Synthesis and enantioselective transport studies of optically active lipophilic proton-ionizable crown ethers containing a diarylphosphinic acid unit

Push or Pull for a Better Selectivity? A Study on the Electronic Effects of Substituents of the Pyridine Ring on the Enantiomeric Recognition of Chiral Pyridino-18-Crown-6 Ethers

Seven dimethyl-substituted optically active pyridino-18-crown-6 ethers containing various substituents at position 4 of the pyridine ring were studied with regards to the electron-donating and -withdrawing effects of substituents on enantiomeric recognition. In order to compile this set of compounds, we prepared four novel pyridino-18-crown-6 ethers, including an intermediate of a new synthetic route for a formerly reported crown ether. The discriminating ability of these pyridino-crown ethers with C2-symmetry toward the enantiomers of protonated primary amines was examined by isothermal titration calorimetry.

Manganese-Catalyzed and Mediated Synthesis of Arylphosphinates and Related Compounds

The free-radical arylation of H-phosphinates and related compounds was examined. A practical catalytic process with the air as the oxidant could not be found. However, an inexpensive and robust methodology was developed, using catalytic Mn(II) as the radical initiator and excess Mn(IV) as the stoichiometric oxidant. Using these conditions, the inter- and intramolecular arylation of phosphinylidene compounds has a broad scope, including application to the synthesis of P-heterocycles. A full account of this methodology is presented including a discussion of its limitations.