5-Chloro-6-hy­droxy-7,8-dimethyl­chroman-2-one

Cameron, S.A.; Goswami, S.K.; Hanton, L.R.; McAdam, C.J.; Moratti, S.C.; Simpson, J.

doi:10.1107/S1600536811029345

organic compounds

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ISSN: 2056-9890

Volume 67| Part 8| August 2011| Pages o2141-o2142

doi:10.1107/S1600536811029345

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5-Chloro-6-hydroxy-7,8-dimethylchroman-2-one

Scott A. Cameron,^a Shailesh K. Goswami,^a Lyall R. Hanton,^a C. John McAdam,^a Stephen C. Moratti ^a and Jim Simpson ^a ^*

^aDepartment of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand
^*Correspondence e-mail: jsimpson@alkali.otago.ac.nz

(Received 15 July 2011; accepted 20 July 2011; online 30 July 2011)

In the title molecule, C₁₁H₁₁ClO₃, the fused pyran ring adopts a half-chair conformation. In the crystal, intermolecular O—H⋯O hydrogen bonds link molecules into chains along [100]. These chains are interconnected by weak intermolecular C—H⋯O contacts which generate R₂²(8) ring motifs, forming sheets parallel to (001). Tetragonal symmetry generates an equivalent motif along b. Furthermore, the sheets are linked along the c axis by offset π–π stacking interactions involving the benzene rings of adjacent molecules [with centroid–centroid distances of 3.839 (2) Å], together with an additional weak C—H⋯O hydrogen bond, resulting in an overall three-dimensional network.

Related literature

For the synthesis of the starting materials, see: Fieser & Ardao (1956 ); Bishop et al. (1963 ). For related structures, see: Budzianowski & Katrusiak (2002 ); Goswami et al. (2011 ). For standard bond lengths, see Allen et al. (1987 ). For hydrogen-bond motifs, see: Bernstein et al. (1995 ).

Experimental

Crystal data

C₁₁H₁₁ClO₃
M_r = 226.65
Tetragonal, $[P \overline 42_1 c ]$
a = 16.1375 (6) Å
c = 7.5887 (6) Å
V = 1976.24 (19) Å³
Z = 8
Mo Kα radiation
μ = 0.37 mm⁻¹
T = 89 K
0.40 × 0.07 × 0.05 mm

Data collection

Bruker APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker 2009 ) T_min = 0.792, T_max = 1.00
22360 measured reflections
2030 independent reflections
1618 reflections with I > 2σ(I)
R_int = 0.095

Refinement

R[F² > 2σ(F²)] = 0.050
wR(F²) = 0.143
S = 1.07
2030 reflections
141 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.33 e Å⁻³
Δρ_min = −0.39 e Å⁻³
Absolute structure: Flack (1983 ), 859 Friedel pairs
Flack parameter: −0.04 (12)

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C8—H8A⋯O9ⁱ	0.99	2.55	3.463 (5)	154
C7—H7B⋯O1ⁱⁱ	0.99	2.64	3.588 (5)	160
C7—H7B⋯O9ⁱⁱ	0.99	2.68	3.357 (5)	126
O4—H4O⋯O9ⁱⁱⁱ	0.78 (4)	2.12 (5)	2.748 (4)	137 (4)
C8—H8B⋯O4^iv	0.99	2.39	3.328 (5)	158
Symmetry codes: (i) -x+1, -y+1, z; (ii) -y+1, x, -z+2; (iii) $[-x+{\script{1\over 2}}, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (iv) $[-y+{\script{1\over 2}}, -x+{\script{1\over 2}}, z-{\script{1\over 2}}]$ .

Data collection: APEX2 (Bruker 2009); cell refinement: SAINT (Bruker 2009); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008) and TITAN2000 (Hunter & Simpson, 1999 ); molecular graphics: SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 2008 ); software used to prepare material for publication: SHELXL97, enCIFer (Allen et al., 2004 ), PLATON (Spek, 2009 ) and publCIF (Westrip, 2010 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811029345/lh5289sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811029345/lh5289Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811029345/lh5289Isup3.cml

checkCIF report

Comment top

The title compound (I) was isolated as an intermediate during the synthesis of redox-active quinone monomers currently of interest to us in our electro-mechanical actuator programme.

Compound (I), Fig 1, consists of a chromanone unit with an OH substituent at C4, a chloro substituent at C5 and methyl substituents on C2 and C3. The fused C1/C6-C9/O1 ring is in a half-chair conformation. Bond distances (Allen et al., 1987) and angles are normal and similar to those in closely related structures (Budzianowski & Katrusiak, 2002; Goswami et al., 2011).

