Chirality transfer in metal-­‐catalysed intermolecular addition reactions involving allenes

Allene chemistry in the presence of transition metal complexes is nowadays a very important topic that underpins many challenges and advances in organic synthesis. The amount of research articles covering new transformations of allenes is vast and the development of enantioselective reactions involving allenes has flourished in the last 10-15 years. In this review we cover three important topics in allene chemistry that we feel are timely appropriate for this special issue celebrating the work of Prof Trost: the metal-catalysed reactions involving chirality transfer from chiral allenes to products; the analysis of the possible racemization processes that have been observed in the interaction of some metals with allenes; and the chirality transfer using racemic allenes in reactions catalysed by metal complexes bearing chiral ligands to produce enantioriched products. We have focussed the review on intermolecular addition reactions as they are still much less explored than the intramolecular version

Nouveaux ligands en catalyse asymétrique par des allènes

This thesis has focused on the synthesis of new ligands bearing chirality for asymmetric catalysis. We first aimed to synthesize chiral allenes with phosphine moieties and use them as ligands of transition metals such as gold(I) species. Allenes bearing a phosphine oxide group were prepared from the corresponding propargylic acetate precursors in moderate to high yields. When substituted by a pyridine substituent, these substrates efficiently combined with gold(I) species to afford two types of new vinyl gold complexes. One cationic vinyl complex featuring a triphenylphosphine gold(I) moiety can be further functionalized to give an indolizinium salt and a vinyliodide derivative. The other one bearing a chlorogold(I) group can be used as a catalyst in gold-catalyzed cyclization. Moreover, other allenes have been investigated in gold(I)-catalyzed rearrangements. To our delight, the allenes featuring a 3,5-methoxyphenyl substituent and a vinylallene can produce respectively indenyl and cyclopentadienyl phosphine oxide products bearing stereogenic centers. In addition, a complete axial-to-center chirality transfer was observed on the indenylphosphine oxide product starting from the optically pure allene. In a next attempt, we have prepared some new digold-allenyl bisphosphine precatalysts. These new complexes can be used in gold-catalyzed intermolecular reactions and cyclization reactions. Several carbo- and heterocyclic products were produced in moderate to excellent yields. These chiral gold complexes could be separated by preparative chiral HPLC. Some promising enantiomeric excesses were observed in cycloisomerization reactions.Ce travail de thèse décrit la synthèse de nouveaux ligands chiraux pour des applications en catalyse asymétrique. Nous avons ainsi synthétisé différents allènes chiraux possédant des groupements phosphines et nous les avons testés sur des métaux de transition comme l'or(I). Les allènes possédant des oxydes de phosphine ont été préparés à partir de précurseurs de l'acétate propargylique correspondant avec des rendements modérés à élevés. Nous avons pu montrer que les allènes possédant un motif pyridine se coordinent efficacement avec de l'or(I), donnant deux nouveaux types de complexes d'or vinylique. Un complexe cationique vinylique avec un fragment triphénylphosphine d’or(I) permet de préparer des dérivés fonctionnalisés tels qu’un sel d'indolizinium et un iodure de vinyle. L’autre complexe contenant le groupement de chlore d’or a été utilisé comme catalyseur dans des réactions de cyclisation catalysées par de l'or. De plus, les différents allènes synthétisés ont été étudiés dans le cadre de réarrangements catalysés par l'or. Les allènes avec les groupements 3,5-methoxyphenyl et vinylallène peuvent conduire respectivement à des produits indényle et cyclopentadiényle, portant tous deux un centre stéréogène. En outre, un transfert complet de chiralité axiale en chiralité centrée a été observé sur le produit d’indényle -oxyde de phosphine à partir de l’allène optiquement pur. L’étape suivante, nous avons préparé quelques nouveaux précatalyseurs alléniques bisphosphine bimétalliques à base d’or. Ces nouveaux complexes peuvent être utilisés dans des réactions intermoléculaires et des réactions de cyclisation catalysées à l’or. Plusieurs produits carbocycliques et hétéocycliques ont été obtenus avec des rendements modérées à excellents. Ces complexes d’or chiraux peuvent être séparés par HPLC chirale préparative. Certains des excès énantiomériques obtenus dans les réactions des cycloisomérisations sont prometteurs

Bis-phosphine allene ligand: coordination chemistry and preliminary applications in catalysis

International audienceA 1,3-bis-diphenylphosphine allene can give rise to new coordination complexes with palladium, platinum and gold metals. These complexes were fully characterized by NMR, HRMS and X-ray diffraction analysis. For gold(I), the corresponding dinuclear complex has been used in a series of diagnostic catalytic reactions and gave promising preliminary results in asymmetric catalysis

Synthesis of Allenes Bearing Phosphine Oxide Groups and Investigation of Their Reactivity toward Gold Complexes

International audienceA collection of phosphine oxide allenes has been prepared. Their coordination to gold(I) has been studied giving new coordination complexes when a pendant pyridine moiety was present. Alternatively, their gold(I)-catalyzed cycloisomerization has proven to be quite efficient. An almost complete axial-to-central chirality transfer in the cyclization process was observed, opening the potential access to valuable enantiopure phosphorus derivatives

Indolizy Carbene Ligand. Evaluation of Electronic Properties and Applications in Asymmetric Gold(I) Catalysis

International audienceWe report herein a new family of carbene ligands based on an indolizine-ylidene (Indolizy) moiety. The corresponding gold(I) complexes are easily obtained from the gold(I)-promoted cyclization of allenylpyridine precursors. Evaluation of the electronic properties by experimental methods and also by DFT calculations confirms strong σ-donating and π-accepting properties of these ligands. Cationization of the gold(I) complexes generates catalytic species that trigger diverse reactions of (poly)unsaturated precursors. When armed with a methylene phosphine oxide moiety on the stereogenic center adjacent to the nitrogen atom, the corresponding bifunctional carbene ligands give rise to highly enantioselective heterocyclizations. DFT calculations brought some rationalization and highlighted the critical roles played by the phosphine oxide group and the tosylate anion in the asymmetric cyclization of γ-allenol