Ruthenium Catalyzed Reductive Coupling of Paraformaldehyde to Trifluoromethyl Allenes: CF₃‑Bearing All-Carbon Quaternary Centers

Trifluoromethyl substituted allenes engage in ruthenium catalyzed reductive couplings with paraformaldehyde to form products of hydrohydroxymethylation as single regioisomers. This method enables generation of CF₃-bearing all-carbon quaternary stereocenters

Synthesis and Evaluation of Sterically Demanding Ruthenium Dithiolate Catalysts for Stereoretentive Olefin Metathesis

Dithiolate ligands have recently been used in ruthenium-catalyzed olefin metathesis and have provided access to a kinetically <i>E</i> selective pathway through stereoretentive olefin metathesis. The typical dithiolate used is relatively simple with low steric demands imparted on the catalyst. We have developed a synthetic route that allows access to sterically demanding dithiolate ligands. The catalysts generated provided a pathway to study the intricate structure–activity relationships in olefin metathesis. It was found that DFT calculations can predict the ligand arrangement around the ruthenium center with remarkable accuracy. These dithiolate catalysts proved resistant to ligand isomerization and were stable even under forcing conditions. Additionally, catalyst initiation and olefin metathesis studies delivered a better understanding to the interplay between dithiolate ligand structure and catalyst activity and selectivity

Enantioselective Conversion of Primary Alcohols to α-<i>exo</i>-Methylene γ-Butyrolactones via Iridium-Catalyzed C–C Bond-Forming Transfer Hydrogenation: 2-(Alkoxycarbonyl)allylation

Upon exposure of acrylic ester <b>1</b> to alcohols <b>2a</b>–<b>i</b> in the presence of a cyclometalated iridium catalyst modified by (−)-TMBTP, catalytic C–C coupling occurs, providing enantiomerically enriched 5-substituted α-<i>exo</i>-methylene γ-butyrolactones <b>3a</b>–<b>i</b>. Bromination of the methylene butyrolactone products followed by zinc-mediated reductive aldehyde addition provides the disubstituted α-<i>exo</i>-methylene γ-butyrolactones <b>6a</b> and <b>6b</b> with good to excellent levels of diastereoselectivity

Ruthenium Catalyzed Hydrohydroxyalkylation of Isoprene with Heteroaromatic Secondary Alcohols: Isolation and Reversible Formation of the Putative Metallacycle Intermediate

Heteroaromatic secondary alcohols react with isoprene to form products of hydrohydroxyalkylation in the presence of ruthenium(0) catalysts generated from Ru₃(CO)₁₂ and tricyclohexylphosphine, enabling direct conversion of secondary to tertiary alcohols in the absence of premetalated reagents or stoichiometric byproducts. The putative oxaruthenacycle intermediate has been isolated and characterized, and reversible metallacycle formation has been demonstrated

Ruthenium Catalyzed Hydrohydroxyalkylation of Isoprene with Heteroaromatic Secondary Alcohols: Isolation and Reversible Formation of the Putative Metallacycle Intermediate

Heteroaromatic secondary alcohols react with isoprene to form products of hydrohydroxyalkylation in the presence of ruthenium(0) catalysts generated from Ru₃(CO)₁₂ and tricyclohexylphosphine, enabling direct conversion of secondary to tertiary alcohols in the absence of premetalated reagents or stoichiometric byproducts. The putative oxaruthenacycle intermediate has been isolated and characterized, and reversible metallacycle formation has been demonstrated

Benzannulation via Ruthenium-Catalyzed Diol–Diene [4+2] Cycloaddition: One- and Two-Directional Syntheses of Fluoranthenes and Acenes

A new benzannulation protocol is described and applied to the synthesis of polycyclic aromatic hydrocarbons. Ruthenium(0)-catalyzed diol–diene [4+2] cycloaddition delivers cyclohex-1-ene-4,5-diols, which are subject to aromatization upon dehydration or Nicholas diol deoxydehydration. Employing diol and tetraol reactants, benzannulation can be conducted efficiently in one- and two-directional modes, respectively, as illustrated in the construction of substituted fluoranthenes and acenes

Ruthenium-Catalyzed C–C Coupling of Amino Alcohols with Dienes via Transfer Hydrogenation: Redox-Triggered Imine Addition and Related Hydroaminoalkylations

Ruthenium-catalyzed hydrogen transfer from 4-aminobutanol to butadiene results in the pairwise generation of 3,4-dihydro-2<i>H</i>-pyrrole and an allylruthenium complex, which combine to form products of imine <i>anti</i>-crotylation. In couplings of 1-substituted-1,3-dienes, novel C2 regioselectivity is observed. As corroborated by deuterium labeling studies, kinetically preferred hydrometalation of the terminal olefin of the 1-substituted-1,3-diene delivers a 1,1-disubstituted π-allylruthenium complex that isomerizes to a thermodynamically more stable monosubstituted π-allylruthenium complex, which undergoes imine addition with allylic inversion through a closed transition structure. Direct ruthenium-catalyzed diene hydroaminoalkylations with pyrrolidine also are described