Classical O4—H4O···O9ⁱⁱⁱ hydrogen bonds link molecules into chains along a. These chains are interconnected by weak C8—H8A···O9ⁱ contacts which generate R²₂(8) ring motifs (Bernstein et al., 1995) forming sheets in (0 0 1), Fig 2. Tetragonal symmetry generates an equivalent motif along b. These sheets are stacked along c by offset π–π stacking interactions involving the benzene rings of adjacent molecules with centroid to centroid distances of 3.839 (2) Å together with an additional C8–H8B···O4^iv hydrogen bond, Fig 3, resulting in a three dimensional network structure, Fig 4.

Related literature top

For the synthesis of the starting materials, see: Fieser & Ardao (1956); Bishop et al. (1963). For related structures, see: Budzianowski & Katrusiak (2002); Goswami et al. (2011). For standard bond lengths, see Allen et al. (1987). For hydrogen-bond motifs, see: Bernstein et al. (1995).

Experimental top

The title compound was synthesized in three steps. In the first step trimethyl-p-hydroquinone (Fieser & Ardao, 1956) (15.2 g, 100 mmol) was oxidized using sodium dichromate (10.8 g, 41 mmol) in acetic acid (50 ml). The product was characterized using NMR spectroscopy and the data were consistent with reported data of trimethyl-p-benzoquinone. The second step (chlorination) is an alternative to the existing literature (Bishop et al., 1963). Trimethyl-p-benzoquinone (10 g, 67 mmol) was added to conc. hydrochloric acid (100 ml) with vigorous stirring. The resulting suspension was heated to reflux for 3 hr. After dilution with water the solid was filtered out and re-dissolved in aqueous acetic acid. Aqueous sodium dichromate (10 g, 38 mmol) was added in portions. After the mixture had stood for 15 min, a yellow solid was precipitated by dilution with water. Crystallization from ethanol-water solution gave a yellow material, m.p. 337-338K; (lit. m.p. 337-338K). In the final step, a solution of methyl malonate (5.7 g, 43 mmol) in dry MeOH (25 ml) was refluxed for one hour with finely powdered MgOMe (3.85 g, 70 mmol). A solution of chlorotrimethyl-p-quinone (4 g, 21 mmol) in dry MeOH (25 ml) was added dropwise to the refluxing solution and reflux continued for 13 hr. The solid was removed from the cooled mixture, washed with ether and carefully mixed with HCl (10%, 50 ml) and stirred at 283K to remove impurities. The yellow solid product (3 g) was filtered out and dissolved in acetone and stirred with dil. hydrochloric acid (100 ml). The resulting white suspension was then refluxed for 5 hr. The solution was cooled and extracted with ether (3 × 30 mL) and the combined organic extracts washed with brine, dried (MgSO₄) and evaporated. To the crude residue in toluene (60 ml), 4-methylbenzenesulfonic acid (0.47 g, 27 mmol) was added with stirring, and the mixture then refluxed. After 12 hr, the nearly colourless solution was cooled to room temp. and extracted with EtOAc (3 × 30 ml). The organic extract was washed with sat. aqueous NaHCO₃ and the aqueous layer back-extracted once with EtOAc (30 ml). The combined organic extracts were washed with brine and dried over MgSO₄. X-ray quality crystals of the title compound, 5-chloro-6-hydroxy-7,8-dimethylchroman-2-one were obtained from EtOAc/hexane (1.76 g, 80%): m.p. 139–41°C; FT—IR cm^-1 1777 (O—C=O); ¹H-NMR (400 MHz, CDCl₃): δ 2.20 (s, 3H), 2.33 (s, 3H), 2.74 (t, J = 8 Hz, 2H), 3.02 (t, J = 8 Hz, 2H), 5.5 (s, 1H); ¹³C-NMR (100 MHz, CDCl₃): δ 12.0, 12.6, 22.0, 28.6,115.1, 117.8, 123.8, 125.0, 143.8, 145.9, 165.3.

Computing details top

Data collection: APEX2 (Bruker 2009); cell refinement: SAINT (Bruker 2009); data reduction: SAINT (Bruker 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008) and TITAN2000 (Hunter & Simpson, 1999); molecular graphics: SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008), enCIFer (Allen et al., 2004), PLATON (Spek, 2009) and publCIF (Westrip, 2010).

Figures top

	Fig. 1. The molecular structure of (I) showing ellipsoids drawn at the 50% probability level.
	Fig. 2. The (0 0 1) layer of (I). Dashed lines show O–H···O hydrogen bonds and C–H···O interactions.
	Fig. 3. The π..π stacking interactions in the structure of (I) with C–H···O interactions drawn as dashed lines.
	Fig. 4. Crystal packing of (I) viewed along the c axis showing the three- dimensional network.

