Functionalized imidazo[1,5-a]pyridin-3-ylidene ligands : synthesis, coordination chemistry and implementation in Au(I) catalysis / Idir Benaissa  

Public ISBD Titre : Functionalized imidazo[1,5-a]pyridin-3-ylidene ligands : synthesis, coordination chemistry and implementation in Au(I) catalysis Type de document : texte imprimé Auteurs : Idir Benaissa, Auteur ; Vincent Cesar, Directeur de thèse ; Bastin, Stéphanie, Directeur de thèse Langues : Français (fre) Tags : CARBENES  SYNTHESIS  HOMOGENEOUS CATALYSIS  HETEROCYCLES  GOLD  LIGANDS Résumé : "This PhD work concerns the chemistry of N-heterocyclic carbenes (NHCs) and its main objective consists in the development of new NHC ligands based on the imidazo[1,5-a]pyridin-3-ylidene (IPy) platform whose position 5 is functionalized by an anionic or neutral, and potentially chiral barbituric heterocycle. The major advantage of this rigid bicyclic structure lies in the "L-shaped" geometry of the generated ligands, which is particularly well adapted to gold (I) catalysis. In a first time, the chemistry of an achiral version of this family is reported. After describing the synthetic pathway to the zwitterionic precursors, the anionic and neutral gold(I) complexes supported respectively by an anionic NHC and neutral NHC ligands obtained by C- and O-functionalization of the malonate part of the barbiturate heterocycle were synthesized and characterized. The comparative study of these complexes as pre-catalysts in alkyne hydroelementation and domino reaction reactions, involving cycloisomerization of 1,6-enyne followed by nucleophilic addition, showed that the O-methylated ligand complex is the best in the series, as well as superior to conventional NHCs in both activity and selectivity (TON and TOF). The remarkable efficacy of these Au(I) complexes has been rationalized by the electronic and steric stabilization of the active species of cationic gold(I) by the NHC ligand. In a second step, the oxidation process of Au(I) to Au(III) complexes using an external oxidant was studied in detail, and showed that the anionic ligand rearranged from monodentate in Au(I) complex to LX-type bidentate ligand in Au(III) complexes, resulting from a deformation of the barbituric heterocycle and rehybridization of the central malonic carbon atom. This behavior is general as soon as the coordination geometry of the metal center leaves a cis coordination site next to the carbenic center. The complexes of Pd(II), Rh(I), Ir(I) and Mn(I) are thus synthesized and characterized. Structural analysis of the complexes shows that the degree of malonic carbon hybridization is a function of the electrophilicity of the metal, with a more pronounced sp3 character when the electron-density on the metal is lower. A library of three chiral ligands has been synthesized from (S)-(-)-1-phenylethylamine as the source of chiral information through a convergent synthesis strategy similar to that of achiral derivatives. The corresponding Au(I) complexes have been synthesized and used as pre-catalysts in 1,6-enyne domino reactions and provide access to good yields and enantiomeric excesses of up to 70%. In parallel, the reactivity of the 5-bromoimidazo[1,5-a]pyridinium platform with malonate esters and 2-arylacetate esters has been developed. This study proves the intermediacy of free NHCs as reaction intermediates in the synthesis of fused heterotricyclic mesoionic compounds." Document : Thèse de Doctorat Etablissement_delivrance : Université de Toulouse 3 Date_soutenance : 26/11/2019 Ecole_doctorale : Sciences de la Matière (SdM) (Toulouse) Domaine : Chimie organométallique de coordination Localisation : lcc En ligne : http://thesesups.ups-tlse.fr/4517/ Functionalized imidazo[1,5-a]pyridin-3-ylidene ligands : synthesis, coordination chemistry and implementation in Au(I) catalysis [texte imprimé] / Idir Benaissa, Auteur ; Vincent Cesar, Directeur de thèse ; Bastin, Stéphanie, Directeur de thèse . - [s.d.]