Muriel Amatore

C-H activation/functionalization catalyzed by simple, well-defined low-valent cobalt complexes.

A facile C-H activation and functionalization of aromatic imines is presented using low-valent cobalt catalysts. Using Co(PMe3)4 as catalyst we have developed an efficient and simple protocol for the C-H/hydroarylation of alkynes with an anti selectivity. Deuterium-labeling experiments, DFT calculations coupled with the use of a well-defined catalyst have for the first time shed light on the elusive black box of cobalt catalyzed C-H functionalization.

Highly Enantioselective Rhodium-Catalyzed [2+2+2] Cycloaddition of Diynes to Sulfonimines

A new asymmetric [2+2+2] cycloaddition of diynes to sulfonimines under rhodium catalysis that provides the corresponding enantioenriched 1,2-dihydropyridines in good yields is described.

C2-Alkylation and Alkenylation of Indoles Catalyzed by a Low-Valent Cobalt Complex in the Absence of Reductant

Herein an extremely versatile, well-defined, low-valent cobalt catalyst [Co(PMe3)4] capable of intermolecular and intramolecular imine-directed C2-alkylation and alkenylation of indoles is reported. The reaction proceeds in the absence of reducing agents or additives, affording a range of substituted indoles and dihydropyrroloindoles in high yields and regioselectivities. With the aid of deuterium labeling studies and DFT (Density Functional Theory) calculations, a mechanism is proposed that is based on a Ligand-to-Ligand Hydrogen Transfer pathway.

Regio- and Stereoselective Hydrosilylation of Unsymmetrical Alkynes Catalyzed by a Well-Defined, Low-Valent Cobalt Catalyst.

Herein, the use of a well-defined low-valent cobalt(I) catalyst [HCo(PMe3)4] capable of performing the highly regio- and stereoselective hydrosilylation of internal alkynes is reported. The reaction can be applied to a variety of hydrosilanes, symmetrical and unsymmetrical alkynes, giving in many cases a single hydrosilylation isomer. Experimental and theoretical studies suggest the key step to be a hydro-cobaltation and that the reaction proceeds through a classical Chalk-Harrod mechanism.

Catalytic version of enediyne cobalt-mediated cycloaddition and selective access to unusual bicyclic trienes.

Go cyclic! The use of [Co(H)(PMe3)4] as a cobalt catalyst allows the previously unattainable catalytic version of the cobalt-mediated cycloaddition of enediynes without the requirement of thermal or light activation (see scheme). The importance of a chelating group on the substrate that can selectively direct the reaction pathway toward the classical polycyclic 1,3-cyclohexadienes or a new family of bicyclic trienes is also demonstrated.

Mild niobium-catalyzed [2 + 2 + 2] cycloaddition of sila-triynes: easy access to polysubstituted benzosilacyclobutenes.

A new and efficient synthesis of highly sensitive benzosilacyclobutenes has been developed. For the first time, these compounds can be synthesized in very high yields by a mild, unprecedented intramolecular niobium-catalyzed [2 + 2 + 2] cycloaddition of easily accessible tetrasubstituted sila-triynes. An easy access to highly functionalized benzosilacyclobutenes enlarging the number of potential applications in organic and material chemistry is described.

Niobium-Catalyzed Intramolecular Addition of O–H and N–H Bonds to Alkenes: A Tool for Hydrofunctionalization

A convenient, versatile, and easy to handle intramolecular hydrofunctionalization of alkenes (C-O and C-N bonds formation) is reported using a novel niobium-based catalytic system. This atom economic and eco-friendly methodology provides an additional synthetic tool for the straightforward formation of valuable building blocks enabling molecular complexity. Various pyran, furan, pyrrolidine, piperidine, lactone, and lactam derivatives as well as spirocyclic compounds are produced in high yields and selectivities.

A well-defined low-valent cobalt catalyst Co(PMe3)4 with dimethylzinc: a simple catalytic approach for the reductive dimerization of benzyl halides

Herein, we report the first catalytic version of a cobalt-catalysed reductive homocoupling of benzyl halides which proceeds with low catalyst loadings (0.5 to 5 mol%). By synthetizing each cobalt intermediate we demonstrate that reaction proceeds through two single electron transfers (SET) and that dimethylzinc is only involved in the regeneration of the catalytic species.