Enantiomerically pure chiral phenazino-crown ethers: synthesis, preliminary circular dichroism spectroscopic studies and complexes with the enantiomers of 1-arethyl ammonium salts

Abstract

Enantiomerically pure chiral crown ethers containing the phenazine unit [( R,R)- 2–( S,S)- 8] were prepared by two types of cyclization reactions. Ligands ( R,R)- 2, ( R,R)- 3, ( S,S)- 4, ( R,R)- 5, ( R,R)- 6 and ( R,R)- 7 were prepared from phenazine-1,9-diol 9 and the appropriate ditosylates ( S,S)- 10–( S,S)- 15 in weak basic conditions with complete inversion of configuration. Ligands ( S,S)- 2, ( S,S)- 7 and ( S,S)- 8, however, were prepared from 1,9-dichlorophenazine 19 and the appropriate diols ( S,S)- 16–( S,S)- 18 in strong basic conditions with retention of configuration. Enantiomeric recognition of most of the chiral ligands with α-(1-naphthyl)ethylammonium perchlorate (NEA) and α-phenylethylammonium perchlorate (PEA) has been studied by CD spectroscopy.