Naphthyl Groups in Chiral Recognition: Structures of Salts and Esters of 2-Methoxy-2-naphthylpropanoic Acids

The crystal structures of salt 8, which was prepared from (R)‐2‐methoxy‐2‐(2‐naphthyl)propanoic acid ((R)‐MβNP acid, (R)‐2) and (R)‐1‐phenylethylamine ((R)‐PEA, (R)‐6), and salt 9, which was prepared from (R)‐2‐methoxy‐2‐(1‐naphthyl)propanoic acid ((R)‐MαNP acid, (R)‐1) and (R)‐1‐(p‐tolyl)ethylamine ((R)‐TEA, (R)‐7), were determined by X‐ray crystallography. The MβNP and MαNP anions formed ion‐pairs with the PEA and TEA cations, respectively, through a methoxy‐group‐assisted salt bridge and aromatic CH⋅⋅⋅π interactions. The networks of salt bridges formed 21 columns in both salts. Finally, (S)‐(2E,6E)‐(1‐2H1)farnesol ((S)‐13) was prepared from the reaction of (2E,6E)‐farnesal (11) with deuterated (R)‐BINAL‐H (i.e., (R)‐BINAL‐D). The enantiomeric excess of compound (S)‐13 was determined by NMR analysis of (S)‐MαNP ester 14. The solution‐state structures of MαNP esters that were prepared from primary alcohols were also elucidated. Princess and the PEA: The crystal structures of the MαNP and MβNP salts were determined by X‐ray crystallography. The 1‐naphthyl group of the MαNP anion and the 2‐naphthyl group of the MβNP anion acted as a CH donor and ‐acceptor, respectively.