4,5-Di­chloro-2H-1,3-oxazine-2,6(3H)-dione

In the title compound, C₄HCl₂NO₃, the essentially planar (maximum deviation = 0.023 Å for the ring O atom) mol­ecules form N—H⋯O hydrogen bonds between mol­ecules lying about inversion centers, forming eight-membered rings with an R₂²(8) motif in graph-set notation.

Related literature

For synthetic background, see: Warren et al. (1975); Rehberg & Glass (1995). For related structures, see: Copley et al. (2005); Parrish, Leuschner et al. (2009); Parrish, Tivitmahaisoon et al. (2009). For graph-set notation in hydrogen bonding, see: Bernstein et al. (1994).

Experimental

Crystal data

• C₄HCl₂NO₃

• M_r = 181.96

• Monoclinic, P 2₁ /c

• a = 10.2290 (16) Å

• b = 5.2549 (8) Å

• c = 12.2766 (16) Å

• β = 112.359 (11)°

• V = 610.28 (16) ų

• Z = 4

• Mo Kα radiation

• μ = 1.00 mm⁻¹

• T = 293 K

• 0.38 × 0.33 × 0.15 mm

Data collection

• Siemens R3m/V diffractometer

• Absorption correction: none

• 1566 measured reflections

• 1405 independent reflections

• 1235 reflections with I > 2σ(I)

• R_int = 0.053

• 3 standard reflections every 97 reflections intensity decay: none

Refinement

• R[F² > 2σ(F²)] = 0.034

• wR(F²) = 0.100

• S = 0.95

• 1405 reflections

• 92 parameters

• H-atom parameters constrained

• Δρ_max = 0.41 e Å⁻³

• Δρ_min = −0.38 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N3—H3⋯O2^i	0.86	1.99	2.845 (2)	174
Symmetry code: (i) -x+2, -y+1, -z.

Data collection: XSCANS (Bruker, 1996); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.

Supporting information

S1. Comment

The synthesis of derivatives of 3-oxauracil has previously been reported (Warren et al., 1975) and an improved synthesis of the unsubstituted 3-oxauracil was reported by Rehberg & Glass (1995). The structure of the unsubstituted 3-oxauracil and its monohydrate have been reported (Copley et al., 2005). Three derivatives of 3-oxauracil (4-methyl, 4-bromo, and 4,5-dichloro) have been prepared in our laboratory in route to the synthesis of 1-aza-1,3-butadienes. In this paper, we report the crystal structure of the title compound, (I).

Unlike the hydrogen bonding observed in 4-methyl derivative (Parrish, Leuschner et al., 2009) resulting in staggered chains of molecules, in the crystal structure of of the title compound (Fig. 1), the molecules of (I) are held together by classical intermolecular hydrogen bonds of the type N—H···O resulting in dimeric units about inversion centers, forming eight membered ring systems which may be described in terms of graph set notation (Bernstein et al. 1994) as R₂²(8) ring motif (details have been given in Table 1 and Figure 2). The molecular dimensions in (I) agree well with the corresponding bond distances and angles reported for the above mentioned structures and 4-boromo derivative of 3-oxauracil (Parrish, Tivitmahaisoon et al., 2009).

Related literature

For synthetic background, see: Warren et al. (1975); Rehberg & Glass (1995). For related structures, see: Copley et al. (2005); Parrish, Leuschner et al. (2009); Parrish, Tivitmahaisoon et al. (2009). For graph-set notation in hydrogen bonding, see: Bernstein et al. (1994).

S2. Experimental

Dichloromaleic anhydride (3,4-dichlorofuran-2,5-dione) and trimethylsilyl azide were treated analogously to the syntheses reported for the 4-methyl (Parrish, Leuschner et al., 2009) and 4-bromo derivatives. Crystals of the title compound were grown from a solution of acetone at room temperature by slow evaporation.

S3. Refinement

Hydrogen atom bonded to N3 was calculated and refined using a riding model using the N—H distance 0.88 Å with U_iso(H) = 1.2U_eq(N).

Computing details

Data collection: XSCANS (Bruker, 1996); cell refinement: XSCANS (Bruker, 1996); data reduction: XSCANS (Bruker, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. The molecular structure of the title compound, with atom labels and 50% probability displacement ellipsoids for non-H atoms.
	Fig. 2. The packing of the title compound viewed along the b axis and showing the H-bonded dimer formed by inversion related molecules.

4,5-Dichloro-2H-1,3-oxazine-2,6(3H)-dione

Crystal data

C4HCl2NO3	F(000) = 360
Mr = 181.96	Dx = 1.980 Mg m^−3 Dm = 1.92 Mg m^−3 Dm measured by floatation
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 20 reflections
a = 10.2290 (16) Å	θ = 10–12.5°
b = 5.2549 (8) Å	µ = 1.00 mm^−1
c = 12.2766 (16) Å	T = 293 K
β = 112.359 (11)°	Plates, colorless
V = 610.28 (16) Å^3	0.38 × 0.33 × 0.15 mm
Z = 4

