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The crystal structure of the title compound, C23H28Br4O6, confirms that it consists of two hexa­substituted aromatic units linked by a central methyl­ene group. The mol­ecule lies on a crystallographic twofold axis that passes through the methyl­ene bridging atom. Examination of the extended structure reveals the presence of ribbons of mol­ecules held together by C—H...O and C—H...Br inter­actions.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536805040559/ci6723sup1.cif
Contains datablocks global, 5

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536805040559/ci67235sup2.hkl
Contains datablock 5

CCDC reference: 296542

Key indicators

  • Single-crystal X-ray study
  • T = 173 K
  • Mean [sigma](C-C) = 0.003 Å
  • R factor = 0.028
  • wR factor = 0.073
  • Data-to-parameter ratio = 20.0

checkCIF/PLATON results

No syntax errors found



Alert level C PLAT480_ALERT_4_C Long H...A H-Bond Reported H8B .. BR2 .. 3.04 Ang. PLAT480_ALERT_4_C Long H...A H-Bond Reported H8C .. BR2 .. 3.06 Ang.
0 ALERT level A = In general: serious problem 0 ALERT level B = Potentially serious problem 2 ALERT level C = Check and explain 0 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

Comment top

The synthesis of hexasubstituted aromatic compounds has always been a particular challenge (Saito & Yamamoto, 2000; Gevorgyan & Yamamoto, 1999). Apart from being found as structural components of natural products such as in compound (1) (Blackman & Matthews, 1982) these types of compounds have also been used as candidates for nonlinear optical materials, for example, as in compound (2) (Cho et al., 2002).

Our research group has utilized polysubstituted aromatic rings in our synthetic endeavours (van Otterlo et al., 2004; Michael et al., 2001; de Koning et al., 2000) and we wanted to synthesize a number of hexasubstituted aromatic systems to use as potential molecular scaffolds. Towards this end we repeated experimental work reported by Cho and coworkers (Cho et al., 2002) and were able to successfully isolate 22% of the hexa-substituted product (4), by treating 1,3,5-trimethoxybenzene (3) with paraformaldehyde and hydrobromic acid (See Scheme). However, another crystalline product was obtained in a yield of 6% after chromatography and recrystallization. NMR spectroscopic evidence suggested that the compound was a dimer and the structure of (5) was confirmed by a single-crystal X-ray diffraction study. This compound is probably formed when the protonated hydroxymethyl intermediate is attacked in a nucleophilic manner by another aromatic molecule.

The title compound crystallizes in the space group Pbcn with half the molecule in the asymmetric unit. The other half is related by a crystallographic twofold axis through the methylene (C2) bridging atom (Fig. 1). As a consequence the molecule possesses C2 point group symmetry. Though the molecule has two aryl rings there are no C—H···π or π···π interactions. There are, however, intermolecular C—H···O (C11—H11B···O1; Table 1) and C—H···Br (C8–H8B···Br2; Table 1) hydrogen bonds and these act along the c axis, the interaction being between a benzyl bromide group and a methoxy group, to produce a ribbon of molecules running down the c axis (Fig. 2). Each molecule within the ribbon is related to the next by an inversion centre. These ribbons are further hydrogen bonded to neighbouring ribbons related by b glide planes through C—H···O interactions (C10—H10C···O2; Table 1) and to ribbons related by translation along the b axis through C—H···Br interactions (C8—H8C···Br2; Table 1 and Fig. 3).

