Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270105043052/sf1028sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270105043052/sf1028IIsup2.hkl |
CCDC reference: 299642
3,4-Dihydroxybenzaldehyde, di-tert-butyldichlorosilane, 1-hydroxybenzotriazole were obtained from Sigma (Sintra, Portugal). All other reagents and solvents were pro analysis grade, purchased from Merck (Lisbon, Portugal). 3,4-Dihydroxybenzaldehyde (0.5 g, 3.62 mmol) was dissolved in a mixture of acetonitrile (3 ml) and triethylamine (1 ml). The aldehyde was then added to a reaction flask flushed with nitrogen containing di-tert-butyldichlorosilane (2 ml, 9.38 mmol) and 1-hydroxybenzotriazole (50 mg, 0.37 mmol) in solution in acetonitrile (3 ml) at 333 K. The reaction mixture was stirred for 2 h at 333 K. Diethyl ether (15 ml) was then added, and the organic phase was washed with HCl (2M, 3 × 10 ml), water (3 × 10 ml) and brine (3 × 10 ml). The organic phase was dried on Na2SO4 and evaporated. The crude product was purified by column chromatography (petroleum ether/diethyl ether, 2:1) to give 630 mg (yield 57%) of (II). M.p. 366–368 K. 1H NMR (CDCl3, 300 MHz): δ 9.83 (s, 1H), 7.44 (d, 1H, J = 2.02 Hz), 7.41 (dd, 1H, J = 2.12 and 8.13 Hz), 7.01 (d, 1H, J = 8.13 Hz), 1.10 (s, 36H). 13C NMR (CDCl3, 75 MHz): δ 190.93 (CHO), 146.51, 151.88 (COSi), 131.34 (CCHO), 121.90, 122.03, 125.22(C6H3), 27.92 [C(CH3)3], 21.41 [C(CH3)3]. MS (m/z): 436 (molecular peak), 379, 337, 295, 253 (base peak), 223.
All H atoms were refined as riding on their parent [C—H = 0.93 and 0.96 Å, and Uiso(H) = 1.2Ueq(C) and 1.5Ueq(Cmethyl)]. The disordered carbaldehyde group was refined using two parts constrained to add to 100% occupancy.
Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software; data reduction: HELENA (Spek,1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson,1976); software used to prepare material for publication: SHELXL97.
C23H40O4Si2 | Z = 2 |
Mr = 436.73 | F(000) = 476 |
Triclinic, P1 | Dx = 1.110 Mg m−3 |
Hall symbol: -P 1 | Cu Kα radiation, λ = 1.54178 Å |
a = 8.8451 (5) Å | Cell parameters from 25 reflections |
b = 9.751 (3) Å | θ = 8.3–23.8° |
c = 16.1106 (10) Å | µ = 1.42 mm−1 |
α = 98.127 (8)° | T = 291 K |
β = 90.392 (5)° | Prism, colourless |
γ = 107.899 (10)° | 0.32 × 0.22 × 0.12 mm |
V = 1307.2 (4) Å3 |
Enraf–Nonius MACH3 diffractometer | 3922 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.020 |
Graphite monochromator | θmax = 72.3°, θmin = 4.8° |
ω–2θ scans | h = −10→10 |
Absorption correction: ψ scan (North et al., 1968) | k = −12→11 |
Tmin = 0.773, Tmax = 0.845 | l = 0→19 |
5292 measured reflections | 3 standard reflections every 180 min |
5079 independent reflections | intensity decay: 0.1% |
