1-[3,5-Bis(bromomethyl)-2,4,6-trimethoxybenzyl]-3,5-bis(bromomethyl)-2,4,6-trimethoxybenzene
Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536805040559/ci6723sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536805040559/ci67235sup2.hkl |
CCDC reference: 296542
Key indicators
- Single-crystal X-ray study
- T = 173 K
- Mean (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
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).
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.
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.
C23H28Br4O6 | F(000) = 1416 |
Mr = 720.09 | Dx = 1.891 Mg m−3 |
Orthorhombic, Pbcn | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2n 2ab | Cell parameters from 863 reflections |
a = 22.737 (7) Å | θ = 2.7–28.1° |
b = 7.280 (2) Å | µ = 6.40 mm−1 |
c = 15.280 (4) Å | T = 173 K |
V = 2529.2 (13) Å3 | Block, pale brown |
Z = 4 | 0.34 × 0.25 × 0.21 mm |
Bruker SMART CCD area-detector diffractometer | 3056 independent reflections |
Radiation source: fine-focus sealed tube | 2374 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.052 |
ϕ and ω scans | θmax = 28.0°, θmin = 1.8° |
Absorption correction: integration (XPREP; Bruker, 1999) | h = −30→29 |
Tmin = 0.220, Tmax = 0.347 | k = −9→7 |
13104 measured reflections | l = −19→20 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.028 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.073 | H-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 parameters | Δρmax = 0.67 e Å−3 |
0 restraints | Δρmin = −0.61 e Å−3 |
C23H28Br4O6 | V = 2529.2 (13) Å3 |
Mr = 720.09 | Z = 4 |
Orthorhombic, Pbcn | Mo Kα radiation |
a = 22.737 (7) Å | µ = 6.40 mm−1 |
b = 7.280 (2) Å | T = 173 K |
c = 15.280 (4) Å | 0.34 × 0.25 × 0.21 mm |
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 = 0.347 | Rint = 0.052 |
13104 measured reflections |
R[F2 > 2σ(F2)] = 0.028 | 0 restraints |
wR(F2) = 0.073 | H-atom parameters constrained |
S = 0.98 | Δρmax = 0.67 e Å−3 |
3056 reflections | Δρmin = −0.61 e Å−3 |
153 parameters |
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. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
C1 | 0.05570 (10) | −0.1084 (3) | 0.25887 (15) | 0.0188 (5) | |
C2 | 0.10130 (10) | −0.1211 (3) | 0.19776 (15) | 0.0193 (5) | |
C3 | 0.15198 (10) | −0.0137 (3) | 0.20259 (16) | 0.0195 (5) | |
C4 | 0.15720 (10) | 0.1088 (3) | 0.27285 (16) | 0.0187 (5) | |
C5 | 0.11400 (11) | 0.1232 (3) | 0.33784 (16) | 0.0204 (5) | |