. Langues : Français (fre) Tags : CARBENES  SYNTHESIS  HOMOGENEOUS CATALYSIS  HETEROCYCLES  GOLD  LIGANDS Résumé : "This PhD work concerns the chemistry of N-heterocyclic carbenes (NHCs) and its main objective consists in the development of new NHC ligands based on the imidazo[1,5-a]pyridin-3-ylidene (IPy) platform whose position 5 is functionalized by an anionic or neutral, and potentially chiral barbituric heterocycle. The major advantage of this rigid bicyclic structure lies in the "L-shaped" geometry of the generated ligands, which is particularly well adapted to gold (I) catalysis. In a first time, the chemistry of an achiral version of this family is reported. After describing the synthetic pathway to the zwitterionic precursors, the anionic and neutral gold(I) complexes supported respectively by an anionic NHC and neutral NHC ligands obtained by C- and O-functionalization of the malonate part of the barbiturate heterocycle were synthesized and characterized. The comparative study of these complexes as pre-catalysts in alkyne hydroelementation and domino reaction reactions, involving cycloisomerization of 1,6-enyne followed by nucleophilic addition, showed that the O-methylated ligand complex is the best in the series, as well as superior to conventional NHCs in both activity and selectivity (TON and TOF). The remarkable efficacy of these Au(I) complexes has been rationalized by the electronic and steric stabilization of the active species of cationic gold(I) by the NHC ligand. In a second step, the oxidation process of Au(I) to Au(III) complexes using an external oxidant was studied in detail, and showed that the anionic ligand rearranged from monodentate in Au(I) complex to LX-type bidentate ligand in Au(III) complexes, resulting from a deformation of the barbituric heterocycle and rehybridization of the central malonic carbon atom. This behavior is general as soon as the coordination geometry of the metal center leaves a cis coordination site next to the carbenic center. The complexes of Pd(II), Rh(I), Ir(I) and Mn(I) are thus synthesized and characterized. Structural analysis of the complexes shows that the degree of malonic carbon hybridization is a function of the electrophilicity of the metal, with a more pronounced sp3 character when the electron-density on the metal is lower. A library of three chiral ligands has been synthesized from (S)-(-)-1-phenylethylamine as the source of chiral information through a convergent synthesis strategy similar to that of achiral derivatives. The corresponding Au(I) complexes have been synthesized and used as pre-catalysts in 1,6-enyne domino reactions and provide access to good yields and enantiomeric excesses of up to 70%. In parallel, the reactivity of the 5-bromoimidazo[1,5-a]pyridinium platform with malonate esters and 2-arylacetate esters has been developed. This study proves the intermediacy of free NHCs as reaction intermediates in the synthesis of fused heterotricyclic mesoionic compounds." Document : Thèse de Doctorat Etablissement_delivrance : Université de Toulouse 3 Date_soutenance : 26/11/2019 Ecole_doctorale : Sciences de la Matière (SdM) (Toulouse) Domaine : Chimie organométallique de coordination Localisation : lcc En ligne : http://thesesups.ups-tlse.fr/4517/

Helicenic N-heterocyclic carbenes (helicenic NHCs) : synthesis and study of the physico-chemical and catalytic properties / Pallova, Lenka  