Experimental top

A thick-walled Carius tube (100 ml) was charged with 1,3,5-trimethoxybenzene (3.421 g, 20.34 mmol), dry glacial acetic acid (10 ml) and paraformaldehyde (2.016 g, 67.13 mmol). The solution was shaken to disolve the solids and then cooled to 273 K. HBr (30%) in glacial acetic acid (15 ml) was added and the contents of the tube were frozen in liquid N2 and sealed. The tube was warmed to room temperature and then heated in an oil bath at 333 K for 3 h. After cooling to room temperature the tube contents were poured into water (100 ml) and extracted once with ethyl acetate (200 ml). The organic phase was dried (magnesium sulfate), filtered and evaporated under reduced pressure to give a red residue. Silica gel column chromatography with ethyl acetate:hexane (1:19) first afforded known compound 4 as a white powder (1.919 g, 4.29 mmol, 22%) followed by product 5 as a beige-coloured powder. Recrystallization of the latter powder from hexane:acetone (4:1) afforded pale brown cube-shaped crystals (0.823 g, 1.14 mmol, 6%, m.p. 350–352 K). Spectroscopic data: δH (300 MHz, CDCl3): 3.78 (12H, s, 4 x OCH3), 4.08 (2H, s, CH2), 4.11 (6H, s, 2 x OCH3), 4.60 (8H, s, 4 x CH2Br); δC(75 MHz, CDCl3): 20.0 (CH2), 23.3 (4 x CH2Br), 61.7 (4 x OCH3), 62.5 (2 x OCH3), 122.3 (4 x ArC), 124.5 (2 x ArC), 157.5 (2 x ArC-O), 159.7 (4 x ArC-O); νmax/cm−1 (Thin film, NaCl plate): 1578, 1457, 1414, 1324, 1265, 1216, 1195, 1152, 1102, 1002; m/z 720.1 (M+, 5%), 644.2 (9), 643.2 (36), 642.1 (25), 641.2 (100), 640.2 (26), 639.1 (99), 638.2 (9), 545.1 (16), 419.2 (6), 369.1 (9), 367.1 (18), 365.1 (9), 280.1 (9), 207.2 (15), 193.2 (11), 177.1 (10), 163.1 (9) 147.1 (9).

Refinement top

H atoms were positioned geometrically and allowed to ride on their respective parent atoms, with C—H bond lengths of 0.99 (CH2) or 0.98 Å (CH3), and isotropic displacement parameters equal to 1.2 (CH2) or 1.5 (CH3) times that of the parent atom.

