Chiral Tetraaryl‐ and Tetraalkynylborates as Chiral Solvating Agents for Tetraalkylammonium Salts

The application of tetracarbon‐substituted chiral borate sodium salts (NaBR* 4 ) as NMR chiral solvating agents for various tetraalkylammonium salts (R 4 NX) has been successfully demonstrated. Ion exchange between R 4 NX and NaBR* 4 proceeded in excellent yields and provided the corresponding diastereomeric salts (R 4 NBR* 4 ). The ee values of the R 4 NX salts were determined by 1 H NMR analysis of R 4 NBR* 4 . Two types of chiral borates, tetraaryl‐ and tetraalkynylborates with optically active 1,1′‐binaphthyl components were used. At the beginning of this research, we investigated the efficacy of a known chiral tetraarylborate developed by Pommerening et al. for R 4 NX. To expand the possibility of further structural design of the chiral borate, we designed chiral tetraalkynylborates as a new structure. Their synthesis and application are also described.