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)] = 0.048 | H-atom parameters constrained |
wR(F2) = 0.148 | w = 1/[σ2(Fo2) + (0.0607P)2 + 0.8484P] where P = (Fo2 + 2Fc2)/3 |
S = 1.06 | (Δ/σ)max < 0.001 |
5079 reflections | Δρmax = 0.37 e Å−3 |
285 parameters | Δρmin = −0.30 e Å−3 |
0 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0027 (4) |
C23H40O4Si2 | γ = 107.899 (10)° |
Mr = 436.73 | V = 1307.2 (4) Å3 |
Triclinic, P1 | Z = 2 |
a = 8.8451 (5) Å | Cu Kα radiation |
b = 9.751 (3) Å | µ = 1.42 mm−1 |
c = 16.1106 (10) Å | T = 291 K |
α = 98.127 (8)° | 0.32 × 0.22 × 0.12 mm |
β = 90.392 (5)° |
Enraf–Nonius MACH3 diffractometer | 3922 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.020 |
Tmin = 0.773, Tmax = 0.845 | 3 standard reflections every 180 min |
5292 measured reflections | intensity decay: 0.1% |
5079 independent reflections |
R[F2 > 2σ(F2)] = 0.048 | 0 restraints |
wR(F2) = 0.148 | H-atom parameters constrained |
S = 1.06 | Δρmax = 0.37 e Å−3 |
5079 reflections | Δρmin = −0.30 e Å−3 |
285 parameters |
Experimental. 1H and 13 C NMR data were acquired, at room temperature, on a Bruker AMX 300 spectrometer. Electron impact mass spectra (EI—MS) were carried out on a VG AutoSpec instrument. Melting points were obtained on a Kofler microscope (Reichert Thermovar) and are uncorrected. |
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) | |
O1 | 0.5752 (2) | 0.68327 (18) | 0.34745 (11) | 0.0579 (5) | |
Si2 | 0.58456 (8) | 0.53872 (7) | 0.28322 (4) | 0.0492 (2) | |
O3 | 0.6485 (2) | 0.59544 (17) | 0.19479 (10) | 0.0518 (4) | |
Si4 | 0.74686 (8) | 0.75653 (7) | 0.17215 (4) | 0.0492 (2) | |
O5 | 0.8361 (2) | 0.85593 (19) | 0.26083 (11) | 0.0609 (5) | |
C6 | 0.7990 (3) | 0.9014 (3) | 0.33946 (16) | 0.0511 (6) | |
C7 | 0.6762 (3) | 0.8160 (3) | 0.38232 (16) | 0.0510 (6) | |
C8 | 0.6518 (3) | 0.8696 (3) | 0.46349 (16) | 0.0591 (6) | |
H8 | 0.5708 | 0.8134 | 0.4923 | 0.071* | |
C9 | 0.7459 (4) | 1.0056 (3) | 0.50292 (18) | 0.0664 (7) | |
C10 | 0.8661 (4) | 1.0883 (3) | 0.4603 (2) | 0.0713 (8) | |
H10 | 0.9293 | 1.1797 | 0.4861 | 0.086* | |
C11 | 0.8931 (3) | 1.0361 (3) | 0.37957 (18) | 0.0635 (7) | |
H11 | 0.9758 | 1.0921 | 0.3516 | 0.076* | |
C12 | 0.3709 (3) | 0.4178 (3) | 0.26588 (18) | 0.0618 (7) | |
C13 | 0.3588 (5) | 0.2720 (4) | 0.2126 (3) | 0.1153 (16) | |
H13A | 0.2490 | 0.2186 | 0.1980 | 0.173* | |
H13B | 0.4050 | 0.2168 | 0.2440 | 0.173* | |
H13C | 0.4149 | 0.2890 | 0.1624 | 0.173* | |
C14 | 0.2896 (4) | 0.3914 (5) | 0.3490 (3) | 0.1036 (13) | |
H14A | 0.1774 | 0.3447 | 0.3376 | 0.155* | |
H14B | 0.3070 | 0.4831 | 0.3847 | 0.155* | |
H14C | 0.3337 | 0.3302 | 0.3765 | 0.155* | |
C15 | 0.2743 (4) | 0.4932 (4) | 0.2200 (3) | 0.0926 (12) | |
