6-Chloro-2H-1,4-benzoxazin-3(4H)-one

In the title compound, C₈H₆ClNO₂, the conformation of the six-membered heterocyclic ring is close to screw boat and the mol­ecules are linked via inter­molecular N—H...O hydrogen bonds along the b axis.

Key indicators

• Single-crystal X-ray study
• T = 273 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.038
• wR factor = 0.088
• Data-to-parameter ratio = 12.1

checkCIF/PLATON results

No syntax errors found



Alert level C
            Value of measurement temperature given =   273.000
            Value of melting point given =     0.000
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .......          ?

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           25.03
           From the CIF: _reflns_number_total               1314
           Count of symmetry unique reflns          813
           Completeness (_total/calc)            161.62%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured       501
           Fraction of Friedel pairs measured     0.616
           Are heavy atom types Z>Si present        yes

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

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

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S1. Comment

Benzo[1,4]oxazin-3(4H)-one derivatives are one of the important classes of heterocyclic compounds and have been shown to exhibit a wide range of biological activities such as herbicidal (Huang et al., 2005) and antifungal (Macchiarulo et al., 2002). We report here the crystal structure of 6-chloro-2H-benzo[b][1,4]oxazin-3(4H)-one.

The molecular structure is illustrated in Fig. 1. The conformation of the six-membered heterocyclic ring is close to screw boat, with atoms C1 and C2 out of the plane of the remaining four atoms by 0.301 (5) and 0.635 (5) Å, respectively. In a related compound containing the benzo[1,4]oxazin-3(4H)-one system (Pang et al., 2006), the heterocyclic ring also adopts a screw boat conformation. The molecules are connected via N - H ··· O hydrogen bonding into chains along the b axis.

Related literature

For biological activities of benzo[1,4]oxazin-3(4H)-one derivatives, see: Huang et al. (2005); Macchiarulo et al. (2002). For a related compound, see: Pang et al. (2006).

S2. Experimental

To a 25 ml round-bottomed flask equipped with a reflux condenser were added 2-chloro-N-(5-chloro-2-hydroxyphenyl)acetamide (2.19 g, 10 mmol), potassium carbonate (2.76 g, 20 mmol) and anhydrous DMF (20 ml). The resulting mixture was heated under reflux for 90 min. After this time, the reaction mixture was poured into 80 g of water, and stirred for 15 min. The mixture was extracted with ethyl acetate (2 x 20 ml). The ethyl acetate extract was washed with saturated brine (10 ml). After drying over Na₂SO₄, the solvent was removed under vacuum and a colourless solid was obtained in 80% yield (1.46 g). Suitable crystals were grown by evaporation of a CH₂Cl₂ solution at room temperature for 4 d.

S3. Refinement

All H atoms were positioned geometrically (N - H = 0.86 Å, aromatic C - H = 0.93 Å, methylene C - H = 0.97 Å) and refined using a riding model; U_iso(H) = 1.2 U_eq(C, N).

Computing details

Data collection: SMART (Bruker 2002); cell refinement: SAINT (Bruker 2002); data reduction: SAINT (Bruker 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

Fig. 1. The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level. H atoms are shown as spheres of arbitrary radius.

6-Chloro-2H-1,4-benzoxazin-3(4H)-one

Crystal data

C8H6ClNO2	Dx = 1.641 Mg m^−3
Mr = 183.59	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P212121	Cell parameters from 1287 reflections
a = 4.5359 (6) Å	θ = 3.3–24.4°
b = 7.700 (1) Å	µ = 0.46 mm^−1
c = 21.281 (3) Å	T = 273 K
V = 743.28 (17) Å^3	Plate, colourless
Z = 4	0.12 × 0.10 × 0.06 mm
F(000) = 376

Data collection

Bruker SMART CCD area-detector diffractometer	1314 independent reflections
Radiation source: fine-focus sealed tube	1143 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.047
ϕ and ω scans	θmax = 25.0°, θmin = 1.9°
Absorption correction: multi-scan (SADABS; Bruker, 2002)	h = −5→4
Tmin = 0.878, Tmax = 0.973	k = −8→9
3857 measured reflections	l = −25→23

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)] = 0.038	H-atom parameters constrained
wR(F^2) = 0.088	w = 1/[σ^2(Fo^2) + (0.0401P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.07	(Δ/σ)max < 0.001
1314 reflections	Δρmax = 0.16 e Å^−3
109 parameters	Δρmin = −0.21 e Å^−3
0 restraints	Absolute structure: Flack (1983), 500 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.06 (11)