5-Chloro-6-hydroxy-7,8-dimethylchroman-2-one top

Crystal data top

C₁₁H₁₁ClO₃	D_x = 1.524 Mg m⁻³
M_r = 226.65	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P42₁c	Cell parameters from 1966 reflections
Hall symbol: P -4 2n	θ = 2.5–20.6°
a = 16.1375 (6) Å	µ = 0.37 mm⁻¹
c = 7.5887 (6) Å	T = 89 K
V = 1976.24 (19) Å³	Needle, colourless
Z = 8	0.40 × 0.07 × 0.05 mm
F(000) = 944

Data collection top

Bruker APEXII CCD area-detector diffractometer	2030 independent reflections
Radiation source: fine-focus sealed tube	1618 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.095
ω scans	θ_max = 26.4°, θ_min = 3.9°
Absorption correction: multi-scan (SADABS; Bruker 2009)	h = −20→20
T_min = 0.792, T_max = 1.00	k = −20→19
22360 measured reflections	l = −9→8

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.050	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.143	w = 1/[σ²(F_o²) + (0.0781P)² + 0.6384P] where P = (F_o² + 2F_c²)/3
S = 1.07	(Δ/σ)_max < 0.001
2030 reflections	Δρ_max = 0.33 e Å⁻³
141 parameters	Δρ_min = −0.39 e Å⁻³
0 restraints	Absolute structure: Flack (1983), 859 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: −0.04 (12)

Crystal data top

C₁₁H₁₁ClO₃	Z = 8
M_r = 226.65	Mo Kα radiation
Tetragonal, P42₁c	µ = 0.37 mm⁻¹
a = 16.1375 (6) Å	T = 89 K
c = 7.5887 (6) Å	0.40 × 0.07 × 0.05 mm
V = 1976.24 (19) Å³

Data collection top

Bruker APEXII CCD area-detector diffractometer	2030 independent reflections
Absorption correction: multi-scan (SADABS; Bruker 2009)	1618 reflections with I > 2σ(I)
T_min = 0.792, T_max = 1.00	R_int = 0.095
22360 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.050	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.143	Δρ_max = 0.33 e Å⁻³
S = 1.07	Δρ_min = −0.39 e Å⁻³
2030 reflections	Absolute structure: Flack (1983), 859 Friedel pairs
141 parameters	Absolute structure parameter: −0.04 (12)
0 restraints