C6 | 0.06330 (11) | 0.0130 (3) | 0.32893 (16) | 0.0204 (5) | |
C7 | 0.0000 | −0.2223 (5) | 0.2500 | 0.0224 (7) | |
H7A | −0.0037 | −0.3025 | 0.3020 | 0.027* | 0.50 |
H7B | 0.0037 | −0.3025 | 0.1980 | 0.027* | 0.50 |
C8 | 0.11296 (13) | −0.4240 (4) | 0.14365 (18) | 0.0331 (6) | |
H8A | 0.1553 | −0.4279 | 0.1557 | 0.050* | |
H8B | 0.1042 | −0.5006 | 0.0926 | 0.050* | |
H8C | 0.0914 | −0.4704 | 0.1945 | 0.050* | |
C9 | 0.19905 (11) | −0.0284 (4) | 0.13465 (17) | 0.0246 (6) | |
H9A | 0.1996 | −0.1548 | 0.1108 | 0.030* | |
H9B | 0.2378 | −0.0044 | 0.1620 | 0.030* | |
C10 | 0.25543 (11) | 0.1470 (4) | 0.32365 (19) | 0.0273 (6) | |
H10A | 0.2434 | 0.1118 | 0.3829 | 0.041* | |
H10B | 0.2869 | 0.2386 | 0.3271 | 0.041* | |
H10C | 0.2697 | 0.0383 | 0.2923 | 0.041* | |
C11 | 0.12367 (12) | 0.2437 (3) | 0.41538 (16) | 0.0230 (5) | |
H11A | 0.1656 | 0.2370 | 0.4327 | 0.028* | |
H11B | 0.0999 | 0.1971 | 0.4649 | 0.028* | |
C12 | −0.01480 (13) | 0.1717 (4) | 0.4048 (2) | 0.0364 (7) | |
H12A | 0.0057 | 0.2584 | 0.4433 | 0.055* | |
H12B | −0.0525 | 0.1370 | 0.4312 | 0.055* | |
H12C | −0.0219 | 0.2297 | 0.3479 | 0.055* | |
O1 | 0.09557 (7) | −0.2386 (2) | 0.12636 (11) | 0.0228 (4) | |
O2 | 0.20577 (7) | 0.2238 (2) | 0.27750 (12) | 0.0227 (4) | |
O3 | 0.02102 (8) | 0.0095 (2) | 0.39300 (12) | 0.0271 (4) | |
Br1 | 0.186343 (13) | 0.14802 (4) | 0.037930 (17) | 0.03150 (9) | |
Br2 | 0.102626 (13) | 0.50411 (4) | 0.393486 (19) | 0.03050 (9) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0216 (11) | 0.0159 (12) | 0.0190 (12) | 0.0010 (9) | −0.0013 (10) | 0.0010 (9) |
C2 | 0.0257 (12) | 0.0165 (12) | 0.0157 (11) | 0.0040 (9) | −0.0010 (10) | −0.0011 (9) |
C3 | 0.0211 (11) | 0.0190 (12) | 0.0184 (12) | 0.0045 (10) | −0.0006 (9) | 0.0010 (9) |
C4 | 0.0186 (11) | 0.0145 (12) | 0.0229 (12) | 0.0004 (9) | −0.0017 (10) | 0.0018 (9) |
C5 | 0.0251 (12) | 0.0176 (12) | 0.0185 (12) | 0.0031 (9) | −0.0002 (10) | −0.0001 (10) |
C6 | 0.0246 (12) | 0.0183 (12) | 0.0182 (12) | 0.0037 (10) | 0.0023 (10) | 0.0004 (9) |
C7 | 0.0214 (16) | 0.0210 (17) | 0.0247 (18) | 0.000 | 0.0012 (14) | 0.000 |
C8 | 0.0475 (17) | 0.0202 (14) | 0.0317 (15) | 0.0045 (13) | 0.0005 (13) | −0.0075 (12) |
C9 | 0.0247 (12) | 0.0249 (14) | 0.0242 (13) | 0.0024 (10) | 0.0004 (10) | −0.0010 (10) |
C10 | 0.0215 (12) | 0.0252 (14) | 0.0352 (15) | −0.0005 (11) | −0.0053 (11) | 0.0008 (11) |
C11 | 0.0280 (12) | 0.0237 (14) | 0.0174 (12) | 0.0018 (10) | −0.0032 (10) | −0.0008 (10) |
C12 | 0.0329 (15) | 0.0342 (16) | 0.0420 (17) | 0.0036 (12) | 0.0102 (13) | −0.0120 (13) |
