Towards an Observation of Active Conformations in Asymmetric Catalysis: Interaction‐Induced Conformational Preferences of a Chiral Thiourea Model Compound

The observation of the active species is the goal of most spectroscopic investigations on enantioselective organocatalysts in solution. Although NMR spectroscopy is widely applied, it has low sensitivity for conformational changes or the chiral nature of the interactions. In the present work, we exemplify the use of vibrational circular dichroism (VCD) spectroscopy for the characterization of a chiral thiourea model compound in nonpolar and polar solvents, as well as for a detailed analysis of its interaction with a model reactant. We discuss solvent‐induced conformational changes of the thiourea, and provide evidence for an unexpected binding topology between the thiourea and an acetate anion. The results clearly showcase the possibilities offered by using VCD spectroscopy in the characterization of chiral organocatalysts.     

Cyclopropylidenebis(diphenylphosphine): Note on its Synthesis,Properties and Spectral Data

The title compound has been synthesized through cyclopropanation of vinylidenebis(diphenylphosphine) using dimethylsulfoxonium methylide. It is easily converted into its dioxide and disulfide. NMR data of these first geminal diphosphinocyclopropanes are presented.     

Quantitative Spektralanalyse

Ohne Zusammenfassung