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq
O1	0.29181 (15)	0.46995 (15)	0.9081 (4)	0.0286 (6)
C1	0.2457 (2)	0.3970 (2)	0.8839 (5)	0.0246 (8)
C2	0.1624 (2)	0.4026 (2)	0.9338 (5)	0.0246 (8)
C21	0.1277 (2)	0.4829 (2)	1.0015 (6)	0.0295 (9)
H2A	0.1709	0.5132	1.0655	0.044*
H2B	0.0812	0.4715	1.0810	0.044*
H2C	0.1083	0.5165	0.9021	0.044*
C3	0.1126 (2)	0.3318 (2)	0.9168 (5)	0.0243 (8)
C31	0.02056 (19)	0.3310 (2)	0.9744 (4)	0.0166 (7)
H3A	−0.0132	0.3587	0.8847	0.025*
H3B	0.0148	0.3602	1.0870	0.025*
H3C	0.0019	0.2736	0.9879	0.025*
C4	0.1472 (2)	0.2595 (2)	0.8461 (5)	0.0239 (8)
O4	0.09528 (17)	0.19372 (16)	0.8261 (4)	0.0308 (7)
H4O	0.121 (3)	0.162 (3)	0.769 (6)	0.037*
C5	0.2308 (2)	0.2574 (2)	0.8003 (5)	0.0256 (8)
Cl5	0.27140 (6)	0.16405 (6)	0.72670 (15)	0.0370 (3)
C6	0.2815 (2)	0.3256 (2)	0.8168 (5)	0.0253 (8)
C7	0.3714 (2)	0.3268 (2)	0.7691 (6)	0.0294 (9)
H7A	0.3812	0.2882	0.6699	0.035*
H7B	0.4045	0.3074	0.8709	0.035*
C8	0.3994 (2)	0.4131 (3)	0.7170 (6)	0.0347 (9)
H8A	0.4607	0.4149	0.7194	0.042*
H8B	0.3815	0.4239	0.5943	0.042*
C9	0.3668 (2)	0.4805 (2)	0.8318 (6)	0.0279 (9)
O9	0.40023 (17)	0.54650 (16)	0.8556 (4)	0.0348 (7)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0223 (13)	0.0216 (13)	0.0419 (16)	0.0005 (11)	0.0013 (11)	−0.0028 (11)
C1	0.0241 (19)	0.0182 (17)	0.032 (2)	−0.0010 (15)	−0.0035 (15)	0.0018 (16)
C2	0.0260 (19)	0.0201 (18)	0.0278 (19)	0.0045 (16)	−0.0020 (16)	0.0018 (15)
C21	0.027 (2)	0.0183 (19)	0.043 (2)	−0.0007 (16)	−0.0001 (18)	−0.0065 (17)
C3	0.0210 (19)	0.0255 (18)	0.0263 (18)	0.0006 (15)	−0.0035 (15)	0.0032 (16)
C31	0.0134 (16)	0.0129 (16)	0.0235 (18)	−0.0005 (13)	−0.0005 (13)	0.0001 (14)
C4	0.0262 (19)	0.0184 (17)	0.0270 (18)	−0.0008 (14)	−0.0024 (15)	0.0024 (15)
O4	0.0281 (15)	0.0227 (14)	0.0418 (17)	−0.0042 (12)	−0.0004 (13)	−0.0031 (12)
C5	0.0287 (19)	0.0177 (17)	0.031 (2)	0.0034 (15)	−0.0003 (17)	0.0001 (15)
Cl5	0.0364 (6)	0.0255 (5)	0.0492 (6)	0.0042 (4)	−0.0028 (5)	−0.0048 (5)
C6	0.0259 (19)	0.0222 (19)	0.0279 (19)	0.0049 (15)	−0.0044 (15)	0.0016 (15)
C7	0.0213 (17)	0.0247 (18)	0.042 (2)	0.0044 (14)	−0.0024 (17)	−0.0012 (18)
C8	0.0212 (19)	0.042 (2)	0.041 (2)	−0.0005 (16)	−0.0001 (17)	−0.002 (2)
C9	0.0193 (18)	0.025 (2)	0.039 (2)	0.0000 (15)	−0.0036 (16)	0.0061 (17)
O9	0.0273 (14)	0.0227 (14)	0.0543 (19)	−0.0014 (12)	−0.0046 (14)	0.0067 (13)

Geometric parameters (Å, º) top

O1—C9	1.353 (4)	C4—O4	1.361 (4)
O1—C1	1.404 (4)	C4—C5	1.394 (5)
C1—C6	1.386 (5)	O4—H4O	0.78 (4)
C1—C2	1.399 (5)	C5—C6	1.377 (5)
C2—C3	1.402 (5)	C5—Cl5	1.735 (3)
C2—C21	1.503 (5)	C6—C7	1.495 (5)
C21—H2A	0.9800	C7—C8	1.517 (5)
C21—H2B	0.9800	C7—H7A	0.9900
C21—H2C	0.9800	C7—H7B	0.9900
C3—C4	1.401 (5)	C8—C9	1.489 (6)
C3—C31	1.549 (5)	C8—H8A	0.9900
C31—H3A	0.9800	C8—H8B	0.9900
C31—H3B	0.9800	C9—O9	1.207 (4)
C31—H3C	0.9800

C9—O1—C1	121.6 (3)	C5—C4—C3	120.1 (3)
C6—C1—C2	123.6 (3)	C4—O4—H4O	104 (3)
C6—C1—O1	121.6 (3)	C6—C5—C4	122.2 (3)
C2—C1—O1	114.8 (3)	C6—C5—Cl5	120.0 (3)
C1—C2—C3	118.2 (3)	C4—C5—Cl5	117.8 (3)
C1—C2—C21	120.4 (3)	C5—C6—C1	116.8 (3)
C3—C2—C21	121.3 (3)	C5—C6—C7	124.3 (3)
C2—C21—H2A	109.5	C1—C6—C7	118.9 (3)
C2—C21—H2B	109.5	C6—C7—C8	111.3 (3)
H2A—C21—H2B	109.5	C6—C7—H7A	109.4
C2—C21—H2C	109.5	C8—C7—H7A	109.4
H2A—C21—H2C	109.5	C6—C7—H7B	109.4
H2B—C21—H2C	109.5	C8—C7—H7B	109.4
C4—C3—C2	119.1 (3)	H7A—C7—H7B	108.0
C4—C3—C31	118.9 (3)	C9—C8—C7	114.4 (3)
C2—C3—C31	122.1 (3)	C9—C8—H8A	108.7
C3—C31—H3A	109.5	C7—C8—H8A	108.7
C3—C31—H3B	109.5	C9—C8—H8B	108.7
H3A—C31—H3B	109.5	C7—C8—H8B	108.7
C3—C31—H3C	109.5	H8A—C8—H8B	107.6
H3A—C31—H3C	109.5	O9—C9—O1	116.5 (4)
H3B—C31—H3C	109.5	O9—C9—C8	125.1 (4)
O4—C4—C5	123.3 (3)	O1—C9—C8	118.3 (3)
O4—C4—C3	116.6 (3)