H15A | 0.3177 | 0.5102 | 0.1666 | 0.139* | |
H15B | 0.2791 | 0.5846 | 0.2531 | 0.139* | |
H15C | 0.1656 | 0.4321 | 0.2116 | 0.139* | |
C16 | 0.7281 (4) | 0.4590 (3) | 0.33137 (19) | 0.0649 (7) | |
C17 | 0.8844 (4) | 0.5788 (4) | 0.3606 (2) | 0.0854 (10) | |
H17A | 0.8649 | 0.6480 | 0.4043 | 0.128* | |
H17B | 0.9278 | 0.6272 | 0.3142 | 0.128* | |
H17C | 0.9587 | 0.5363 | 0.3816 | 0.128* | |
C18 | 0.7669 (5) | 0.3421 (4) | 0.2678 (3) | 0.0936 (11) | |
H18A | 0.8049 | 0.3826 | 0.2181 | 0.140* | |
H18B | 0.6726 | 0.2603 | 0.2534 | 0.140* | |
H18C | 0.8474 | 0.3106 | 0.2923 | 0.140* | |
C19 | 0.6587 (5) | 0.3878 (5) | 0.4078 (3) | 0.1084 (14) | |
H19A | 0.7380 | 0.3583 | 0.4349 | 0.163* | |
H19B | 0.5682 | 0.3039 | 0.3896 | 0.163* | |
H19C | 0.6266 | 0.4566 | 0.4465 | 0.163* | |
C20 | 0.6074 (4) | 0.8472 (3) | 0.12998 (19) | 0.0640 (7) | |
C21 | 0.5049 (4) | 0.8861 (4) | 0.2008 (2) | 0.0761 (9) | |
H21A | 0.4290 | 0.9256 | 0.1787 | 0.114* | |
H21B | 0.5721 | 0.9571 | 0.2440 | 0.114* | |
H21C | 0.4498 | 0.8000 | 0.2240 | 0.114* | |
C22 | 0.7006 (5) | 0.9915 (4) | 0.0998 (3) | 0.1006 (13) | |
H22A | 0.6284 | 1.0432 | 0.0880 | 0.151* | |
H22B | 0.7530 | 0.9708 | 0.0497 | 0.151* | |
H22C | 0.7785 | 1.0503 | 0.1428 | 0.151* | |
C23 | 0.4961 (5) | 0.7465 (5) | 0.0576 (2) | 0.0954 (11) | |
H23A | 0.4413 | 0.6551 | 0.0755 | 0.143* | |
H23B | 0.5575 | 0.7300 | 0.0105 | 0.143* | |
H23C | 0.4201 | 0.7914 | 0.0416 | 0.143* | |
C24 | 0.9178 (4) | 0.7444 (3) | 0.10486 (18) | 0.0649 (7) | |
C25 | 1.0450 (5) | 0.8934 (5) | 0.1079 (3) | 0.1112 (15) | |
H25A | 1.0810 | 0.9331 | 0.1651 | 0.167* | |
H25B | 1.0004 | 0.9582 | 0.0841 | 0.167* | |
H25C | 1.1332 | 0.8820 | 0.0763 | 0.167* | |
C26 | 0.8623 (6) | 0.6850 (6) | 0.0136 (3) | 0.1323 (19) | |
H26A | 0.9523 | 0.6816 | −0.0187 | 0.198* | |
H26B | 0.8113 | 0.7472 | −0.0081 | 0.198* | |
H26C | 0.7884 | 0.5885 | 0.0100 | 0.198* | |
C27 | 1.0036 (5) | 0.6483 (5) | 0.1384 (3) | 0.1155 (16) | |
H27A | 0.9316 | 0.5512 | 0.1358 | 0.173* | |
H27B | 1.0409 | 0.6871 | 0.1956 | 0.173* | |
H27C | 1.0925 | 0.6461 | 0.1049 | 0.173* | |
C28 | 0.7166 (6) | 1.0566 (5) | 0.5905 (2) | 0.0990 (12) | |
H28A | 0.7631 | 1.1554 | 0.6101 | 0.119* | 0.558 (8) |
H28B | 0.6472 | 0.9867 | 0.6177 | 0.119* | 0.442 (8) |
O28A | 0.6445 (8) | 0.9893 (6) | 0.6357 (3) | 0.119 (2) | 0.558 (8) |
O28B | 0.7684 (9) | 1.1729 (8) | 0.6307 (5) | 0.138 (4) | 0.442 (8) |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0594 (10) | 0.0457 (9) | 0.0567 (10) | 0.0011 (8) | 0.0092 (8) | 0.0025 (8) |
Si2 | 0.0508 (4) | 0.0406 (4) | 0.0505 (4) | 0.0045 (3) | 0.0006 (3) | 0.0097 (3) |
O3 | 0.0578 (10) | 0.0445 (9) | 0.0485 (9) | 0.0084 (7) | 0.0024 (7) | 0.0088 (7) |