Data collection

Siemens R3m/V diffractometer	Rint = 0.053
Radiation source: fine-focus sealed tube	θmax = 27.6°, θmin = 2.2°
Graphite monochromator	h = 0→13
θ–2θ scans	k = 0→6
1566 measured reflections	l = −15→14
1405 independent reflections	3 standard reflections every 97 reflections
1235 reflections with I > 2σ(I)	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.034	H-atom parameters constrained
wR(F^2) = 0.100	w = 1/[σ^2(Fo^2) + (0.0666P)^2 + 0.3617P] where P = (Fo^2 + 2Fc^2)/3
S = 0.95	(Δ/σ)max < 0.001
1405 reflections	Δρmax = 0.41 e Å^−3
92 parameters	Δρmin = −0.38 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.042 (5)

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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	0.89484 (14)	0.7547 (3)	0.20549 (12)	0.0405 (4)
C2	0.9358 (2)	0.6588 (4)	0.12050 (17)	0.0362 (4)
O2	1.03514 (16)	0.7544 (3)	0.10600 (14)	0.0474 (4)
N3	0.86084 (17)	0.4586 (3)	0.05845 (14)	0.0363 (4)
H3	0.8864	0.3892	0.0062	0.044*
C4	0.74604 (19)	0.3625 (3)	0.07572 (15)	0.0325 (4)
Cl4	0.66660 (6)	0.11274 (10)	−0.01234 (4)	0.0453 (2)
C5	0.7009 (2)	0.4611 (4)	0.15609 (16)	0.0347 (4)
Cl5	0.55557 (6)	0.35198 (11)	0.17764 (5)	0.0491 (2)
C6	0.7780 (2)	0.6694 (4)	0.22914 (17)	0.0366 (4)
O6	0.75456 (18)	0.7746 (3)	0.30575 (15)	0.0533 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0479 (8)	0.0401 (8)	0.0369 (7)	−0.0084 (6)	0.0199 (6)	−0.0094 (6)
C2	0.0401 (10)	0.0363 (9)	0.0321 (9)	−0.0007 (8)	0.0138 (8)	0.0003 (7)
O2	0.0479 (8)	0.0484 (9)	0.0515 (9)	−0.0126 (7)	0.0251 (7)	−0.0079 (7)
N3	0.0405 (8)	0.0411 (9)	0.0317 (8)	−0.0050 (7)	0.0188 (6)	−0.0060 (7)
C4	0.0366 (9)	0.0333 (9)	0.0256 (8)	−0.0020 (7)	0.0097 (7)	0.0002 (7)
Cl4	0.0530 (3)	0.0453 (3)	0.0375 (3)	−0.0132 (2)	0.0172 (2)	−0.0125 (2)
C5	0.0387 (9)	0.0387 (10)	0.0286 (8)	−0.0019 (8)	0.0148 (7)	0.0005 (7)
Cl5	0.0526 (3)	0.0587 (4)	0.0464 (3)	−0.0136 (2)	0.0303 (3)	−0.0082 (2)
C6	0.0442 (10)	0.0362 (9)	0.0317 (9)	−0.0008 (8)	0.0171 (8)	−0.0007 (7)
O6	0.0691 (10)	0.0521 (9)	0.0484 (9)	−0.0073 (8)	0.0334 (8)	−0.0166 (7)

Geometric parameters (Å, º)

O1—C2	1.360 (2)	C4—C5	1.342 (3)
O1—C6	1.406 (2)	C4—Cl4	1.698 (2)
C2—O2	1.206 (2)	C5—C6	1.444 (3)
C2—N3	1.353 (3)	C5—Cl5	1.706 (2)
N3—C4	1.367 (2)	C6—O6	1.192 (2)
N3—H3	0.8600
C2—O1—C6	125.02 (15)	C5—C4—Cl4	123.46 (15)
O2—C2—N3	124.69 (18)	N3—C4—Cl4	114.72 (14)
O2—C2—O1	118.79 (18)	C4—C5—C6	119.33 (17)
N3—C2—O1	116.51 (16)	C4—C5—Cl5	123.23 (15)
C2—N3—C4	122.41 (16)	C6—C5—Cl5	117.44 (14)
C2—N3—H3	118.8	O6—C6—O1	117.20 (18)
C4—N3—H3	118.8	O6—C6—C5	127.99 (19)
C5—C4—N3	121.82 (17)	O1—C6—C5	114.81 (16)
C6—O1—C2—O2	177.41 (18)	N3—C4—C5—Cl5	178.26 (14)
C6—O1—C2—N3	−3.1 (3)	Cl4—C4—C5—Cl5	−1.5 (3)
O2—C2—N3—C4	−177.81 (19)	C2—O1—C6—O6	−179.15 (19)
O1—C2—N3—C4	2.7 (3)	C2—O1—C6—C5	1.0 (3)
C2—N3—C4—C5	−0.3 (3)	C4—C5—C6—O6	−178.2 (2)
C2—N3—C4—Cl4	179.47 (15)	Cl5—C5—C6—O6	1.5 (3)
N3—C4—C5—C6	−2.0 (3)	C4—C5—C6—O1	1.6 (3)
Cl4—C4—C5—C6	178.29 (14)	Cl5—C5—C6—O1	−178.62 (13)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N3—H3···O2^i	0.86	1.99	2.845 (2)	174

Symmetry code: (i) −x+2, −y+1, −z.