NMR enantiodifferentiation of quaternary ammonium salts of Tröger base.

Hexacoordinated phosphorus BINPHAT anion 1 is an efficient NMR chiral solvating agent for quaternary ammonium cations (quats) derived from Tröger base leading to large separations of the proton signals of the enantiomers and even in polar solvent media such as CD(3)CN (Delta Delta delta up to 0.12 ppm). Quite surprisingly, this efficacy in the NMR split efficiency is not translated into a supramolecular stereocontrol (Pfeiffer effect) of the cation configuration by the anion.

Enantioselective [1,2]-Stevens rearrangement of quaternary ammonium salts. A mechanistic evaluation.

Using a supramolecular asymmetric ion pairing strategy, an enantioselective [1,2]-Stevens is feasible on substrates devoid of stereogenic quaternary nitrogen atoms.