Enantiospecific recognition of 2-butanol by an inherently chiral cavitand in the solid state

Abstract

A new inherently chiral cavitand is described, in which the desymmetrization of the rigid concave cavity is achieved by introducing three different bridging groups at the upper rim, namely two inward P=O groups, one inward P=S moiety and one methylene bridge in the AABC mode. The racemic mixture of cR and cS enantiomers is resolved by semi-preparative chiral HPLC and the enantiopurity confirmed through circular dichroism. The properties of the enantiopure cR-cav in the enantioselective recognition of racemic 2-butanol is studied by co-crystallization experiments. The exclusive formation of the complex R-BuOH@cR-cav demonstrates that cR-cav is able to discriminate between the two enantiomers of the alcohol in the solid state. The enantiospecific recognition exhibited by the cR-cav towards racemic 2-butanol is particularly relevant because of the low degree of chirality of the alcohol (1.9 calculated by CCM algorithm)