4-Nitro-benzyl 3,4-bis-(acet-yloxy)-2-(4-meth-oxy-phen-yl)pyrrolidine-1-carboxyl-ate: crystal structure, Hirshfeld surface analysis and computational chemistry.

The title compound, C23H24N2O9, is a tetra-substituted pyrrolidine derivative with a twisted conformation, with the twist evident in the C-C bond bearing the adjacent acet-yloxy substituents. These are flanked on one side by a C-bound 4-meth-oxy-phen-yl group and on the other by a methyl-ene group. The almost sp 2-N atom [sum of angles = 357°] bears a 4-nitro-benzyl-oxycarbonyl substituent. In the crystal, ring-methyl-ene-C-H⋯O(acet-yloxy-carbon-yl) and methyl-ene-C-H⋯O(carbon-yl) inter-actions lead to supra-molecular layers lying parallel to (01); the layers stack without directional inter-actions between them. The analysis of the calculated Hirshfeld surfaces indicates the combined importance of H⋯H (42.3%), H⋯O/O⋯H (37.3%) and H⋯C/C⋯H (14.9%) surface contacts. Further, the inter-action energies, largely dominated by the dispersive term, point to the stabilizing influence of H⋯H and O⋯O contacts in the inter-layer region.

1-Ethyl 2-methyl 3,4-bis-(acet-yloxy)pyrrolidine-1,2-di-carboxyl-ate: crystal structure, Hirshfeld surface analysis and computational chemistry.

The title compound, C13H19NO8, is based on a tetra-substituted pyrrolidine ring, which has a twisted conformation about the central C-C bond; the Cm-Ca-Ca-Cme torsion angle is 38.26 (15)° [m = methyl-carboxyl-ate, a = acet-yloxy and me = methyl-ene]. While the N-bound ethyl-carboxyl-ate group occupies an equatorial position, the remaining substituents occupy axial positions. In the crystal, supra-molecular double-layers are formed by weak methyl- and methyl-ene-C-H⋯O(carbon-yl) inter-actions involving all four carbonyl-O atoms. The two-dimensional arrays stack along the c axis without directional inter-actions between them. The Hirshfeld surface is dominated by H⋯H (55.7%) and H⋯C/C⋯H (37.0%) contacts; H⋯H contacts are noted in the inter-double-layer region. The inter-action energy calculations point to the importance of the dispersion energy term in the stabilization of the crystal.

Ethyl 3,4-bis-(acet-yloxy)-2-(4-meth-oxy-phen-yl)pyrrol-idine-1-carboxyl-ate.

The title pyrrolidine compound, C18H23NO7, is a tetra-substituted species in which the five-membered ring has a twisted conformation with the twist occurring in the C-C bond bearing the adjacent acet-yloxy substituents; the Cm-Ca-Ca-Cp torsion angle is -40.76 (18)° [m = methyl-ene, a = acet-yloxy and p = phen-yl]. The N atom, which is sp 2-hybridized [sum of bond angles = 359.4°], bears an ethyl-carboxyl-ate substitutent and is connected to a methyl-ene-C atom on one side and a carbon atom bearing a 4-meth-oxy-phenyl group on the other side. Minor disorder is noted in the ethyl-carboxyl-ate substituent as well as in one of the acet-yloxy groups; the major components of the disorder have site occupancies of 0.729 (9) and 0.62 (3), respectively. The most notable feature of the mol-ecular packing is the formation of helical, supra-molecular chains aligned along the b-axis direction whereby the carbonyl-O atom not involved in a disordered residue accepts C-H⋯O inter-actions from methyl-ene-H and two-C atom separated methine-H atoms to form a six-membered {⋯HCCCH⋯O} synthon.

4-Benzyl-1-(4-nitro-phen-yl)-1H-1,2,3-triazole: crystal structure and Hirshfeld analysis.

The mol-ecule in the title compound, C15H12N4O2, has a twisted L-shape with the dihedral angle between the aromatic rings of the N-bound benzene and C-bound benzyl groups being 70.60 (9)°. The nitro group is co-planar with the benzene ring to which it is connected [C-C-N-O torsion angle = 0.4 (3)°]. The three-dimensional packing is stabilized by a combination of methyl-ene-C-H⋯O(nitro), methyl-ene-C-H⋯π(phen-yl), phenyl-C-H⋯π(triazol-yl) and nitro-O⋯π(nitro-benzene) inter-actions, along with weak π(triazol-yl)-π(nitrobenzene) contacts [inter-centroid distance = 3.8386 (10) Å]. The importance of the specified inter-molecular contacts has been verified by an analysis of the calculated Hirshfeld surface.