Si4 | 0.0527 (4) | 0.0462 (4) | 0.0471 (4) | 0.0110 (3) | 0.0069 (3) | 0.0117 (3) |
O5 | 0.0603 (10) | 0.0562 (10) | 0.0530 (10) | −0.0009 (8) | 0.0081 (8) | 0.0072 (8) |
C6 | 0.0549 (14) | 0.0445 (13) | 0.0501 (13) | 0.0096 (11) | −0.0002 (11) | 0.0084 (10) |
C7 | 0.0539 (14) | 0.0431 (12) | 0.0520 (13) | 0.0082 (10) | 0.0023 (11) | 0.0091 (10) |
C8 | 0.0706 (17) | 0.0535 (15) | 0.0508 (14) | 0.0152 (12) | 0.0078 (12) | 0.0085 (11) |
C9 | 0.0808 (19) | 0.0577 (16) | 0.0557 (16) | 0.0189 (14) | −0.0030 (14) | −0.0009 (13) |
C10 | 0.082 (2) | 0.0500 (15) | 0.0683 (18) | 0.0079 (14) | −0.0121 (15) | −0.0060 (13) |
C11 | 0.0639 (16) | 0.0498 (15) | 0.0656 (17) | 0.0012 (12) | −0.0031 (13) | 0.0101 (12) |
C12 | 0.0588 (15) | 0.0498 (14) | 0.0673 (17) | 0.0014 (12) | −0.0038 (13) | 0.0126 (12) |
C13 | 0.096 (3) | 0.064 (2) | 0.158 (4) | 0.0017 (19) | −0.030 (3) | −0.025 (2) |
C14 | 0.071 (2) | 0.121 (3) | 0.099 (3) | −0.009 (2) | 0.0085 (19) | 0.041 (2) |
C15 | 0.0565 (18) | 0.092 (2) | 0.121 (3) | 0.0024 (16) | −0.0161 (18) | 0.037 (2) |
C16 | 0.0654 (17) | 0.0590 (16) | 0.0714 (18) | 0.0156 (13) | −0.0003 (14) | 0.0221 (14) |
C17 | 0.0674 (19) | 0.082 (2) | 0.105 (3) | 0.0183 (16) | −0.0204 (18) | 0.0181 (19) |
C18 | 0.093 (2) | 0.071 (2) | 0.125 (3) | 0.0357 (19) | 0.002 (2) | 0.017 (2) |
C19 | 0.105 (3) | 0.134 (4) | 0.104 (3) | 0.041 (3) | 0.011 (2) | 0.070 (3) |
C20 | 0.0695 (17) | 0.0650 (17) | 0.0653 (17) | 0.0258 (14) | 0.0110 (14) | 0.0238 (14) |
C21 | 0.075 (2) | 0.080 (2) | 0.087 (2) | 0.0369 (17) | 0.0171 (17) | 0.0295 (17) |
C22 | 0.117 (3) | 0.089 (3) | 0.123 (3) | 0.050 (2) | 0.040 (3) | 0.063 (2) |
C23 | 0.091 (3) | 0.128 (3) | 0.074 (2) | 0.043 (2) | −0.0112 (19) | 0.020 (2) |
C24 | 0.0673 (17) | 0.0684 (18) | 0.0606 (16) | 0.0210 (14) | 0.0154 (13) | 0.0146 (14) |
C25 | 0.082 (2) | 0.106 (3) | 0.143 (4) | 0.014 (2) | 0.050 (3) | 0.040 (3) |
C26 | 0.114 (3) | 0.206 (6) | 0.074 (3) | 0.064 (4) | 0.018 (2) | −0.020 (3) |
C27 | 0.105 (3) | 0.142 (4) | 0.143 (4) | 0.077 (3) | 0.061 (3) | 0.072 (3) |
C28 | 0.138 (4) | 0.080 (3) | 0.066 (2) | 0.026 (2) | 0.002 (2) | −0.010 (2) |
O28A | 0.164 (5) | 0.113 (4) | 0.070 (3) | 0.033 (4) | 0.047 (3) | 0.004 (3) |
O28B | 0.129 (6) | 0.125 (6) | 0.105 (5) | −0.009 (4) | 0.014 (4) | −0.052 (4) |
O1—C7 | 1.366 (3) | C17—H17B | 0.9600 |
O1—Si2 | 1.6508 (19) | C17—H17C | 0.9600 |
Si2—O3 | 1.6422 (17) | C18—H18A | 0.9600 |
Si2—C12 | 1.890 (3) | C18—H18B | 0.9600 |
Si2—C16 | 1.893 (3) | C18—H18C | 0.9600 |
O3—Si4 | 1.6383 (17) | C19—H19A | 0.9600 |
Si4—O5 | 1.6513 (19) | C19—H19B | 0.9600 |
Si4—C24 | 1.890 (3) | C19—H19C | 0.9600 |
Si4—C20 | 1.896 (3) | C20—C23 | 1.536 (5) |
O5—C6 | 1.359 (3) | C20—C21 | 1.540 (4) |
C6—C11 | 1.384 (3) | C20—C22 | 1.544 (4) |