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
Cl1	0.59509 (18)	0.16633 (10)	0.92672 (4)	0.0538 (3)
O1	1.5486 (5)	0.7552 (2)	0.74891 (10)	0.0488 (6)
O2	1.1177 (4)	0.8424 (2)	0.88354 (9)	0.0466 (6)
N1	1.2830 (5)	0.5732 (3)	0.80882 (10)	0.0347 (6)
H1	1.3651	0.4842	0.7918	0.042*
C1	1.3640 (6)	0.7302 (3)	0.79030 (14)	0.0350 (7)
C2	1.2111 (7)	0.8777 (3)	0.82142 (15)	0.0448 (8)
H2A	1.3430	0.9768	0.8222	0.054*
H2B	1.0404	0.9094	0.7965	0.054*
C3	0.9870 (6)	0.6859 (3)	0.89160 (13)	0.0346 (7)
C4	1.0683 (6)	0.5467 (3)	0.85521 (12)	0.0295 (6)
C5	0.9496 (6)	0.3866 (3)	0.86535 (13)	0.0339 (6)
H5	1.0043	0.2924	0.8406	0.041*
C6	0.7466 (6)	0.3675 (3)	0.91299 (13)	0.0369 (7)
C7	0.6661 (6)	0.5045 (4)	0.94990 (13)	0.0408 (7)
H7	0.5317	0.4889	0.9824	0.049*
C8	0.7839 (6)	0.6642 (4)	0.93876 (13)	0.0402 (7)
H8	0.7267	0.7586	0.9631	0.048*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0588 (5)	0.0489 (4)	0.0537 (5)	−0.0086 (4)	0.0042 (4)	0.0129 (4)
O1	0.0582 (14)	0.0464 (11)	0.0420 (13)	−0.0049 (10)	0.0170 (12)	0.0038 (9)
O2	0.0600 (14)	0.0389 (10)	0.0410 (13)	−0.0064 (12)	0.0119 (11)	−0.0098 (9)
N1	0.0375 (13)	0.0348 (12)	0.0319 (14)	0.0014 (11)	0.0068 (11)	−0.0017 (10)
C1	0.0401 (17)	0.0378 (14)	0.0272 (16)	−0.0022 (13)	−0.0029 (14)	−0.0005 (12)
C2	0.0532 (19)	0.0390 (15)	0.0423 (19)	−0.0032 (14)	0.0061 (16)	0.0019 (14)
C3	0.0362 (16)	0.0372 (14)	0.0305 (16)	−0.0012 (13)	−0.0001 (12)	−0.0028 (12)
C4	0.0291 (14)	0.0372 (14)	0.0221 (14)	0.0016 (13)	0.0002 (13)	−0.0008 (11)
C5	0.0370 (15)	0.0365 (14)	0.0282 (15)	0.0021 (13)	−0.0049 (13)	−0.0006 (11)
C6	0.0357 (15)	0.0424 (15)	0.0327 (17)	−0.0011 (13)	−0.0026 (13)	0.0083 (13)
C7	0.0392 (18)	0.0534 (17)	0.0297 (17)	−0.0007 (15)	0.0057 (13)	0.0011 (15)
C8	0.0425 (16)	0.0464 (15)	0.0315 (17)	0.0058 (16)	0.0041 (13)	−0.0052 (14)

Geometric parameters (Å, º)

Cl1—C6	1.720 (3)	C3—C8	1.373 (4)
O1—C1	1.231 (3)	C3—C4	1.373 (4)
O2—C3	1.354 (3)	C4—C5	1.362 (4)
O2—C2	1.414 (4)	C5—C6	1.377 (4)
N1—C1	1.324 (3)	C5—H5	0.9300
N1—C4	1.402 (3)	C6—C7	1.365 (4)
N1—H1	0.8600	C7—C8	1.362 (4)
C1—C2	1.486 (4)	C7—H7	0.9300
C2—H2A	0.9700	C8—H8	0.9300
C2—H2B	0.9700
C3—O2—C2	114.9 (2)	C5—C4—C3	120.7 (3)
C1—N1—C4	122.4 (2)	C5—C4—N1	121.2 (2)
C1—N1—H1	118.8	C3—C4—N1	118.0 (2)
C4—N1—H1	118.8	C4—C5—C6	118.5 (3)
O1—C1—N1	123.0 (3)	C4—C5—H5	120.7
O1—C1—C2	121.1 (2)	C6—C5—H5	120.7
N1—C1—C2	115.8 (3)	C7—C6—C5	121.3 (3)
O2—C2—C1	114.2 (2)	C7—C6—Cl1	119.4 (2)
O2—C2—H2A	108.7	C5—C6—Cl1	119.2 (2)
C1—C2—H2A	108.7	C8—C7—C6	119.5 (3)
O2—C2—H2B	108.7	C8—C7—H7	120.2
C1—C2—H2B	108.7	C6—C7—H7	120.2
H2A—C2—H2B	107.6	C7—C8—C3	120.1 (3)
O2—C3—C8	119.7 (2)	C7—C8—H8	120.0
O2—C3—C4	120.4 (2)	C3—C8—H8	120.0
C8—C3—C4	119.8 (3)
C4—N1—C1—O1	−178.8 (2)	C1—N1—C4—C5	167.7 (3)
C4—N1—C1—C2	−0.5 (4)	C1—N1—C4—C3	−14.2 (4)
C3—O2—C2—C1	−44.4 (3)	C3—C4—C5—C6	−0.1 (4)
O1—C1—C2—O2	−152.3 (3)	N1—C4—C5—C6	177.9 (2)
N1—C1—C2—O2	29.4 (4)	C4—C5—C6—C7	−0.5 (4)
C2—O2—C3—C8	−152.6 (3)	C4—C5—C6—Cl1	−179.8 (2)
C2—O2—C3—C4	31.1 (3)	C5—C6—C7—C8	1.3 (4)
O2—C3—C4—C5	176.3 (3)	Cl1—C6—C7—C8	−179.4 (2)
C8—C3—C4—C5	0.0 (4)	C6—C7—C8—C3	−1.4 (4)
O2—C3—C4—N1	−1.7 (4)	O2—C3—C8—C7	−175.6 (2)
C8—C3—C4—N1	−178.1 (2)	C4—C3—C8—C7	0.8 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O1^i	0.86	2.00	2.844 (3)	166

Symmetry code: (i) −x+3, y−1/2, −z+3/2.