Naphthyl groups in chiral recognition: structures of salts and esters of 2-methoxy-2-naphthylpropanoic acids

Abstract

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 2(1) columns in both salts. Finally, (S)-(2E,6E)-(1-(2) H(1) )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.