Selective carbene transfer to amines and olefins catalyzed by ruthenium phthalocyanine complexes with donor substituents

Electron-rich ruthenium phthalocyanine complexes were evaluated in carbene transfer reactions from ethyl diazoacetate (EDA) to aromatic and aliphatic olefins as well as to a wide range of aromatic, heterocyclic and...

Tuning Rh(II)-Catalyzed Cyclopropanation with Tethered Thioether Ligands

Dirhodium(II) paddlewheel complexes have high utility in diazo-mediated cyclopropanation reactions and ethyl diazoacetate is one of the most commonly used diazo compounds in this reaction. In this study, we report our efforts to use tethered thioether ligands to tune the reactivity of Rh-carbene mediated cyclopropanation of olefins with ethyl diazoacetate. Microwave methods enabled the synthesis of a family of Rh-complexes in which tethered thioether moieties were coordinated to axial sites of the complex. Different tether lengths and thioether substituents were screened to optimize cyclopropane yeilds and minimize side product formation. Furthermore, good yields were obtained when equimolar diazo and olefin were used. Structural and spectroscopic investigation revealed that tethered thioethers changed the electronic structure of the rhodium core, which was instrumental in the performance of the catalysts. Computational modeling of the catalysts provided further support that the tethered thioethers were responsible for increased yields.

Tuning Rh(II)-Catalyzed Cyclopropanation with Tethered Thioether Ligands

Dirhodium(II) paddlewheel complexes have high utility in diazo-mediated cyclopropanation reactions and ethyl diazoacetate is one of the most commonly used diazo compounds in this reaction. In this study, we report our efforts to use tethered thioether ligands to tune the reactivity of Rh-carbene mediated cyclopropanation of olefins with ethyl diazoacetate. Microwave methods enabled the synthesis of a family of Rh-complexes in which tethered thioether moieties were coordinated to axial sites of the complex. Different tether lengths and thioether substituents were screened to optimize cyclopropane yeilds and minimize side product formation. Furthermore, good yields were obtained when equimolar diazo and olefin were used. Structural and spectroscopic investigation revealed that tethered thioethers changed the electronic structure of the rhodium core, which was instrumental in the performance of the catalysts. Computational modeling of the catalysts provided further support that the tethered thioethers were responsible for increased yields.

Catalytic Asymmetric Aziridination of Benzhydryl Imines and Diazoacetate­ Esters with BOROX Catalysts from 3,3′-Disubstituted VANOL Ligands

This work details the synthesis of 22 new chiral VANOL ligands that differ by the nature of the substituent in the 3- and 3′-positions of the ligand. These ligands were incorporated into boroxinate catalysts that were used to screen the catalytic asymmetric aziridination of benzhydryl imines with ethyl diazoacetate. Each catalyst was screened in the reaction of imines generated from benzaldehyde and cyclohexanecarboxaldehyde and some with 4-nitro- and 4-methoxybenzaldehyde. In addition, the first report of the effect of the ester substituent of the diazoacetate ester on the asymmetric induction in these aziridination reactions is presented. The first X-ray structure of a boroxinate catalyst generated from a VANOL-derived ligand is also reported.