Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100013123/fr1298sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270100013123/fr1298Isup2.hkl |
CCDC reference: 156167
A mixture of tetramethyl 1,4-cyclohexadiene-1,2,4,5-tetracarboxylate, (II) (0.817 g, 2.6 mmol), and 10% palladium (42 mg) on carbon in methanol (60 ml) was shaken at room temperature for 18 h in a bottle attached to a hydrogenator maintaining a pressure of 80 p.s.i. of hydrogen. The resulting mixture was diluted with ethyl acetate (150 ml), filtered through Celite, and the solids were carefully washed with ethyl acetate. The combined filtrates were concentrated and column-chromatographed on silica gel, using a gradient mixture of hexane and diethyl ether as eluent, to give 0.752 g (91% yield) of compound (I). Recrystallization from diethyl ether provided long colorless needles, m.p. 388–391 K, used for the X-ray study.
The rotational orientations of the methyl groups were refined by the circular Fourier method available in SHELXL97 (Sheldrick, 1997). C—H riding distances for methyl, methylene and methine groups were fixed at 0.96, 0.97 and 0.98 Å, respectively. Uiso values for H atoms were calculated as B x Uiso of their associated C atoms where B = 1.5 for methyl H atoms and B = 1.2 for methylene and methine H atoms. All H atoms are riding.
Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1996); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: PROCESS in TEXSAN (Molecular Structure Corporation, 1997); program(s) used to solve structure: SIR92 (Burla et al., 1989); program(s) used to refine structure: LS in TEXSAN and SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP in TEXSAN (Johnson, 1965); software used to prepare material for publication: TEXSAN, SHELXL97, and PLATON (Spek, 2000).
Fig. 1. The molecular structure and atom numbering scheme for (I) with displacement ellipsoids at the 30% probability level. |
C14H20O8 | Dx = 1.341 Mg m−3 |
Mr = 316.3 | Melting point = 388–391 K |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71069 Å |
a = 18.6901 (19) Å | Cell parameters from 25 reflections |
b = 10.031 (2) Å | θ = 7.7–11.9° |
c = 17.781 (2) Å | µ = 0.11 mm−1 |
β = 109.910 (8)° | T = 296 K |
V = 3134.3 (9) Å3 | Plate, colorless |
Z = 8 | 0.49 × 0.30 × 0.05 mm |
F(000) = 1344 |
Rigaku AFC-5S diffractometer | Rint = 0.027 |
Radiation source: X-ray tube | θmax = 25.0°, θmin = 2.3° |
Graphite monochromator | h = −22→20 |
ω (rate 2° min–1 in ω) scans | k = 0→11 |
2864 measured reflections | l = 0→21 |
2766 independent reflections | 3 standard reflections every 100 reflections |
1039 reflections with I > 2σ(I) | intensity decay: −0.1% |