C6—C7 | 1.402 (3) | C21—H21A | 0.9600 |
C7—C8 | 1.381 (4) | C21—H21B | 0.9600 |
C8—C9 | 1.390 (4) | C21—H21C | 0.9600 |
C8—H8 | 0.9300 | C22—H22A | 0.9600 |
C9—C10 | 1.375 (4) | C22—H22B | 0.9600 |
C9—C28 | 1.481 (5) | C22—H22C | 0.9600 |
C10—C11 | 1.379 (4) | C23—H23A | 0.9600 |
C10—H10 | 0.9300 | C23—H23B | 0.9600 |
C11—H11 | 0.9300 | C23—H23C | 0.9600 |
C12—C13 | 1.526 (4) | C24—C26 | 1.521 (5) |
C12—C15 | 1.532 (4) | C24—C27 | 1.523 (5) |
C12—C14 | 1.541 (5) | C24—C25 | 1.534 (5) |
C13—H13A | 0.9600 | C25—H25A | 0.9600 |
C13—H13B | 0.9600 | C25—H25B | 0.9600 |
C13—H13C | 0.9600 | C25—H25C | 0.9600 |
C14—H14A | 0.9600 | C26—H26A | 0.9600 |
C14—H14B | 0.9600 | C26—H26B | 0.9600 |
C14—H14C | 0.9600 | C26—H26C | 0.9600 |
C15—H15A | 0.9600 | C27—H27A | 0.9600 |
C15—H15B | 0.9600 | C27—H27B | 0.9600 |
C15—H15C | 0.9600 | C27—H27C | 0.9600 |
C16—C17 | 1.530 (4) | C28—O28A | 1.118 (6) |
C16—C19 | 1.537 (4) | C28—O28B | 1.176 (7) |
C16—C18 | 1.543 (5) | C28—H28A | 0.9300 |
C17—H17A | 0.9600 | C28—H28B | 0.9300 |
C7—O1—Si2 | 137.83 (17) | C16—C18—H18B | 109.5 |
O3—Si2—O1 | 106.59 (9) | H18A—C18—H18B | 109.5 |
O3—Si2—C12 | 109.37 (11) | C16—C18—H18C | 109.5 |
O1—Si2—C12 | 104.18 (12) | H18A—C18—H18C | 109.5 |
O3—Si2—C16 | 110.85 (12) | H18B—C18—H18C | 109.5 |
O1—Si2—C16 | 109.01 (12) | C16—C19—H19A | 109.5 |
C12—Si2—C16 | 116.22 (13) | C16—C19—H19B | 109.5 |
Si4—O3—Si2 | 132.40 (11) | H19A—C19—H19B | 109.5 |
O3—Si4—O5 | 106.64 (9) | C16—C19—H19C | 109.5 |
O3—Si4—C24 | 110.27 (12) | H19A—C19—H19C | 109.5 |
O5—Si4—C24 | 103.48 (12) | H19B—C19—H19C | 109.5 |
O3—Si4—C20 | 111.13 (11) | C23—C20—C21 | 108.5 (3) |
O5—Si4—C20 | 108.72 (12) | C23—C20—C22 | 109.3 (3) |
C24—Si4—C20 | 115.93 (13) | C21—C20—C22 | 106.7 (3) |
C6—O5—Si4 | 139.40 (17) | C23—C20—Si4 | 111.6 (2) |
O5—C6—C11 | 117.4 (2) | C21—C20—Si4 | 109.4 (2) |
O5—C6—C7 | 123.2 (2) | C22—C20—Si4 | 111.3 (2) |
C11—C6—C7 | 119.3 (2) | C20—C21—H21A | 109.5 |
O1—C7—C8 | 117.5 (2) | C20—C21—H21B | 109.5 |
O1—C7—C6 | 123.6 (2) | H21A—C21—H21B | 109.5 |
C8—C7—C6 | 118.9 (2) | C20—C21—H21C | 109.5 |
C7—C8—C9 | 121.4 (3) | H21A—C21—H21C | 109.5 |
C7—C8—H8 | 119.3 | H21B—C21—H21C | 109.5 |
C9—C8—H8 | 119.3 | C20—C22—H22A | 109.5 |
C10—C9—C8 | 119.3 (3) | C20—C22—H22B | 109.5 |
C10—C9—C28 | 121.6 (3) | H22A—C22—H22B | 109.5 |
C8—C9—C28 | 119.2 (3) | C20—C22—H22C | 109.5 |
C9—C10—C11 | 120.2 (3) | H22A—C22—H22C | 109.5 |
C9—C10—H10 | 119.9 | H22B—C22—H22C | 109.5 |
C11—C10—H10 | 119.9 | C20—C23—H23A | 109.5 |
C10—C11—C6 | 121.0 (3) | C20—C23—H23B | 109.5 |
C10—C11—H11 | 119.5 | H23A—C23—H23B | 109.5 |
C6—C11—H11 | 119.5 | C20—C23—H23C | 109.5 |
C13—C12—C15 | 108.3 (3) | H23A—C23—H23C | 109.5 |