Public ISBD Titre : Helicenic N-heterocyclic carbenes (helicenic NHCs) : synthesis and study of the physico-chemical and catalytic properties Type de document : texte imprimé Auteurs : Pallova, Lenka, Auteur ; Vincent Cesar, Directeur de thèse ; Bastin, Stéphanie, Directeur de thèse ; Bastin, Stéphanie Année de publication : 2020 Langues : Anglais (eng) Tags : HELICENES  CARBENES N-HETEROCYCLIQUES  CATALYSE ASYMETRIQUES A L'OR(I) Résumé : "This PhD thesis is focused on the chemistry of helicenic N-heterocyclic carbenes (NHCs) thus merging two domains of intense research, namely the chemistries of helicenes and of N-heterocyclic carbenes. The main objective is to develop new classes of helicenic NHC ligands based on the imidazo[1,5-a]pyridin-3-ylidene (IPy) platform functionalised in position 5 of the heterobicycle with adequate helicenic moieties. The functionalisation of the rigid bicyclic IPy structure in position 5 provides L-shaped helicenic NHC ligands which are expected to be well-suited for asymmetric gold(I) catalysis. The synthesis, the study of physico-chemical and catalytic properties of new helicenic NHCs are displayed. First the novel synthesis of C2-symmetric fluorenyl-derived [5] and [7] helicene-like molecules (flu[n]helicenes) is described. The developed synthetic pathway to access flu[5]- and flu[7]helicenes comprises three synthetic steps and has been optimised on a multi-gram scale. Firstly, the symmetrical 1,5-diketones are prepared by base-assisted condensation of formaldehyde with two equivalents of ?-tetralone or 3,4-dihydrophenanthren-4-one. Then an intramolecular McMurry reaction between the two carbonyl moieties of 1,5-diketones affords the partially-hydrogenated (or saturated) fluoreno[5]- and fluoreno[7]helicenes with an internal tetra-substituted, overcrowded C=C bond. The chiral separation and structural characterisation of the different diastereomers are presented as well as their chiroptical properties. The desired fluorenyl-derived [5] and [7] helicene-like molecules are obtained in a final dehydrogenative aromatisation of the saturated fluoreno[5]- and fluoreno[7]helicenes with overall yields of 43% and 22% respectively. The prepared flu[5]- and flu[7]helicenes were then grafted on the 5-bromoimidazo[1,5-a]pyridinium bromide salts via a nucleophilic aromatic substitution (SNAr) to afford the L-shaped helicenic imidazopyridinium salts functionalised at the C5 position of the IPy platform. The latter precursors were monodeprotonated to generate zwitterionic fluorenide-imidazopyridinium compounds or deprotonated twice to yield the corresponding stable free anionic NHCs. The latter were cleanly coordinated to gold(I) centre generating in situ anionic gold(I) complexes, which could be further transformed into a zwitterionic helicenic gold(I) complex by addition of triphenylphosphine, or reprotonated on the helicenic moiety with an acid affording the helicenic NHC-gold(I) complexes. The detailed study of the kinetic and thermodynamic conformers of these gold(I) complexes is presented indicating a possible Au···H-C contact between the acidic helicene proton of the cyclopentadiene ring and the AuI centre. The preliminary results obtained in cycloisomerisation of 1,6-enynes showed low catalytic activity, which might be due to the presence of the acidic helicenic proton of the cyclopentadiene ring in the gold(I) complex. In order to avoid this deleterious acidic proton on the fluorenyl-derived helicenic moiety, the latter was derivatized by alkylation. Depending on the protocol, the alkyl moiety was either installed on the central apical position or on one carbon of the inner rim of the cyclopentadiene ring creating a new centre of chirality on the helicene moiety and inducing axial and helical chirality. The derivatized helicenic NHC-gold(I) complexes were prepared in hundreds of mg and were resolved by chiral HPLC. Their activity in the asymmetric gold(I)-catalysed transformations notably in cycloisomerisation of 1,6-enynes is presented." Document : Thèse de Doctorat Etablissement_delivrance : Université de Toulouse 3 Date_soutenance : 05/11/2020 Ecole_doctorale : Sciences de la Matière (SdM) (Toulouse) Domaine : Chimie moléculaire Localisation : LCC En ligne : http://www.theses.fr/2020TOU30265 Helicenic N-heterocyclic carbenes (helicenic NHCs) : synthesis and study of the physico-chemical and catalytic properties [texte imprimé] / Pallova, Lenka, Auteur ; Vincent Cesar, Directeur de thèse ; Bastin, Stéphanie, Directeur de thèse ; Bastin, Stéphanie . - 2020. Langues : Anglais (eng) Tags : HELICENES  CARBENES N-HETEROCYCLIQUES  CATALYSE ASYMETRIQUES A L'OR(I) Résumé : "This PhD thesis is focused on the chemistry of helicenic N-heterocyclic carbenes (NHCs) thus merging two domains of intense research, namely the chemistries of helicenes and of N-heterocyclic carbenes. The main objective is to develop new classes of helicenic NHC ligands based on the imidazo[1,5-a]pyridin-3-ylidene (IPy) platform functionalised in position 5 of the heterobicycle with adequate helicenic moieties. The functionalisation of the rigid bicyclic IPy structure in position 5 provides L-shaped helicenic NHC ligands which are expected to be well-suited for asymmetric gold(I) catalysis. The synthesis, the study of physico-chemical and catalytic properties of new helicenic NHCs are displayed. First the novel synthesis of C2-symmetric fluorenyl-derived [5] and [7] helicene-like molecules (flu[n]helicenes) is described. The developed synthetic pathway to access flu[5]- and flu[7]helicenes comprises three synthetic steps and has been optimised on a multi-gram scale. Firstly, the symmetrical 1,5-diketones are prepared by base-assisted condensation of formaldehyde with two equivalents of ?-tetralone or 3,4-dihydrophenanthren-4-one. Then an intramolecular McMurry reaction between the two carbonyl moieties of 1,5-diketones affords the partially-hydrogenated (or saturated) fluoreno[5]- and fluoreno[7]helicenes with an internal tetra-substituted, overcrowded C=C bond. The chiral separation and structural characterisation of the different diastereomers are presented as well as their chiroptical properties. The desired fluorenyl-derived [5] and [7] helicene-like molecules are obtained in a final dehydrogenative aromatisation of the saturated fluoreno[5]- and fluoreno[7]helicenes with overall yields of 43% and 22% respectively. The prepared flu[5]- and flu[7]helicenes were then grafted on the 5-bromoimidazo[1,5-a]pyridinium bromide salts via a nucleophilic aromatic substitution (SNAr) to afford the L-shaped helicenic imidazopyridinium salts functionalised at the C5 position of the IPy platform. The latter precursors were monodeprotonated to generate zwitterionic fluorenide-imidazopyridinium compounds or deprotonated twice to yield the corresponding stable free anionic NHCs. The latter were cleanly coordinated to gold(I) centre generating in situ anionic gold(I) complexes, which could be further transformed into a zwitterionic helicenic gold(I) complex by addition of triphenylphosphine, or reprotonated on the helicenic moiety with an acid affording the helicenic NHC-gold(I) complexes. The detailed study of the kinetic and thermodynamic conformers of these gold(I) complexes is presented indicating a possible Au···H-C contact between the acidic helicene proton of the cyclopentadiene ring and the AuI centre. The preliminary results obtained in cycloisomerisation of 1,6-enynes showed low catalytic activity, which might be due to the presence of the acidic helicenic proton of the cyclopentadiene ring in the gold(I) complex. In order to avoid this deleterious acidic proton on the fluorenyl-derived helicenic moiety, the latter was derivatized by alkylation. Depending on the protocol, the alkyl moiety was either installed on the central apical position or on one carbon of the inner rim of the cyclopentadiene ring creating a new centre of chirality on the helicene moiety and inducing axial and helical chirality. The derivatized helicenic NHC-gold(I) complexes were prepared in hundreds of mg and were resolved by chiral HPLC. Their activity in the asymmetric gold(I)-catalysed transformations notably in cycloisomerisation of 1,6-enynes is presented." Document : Thèse de Doctorat Etablissement_delivrance : Université de Toulouse 3 Date_soutenance : 05/11/2020 Ecole_doctorale : Sciences de la Matière (SdM) (Toulouse) Domaine : Chimie moléculaire Localisation : LCC En ligne : http://www.theses.fr/2020TOU30265

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