Computing details top

Data collection: SMART-NT (Bruker, 1998); cell refinement: SAINT-Plus (Bruker, 1999); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Bruker, 1999); program(s) used to refine structure: SHELXTL; molecular graphics: PLATON (Spek, 2003) and SCHAKAL97 (Keller, 1997); software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. View of the title molecule showing the atom numbering scheme for the asymmetric unit. Unlabelled atoms are related to labelled atoms by (−x, y, 1/2 − z) with the C7 atom sitting on the twofold axis. Displacement ellipsoids are drawn at the 50% probability level. H atoms are shown with an arbitrary radius.
[Figure 2] Fig. 2. C—H···O and C—H···Br (see Table 1 for details) hydrogen bonding in the title compound, forming a chain of molecules (or ribbon) running down the c axis. Each molecule is related to the next by a centre of inversion. Symmetry codes for the various molecules (and independent unit making up each molecule) are as follows: (i) x, y, z; (ii) −x, y, 1/2 − z; (iii) −x, −y, −z; (iv) x, −y, −1/2 + z; (v) −x, −y, 1 − z; (vi) x, −y, 1/2 + z.
[Figure 3] Fig. 3. Each molecule in the ribbon described in Fig. 2 is C—H···O hydrogen bonded to neighbouring ribbon related by a b glide. In addition molecules in ribbons related by translation along the b axis are involved in a C—H···Br interaction (see Table 1 for details). Symmetry codes for the various molecules (and independent unit making up each molecule) are as follows: (i)x, y, z; (ii) −x, y, 1/2 − z; (iii) x, 1 + y, z; (iv) −x, 1 + y, 1/2 − z; (v) 1/2 − x, −1/2 + y, z; (vi) 1/2 + x, −1/2 + y, 1/2 − z; (vii) 1/2 − x, 1/2 + y,z; (viii) 1/2 + x, 1/2 + y, 1/2 − z.
1-[3,5-Bis(bromomethyl)-2,4,6-trimethoxybenzyl]-3,5-bis(bromomethyl)-2,4,6- trimethoxybenzene top
Crystal data top
C23H28Br4O6F(000) = 1416
Mr = 720.09Dx = 1.891 Mg m3
Orthorhombic, PbcnMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2n 2abCell parameters from 863 reflections
a = 22.737 (7) Åθ = 2.7–28.1°
b = 7.280 (2) ŵ = 6.40 mm1
c = 15.280 (4) ÅT = 173 K
V = 2529.2 (13) Å3Block, pale brown
Z = 40.34 × 0.25 × 0.21 mm
Data collection top
Bruker SMART CCD area-detector
diffractometer
3056 independent reflections
Radiation source: fine-focus sealed tube2374 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.052
ϕ and ω scansθmax = 28.0°, θmin = 1.8°
Absorption correction: integration
(XPREP; Bruker, 1999)
h = 3029
Tmin = 0.220, Tmax = 0.347k = 97
13104 measured reflectionsl = 1920
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.028Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.073H-atom parameters constrained
S = 0.98 w = 1/[σ2(Fo2) + (0.0418P)2]
where P = (Fo2 + 2Fc2)/3
3056 reflections(Δ/σ)max = 0.001
153 parametersΔρmax = 0.67 e Å3
0 restraintsΔρmin = 0.61 e Å3
Crystal data top
C23H28Br4O6V = 2529.2 (13) Å3
Mr = 720.09Z = 4
Orthorhombic, PbcnMo Kα radiation
a = 22.737 (7) ŵ = 6.40 mm1
b = 7.280 (2) ÅT = 173 K
c = 15.280 (4) Å0.34 × 0.25 × 0.21 mm
Data collection top
Bruker SMART CCD area-detector
diffractometer
3056 independent reflections
Absorption correction: integration
(XPREP; Bruker, 1999)
2374 reflections with I > 2σ(I)
Tmin = 0.220, Tmax = 0.347Rint = 0.052
13104 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0280 restraints
wR(F2) = 0.073H-atom parameters constrained
S = 0.98Δρmax = 0.67 e Å3
3056 reflectionsΔρmin = 0.61 e Å3
153 parameters
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
xyzUiso*/UeqOcc. (<1)
C10.05570 (10)0.1084 (3)0.25887 (15)0.0188 (5)
C20.10130 (10)0.1211 (3)0.19776 (15)0.0193 (5)
C30.15198 (10)0.0137 (3)0.20259 (16)0.0195 (5)
C40.15720 (10)0.1088 (3)0.27285 (16)0.0187 (5)
C50.11400 (11)0.1232 (3)0.33784 (16)0.0204 (5)
C60.06330 (11)0.0130 (3)0.32893 (16)0.0204 (5)
C70.00000.2223 (5)0.25000.0224 (7)
H7A0.00370.30250.30200.027*0.50
H7B0.00370.30250.19800.027*0.50
C80.11296 (13)0.4240 (4)0.14365 (18)0.0331 (6)
H8A0.15530.42790.15570.050*
H8B0.10420.50060.09260.050*
H8C0.09140.47040.19450.050*
C90.19905 (11)0.0284 (4)0.13465 (17)0.0246 (6)
H9A0.19960.15480.11080.030*
H9B0.23780.00440.16200.030*
C100.25543 (11)0.1470 (4)0.32365 (19)0.0273 (6)
H10A0.24340.11180.38290.041*
H10B0.28690.23860.32710.041*
