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Développement De Réactions D'hydratation D'alcynes Possédant Un Groupement Fluoré À La Position Propargylique Catalysées À L'or

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Développement De Réactions D'hydratation D'alcynes Possédant Un Groupement Fluoré À La Position Propargylique Catalysées À L'or Développement de réactions d'hydratation d'alcynes possédant un groupement fluoré à la position propargylique catalysées à l'or Mémoire Mélissa Cloutier Maîtrise en chimie - avec mémoire Maître ès sciences (M. Sc.) Québec, Canada © Mélissa Cloutier, 2019 Développement de réactions d’hydratation d’alcynes possédant un groupement fluoré à la position propargylique catalysées à l’or Mémoire Mélissa Cloutier Sous la direction de : Jean-François Paquin Résumé La catalyse à l’or a retenu l’attention ces dernières années à cause de la capacité de cet atome d’activer les alcynes en vue d’une attaque nucléophile, dans des conditions douces, en présence d’autres groupements fonctionnels. Des effets relativistes seraient à l’origine de certaines propriétés uniques de l’or. Si le produit de Markovnikov est généralement obtenu lorsque la réaction d’addition est effectuée sur des alcynes terminaux, l’utilisation d’alcynes internes mène à la formation de régioisomères. Ce problème de régiosélectivité peut être, complètement ou partiellement, résolu en utilisant, entre autres, des groupements électroattracteurs à l’une des positions propargyliques. Dans le cadre de ses travaux, la réactivité de substrats portant un groupement fluoré en position propargylique a été explorée. Ici, l’attaque nucléophile se fera de manière préférentielle au carbone de l’alcyne distal du groupement fluoré, faisant office de groupement électroattracteur. Le premier projet porte sur la réaction d’hydratation d’alcynes trifluorométhylés et pentafluorosulfanylés catalysée à l’or pour la formation de cétone α-CF3 et α-SF5, respectivement. Les groupements fluorés, étant électroattracteurs, jouent le rôle du groupement directeur pour ces transformations et mènent à l’obtention d’un seul régioisomère. De plus, ces travaux représentent le premier exemple d’utilisation d’alcynes- CF3 et -SF5 en catalyse à l’or. Basé sur des travaux antérieurs, le second projet porte sur la réaction d’hydroalcoxylation d’haloalcynes gem-difluorés, ayant donc un substituant difluorométhylène à la position propargylique, catalysée à l’or. Cette étude a permis de déterminer l’influence du groupement fluoré, soit le fragment difluorométhylène, comme étant celui qui dirige l’attaque nucléophile, formant un β,β-difluoroester comme seul régioisomère. La transformation présente une régiosélectivité parfaite et l’origine de cette sélectivité a été étudiée par DFT. iii Abstract Gold catalysis attracted a lot of attention in the past few years for its ability to selectively activate alkynes over other functionalities towards nucleophilic attack under mild reaction conditions. Relativistic effects would be at the root of those unique properties of gold. While the Markovnikov product is typically obtained when performing reaction on terminal alkynes, the use of internal alkynes generally leads to the formation of regioisomeric mixtures. This regioselectivity issue can be completely or partially solved using electron- withdrawing groups at one of the propargylic positions. In that context, the reactivity of alkynes bearing a fluorinated group at the propargylic position have been explored. During this work, we observed that the nucleophilic attacked preferentially at the carbon distal to the fluorinated group, the latter acting as a strong electron-withdrawing fragment. The first project involves the gold-catalyzed hydration of trifluoromethylated and pentafluorosulfanylated alkynes for the synthesis of α-CF3 et α-SF5 ketones, respectively. In this case, the CF3 and SF5 groups, strong electron-withdrawing fragments, act as the directing groups. This led to the formation of only one regioisomer. Notably, this transformation represents the first use of CF3- and SF5-alkynes in gold catalysis. The second project concerns the gold-catalyzed hydroalkoxylation of gem-difluorides haloalkynes with a difluoromethylene substituent at the propargylic position. The formation of β,β-difluoroester, as only the only regioisomer, was observed. This showed the strong influence of the fluorinated group, the difluoromethylene fragment, as the directing group. DFT calculations were performed and suggested that this unusual regioselectivity originated from the significant electronic bias imposed by the difluoromethylene unit. iv Table des matières Résumé .................................................................................................................................. iii Abstract .................................................................................................................................. iv Table des matières .................................................................................................................. v Liste des schémas ................................................................................................................. vii Liste des figures ..................................................................................................................... ix Liste des tableaux ................................................................................................................... x Liste des abréviations ............................................................................................................ xi Remerciements .................................................................................................................... xiv Introduction ............................................................................................................................ 1 Les composés organofluorés ............................................................................................... 1 Histoire du fluor .............................................................................................................. 1 Le fluor………………………………………………………………………………….2 Le lien carbone-fluor ....................................................................................................... 3 Applications des composés organofluorés ...................................................................... 5 Les groupements fluorés ................................................................................................. 8 Création d’un lien C-F ...................................................................................................... 11 Réaction de mono- et difluoration ................................................................................. 11 Réaction de trifluorométhylation .................................................................................. 13 Réaction de pentafluorosulfanylation............................................................................ 14 Catalyse par les métaux π-acide ........................................................................................ 18 Réaction d’hydratation d’alcynes catalysée par métaux π-acides ................................. 19 Réaction d’hydratation d’alcynes catalysée à l’or ......................................................... 24 Objectifs de la maîtrise ..................................................................................................... 31 1. Hydratation d’alcynes-CF3 et -SF5 ................................................................................ 34 1.1 Synthèse d’alcynes terminaux................................................................................ 34 1.2 Trifluorométhylation d’alcynes ............................................................................. 39 1.2.1 Trifluorométhylation d’alcynes fonctionnalisés ............................................. 40 1.2.2 Trifluorométhylation d’alcynes terminaux ..................................................... 45 1.2.3 Résultats et discussions – Alcyne-CF3 ........................................................... 51 1.3 Pentafluorosulfanylation d’alcynes ........................................................................ 55 1.3.1 Pentafluorosulfanylation d’alcyne terminaux ................................................. 55 1.3.2 Résultats et discussion – Alcynes-SF5 ............................................................ 56 1.4 Synthèse de cétones α-CF3 ..................................................................................... 58 1.4.1 Substitution nucléophile ................................................................................. 58 1.4.2 Trifluorométhylation électrophile................................................................... 59 1.4.3 Trifluorométhylation radicalaire..................................................................... 60 1.4.4 Hydratation d’aryl(trifluorométhyl)alcynes ................................................... 71 1.5 Synthèse de cétones α-SF5 ..................................................................................... 73 1.6 Résultats et discussion ........................................................................................... 75 1.6.1 Hydratation des alcynes-CF3 .......................................................................... 76 1.6.2 Hydratation des alcynes-SF5 ........................................................................... 83 1.7 Transformations subséquentes ............................................................................... 87 1.8 Conclusion ............................................................................................................. 92 1.9 Partie expérimentale .............................................................................................. 92 v 1.9.1 General information .......................................................................................
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