Late-Stage Functionalization of ( R)-BINOL-Based Diazacoronands and Their Chiral Recognition of α-Phenylethylamine Hydrochlorides.

Five BINOL-based hosts with a variable macroring size were synthesized in a two-step postfunctionalization protocol by double N-benzylation followed by BMS-mediated reduction of tertiary amide groups (53-93%). UV-vis titration in MeCN reveals that all hosts exhibit a preference for the ( R)-enantiomer over the ( S)-enantiomer of PEA-HCl. The enantioselectivity depends on the number of hydrogen bond (HB) acceptors and the size and flexibility of the macroring. The highest enantiodiscrimination was observed for the 20-membered host 10, containing six HB acceptors ( KR/ KS = 2.13).