kinetic and Electrochemical Studies of the Oxidative Addition of Demanding Organic Halides to Pd(0): the Efficiency of Polyphosphane Ligands in Low P…
2013
International audience; Oxidative addition (OA) of organic halides to palladium(0) species is a fundamental reaction step which initiates the C–C bond formation catalytic processes typical of Pd(0)/Pd(II) chemistry. The use of structurally congested polyphosphane ligands in palladium-catalyzed C–C bond formation has generated very high turnover numbers (TONs) in topical reactions such as Heck, Suzuki, Sonogashira couplings, and direct sp2C–H functionalization. Herein, the OA of aryl bromides to Pd(0) complexes stabilized by ferrocenylpolyphosphane ligands L1 (tetraphosphane), L2 (triphosphane), and L3 (diphosphane) is considered. The investigation of kinetic constants for the addition of Ph…
ChemInform Abstract: A Versatile Palladium/Triphosphane System for Direct Arylation of Heteroarenes with Chloroarenes at Low Catalyst Loading.
2010
The present new catalyst system can be used for the direct arylation of various heteroaromatic compounds at low palladium loadings.
A Versatile Palladium/Triphosphane System for Direct Arylation of Heteroarenes with Chloroarenes at Low Catalyst Loading
2010
International audience; Put a ring on it: The use of an air-stable, robust palladium/tridentate phosphane catalyst in direct C[BOND]H and C[BOND]Cl activation reactions is reported (see scheme; DMAc=N,N-dimethylacetamide, TBAB=tetra-n-butylammonium bromide). Electron-rich, electron-poor, and polysubstituted furans (X=O), thiophenes (X=S), pyrroles (X=NR5), and thiazoles were arylated with chloroarenes in the presence of the catalyst.
Catalytic Efficiency of a New Tridentate Ferrocenyl Phosphine Auxiliary: Sonogashira Cross-Coupling Reactions of Alkynes with Aryl Bromides and Chlor…
2005
[structure: see text] The catalytic activity in Sonogashira cross-coupling reactions of alkynes with a variety of aryl halides (including chlorides) using a multidentate ferrocenyl phosphine is presented. The novel mixed ferrocenyl aryl/alkyl triphosphine is thermally stable and insensitive to air or moisture, and its robustness allows aryl alkynylation at 10(-1) to 10(-4) mol % catalyst loadings with TONs up to 250,000. Copper-free coupling using phenylacetylene is also accessible in good yield.
Conformational Control of Metallocene Backbone by Cyclopentadienyl Ring Substitution: a New Concept in Polyphosphane Ligands Evidenced by “Through-Sp…
2009
The present study deals with the conformational control of the metallocene backbone within ferrocenyl polyphosphane ligands and their performance in the highly topical palladium-catalyzed heteroaromatics arylation by direct C−H activation. New substituted cyclopentadienyl rings were synthesized, which allowed the assembling of original tri- and diphosphanes. The bulky cyclopentadienyl lithium salts diphenylphosphino-3-(triphenyl)methylcyclopentadienyllithium (4) and 1,2-bis(diphenylphosphino)-4-(triphenyl)methylcyclopentadienyllithium (5) were prepared in excellent yield. The assembling of these new hindered cyclopentadienyl salts (Cp) with other Cp fragments was performed in order to prepa…
Direct arylation of heterocycles: the performances of ferrocene-based polyphosphane ligands in palladium-catalyzed C-H bond activation
2010
International audience; The palladium-catalyzed direct arylation of alkylated- furan, thiophene, and thiazole and benzoxazole heterocycles with electronically and sterically deactivated bromoarenes was selectively and efficiently promoted by ferrocenyl polyphosphanes. In this C[BOND]H bond activation reaction of heteroaromatics, the performances of polydentate di-, tri-, and tetraphosphane ligands were compared, showing that the triphosphane 1,1′,2-tris(diphenylphosphino)-4-tert-butylferrocene 3 was the most effective for the coupling. The introduction of more electron-donating (iPr) or electron-withdrawing (furyl) groups on the phosphorus atoms did not improve the ligand performances. The …
Congested ferrocenyl polyphosphanes bearing electron-donating or electron-withdrawing phosphanyl groups: assessment of metallocene conformation from …
2011
International audience; The synthesis of novel substituted cyclopentadienyl salts that incorporate both a congested branched alkyl group (tert-butyl, (triphenyl)methyl, or tri(4-tert-butyl)phenylmethyl) and a phosphanyl group is reported. The introduction of either electron-withdrawing or electron-donating substituents (furyl, i-propyl, cyclohexyl, tert-butyl) on P atoms was generally achieved in high yield. The modular synthesis of ferrocenyl polyphosphanes from an assembly of these cyclopentadienyl salts was investigated, leading to the formation of new triphosphanes (denoted as 9-12) and diphosphanes (denoted as 14-16). The resulting phosphanes are not sensitive to air or moisture, even …
Palladium-Katalysatorsysteme für die Synthese von konjugierten Eninen durch Sonogashira-Kupplungen und verwandte Alkinylierungen
2007
Konjugierte Alkine sind stets wiederkehrende Synthesebausteine in Naturstoffen, zahlreichen unverzichtbaren industriellen Zwischenstufen, in Pharmazeutika und Agrochemikalien sowie in molekularen Materialien fur Optik und Elektronik. Daher zahlt die palladiumkatalysierte Verknupfung der sp2-hybridisierten Kohlenstoffatome von Aryl-, Heteroaryl- und Vinylhalogeniden mit den sp-hybridisierten Kohlenstoffatomen von terminalen Acetylenen in einer Kreuzkupplung unbestreitbar zu den bedeutendsten Entwicklungen der Alkinchemie in den vergangenen funfzig Jahren. Auf die grundlegenden Arbeiten der 1970er folgte eine intensive Suche nach allgemeineren und verlasslicheren Reaktionsbedingungen. Das Int…
Electrosynthesis as a powerful method for the generation of catalytic intermediates: efficient isolation of a palladium aryl halide oxidative additio…
2011
International audience; Polyphosphane ligands of controlled conformation promote highly efficient palladium-catalyzed cross-coupling reactions. Electrosynthesis has been used as a new straightforward method to obtain important intermediates in the search for a better mechanistic understanding. As a proof of concept, the facile synthesis of a phenyl iodopalladium(II) complex (2) was conducted at the electrolysis scale from a readily electrogenerated unstable Pd0 precursor.
Vers une catalyse durable, économe d'atomes et éco-responsable : 0,0001 % de métal, une dose presque homéopathique pour la synthèse pharmaceutique et…
2009
International audience; Comment mettre la chimie en accord avec un développement sociétal durable, harmonieux et respectueux de l'environnement ? Des chimistes de l'Université de Bourgogne cherchent et trouvent des solutions !