Rh2(II)-catalyzed nitro-group migration reactions: selective synthesis of 3-nitroindoles from β-nitro styryl azides

Rhodium carboxylate complexes (1 mol %) catalyze the migration of electron-withdrawing groups to selectively produce 3-substituted indoles from β-substituted styryl azides. The relative order of migratorial aptitude for this transformation is ester ? amide < H < sulfonyl < benzoyl ? nitro.     

Visualizations of coherent center domains in local Polyakov loops

Quantum Chromodynamics exhibits a hadronic confined phase at low to moderate temperatures and, at a critical temperature T_C$T_C$, undergoes a transition to a deconfined phase known as the quark–gluon plasma. The nature of this deconfinement phase transition is probed through visualizations of the Polyakov loop, a gauge independent order parameter. We produce visualizations that provide novel insights into the structure and evolution of center clusters. Using the HMC algorithm the percolation during the deconfinement transition is observed. Using 3D rendering of the phase and magnitude of the Polyakov loop, the fractal structure and correlations are examined. The evolution of the center clusters as the gauge fields thermalize from below the critical temperature to above it are also exposed. We observe deconfinement proceeding through a competition for the dominance of a particular center phase. We use stout-link smearing to remove small-scale noise in order to observe the large-scale evolution of the center clusters. A correlation between the magnitude of the Polyakov loop and the proximity of its phase to one of the center phases of SU(3) is evident in the visualizations.     

Heterogeneous ozone oxidation reactions of 1-pentene, cyclopentene, cyclohexene, and a menthenol derivative studied by sum frequency generation

We report vibrational sum frequency generation (SFG) spectra of glass surfaces functionalized with 1-pentene, 2-hexene, cyclopentene, cyclohexene, and a menthenol derivative. The heterogeneous reactions of ozone with hydrocarbons covalently linked to oxide surfaces serve as models for studying heterogeneous oxidation of biogenic terpenes adsorbed to mineral aerosol surfaces commonly found in the troposphere. Vibrational SFG is also used to track the C=C double bond oxidation reactions initiated by ozone in real time and to characterize the surface-bound product species. Combined with contact angle measurements carried out before and after ozonolysis, the kinetic and spectroscopic studies presented here suggest reaction pathways involving vibrationally hot Criegee intermediates that compete with pathways that involve thermalized surface species. Kinetic measurements suggest that the rate limiting step in the heterogeneous C=C double bond oxidation reactions is likely to be the formation of the primary ozonide. From the determination of the reactive uptake coefficients, we find that ozone molecules undergo between 100 and 10000 unsuccessful collisions with C=C double bonds before the reaction occurs. The magnitude of the reactive uptake coefficients for the cyclic and linear olefins studied here does not follow the corresponding gas-phase reactivities but rather correlates with the accessibility of the C=C double bonds at the surface.     

γ-Lactonizations of 2H-chromenes via cyclopropanation

A two-step synthesis of tetrahydro-2H-furochromenones from 2H-chromenes is reported. The reaction of a series of tert-butyl 2-diazoacetate derivatives with 2H-chromenes, catalyzed by Rh₂(OAc)₄, generated cyclopropane intermediates that rearranged to γ-lactones on treatment with Sn(OTf)₂.