A three-component protocol for the enantiodifferentiation of amines using triphenyl borate and BINOL: is it an ion pair or an amine-coordinated complex?

The structure of the borate complex responsible for the enantiodifferentiation of amines using a previously reported three-component protocol has been established. The choice between an ion pair and an amine-coordinated complex with the N atom of the amine coordinated to the B atom is favored for the former structure based on the DFT-calculated 11B NMR chemical shifts. In contrast to expectations, the anisotropies of the quadrupolar 11B nucleus for the two structures were calculated to be indistinguishable with regard to their effect on the linewidth of the NMR signal.

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