C13—C12—C14 | 109.8 (3) | H23B—C23—H23C | 109.5 |
C15—C12—C14 | 105.5 (3) | C26—C24—C27 | 109.4 (3) |
C13—C12—Si2 | 111.2 (2) | C26—C24—C25 | 108.2 (3) |
C15—C12—Si2 | 109.49 (19) | C27—C24—C25 | 105.0 (3) |
C14—C12—Si2 | 112.3 (2) | C26—C24—Si4 | 111.8 (2) |
C12—C13—H13A | 109.5 | C27—C24—Si4 | 110.3 (2) |
C12—C13—H13B | 109.5 | C25—C24—Si4 | 111.8 (2) |
H13A—C13—H13B | 109.5 | C24—C25—H25A | 109.5 |
C12—C13—H13C | 109.5 | C24—C25—H25B | 109.5 |
H13A—C13—H13C | 109.5 | H25A—C25—H25B | 109.5 |
H13B—C13—H13C | 109.5 | C24—C25—H25C | 109.5 |
C12—C14—H14A | 109.5 | H25A—C25—H25C | 109.5 |
C12—C14—H14B | 109.5 | H25B—C25—H25C | 109.5 |
H14A—C14—H14B | 109.5 | C24—C26—H26A | 109.5 |
C12—C14—H14C | 109.5 | C24—C26—H26B | 109.5 |
H14A—C14—H14C | 109.5 | H26A—C26—H26B | 109.5 |
H14B—C14—H14C | 109.5 | C24—C26—H26C | 109.5 |
C12—C15—H15A | 109.5 | H26A—C26—H26C | 109.5 |
C12—C15—H15B | 109.5 | H26B—C26—H26C | 109.5 |
H15A—C15—H15B | 109.5 | C24—C27—H27A | 109.5 |
C12—C15—H15C | 109.5 | C24—C27—H27B | 109.5 |
H15A—C15—H15C | 109.5 | H27A—C27—H27B | 109.5 |
H15B—C15—H15C | 109.5 | C24—C27—H27C | 109.5 |
C17—C16—C19 | 108.1 (3) | H27A—C27—H27C | 109.5 |
C17—C16—C18 | 107.9 (3) | H27B—C27—H27C | 109.5 |
C19—C16—C18 | 108.0 (3) | O28A—C28—O28B | 103.5 (6) |
C17—C16—Si2 | 110.2 (2) | O28A—C28—C9 | 127.1 (5) |
C19—C16—Si2 | 111.0 (2) | O28B—C28—C9 | 129.3 (6) |
C18—C16—Si2 | 111.6 (2) | O28A—C28—H28A | 116.5 |
C16—C17—H17A | 109.5 | O28B—C28—H28A | 13.4 |
C16—C17—H17B | 109.5 | C9—C28—H28A | 116.5 |
H17A—C17—H17B | 109.5 | O28A—C28—H28B | 12.4 |
C16—C17—H17C | 109.5 | O28B—C28—H28B | 115.3 |
H17A—C17—H17C | 109.5 | C9—C28—H28B | 115.3 |
H17B—C17—H17C | 109.5 | H28A—C28—H28B | 128.0 |
C16—C18—H18A | 109.5 | ||
C7—O1—Si2—O3 | −59.1 (3) | O3—Si2—C12—C14 | −165.7 (2) |
C7—O1—Si2—C12 | −174.7 (2) | O1—Si2—C12—C14 | −52.1 (3) |
C7—O1—Si2—C16 | 60.6 (3) | C16—Si2—C12—C14 | 67.9 (3) |
O1—Si2—O3—Si4 | 21.15 (18) | O3—Si2—C16—C17 | 67.7 (3) |
C12—Si2—O3—Si4 | 133.22 (16) | O1—Si2—C16—C17 | −49.4 (3) |
C16—Si2—O3—Si4 | −97.36 (17) | C12—Si2—C16—C17 | −166.7 (2) |
Si2—O3—Si4—O5 | 20.80 (18) | O3—Si2—C16—C19 | −172.6 (2) |
Si2—O3—Si4—C24 | 132.50 (17) | O1—Si2—C16—C19 | 70.4 (3) |
Si2—O3—Si4—C20 | −97.53 (18) | C12—Si2—C16—C19 | −46.9 (3) |
O3—Si4—O5—C6 | −56.7 (3) | O3—Si2—C16—C18 | −52.1 (2) |
C24—Si4—O5—C6 | −173.0 (3) | O1—Si2—C16—C18 | −169.1 (2) |
C20—Si4—O5—C6 | 63.2 (3) | C12—Si2—C16—C18 | 73.6 (3) |
Si4—O5—C6—C11 | −148.3 (2) | O3—Si4—C20—C23 | −51.6 (2) |
Si4—O5—C6—C7 | 34.8 (4) | O5—Si4—C20—C23 | −168.6 (2) |
Si2—O1—C7—C8 | −143.9 (2) | C24—Si4—C20—C23 | 75.4 (3) |
Si2—O1—C7—C6 | 37.9 (4) | O3—Si4—C20—C21 | 68.4 (2) |
O5—C6—C7—O1 | −4.5 (4) | O5—Si4—C20—C21 | −48.7 (2) |
C11—C6—C7—O1 | 178.6 (2) | C24—Si4—C20—C21 | −164.7 (2) |