O1 | 0.0303 (9) | 0.0210 (10) | 0.0172 (9) | 0.0019 (7) | −0.0008 (7) | −0.0049 (7) |
O2 | 0.0216 (8) | 0.0169 (9) | 0.0296 (9) | −0.0001 (7) | −0.0017 (7) | 0.0013 (8) |
O3 | 0.0318 (10) | 0.0260 (10) | 0.0234 (9) | −0.0012 (8) | 0.0081 (8) | −0.0022 (8) |
Br1 | 0.04146 (17) | 0.02935 (16) | 0.02368 (14) | −0.00516 (12) | 0.00538 (12) | 0.00257 (11) |
Br2 | 0.04193 (17) | 0.02120 (15) | 0.02837 (16) | 0.00298 (11) | −0.00008 (12) | −0.00237 (11) |
C1—C2 | 1.398 (3) | C8—H8B | 0.98 |
C1—C6 | 1.399 (3) | C8—H8C | 0.98 |
C1—C7 | 1.520 (3) | C9—Br1 | 1.979 (3) |
C2—O1 | 1.393 (3) | C9—H9A | 0.99 |
C2—C3 | 1.394 (3) | C9—H9B | 0.99 |
C3—C4 | 1.401 (3) | C10—O2 | 1.444 (3) |
C3—C9 | 1.495 (3) | C10—H10A | 0.98 |
C4—O2 | 1.387 (3) | C10—H10B | 0.98 |
C4—C5 | 1.401 (3) | C10—H10C | 0.98 |
C5—C6 | 1.411 (3) | C11—Br2 | 1.983 (3) |
C5—C11 | 1.491 (3) | C11—H11A | 0.99 |
C6—O3 | 1.372 (3) | C11—H11B | 0.99 |
C7—C1i | 1.520 (3) | C12—O3 | 1.446 (3) |
C7—H7A | 0.99 | C12—H12A | 0.98 |
C7—H7B | 0.99 | C12—H12B | 0.98 |
C8—O1 | 1.431 (3) | C12—H12C | 0.98 |
C8—H8A | 0.98 | ||
C2—C1—C6 | 117.5 (2) | H8B—C8—H8C | 109.5 |
C2—C1—C7 | 121.48 (19) | C3—C9—Br1 | 111.57 (17) |
C6—C1—C7 | 121.1 (2) | C3—C9—H9A | 109.3 |
O1—C2—C3 | 117.6 (2) | Br1—C9—H9A | 109.3 |
O1—C2—C1 | 119.6 (2) | C3—C9—H9B | 109.3 |
C3—C2—C1 | 122.7 (2) | Br1—C9—H9B | 109.3 |
C2—C3—C4 | 117.9 (2) | H9A—C9—H9B | 108.0 |
C2—C3—C9 | 121.0 (2) | O2—C10—H10A | 109.5 |
C4—C3—C9 | 121.1 (2) | O2—C10—H10B | 109.5 |
O2—C4—C3 | 119.4 (2) | H10A—C10—H10B | 109.5 |
O2—C4—C5 | 118.5 (2) | O2—C10—H10C | 109.5 |
C3—C4—C5 | 122.1 (2) | H10A—C10—H10C | 109.5 |
C4—C5—C6 | 117.5 (2) | H10B—C10—H10C | 109.5 |
C4—C5—C11 | 120.3 (2) | C5—C11—Br2 | 113.13 (17) |
C6—C5—C11 | 122.1 (2) | C5—C11—H11A | 109.0 |
O3—C6—C1 | 116.6 (2) | Br2—C11—H11A | 109.0 |
O3—C6—C5 | 120.9 (2) | C5—C11—H11B | 109.0 |
C1—C6—C5 | 122.3 (2) | Br2—C11—H11B | 109.0 |
C1—C7—C1i | 113.9 (3) | H11A—C11—H11B | 107.8 |
C1—C7—H7A | 108.8 | O3—C12—H12A | 109.5 |
C1i—C7—H7A | 108.8 | O3—C12—H12B | 109.5 |
C1—C7—H7B | 108.8 | H12A—C12—H12B | 109.5 |
C1i—C7—H7B | 108.8 | O3—C12—H12C | 109.5 |
H7A—C7—H7B | 107.7 | H12A—C12—H12C | 109.5 |
O1—C8—H8A | 109.5 | H12B—C12—H12C | 109.5 |
O1—C8—H8B | 109.5 | C2—O1—C8 | 114.14 (19) |
H8A—C8—H8B | 109.5 | C4—O2—C10 | 114.43 (18) |
O1—C8—H8C | 109.5 | C6—O3—C12 | 117.9 (2) |
H8A—C8—H8C | 109.5 | ||
C6—C1—C2—O1 | −179.4 (2) | C2—C1—C6—C5 | 1.6 (4) |
