K. Kamal, H. K. Maurya, A. Gupta and P. G. Vasudev
RESEARCH PAPERS
Acta Cryst. (2015). C71, 921-928
doi:10.1107/S2053229615017106
The revived interest in halogen bonding as a tool in pharmaceutical cocrystals and drug design has indicated that cyano-halogen interactions could play an important role. The crystal structures of four closely related![[delta]](http://scripts.iucr.org/logos/entities/delta_rmgif.gif)
-keto esters, which differ only in the substitution at a single C atom (by H, OMe, Cl and Br), are compared, namely ethyl 2-cyano-5-oxo-5-phenyl-3-(piperidin-1-yl)pent-2-enoate, C19H22N2O3, (1), ethyl 2-cyano-5-(4-methoxyphenyl)-5-oxo-3-(piperidin-1-yl)pent-2-enoate, C20H24N2O4, (2), ethyl 5-(4-chlorophenyl)-2-cyano-5-oxo-3-(piperidin-1-yl)pent-2-enoate, C19H21ClN2O3, (3), and the previously published ethyl 5-(4-bromophenyl)-2-cyano-5-oxo-3-(piperidin-1-yl)pent-2-enoate, C19H21BrN2O3, (4) [Maurya, Vasudev & Gupta (2013). RSC Adv. 3, 12955-12962]. The molecular conformations are very similar, while there are differences in the molecular assemblies. Intermolecular C-H
O hydrogen bonds are found to be the primary interactions in the crystal packing and are present in all four structures. The halogenated derivatives have additional aromatic-aromatic interactions and cyano-halogen interactions, further stabilizing the molecular packing. A database analysis of cyano-halogen interactions using the Cambridge Structural Database [CSD; Groom & Allen (2014). Angew. Chem. Int. Ed. 53, 662-671] revealed that about 13% of the organic molecular crystals containing both cyano and halogen groups have cyano-halogen interactions in their packing. Three geometric parameters for the C-XN![[triple bond]](http://scripts.iucr.org/logos/entities/z-tbnd_rmgif.gif)
C interaction (X = F, Cl, Br or I), viz. the NXdistance and the C-XN and C-NX angles, were analysed. The results indicate that all the short cyano-halogen contacts in the CSD can be classified as halogen bonds, which are directional noncovalent interactions.
RESEARCH PAPERS
Acta Cryst. (2015). C71, 921-928
doi:10.1107/S2053229615017106
The revived interest in halogen bonding as a tool in pharmaceutical cocrystals and drug design has indicated that cyano-halogen interactions could play an important role. The crystal structures of four closely related
-keto esters, which differ only in the substitution at a single C atom (by H, OMe, Cl and Br), are compared, namely ethyl 2-cyano-5-oxo-5-phenyl-3-(piperidin-1-yl)pent-2-enoate, C19H22N2O3, (1), ethyl 2-cyano-5-(4-methoxyphenyl)-5-oxo-3-(piperidin-1-yl)pent-2-enoate, C20H24N2O4, (2), ethyl 5-(4-chlorophenyl)-2-cyano-5-oxo-3-(piperidin-1-yl)pent-2-enoate, C19H21ClN2O3, (3), and the previously published ethyl 5-(4-bromophenyl)-2-cyano-5-oxo-3-(piperidin-1-yl)pent-2-enoate, C19H21BrN2O3, (4) [Maurya, Vasudev & Gupta (2013). RSC Adv. 3, 12955-12962]. The molecular conformations are very similar, while there are differences in the molecular assemblies. Intermolecular C-HO hydrogen bonds are found to be the primary interactions in the crystal packing and are present in all four structures. The halogenated derivatives have additional aromatic-aromatic interactions and cyano-halogen interactions, further stabilizing the molecular packing. A database analysis of cyano-halogen interactions using the Cambridge Structural Database [CSD; Groom & Allen (2014). Angew. Chem. Int. Ed. 53, 662-671] revealed that about 13% of the organic molecular crystals containing both cyano and halogen groups have cyano-halogen interactions in their packing. Three geometric parameters for the C-XNC interaction (X = F, Cl, Br or I), viz. the NXdistance and the C-XN and C-NX angles, were analysed. The results indicate that all the short cyano-halogen contacts in the CSD can be classified as halogen bonds, which are directional noncovalent interactions.
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