Medium and Large N-Heterocycle Formation via Allene Hydroamination with a Bimetallic Rh(I) Catalyst

We report the synthesis of a bimetallic Rh(I) complex containing a bridging CO ligand that facilitates Rh–Rh bond formation. This bimetallic complex enables intramolecular allene hydroamination to form seven to ten-member rings in high yield. Monometallic Rh complexes, in contrast, fail to achieve any product formation. We demonstrate a broad substrate scope for formation of a variety of N-heterocycles in good to excellent yields. Macrocyclization reactions that form eleven to fifteen-membered heterocycles are also demonstrated. Mechanistic studies show that the reaction likely proceeds via catalyst protonation by trifluoroacetic acid, followed by reversible allene insertion and C–N bond-forming reductive elimination. The difference in product selectivity observed with our bimetallic catalyst vs monometallic Rh complexes may result from cooperativity between the two metals.

Medium and Large N-Heterocycle Formation via Allene Hydroami-nation with a Bimetallic Rh(I) Catalyst

We report the synthesis of a bimetallic Rh(I) complex containing a bridging CO ligand that facilitates Rh–Rh bond formation. This bimetallic complex enables intramolecular allene hydroamination to form seven to ten-member rings in high yield. Monometallic Rh complexes, in contrast, fail to achieve any product formation. We demonstrate a broad substrate scope for formation of a variety of N-heterocycles in good to excellent yields. Macrocyclization reactions that form eleven to fifteen-membered heterocycles are also demonstrated. Mechanistic studies show that the reaction likely proceeds via catalyst protonation by trifluoroacetic acid, followed by reversible allene insertion and C–N bond-forming reductive elimination. The difference in product selectivity observed with our bimetallic catalyst vs monometallic Rh complexes may result from cooperativity between the two metals.

Di-μ-chlorido-bis(chlorido{8-[2-(dimethylamino)ethylamino]quinoline}cadmium) ethanol monosolvate

The title solvated bimetallic complex, [Cd2Cl4(C13H17N3)2]·C2H5OH, comprises two Cd2+ metal ions linked by a pair of μ2 Cl− ions. The coordination sphere around each Cd2+ ion is completed by three N atoms of a tridentate 8-[2-(dimethylamino)ethylamino]quinoline ligand and another chloride ion to form a distorted fac-CdN3Cl3 octahedron. The ethanol molecule is both an acceptor of an N—H...O and a donor of an O—H...Cl hydrogen bonds to its adjacent complex unit. In the crystal, weak aromatic π–π stacking is observed.