6 research outputs found
Evaluation of gold catalysis in N-acyliminium ion chemistry : application to one-pot synthesis of fused nitrogen-based polycyclic compounds
AGrĂące Ă sa forte carbophilie, lâor est devenu en quelques annĂ©es un mĂ©tal de choix pour la formation de liaisons C-C et C-X (X = O, N, S). Par ailleurs, sa capacitĂ© Ă activer des hĂ©tĂ©roatomes (aciditĂ© Ï-Lewis) a Ă©tĂ© reconnue Ă©galement et justifiĂ©e par de nombreux exemples de transformations de substrats carbonyles, imines, alcools Ï-activĂ©s et Ă©poxydes. Dans le contexte de la recherche de mĂ©thodes Ă©conomiques et respectueuses de l'environnement dans le domaine de la chimie des ions N-acyliminiums, nous nous sommes intĂ©ressĂ©s Ă la capacitĂ© de lâor Ă promouvoir la formation des ions N-acyliminiums. Dans une premiĂšre partie de ce travail, nous avons montrĂ© que l'aciditĂ© de type Ï-Lewis de sels cationiques dâor (I) et (III) pouvait ĂȘtre exploitĂ©e pour catalyser efficacement la substitution nuclĂ©ophile de divers alcoxy-et acĂ©toxylactames, prĂ©curseurs dâions N-acyliminiums. La rĂ©action est compatible avec une large gamme de nuclĂ©ophiles, incluant notamment l'allyltrimĂ©thylsilane, les Ă©thers d'Ă©nols silylĂ©s, les arĂšnes et les dĂ©rivĂ©s de mĂ©thylĂšnes actifs. Dans un second temps, les deux caractĂšres carbophile et oxophile des catalyseurs Ă lâor ont Ă©tĂ© combinĂ©s dans un processus cascade α-amidoalkylation/hydroarylation. Une seconde approche multicatalytique (acide de BrĂžnsted â acide de Lewis) a ensuite Ă©tĂ© dĂ©veloppĂ©e comme alternative pour pallier Ă certaines limites du systĂšme « tout or ». Ces sĂ©quences rĂ©actionnelles one-pot permettent dâaccĂ©der de façon rapide et efficace Ă un large panel de composĂ©s polycycliques fusionnĂ©s Ă partir de matiĂšres triviales.AGold catalysts, as soft carbophilic Lewis acids, have rapidly develop and mature to become nowadays an outstanding tool for new C-C and C-X bonds (X = O, S, N) through Ï-bond activation. Moreover, its Ï-Lewis acidity was also acknowledged and exemplified by numerous examples of carbonyl, imine, Ï-activated alcohol and epoxide activation. As part of our ongoing studies on N-acyliminium ion chemistry, we have been interested in using gold catalysts for N-acyliminium ion generation. First, we have shown that the Ï-Lewis acidity of gold(I) and gold(III) could be exploited to efficiently catalyze the nucleophilic substitution reactions of various alkoxy- and acetoxylactams, precursors of N-acyliminium ions. The reaction was found to tolerate a wide range of nucleophiles, including allyltrimethylsilane, silyl enol ethers, arenes as well as active methylene derivatives. Next, gold catalysis was applied to cascade α-amidoalkylation/hydroarylation sequences unifying both the Ï- and Ï-Lewis acid properties of gold complexes. Alternatively, BrĂžnsted acid/Lewis acid multicatalysis approach has been alternatively developed to override some limitations featuring this unprecedented tandem intermolecular FriedelâCrafts/intramolecular hydroarylation sequence. This two complementary and highly efficient cascade sequences enable expedient access to complex fused polycyclic structures from trivial materials
Dual Hard/Soft Gold Catalysis: Intermolecular Friedel-Crafts-Type α-Amidoalkylation/Alkyne Hydroarylation Sequences by N -Acyliminium Ion Chemistry
International audienc
Gold catalysis: A one-pot intermolecular Fridel-Crafts type α-amidoalkylation/hydroarylation sequences by N-acyliminium ion chemistry
International audienc
Kineococcus radiotolerans Dps forms a heteronuclear Mn-Fe ferroxidase center that may explain the Mn-dependent protection against oxidative stress
International audienceThe combined use of Tf2NH and L(Au)+X- as a dual or binary catalytic system clearly improves the efficiency and enlarges the scope of the tandem intermolecular Friedel-Crafts α-amidoalkylation/intramolecular hydroarylation sequence, compared to an "all gold" multicatalysis approach. © 2015 American Chemical Society