O5—C6—C7—C8 | 177.3 (2) | O3—Si4—C20—C22 | −174.0 (2) |
C11—C6—C7—C8 | 0.5 (4) | O5—Si4—C20—C22 | 69.0 (3) |
O1—C7—C8—C9 | −178.0 (3) | C24—Si4—C20—C22 | −47.0 (3) |
C6—C7—C8—C9 | 0.2 (4) | O3—Si4—C24—C26 | 78.6 (3) |
C7—C8—C9—C10 | −0.3 (5) | O5—Si4—C24—C26 | −167.6 (3) |
C7—C8—C9—C28 | −178.9 (3) | C20—Si4—C24—C26 | −48.7 (3) |
C8—C9—C10—C11 | −0.3 (5) | O3—Si4—C24—C27 | −43.4 (3) |
C28—C9—C10—C11 | 178.3 (3) | O5—Si4—C24—C27 | 70.3 (3) |
C9—C10—C11—C6 | 1.0 (5) | C20—Si4—C24—C27 | −170.8 (3) |
O5—C6—C11—C10 | −178.2 (3) | O3—Si4—C24—C25 | −159.8 (3) |
C7—C6—C11—C10 | −1.1 (4) | O5—Si4—C24—C25 | −46.1 (3) |
O3—Si2—C12—C13 | 70.8 (3) | C20—Si4—C24—C25 | 72.8 (3) |
O1—Si2—C12—C13 | −175.5 (3) | C10—C9—C28—O28A | −163.7 (6) |
C16—Si2—C12—C13 | −55.6 (3) | C8—C9—C28—O28A | 14.9 (8) |
O3—Si2—C12—C15 | −48.8 (3) | C10—C9—C28—O28B | 11.8 (9) |
O1—Si2—C12—C15 | 64.8 (3) | C8—C9—C28—O28B | −169.6 (7) |
C16—Si2—C12—C15 | −175.2 (2) |
Experimental details
Crystal data | |
Chemical formula | C23H40O4Si2 |
Mr | 436.73 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 291 |
a, b, c (Å) | 8.8451 (5), 9.751 (3), 16.1106 (10) |
α, β, γ (°) | 98.127 (8), 90.392 (5), 107.899 (10) |
V (Å3) | 1307.2 (4) |
Z | 2 |
Radiation type | Cu Kα |
µ (mm−1) | 1.42 |
Crystal size (mm) | 0.32 × 0.22 × 0.12 |
Data collection | |
Diffractometer | Enraf–Nonius MACH3 diffractometer |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.773, 0.845 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5292, 5079, 3922 |
Rint | 0.020 |
(sin θ/λ)max (Å−1) | 0.618 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.048, 0.148, 1.06 |
No. of reflections | 5079 |
No. of parameters | 285 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.37, −0.30 |
Computer programs: CAD-4 Software (Enraf–Nonius, 1989), CAD-4 Software, HELENA (Spek,1997), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEPII (Johnson,1976), SHELXL97.
Calculated | Observed | |
C6—C7 | 1.403 | 1.402 (3) |
Si2—-O1 | 1.669 | 1.6508 (19) |
Si2–O3 | 1.661 | 1.6422 (17) |
Si4—O3 | 1.657 | 1.6383 (17) |
Si4—O5 | 1.674 | 1.6513 (19) |
Si2—O3—Si4 | 131.96 | 132.40 (11) |
Si2—O1—C7 | 138.93 | 137.83 (17) |
Si4—O5—C6 | 139.70 | 139.40 (17) |
C7—O1—Si2—O3 | -62.83 | -59.1 (3) |
O1—Si2—O3—Si4 | 20.94 | 21.13 (18) |
Si2—O3—Si4—O5 | 21.81 | 20.80 (19) |
O3—Si4—O5—C6 | -59.95 | -56.7 (3) |
Si4—O5—C6—C7 | 36.63 | 34.8 (4) |
O1—C7—C6—O5 | -4.21 | -4.5 (4) |
In conjunction with an on-going project towards the synthesis of phenolic antioxidant agents (Silva et al., 2001, Borges et al., 2003) one is faced with the problem of suitable protection/deprotection protocols, which are one of the major challenges in organic synthetic chemistry.
