New chiral stationary phases based on (R)-1-naphthylethylamine bound to 2,4,5,6-tetrachloro-1,3-dicyanobenzene

Chiral functionalization of 2,4,5,6-tetrachloro-1,3-dicyanobenzene (1) by r egioselective nucleophilic substitution of one or two chlorine atoms by opt ically pure (R)-(+)-1-naphthylethylamine (NEA), or by a glycine unit as a s pacer to (R)-NEA, enables the preparation of brush-type chiral selectors (2 , 3, 9, 13), By the introduction of the 3-aminopropyltriethoxysilyl (APTES) group, reactive intermediates 4a/b, 5, 10a/b, and 14a/b are obtained (a/b indicate a mixture of regioisomers with APTES in 6- and 2-position). Bindin g of these to silica gel afforded four novel chiral stationary phases (CSPs ) 6, 7, 15, and 16, HPLC columns containing CSPs with (R)-NEA directly link ed to polysubstituted aromatic ring (6, 7) are not very effective in resolu tion of most of the 23 racemic analytes, whereas the columns with distant p i-basic subunits (15, 16) exhibited higher resolving efficacy, in particula r towards the isopropyl esters of racemic N-3,5-dinitrobenzoyl-alpha-amino acids. Effective resolution of test racemates reveals the importance of the presence of the hydrogen bond donor amido group and the distance between t he persubstituted benzene ring in 1 and the pi-basic naphthalene ring of (R )-NEA. (C) 1999 Wiley-Liss, Inc.