H10C0.26970.03830.29230.041*
C110.12367 (12)0.2437 (3)0.41538 (16)0.0230 (5)
H11A0.16560.23700.43270.028*
H11B0.09990.19710.46490.028*
C120.01480 (13)0.1717 (4)0.4048 (2)0.0364 (7)
H12A0.00570.25840.44330.055*
H12B0.05250.13700.43120.055*
H12C0.02190.22970.34790.055*
O10.09557 (7)0.2386 (2)0.12636 (11)0.0228 (4)
O20.20577 (7)0.2238 (2)0.27750 (12)0.0227 (4)
O30.02102 (8)0.0095 (2)0.39300 (12)0.0271 (4)
Br10.186343 (13)0.14802 (4)0.037930 (17)0.03150 (9)
Br20.102626 (13)0.50411 (4)0.393486 (19)0.03050 (9)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0216 (11)0.0159 (12)0.0190 (12)0.0010 (9)0.0013 (10)0.0010 (9)
C20.0257 (12)0.0165 (12)0.0157 (11)0.0040 (9)0.0010 (10)0.0011 (9)
C30.0211 (11)0.0190 (12)0.0184 (12)0.0045 (10)0.0006 (9)0.0010 (9)
C40.0186 (11)0.0145 (12)0.0229 (12)0.0004 (9)0.0017 (10)0.0018 (9)
C50.0251 (12)0.0176 (12)0.0185 (12)0.0031 (9)0.0002 (10)0.0001 (10)
C60.0246 (12)0.0183 (12)0.0182 (12)0.0037 (10)0.0023 (10)0.0004 (9)
C70.0214 (16)0.0210 (17)0.0247 (18)0.0000.0012 (14)0.000
C80.0475 (17)0.0202 (14)0.0317 (15)0.0045 (13)0.0005 (13)0.0075 (12)
C90.0247 (12)0.0249 (14)0.0242 (13)0.0024 (10)0.0004 (10)0.0010 (10)
C100.0215 (12)0.0252 (14)0.0352 (15)0.0005 (11)0.0053 (11)0.0008 (11)
C110.0280 (12)0.0237 (14)0.0174 (12)0.0018 (10)0.0032 (10)0.0008 (10)
C120.0329 (15)0.0342 (16)0.0420 (17)0.0036 (12)0.0102 (13)0.0120 (13)
O10.0303 (9)0.0210 (10)0.0172 (9)0.0019 (7)0.0008 (7)0.0049 (7)
O20.0216 (8)0.0169 (9)0.0296 (9)0.0001 (7)0.0017 (7)0.0013 (8)
O30.0318 (10)0.0260 (10)0.0234 (9)0.0012 (8)0.0081 (8)0.0022 (8)
Br10.04146 (17)0.02935 (16)0.02368 (14)0.00516 (12)0.00538 (12)0.00257 (11)
Br20.04193 (17)0.02120 (15)0.02837 (16)0.00298 (11)0.00008 (12)0.00237 (11)
Geometric parameters (Å, º) top
C1—C21.398 (3)C8—H8B0.98
C1—C61.399 (3)C8—H8C0.98
C1—C71.520 (3)C9—Br11.979 (3)
C2—O11.393 (3)C9—H9A0.99
C2—C31.394 (3)C9—H9B0.99
C3—C41.401 (3)C10—O21.444 (3)
C3—C91.495 (3)C10—H10A0.98
C4—O21.387 (3)C10—H10B0.98
C4—C51.401 (3)C10—H10C0.98
C5—C61.411 (3)C11—Br21.983 (3)
C5—C111.491 (3)C11—H11A0.99
C6—O31.372 (3)C11—H11B0.99
C7—C1i1.520 (3)C12—O31.446 (3)
C7—H7A0.99C12—H12A0.98
C7—H7B0.99C12—H12B0.98
C8—O11.431 (3)C12—H12C0.98
C8—H8A0.98
C2—C1—C6117.5 (2)H8B—C8—H8C109.5
C2—C1—C7121.48 (19)C3—C9—Br1111.57 (17)
C6—C1—C7121.1 (2)C3—C9—H9A109.3
O1—C2—C3117.6 (2)Br1—C9—H9A109.3
O1—C2—C1119.6 (2)C3—C9—H9B109.3
C3—C2—C1122.7 (2)Br1—C9—H9B109.3
C2—C3—C4117.9 (2)H9A—C9—H9B108.0
C2—C3—C9121.0 (2)O2—C10—H10A109.5
C4—C3—C9121.1 (2)O2—C10—H10B109.5
O2—C4—C3119.4 (2)H10A—C10—H10B109.5
O2—C4—C5118.5 (2)O2—C10—H10C109.5
C3—C4—C5122.1 (2)H10A—C10—H10C109.5
C4—C5—C6117.5 (2)H10B—C10—H10C109.5
C4—C5—C11120.3 (2)C5—C11—Br2113.13 (17)
C6—C5—C11122.1 (2)C5—C11—H11A109.0
O3—C6—C1116.6 (2)Br2—C11—H11A109.0
O3—C6—C5120.9 (2)C5—C11—H11B109.0
C1—C6—C5122.3 (2)Br2—C11—H11B109.0
C1—C7—C1i113.9 (3)H11A—C11—H11B107.8
C1—C7—H7A108.8O3—C12—H12A109.5
C1i—C7—H7A108.8O3—C12—H12B109.5
C1—C7—H7B108.8H12A—C12—H12B109.5
C1i—C7—H7B108.8O3—C12—H12C109.5
H7A—C7—H7B107.7H12A—C12—H12C109.5
O1—C8—H8A109.5H12B—C12—H12C109.5
O1—C8—H8B109.5C2—O1—C8114.14 (19)
H8A—C8—H8B109.5C4—O2—C10114.43 (18)
O1—C8—H8C109.5C6—O3—C12117.9 (2)
H8A—C8—H8C109.5
C6—C1—C2—O1179.4 (2)C2—C1—C6—C51.6 (4)
C7—C1—C2—O10.8 (3)C7—C1—C6—C5178.6 (2)
C6—C1—C2—C32.5 (4)C4—C5—C6—O3175.3 (2)
C7—C1—C2—C3177.7 (2)C11—C5—C6—O31.4 (4)
O1—C2—C3—C4178.1 (2)C4—C5—C6—C10.6 (4)
C1—C2—C3—C41.2 (3)C11—C5—C6—C1176.1 (2)
O1—C2—C3—C91.6 (3)C2—C1—C7—C1i119.4 (2)
C1—C2—C3—C9178.5 (2)C6—C1—C7—C1i60.80 (19)
C2—C3—C4—O2177.0 (2)C2—C3—C9—Br191.0 (2)
C9—C3—C4—O22.7 (3)C4—C3—C9—Br188.7 (2)
C2—C3—C4—C51.1 (3)C4—C5—C11—Br284.4 (3)
C9—C3—C4—C5179.2 (2)C6—C5—C11—Br299.0 (2)
O2—C4—C5—C6176.2 (2)C3—C2—O1—C897.2 (3)
C3—C4—C5—C61.9 (4)C1—C2—O1—C885.8 (3)
O2—C4—C5—C117.0 (3)C3—C4—O2—C1089.4 (3)
C3—C4—C5—C11174.8 (2)C5—C4—O2—C1092.4 (3)
C2—C1—C6—O3173.4 (2)C1—C6—O3—C12114.9 (2)
C7—C1—C6—O36.4 (3)C5—C6—O3—C1270.2 (3)
Symmetry code: (i) x, y, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C10—H10C···O2ii0.982.373.281 (3)155
C11—H11B···O1iii0.992.493.287 (3)138
C8—H8B···Br2iv0.983.043.874 (3)143
C8—H8C···Br2v0.983.063.860 (3)140
Symmetry codes: (ii) x+1/2, y1/2, z; (iii) x, y, z+1/2; (iv) x, y, z1/2; (v) x, y1, z.

