Piperazine-2,3,5,6-tetra­one

The mol­ecule of the title compound, C₄H₂N₂O₄, is located around an inversion center and the four O atoms are in the 2,3,5,6-positions of the piperazine ring. In the crystal, bifurcated N—H...O hydrogen bonds link the mol­ecules into a corrugated layer parallel to (101).

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.048
• wR factor = 0.092
• Data-to-parameter ratio = 9.5

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT088_ALERT_3_C Poor Data / Parameter Ratio ....................       9.52
PLAT369_ALERT_2_C Long   C(sp2)-C(sp2) Bond  C1     -   C2_a   ...       1.53 Ang.

Alert level G
PLAT432_ALERT_2_G Short Inter X...Y Contact  O1     ..  C2      ..       3.00 Ang.
PLAT432_ALERT_2_G Short Inter X...Y Contact  O2     ..  C2      ..       2.83 Ang.
PLAT432_ALERT_2_G Short Inter X...Y Contact  O2     ..  C1      ..       2.91 Ang.
PLAT128_ALERT_4_G Alternate Setting of Space-group P21/c   .......      P21/n
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported   _diffrn_ambient_temperature        293 K

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   2 ALERT level C = Check and explain
   6 ALERT level G = General alerts; check

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   4 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The synthesis and antitumor activity of some tetraone compounds have been widely studied (Jin et al., 1998; Sanner et al., 1992). Most tetraone compounds were found from a naturally occurring alkaloid in a variety of leguminous plant and tree species, including broom, lupin, gorse, and laburnum(Norcross et al., 2008). As part of our interest in the synthesis of tetraone derivatives, we report here the structure of the title compound.

The molecule of the title compound is located around inversion center and the four O atoms are in the 2,3,5,6 position on the piperazine ring (Fig. 1). The molecule is planar with rms deviation of 0.013Å. The bond distances and angles are similar to those found in related piperazine derivatives (Sletten et al., 1970; Sarangarajan et al., 2005; Sletten et al., 1980; Ongania et al., 1985).

The N—H donor and the C—O acceptor groups participate in the hydrogen bonding forming corrugated layers parallel to the (1 0 1) plane through bifurcated N-H···O hydrogen bonds (Table 1, Fig. 2).

Related literature

For the synthesis of tetraone, see: Norcross et al. (2008). For related structures, see Sletten et al. (1970, 1980); Sarangarajan et al. (2005); Norcross et al. (2008); Jin et al. (1998); Sanner et al. (1992); Ongania et al. (1985) .

S2. Experimental

For the preparation of the title compound,the 2-mercaptopyrazine (10 mmol,1.1200 g) was dissolved in ethanol (50 ml) at 358 K and a solution of 30% H₂0₂ (10 ml) was added. The resulting solution was stirred at 358 K for 4 h, then concentrating at 388 K,until 3 ml solution remained. Colourless-block crystal suitable for X-ray diffraction were obtained by slow evaporation at room temperature after several days in 55% yield.

S3. Refinement

H atom attached to N atom was positioned geometrically and treated as riding on the parent atom with N-H= 0.86 Å and U_iso(H)=1.2U_eq(N).

Computing details

Data collection: XSCANS (Siemens, 1994); cell refinement: XSCANS (Siemens, 1994); data reduction: XSCANS (Siemens, 1994); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPIII (Burnett & Johnson, 1996), ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2009); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. Molecular view of compound I with the atom labeling scheme. Ellipsoids are drawn at the 30% probability level. H atoms are represented as small spheres of arbitrary radii. [Symmetry code: (i) -x+1, -y+1, -z+1]
	Fig. 2. Partial packing view showing the corrugated layer parallel to the (1 0 1) plane. H bonds are shown as dashed lines. [Symmetry codes: (ii) -x+1/2, y-1/2, -z+3/2; (iii) x-1/2, -y+1/2, z+1/2]

Piperazine-2,3,5,6-tetraone

Crystal data

C4H2N2O4	F(000) = 144
Mr = 142.08	Dx = 1.943 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 438 reflections
a = 5.163 (1) Å	θ = 4.4–25.3°
b = 8.6220 (17) Å	µ = 0.18 mm^−1
c = 5.6540 (11) Å	T = 293 K
β = 105.25 (3)°	Block, colourless
V = 242.83 (8) Å^3	0.42 × 0.32 × 0.12 mm
Z = 2

Data collection

Siemens P4 diffractometer	438 independent reflections
Radiation source: fine-focus sealed tube	383 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.024
ω scans	θmax = 25.3°, θmin = 4.4°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −6→6
Tmin = 0.930, Tmax = 0.978	k = −10→10
1357 measured reflections	l = −6→6

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.048	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.092	H-atom parameters constrained
S = 1.23	w = 1/[σ^2(Fo^2) + (0.0355P)^2 + 0.1147P] where P = (Fo^2 + 2Fc^2)/3
438 reflections	(Δ/σ)max < 0.001
46 parameters	Δρmax = 0.20 e Å^−3
0 restraints	Δρmin = −0.21 e Å^−3

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.1613 (3)	0.55814 (19)	0.7646 (3)	0.0343 (5)
O2	0.8069 (3)	0.25100 (19)	0.6060 (3)	0.0342 (5)
N1	0.4775 (4)	0.3995 (2)	0.6856 (3)	0.0261 (5)
H1	0.4603	0.3362	0.7981	0.031*
C1	0.6621 (5)	0.3635 (2)	0.5614 (4)	0.0233 (5)
C2	0.3169 (4)	0.5281 (2)	0.6461 (4)	0.0233 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0357 (10)	0.0355 (10)	0.0373 (10)	0.0010 (8)	0.0197 (9)	−0.0034 (8)
O2	0.0348 (10)	0.0268 (9)	0.0402 (10)	0.0099 (8)	0.0086 (8)	0.0048 (7)
N1	0.0330 (11)	0.0229 (10)	0.0248 (11)	0.0004 (9)	0.0120 (9)	0.0053 (8)
C1	0.0221 (12)	0.0205 (11)	0.0256 (12)	−0.0019 (10)	0.0034 (10)	−0.0017 (9)
C2	0.0224 (12)	0.0225 (11)	0.0239 (12)	−0.0027 (10)	0.0042 (10)	−0.0038 (9)

Geometric parameters (Å, º)

O1—C2	1.202 (3)	N1—C2	1.368 (3)
O2—C1	1.210 (3)	N1—H1	0.8600
N1—C1	1.360 (3)	C1—C2^i	1.526 (3)
C1—N1—C2	125.31 (19)	N1—C1—C2^i	117.28 (19)
C1—N1—H1	117.3	O1—C2—N1	123.3 (2)
C2—N1—H1	117.3	O1—C2—C1^i	119.3 (2)
O2—C1—N1	123.6 (2)	N1—C2—C1^i	117.35 (18)
O2—C1—C2^i	119.10 (19)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O1^ii	0.86	2.48	3.060 (2)	125
N1—H1···O2^iii	0.86	2.23	3.035 (2)	157

Symmetry codes: (ii) −x+1/2, y−1/2, −z+3/2; (iii) x−1/2, −y+1/2, z+1/2.