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)] = 0.040 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.128 | H-atom parameters constrained |
S = 0.96 | w = 1/[σ2(Fo2) + (0.0431P)2] where P = (Fo2 + 2Fc2)/3 |
2766 reflections | (Δ/σ)max < 0.001 |
203 parameters | Δρmax = 0.17 e Å−3 |
0 restraints | Δρmin = −0.15 e Å−3 |
C14H20O8 | V = 3134.3 (9) Å3 |
Mr = 316.3 | Z = 8 |
Monoclinic, C2/c | Mo Kα radiation |
a = 18.6901 (19) Å | µ = 0.11 mm−1 |
b = 10.031 (2) Å | T = 296 K |
c = 17.781 (2) Å | 0.49 × 0.30 × 0.05 mm |
β = 109.910 (8)° |
Rigaku AFC-5S diffractometer | Rint = 0.027 |
2864 measured reflections | 3 standard reflections every 100 reflections |
2766 independent reflections | intensity decay: −0.1% |
1039 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.040 | 0 restraints |
wR(F2) = 0.128 | H-atom parameters constrained |
S = 0.96 | Δρmax = 0.17 e Å−3 |
2766 reflections | Δρmin = −0.15 e Å−3 |
203 parameters |
x | y | z | Uiso*/Ueq | ||
O8 | 0.11054 (16) | 0.1136 (4) | 0.56690 (15) | 0.0879 (10) | |
O9 | 0.02716 (15) | 0.2089 (3) | 0.61506 (14) | 0.0625 (8) | |
O12 | 0.09483 (14) | −0.0362 (2) | 0.72745 (14) | 0.0563 (7) | |
O13 | 0.11135 (14) | 0.0156 (2) | 0.85442 (13) | 0.0535 (7) | |
O16 | 0.27583 (15) | −0.0498 (3) | 0.86392 (14) | 0.0602 (7) | |
O17 | 0.29319 (15) | 0.0627 (3) | 0.97697 (13) | 0.0624 (7) | |
O20 | 0.38150 (15) | 0.0664 (3) | 0.73795 (16) | 0.0756 (9) | |
O21 | 0.41924 (14) | 0.1285 (3) | 0.86585 (15) | 0.0627 (7) | |
C1 | 0.15544 (19) | 0.2073 (4) | 0.69913 (18) | 0.0455 (9) | |
C2 | 0.1321 (2) | 0.1879 (3) | 0.77329 (19) | 0.0435 (9) | |
C3 | 0.19406 (19) | 0.2468 (3) | 0.84617 (19) | 0.0471 (9) | |
C4 | 0.2747 (2) | 0.1898 (3) | 0.86159 (19) | 0.0453 (9) | |
C5 | 0.29473 (19) | 0.1919 (3) | 0.78425 (18) | 0.0442 (9) | |
C6 | 0.23125 (19) | 0.1406 (3) | 0.71033 (19) | 0.0475 (9) | |
C7 | 0.0969 (2) | 0.1686 (4) | 0.6203 (2) | 0.0550 (10) | |
C10 | −0.0329 (2) | 0.1848 (5) | 0.5395 (2) | 0.0818 (14) | |
C11 | 0.11153 (19) | 0.0423 (4) | 0.7808 (2) | 0.0422 (9) | |
C14 | 0.0907 (2) | −0.1193 (4) | 0.8671 (2) | 0.0645 (11) | |
C15 | 0.28147 (19) | 0.0543 (4) | 0.8989 (2) | 0.0429 (9) | |
C18 | 0.2939 (3) | −0.0608 (4) | 1.0189 (2) | 0.0824 (14) | |
C19 | 0.3681 (2) | 0.1210 (4) | 0.7916 (2) | 0.0515 (10) | |
C22 | 0.4913 (2) | 0.0636 (4) | 0.8779 (3) | 0.0790 (13) | |
H1 | 0.1639 | 0.3032 | 0.6957 | 0.055* | |
H2 | 0.0859 | 0.2406 | 0.7649 | 0.052* | |
H3a | 0.1801 | 0.2312 | 0.8932 | 0.056* | |
H3b | 0.1956 | 0.3425 | 0.8390 | 0.056* | |
H4 | 0.3109 | 0.2484 | 0.9003 | 0.054* | |
H5 | 0.3024 | 0.2857 | 0.7737 | 0.053* | |
H6a | 0.2452 | 0.1566 | 0.6633 | 0.057* | |