Experimental details

Crystal data
Chemical formulaC23H28Br4O6
Mr720.09
Crystal system, space groupOrthorhombic, Pbcn
Temperature (K)173
a, b, c (Å)22.737 (7), 7.280 (2), 15.280 (4)
V3)2529.2 (13)
Z4
Radiation typeMo Kα
µ (mm1)6.40
Crystal size (mm)0.34 × 0.25 × 0.21
Data collection
DiffractometerBruker SMART CCD area-detector
diffractometer
Absorption correctionIntegration
(XPREP; Bruker, 1999)
Tmin, Tmax0.220, 0.347
No. of measured, independent and
observed [I > 2σ(I)] reflections
13104, 3056, 2374
Rint0.052
(sin θ/λ)max1)0.661
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.028, 0.073, 0.98
No. of reflections3056
No. of parameters153
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.67, 0.61

Computer programs: SMART-NT (Bruker, 1998), SAINT-Plus (Bruker, 1999), SAINT-Plus, SHELXTL (Bruker, 1999), SHELXTL, PLATON (Spek, 2003) and SCHAKAL97 (Keller, 1997).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C10—H10C···O2i0.982.373.281 (3)155
C11—H11B···O1ii0.992.493.287 (3)138
C8—H8B···Br2iii0.983.043.874 (3)143
C8—H8C···Br2iv0.983.063.860 (3)140
Symmetry codes: (i) x+1/2, y1/2, z; (ii) x, y, z+1/2; (iii) x, y, z1/2; (iv) x, y1, z.
 

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