1,4-Bis(3-methyl­phen­yl)piperazine-2,5-dione

Yongjun Liu; Xuefeng Sun; Yonghong Wen

doi:10.1107/S1600536812026372

. 2012 Jun 16;68(Pt 7):o2115. doi: 10.1107/S1600536812026372

1,4-Bis(3-methylphenyl)piperazine-2,5-dione

Yongjun Liu ^a,^*, Xuefeng Sun ^a, Yonghong Wen ^a

PMCID: PMC3393927 PMID: 22798792

Abstract

The asymmetric unit of the title compound, C₁₈H₁₈N₂O₂, consists of two independent molecules, each of which is located about a center of inversion. The molecules are not planar, showing dihedral angles of 55.84 (9) and 54.10 (8)° between the piperazinedione and the aromatic rings. The piperazine N atoms exhibit a planar configuration. The crystal packing is stabilized by intermolecular C—H⋯O hydrogen bonds.

Related literature

For background to the applications of piperazinedione and its derivatives, see: Acharya et al. (2001 ▶); Fischer (2003 ▶); Krchnak et al. (1996 ▶); Paradisi et al. (2002 ▶). For the syntheses and structures of piperazinediones, see: Wen et al. (2006 ▶); Zhang et al. (2007 ▶).

Experimental

Crystal data

C₁₈H₁₈N₂O₂
M _r = 294.34
Monoclinic,
a = 12.6608 (15) Å
b = 6.1508 (7) Å
c = 19.223 (2) Å
β = 95.142 (2)°
V = 1490.9 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 153 K
0.38 × 0.12 × 0.10 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.968, T _max = 0.991
7835 measured reflections
2836 independent reflections
2078 reflections with I > 2σ(I)
R _int = 0.029

Refinement

R[F ² > 2σ(F ²)] = 0.052
wR(F ²) = 0.137
S = 1.02
2836 reflections
199 parameters
H-atom parameters constrained
Δρ_max = 0.19 e Å⁻³
Δρ_min = −0.22 e Å⁻³

Data collection: SMART (Bruker, 2001 ▶); cell refinement: SAINT (Bruker, 2001 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812026372/zq2169sup1.cif

e-68-o2115-sup1.cif^{(19KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812026372/zq2169Isup2.hkl

e-68-o2115-Isup2.hkl^{(139.2KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536812026372/zq2169Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C8—H8B⋯O1ⁱ	0.97	2.53	3.494 (2)	173
C14—H14A⋯O2ⁱ	0.93	2.45	3.325 (3)	158

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Symmetry code: (i) Inline graphic .

Acknowledgments

The project was supported by the Promotive Research Fund for Excellent Young and Middle-Aged Scientists of Shandong Province (BS2011CL019).

supplementary crystallographic information

Comment

Piperazinediones form an important class of biologically active natural products (Fischer et al., 2003), and represent important precursors for the synthesis of peptides and non-natural amino acids (Paradisi et al., 2002). Recently, piperazinediones have gained importance in drug discovery (Krchnak et al., 1996), and opioid receptor agonists and antagonists (Acharya et al., 2001). Here, we report the crystal structure of the title compound.

The title compound consists of two crystallographically independent C₁₈H₁₈N₂O₂ molecules in the asymmetric unit of the centrosymmetric space group P2₁/n (Fig. 1). Each molecule is located on a center of inversion. All bond lengths and angles of two independent molecules are comparable with those in the related compounds (Wen et al., 2006; Zhang et al., 2007). The molecules are not planar showing dihedral angles of 55.84 (9)° and 54.10 (8)° between the piperazinedione and the aromatic rings, which is different from the ortho-substituted isomer 1,4-bis(2-methylphenyl)piperazine-2,5-dione (Wen et al., 2006). The sum of the bond angles around N1 (360.00°) and N2 (359.98°) indicates the piperazine N atoms have also a planar configuration, different from the normal pyramidal configuration of the N atom. This difference is mainly due to the π-conjugation effects arising from the presence of the two C=O double bonds. In addition, the crystal packing exhibit intermolecular C—H···O hydrogen bonds (Table 1, Fig. 2).

Experimental

The title compound was prepared according to the literature method (Wen et al., 2006). Colourless single crystals of the title compound suitable for X-ray diffraction study were obtained by slow evaporation of an ethanol solution over a period of 20 d.