title: Novel chiral stationary phases comprising 2,4-(or 2,6)-diamino-5,6-(or 2,5)-dichlorobenzene-1,3-dicarbonitrile and 1-acyl (1R,2R)-diaminocyclohexane.
abstract: Novel chiral selectors 3-5 were prepared by regioselective nucleophilic substitution of 2,4,5,6-tetrachlorobenzene-1,3-dicarbonitrile (TCBDC, 1) at C(4) by (1R,2R)-trans-diaminocyclohexane, followed by acylation of the intermediary 2 with carboxylic acids containing pi-acid or pi-basic unit. On substitution of the second chlorine atom by the spacer 3-aminopropyltriethoxysilane (APTES), a 1:1 mixture of regioisomers of N-(([3, 6-dichloro-2,4-dicyano-5-(4,4,4-triethoxy-4-silabutyl)-amino]phenyl)amino) cyclo-hexylcarboxamides and N-(5,6-dichloro-2,4-dicyano-3-(4,4,4-triethoxy-4-silabutyl)-amino]pheny) amino)cyclohexylcarboxamides (6/7, 8/9, 10/11) was obtained. Their covalent binding to Nucleosil 100-5 provided three new chiral stationary phases (CSP-1-CSP-3). NMR spectra of model compounds 12-14 and MM2 calculations on model compounds 15,16 revealed pi-pi interactions between persubstituted benzene ring and second aromatic ring. The results of the evaluation of new CSPs in the separation of 23 test racemates by HPLC are reported. CSP-2 and CSP-3, that have lower conformational freedom than CSP-1, allow for better separation. In particular, good results are obtained in the separation of some 1,4-benzodiazepines and open-chain aromatic amides by CSP-2 and CSP-3.
authors.affiliation: Ruder Boković Institute, P.O. Box 180, Bijenika cesta 54, 10002 Zagreb, Croatia.
authors.forename: D
authors.initials: D
authors.lastname: Kontrec
authors.forename: V
authors.initials: V
authors.lastname: Vinković
authors.forename: A
authors.initials: A
authors.lastname: Lesac
authors.forename: V
authors.initials: V
authors.lastname: Sunjić
authors.forename: A
authors.initials: A
authors.lastname: Aced