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 regioselective nucleophilic substitution of one or two chlorine atoms by optically pure (R)‐(+)‐1‐naphthylethylamine (NEA), or by a glycine unit as a spacer 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). Binding 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 linked to polysubstituted aromatic ring (6, 7) are not very effective in resolution of most of the 23 racemic analytes, whereas the columns with distant π‐basic subunits (15, 16) exhibited higher resolving efficacy, in particular towards the isopropyl esters of racemic N‐3,5‐dinitrobenzoyl‐α‐amino acids. Effective resolution of test racemates reveals the importance of the presence of the hydrogen bond donor amido group and the distance between the persubstituted benzene ring in 1 and the π‐basic naphthalene ring of (R)‐NEA. Chirality 11:722–730, 1999. © 1999 Wiley‐Liss, Inc.