The behavior of 1,1'-bi-2-naphthol (BINOL) in variety of (super)acid media has been studied by NMR. The results are combined with the theoretical (DFT) study of the role of mono- and diprotonated forms of BINOL in the acid-catalyzed atropisomerization of this compound. It is demonstrated that the process of enantiomeric configuration exchange proceeds mainly via internal rotation around the C1(sp)-C1'(sp) bond in intermediates such as C1-monoprotonated keto or C1,C1'-diprotonated forms of BINOL, depending on the acidity level.
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http://dx.doi.org/10.1021/acs.orglett.6b03696 | DOI Listing |
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