Many of the efforts for a sucessful total synthesis of a phenol-containing product depend not only on the correct strategy but also on the right choice of protecting groups to prevent side reactions. Most of the protective groups developed for alcohol protection are also applicable to the phenol function. In this context, the protection of the hydroxy group by silyl ethers has been recognized as one of the most versatile since its introduction by Corey & Venkateswarlu (1972). Such protection is often selected either because of its ease of introduction or its general stability to basic and mildly acidic conditions (Sharma et al., 2003). In addition a large number of deprotection methods are available for its removal (Crouch, 2004).
Silicon-based protecting groups were also employed for catechol protection, the diethers being obtained by the methods described to protect the hydroxy group. Di-tert-butyldichlorosilane (tBu2SiCl2, DTBS) was one of the reagents used as a convenient protection for diol-like moieties (Trost & Caldwell, 1981; Trost et al., 1983; Evans et al., 1990). Therefore, this reagent was used in a synthetic strategy in which the starting material 3,4-dihydroxybenzaldehyde would be protected by forming a dioxasilole five membered ring (I).
However, results from spectroscopic analysis were not in agreement with this expected O-protected derivative, hence the need for elucidation of the structure through X-ray analysis. This revealed the formation of the title compound, (II), which possesses a trioxadisilepine seven-membered ring. This type of heterocyclic ring has already been obtained using catechol as starting material (Hanson et al., 1986). An ORTEPII (Johnson, 1976) plot of (II) is shown in Fig. 1.
Most bond lengths are within the expected ranges (Allen et al., 1987) with mean Csp3—Csp3, Csp3—Si4, Car—O2 and Car—Car (not including C6—C7) distances of 1.533 (9), 1.892 (4), 1.363 (5) and 1.382 (5) Å, respectively. Being part of the heptane ring, the C6—C7 bond length [1.402 (3) Å] is significantly larger than the average Car—Car distance. Two types of Si—O bonds can be distinguished in the heptane ring, viz. two Si—O(—C) bonds, with a common length of 1.651 (2) Å, and two Si—O(—Si) bonds, with an average value of 1.640 (3) Å. The structure refinement of (II) shows a disorder in the carbaldehyde group, with interchange of the H and O positions, with refined occupancies of 0.568 (8) and 0.432 (8), respectively. This is probably the reason why very short C═O distances [1.118 (6) and 1.176 (7) Å] are determined in this group for both orientations. Large Si—O—C bond angles, of 137.83 (17) and 139.40 (17)°, confirm the proposal of Cragg & Lane (1984), as being characteristic of oxasilacycloalkanes. These values are above those found for several similar structures (Hanson et al., 1986), including 2,4-disila-2,2,4,4-tetraphenyl-1,3,5-trioxa-6,7-benzocycloheptane, with an identical heptane ring. On the other hand, the Si—O—Si bond angle of 132.40 (17)° found for (II) is slightly smaller than the reported value of 134.9°. The three O atoms of the heptane ring are coplanar with the phenyl group, the least-squares plane having a maximum deviation of 0.03 Å. Atoms Si2 and Si4 are symmetrically displaced above [0.5799 (19) Å for Si2] and below [0.5307 (18) Å for Si4:] this plane. Apart from the carbaldehyde group, an approximate non-crystallographic binary axis exists running from O3 towards the middle of the C6—C7 bond.
Owing to the absence of any strong donor group, cohesion of these crystal structures is mainly achieved by weak van der Waals interactions. No close-contacts with suitable geometry to classify as weak hydrogen-bond interactions were found.
We have also performed a quantum chemistry calculation of the optimized geometry of the isolated molecule to check whether such calculation could accurately reproduce the conformation of the trioxadisilepine ring. The ab initio calculations were performed with the computer program GAMESS (Schmidt et al., 1993), using the Roothaan Hartree–Fock molecular orbital (MO) method. An extended 6–31 G(d,p) basis set was used with tight conditions for convergence of both the self-consistent field (SCF) cycles and maximum energy and density gradients at the final optimized geometry (10−5 atomic units). The code was executed in parallel on a cluster of 12 Pentium IV workstations running Linux.
The calculated equilibrium geometry of the molecule is well reproduced by the quantum mechanical calculations, with overall good agreement between the observed and calculated valence and torsion angles (Table 1). However, we have found that the calculation tends to slightly overestimate the Si—O bond lengths.