C9—O1—C1—C6	15.2 (5)	C3—C4—C5—Cl5	176.0 (3)
C9—O1—C1—C2	−165.2 (3)	C4—C5—C6—C1	0.8 (6)
C6—C1—C2—C3	0.7 (6)	Cl5—C5—C6—C1	−177.1 (3)
O1—C1—C2—C3	−178.9 (3)	C4—C5—C6—C7	−179.8 (4)
C6—C1—C2—C21	−178.5 (4)	Cl5—C5—C6—C7	2.2 (5)
O1—C1—C2—C21	1.9 (5)	C2—C1—C6—C5	−0.2 (6)
C1—C2—C3—C4	−1.8 (5)	O1—C1—C6—C5	179.3 (3)
C21—C2—C3—C4	177.4 (3)	C2—C1—C6—C7	−179.6 (4)
C1—C2—C3—C31	177.9 (3)	O1—C1—C6—C7	0.0 (6)
C21—C2—C3—C31	−2.9 (6)	C5—C6—C7—C8	152.5 (4)
C2—C3—C4—O4	−177.5 (3)	C1—C6—C7—C8	−28.2 (5)
C31—C3—C4—O4	2.8 (5)	C6—C7—C8—C9	42.6 (5)
C2—C3—C4—C5	2.5 (6)	C1—O1—C9—O9	177.5 (4)
C31—C3—C4—C5	−177.2 (3)	C1—O1—C9—C8	1.3 (5)
O4—C4—C5—C6	177.9 (4)	C7—C8—C9—O9	153.5 (4)
C3—C4—C5—C6	−2.0 (6)	C7—C8—C9—O1	−30.7 (5)
O4—C4—C5—Cl5	−4.0 (5)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C8—H8A···O9ⁱ	0.99	2.55	3.463 (5)	154
C7—H7B···O1ⁱⁱ	0.99	2.64	3.588 (5)	160
C7—H7B···O9ⁱⁱ	0.99	2.68	3.357 (5)	126
O4—H4O···O9ⁱⁱⁱ	0.78 (4)	2.12 (5)	2.748 (4)	137 (4)
C8—H8B···O4^iv	0.99	2.39	3.328 (5)	158

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

Experimental details

Crystal data
Chemical formula	C₁₁H₁₁ClO₃
M_r	226.65
Crystal system, space group	Tetragonal, P42₁c
Temperature (K)	89
a, c (Å)	16.1375 (6), 7.5887 (6)
V (Å³)	1976.24 (19)
Z	8
Radiation type	Mo Kα
µ (mm⁻¹)	0.37
Crystal size (mm)	0.40 × 0.07 × 0.05

Data collection
Diffractometer	Bruker APEXII CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker 2009)
T_min, T_max	0.792, 1.00
No. of measured, independent and observed [I > 2σ(I)] reflections	22360, 2030, 1618
R_int	0.095
(sin θ/λ)_max (Å⁻¹)	0.626

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.050, 0.143, 1.07
No. of reflections	2030
No. of parameters	141
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.33, −0.39
Absolute structure	Flack (1983), 859 Friedel pairs
Absolute structure parameter	−0.04 (12)

Computer programs: APEX2 (Bruker 2009), SAINT (Bruker 2009), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008) and TITAN2000 (Hunter & Simpson, 1999), SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 2008), SHELXL97 (Sheldrick, 2008), enCIFer (Allen et al., 2004), PLATON (Spek, 2009) and publCIF (Westrip, 2010).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C8—H8A···O9ⁱ	0.99	2.55	3.463 (5)	153.5
C7—H7B···O1ⁱⁱ	0.99	2.64	3.588 (5)	160.0
C7—H7B···O9ⁱⁱ	0.99	2.68	3.357 (5)	126.0
O4—H4O···O9ⁱⁱⁱ	0.78 (4)	2.12 (5)	2.748 (4)	137 (4)
C8—H8B···O4^iv	0.99	2.39	3.328 (5)	157.8

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

Acknowledgements

We thank the New Economy Research Fund (grant No. UOO-X0808) for support of this work and the University of Otago for the purchase of the diffractometer.

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