Enantiomeric Separation of Chiral Alpha-(1-Naphthyl)Ethyl Ammonium Perchlorate by Silica Gel-Bound Chiral Pyridino-18-Crown-6 Ligands.

摘要

The separation of (alpha-(1-naphthyl)ethyl) ammonium perchlorate (NapEt) into its (R) and (S) forms using silica gel-bound dimethylpyridino-18-crown-6 ligand (S,S)-l with methanol as an element is reported. We also report the synthesis of a new silica gel-bound diphenyl-substituted pyridino-18-crown-6 ligand (R,R)-2 by the following reactions. Dimethyl chelidamate (7) was first alkylated with 11-iodoundec-l-ene (6) on the phenolic oxygen and the resulting ether diester was reduced to form 4-undecenyloxy-2,6-pyridinedimethanol (8). Tosylation of 8 gave ditosylate 9 which was cyclized with (R,R)-diphenyl-substituted tetraethylene glycol (R,R)-10 to form crown (R,R)-II. Ligand (R,R)-II was treated with triethoxysilane using a platinum catalyst. The resulting chiral crown-substituted triethoxysilane, (R,R)-12, was reacted with silica gel in toluene at 90 deg to attach the ligand to silica gel. The results of the separation of (R)- and (S)-NapEt using new silica gel-bound crown (R,R)-2 with methanol as the eluent are also presented.