(Salen)chromium(III)/DMAP: An Efficient Catalyst System for the Selective Synthesis of 5-Substituted Oxazolidinones from Carbon Dioxide and Aziridines

(Salen)chromium(III)/DMAP was found to be an active catalyst system for the coupling of CO2 and aziridines. The oxazolidinone products were produced in high yield and selectivity from the opening of the aziridine at the most substituted N−C bond. This catalyst system worked well for a wide variety of monosubstituted N-aryl and N-alkyl aziridines as well as a 2,3-disubstituted N-alkyl aziridine

Alternating Copolymerization of CO₂ and Propylene Oxide Catalyzed by Co^III(salen)/Lewis Base

Alternating Copolymerization of CO2 and Propylene Oxide Catalyzed by CoIII(salen)/Lewis Bas

Chemical CO₂ Fixation: Cr(III) Salen Complexes as Highly Efficient Catalysts for the Coupling of CO₂ and Epoxides

Chemical CO2 Fixation:  Cr(III) Salen Complexes as Highly Efficient Catalysts for the Coupling of CO2 and Epoxide

Chemical CO₂ Fixation: Cr(III) Salen Complexes as Highly Efficient Catalysts for the Coupling of CO₂ and Epoxides

Chemical CO2 Fixation:  Cr(III) Salen Complexes as Highly Efficient Catalysts for the Coupling of CO2 and Epoxide

Substrate Encapsulation: An Efficient Strategy for the RCM Synthesis of Unsaturated ϵ-Lactones

A facile substrate-encapsulated RCM-based synthesis of 7-membered lactones is reported. Coordination of the α,ω-dienyl ester precursor to the bulky Lewis acid (LA) aluminum tris(2,6-diphenylphenoxide) (ATPH) provides a protective extended steric pocket to the olefin moieties, thereby favoring intramolecular RCM over intermolecular ADMET oligomerization. The LA-encapsulated esters undergo ring-closure in the presence of Ru-based olefin metathesis catalysts to give previously difficult-to-access 7-membered β,γ- and γ,δ-unsaturated lactones in good yields

Catalytic Meerwein−Pondorf−Verley Reduction by Simple Aluminum Complexes

Catalytic MPV reduction was successfully carried out using simple aluminum precatalysts. Alkylaluminum reagents were converted to a low-aggregation aluminum alkoxide that was highly active for the MPV reduction of several carbonyl substrates in high yield (50−99%) using iPrOH as the reducing agent. A high degree of cis/trans selectivity was achieved in the reduction of 2-methylcyclohexanone (cis/trans = 20/80) by iPrOH. When chiral hydride sources were utilized in the reduction of 2-chloroacetophenone, high enantioselectivity (68−80% ee) was observed

Substrate Encapsulation: An Efficient Strategy for the RCM Synthesis of Unsaturated ϵ-Lactones

A facile substrate-encapsulated RCM-based synthesis of 7-membered lactones is reported. Coordination of the α,ω-dienyl ester precursor to the bulky Lewis acid (LA) aluminum tris(2,6-diphenylphenoxide) (ATPH) provides a protective extended steric pocket to the olefin moieties, thereby favoring intramolecular RCM over intermolecular ADMET oligomerization. The LA-encapsulated esters undergo ring-closure in the presence of Ru-based olefin metathesis catalysts to give previously difficult-to-access 7-membered β,γ- and γ,δ-unsaturated lactones in good yields

A Highly Modular and Convergent Approach for the Synthesis of Stimulant-Responsive Heteroligated Cofacial Porphyrin Tweezer Complexes

The synthesis of new hemilabile phosphine ligands and their reaction with [Rh(COE)2Cl]2 to form dissymmetric heteroligated tweezer complexes using a halide-induced ligand rearrangement reaction are reported. These complexes can undergo reactions with small-molecule ligands and elemental anions quantitatively in situ, which serve to regulate the porphyrin−porphyrin distances and interactions within the assembly

Enantioselective MSPV Reduction of Ketimines Using 2-Propanol and (BINOL)Al^III

A highly enantioselective Meerwein−Schmidt−Ponndorf−Verley (MSPV) reduction of N-phosphinoyl ketimines by (BINOL)AlIII/2-propanol is reported. Yields ranging between 79 and 85% with high enantiomeric excesses (93−98%) are observed for a wide range of structurally diverse ketimines. A [2.0.4] bicyclic chelation model is proposed to account for this high selectivity

Signal Amplification and Detection via a Supramolecular Allosteric Catalyst

The design of a supramolecular allosteric catalyst system for catalytic signal amplification and detection is presented. The catalyst was switched “on” by the introduction of an analyte that also behaves as an allosteric activator. Concentrations of Cl- ions as low as 800 nM were catalytically amplified and detected. The signal was transduced via a pH-sensitive fluorescent probe and observed visually using a laboratory, handheld UV lamp and by spectrophotometry. Furthermore, the allosteric effect was quantified using gas chromatography for a range of Cl- concentrations. This three-part detection scheme involving analyte binding, allosteric catalyst activation, and signal transduction represents a new approach to small-molecule detection