C7—C1—C2—O1 | 0.8 (3) | C7—C1—C6—C5 | −178.6 (2) |
C6—C1—C2—C3 | −2.5 (4) | C4—C5—C6—O3 | 175.3 (2) |
C7—C1—C2—C3 | 177.7 (2) | C11—C5—C6—O3 | −1.4 (4) |
O1—C2—C3—C4 | 178.1 (2) | C4—C5—C6—C1 | 0.6 (4) |
C1—C2—C3—C4 | 1.2 (3) | C11—C5—C6—C1 | −176.1 (2) |
O1—C2—C3—C9 | −1.6 (3) | C2—C1—C7—C1i | −119.4 (2) |
C1—C2—C3—C9 | −178.5 (2) | C6—C1—C7—C1i | 60.80 (19) |
C2—C3—C4—O2 | −177.0 (2) | C2—C3—C9—Br1 | 91.0 (2) |
C9—C3—C4—O2 | 2.7 (3) | C4—C3—C9—Br1 | −88.7 (2) |
C2—C3—C4—C5 | 1.1 (3) | C4—C5—C11—Br2 | 84.4 (3) |
C9—C3—C4—C5 | −179.2 (2) | C6—C5—C11—Br2 | −99.0 (2) |
O2—C4—C5—C6 | 176.2 (2) | C3—C2—O1—C8 | 97.2 (3) |
C3—C4—C5—C6 | −1.9 (4) | C1—C2—O1—C8 | −85.8 (3) |
O2—C4—C5—C11 | −7.0 (3) | C3—C4—O2—C10 | −89.4 (3) |
C3—C4—C5—C11 | 174.8 (2) | C5—C4—O2—C10 | 92.4 (3) |
C2—C1—C6—O3 | −173.4 (2) | C1—C6—O3—C12 | −114.9 (2) |
C7—C1—C6—O3 | 6.4 (3) | C5—C6—O3—C12 | 70.2 (3) |
Symmetry code: (i) −x, y, −z+1/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
C10—H10C···O2ii | 0.98 | 2.37 | 3.281 (3) | 155 |
C11—H11B···O1iii | 0.99 | 2.49 | 3.287 (3) | 138 |
C8—H8B···Br2iv | 0.98 | 3.04 | 3.874 (3) | 143 |
C8—H8C···Br2v | 0.98 | 3.06 | 3.860 (3) | 140 |
Symmetry codes: (ii) −x+1/2, y−1/2, z; (iii) x, −y, z+1/2; (iv) x, −y, z−1/2; (v) x, y−1, z. |
Experimental details
Crystal data | |
Chemical formula | C23H28Br4O6 |
Mr | 720.09 |
Crystal system, space group | Orthorhombic, Pbcn |
Temperature (K) | 173 |
a, b, c (Å) | 22.737 (7), 7.280 (2), 15.280 (4) |
V (Å3) | 2529.2 (13) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 6.40 |
Crystal size (mm) | 0.34 × 0.25 × 0.21 |
Data collection | |
Diffractometer | Bruker SMART CCD area-detector diffractometer |
Absorption correction | Integration (XPREP; Bruker, 1999) |
Tmin, Tmax | 0.220, 0.347 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 13104, 3056, 2374 |
Rint | 0.052 |
(sin θ/λ)max (Å−1) | 0.661 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.028, 0.073, 0.98 |
No. of reflections | 3056 |
No. of parameters | 153 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 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).
D—H···A | D—H | H···A | D···A | D—H···A |
C10—H10C···O2i | 0.98 | 2.37 | 3.281 (3) | 155 |
C11—H11B···O1ii | 0.99 | 2.49 | 3.287 (3) | 138 |
C8—H8B···Br2iii | 0.98 | 3.04 | 3.874 (3) | 143 |
C8—H8C···Br2iv | 0.98 | 3.06 | 3.860 (3) | 140 |
Symmetry codes: (i) −x+1/2, y−1/2, z; (ii) x, −y, z+1/2; (iii) x, −y, z−1/2; (iv) x, y−1, z. |
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).