H6b | 0.2260 | 0.0452 | 0.7153 | 0.057* | |
H10a | −0.0193 | 0.2239 | 0.4970 | 0.123* | |
H10b | −0.0793 | 0.2241 | 0.5407 | 0.123* | |
H10c | −0.0398 | 0.0905 | 0.5309 | 0.123* | |
H14a | 0.0392 | −0.1364 | 0.8333 | 0.097* | |
H14b | 0.0948 | −0.1304 | 0.9221 | 0.097* | |
H14c | 0.1242 | −0.1808 | 0.8543 | 0.097* | |
H18a | 0.2425 | −0.0895 | 1.0093 | 0.124* | |
H18b | 0.3191 | −0.0475 | 1.0752 | 0.124* | |
H18c | 0.3204 | −0.1276 | 1.0000 | 0.124* | |
H22a | 0.4832 | −0.0302 | 0.8677 | 0.118* | |
H22b | 0.5243 | 0.0770 | 0.9321 | 0.118* | |
H22c | 0.5144 | 0.1008 | 0.8420 | 0.118* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O8 | 0.0680 (19) | 0.151 (3) | 0.0475 (16) | −0.006 (2) | 0.0231 (15) | −0.0246 (19) |
O9 | 0.0573 (18) | 0.075 (2) | 0.0506 (16) | 0.0103 (15) | 0.0120 (15) | 0.0113 (14) |
O12 | 0.0705 (18) | 0.0548 (17) | 0.0447 (15) | −0.0137 (15) | 0.0211 (14) | −0.0047 (14) |
O13 | 0.0712 (19) | 0.0508 (17) | 0.0473 (15) | −0.0021 (14) | 0.0318 (14) | 0.0031 (12) |
O16 | 0.090 (2) | 0.0388 (15) | 0.0590 (16) | 0.0053 (15) | 0.0349 (15) | −0.0023 (14) |
O17 | 0.089 (2) | 0.0609 (18) | 0.0378 (14) | −0.0041 (16) | 0.0215 (13) | 0.0001 (13) |
O20 | 0.064 (2) | 0.101 (2) | 0.0680 (19) | 0.0008 (17) | 0.0304 (16) | −0.0218 (17) |
O21 | 0.0474 (16) | 0.0756 (19) | 0.0604 (17) | −0.0016 (15) | 0.0122 (14) | −0.0064 (15) |
C1 | 0.054 (3) | 0.043 (2) | 0.040 (2) | −0.0008 (19) | 0.0166 (18) | 0.0047 (18) |
C2 | 0.052 (2) | 0.035 (2) | 0.047 (2) | 0.0084 (19) | 0.0219 (19) | 0.0031 (18) |
C3 | 0.063 (3) | 0.038 (2) | 0.045 (2) | 0.000 (2) | 0.0245 (19) | −0.0044 (18) |
C4 | 0.055 (2) | 0.042 (2) | 0.040 (2) | −0.004 (2) | 0.0176 (18) | −0.0067 (17) |
C5 | 0.054 (2) | 0.035 (2) | 0.044 (2) | −0.0024 (19) | 0.0168 (19) | 0.0002 (17) |
C6 | 0.057 (2) | 0.052 (2) | 0.0396 (19) | −0.001 (2) | 0.0231 (18) | 0.0015 (18) |
C7 | 0.059 (3) | 0.065 (3) | 0.044 (2) | 0.000 (2) | 0.021 (2) | 0.010 (2) |
C10 | 0.066 (3) | 0.121 (4) | 0.050 (2) | −0.001 (3) | 0.009 (2) | 0.022 (3) |
C11 | 0.041 (2) | 0.049 (3) | 0.040 (2) | 0.0053 (19) | 0.0196 (18) | 0.004 (2) |
C14 | 0.077 (3) | 0.057 (3) | 0.063 (2) | −0.006 (2) | 0.028 (2) | 0.016 (2) |
C15 | 0.043 (2) | 0.045 (2) | 0.042 (2) | 0.0002 (19) | 0.0175 (17) | −0.0028 (19) |
C18 | 0.106 (4) | 0.082 (3) | 0.056 (3) | −0.001 (3) | 0.024 (3) | 0.030 (2) |
C19 | 0.055 (3) | 0.046 (2) | 0.058 (3) | −0.013 (2) | 0.026 (2) | −0.004 (2) |
C22 | 0.052 (3) | 0.086 (3) | 0.091 (3) | 0.001 (3) | 0.014 (2) | −0.001 (3) |
C1—C2 | 1.536 (4) | C5—C19 | 1.511 (5) |
C2—C3 | 1.532 (4) | C1—H1 | 0.9800 |
C3—C4 | 1.547 (4) | C2—H2 | 0.9800 |
C4—C5 | 1.543 (4) | C3—H3a | 0.9700 |
C5—C6 | 1.529 (4) | C3—H3b | 0.9700 |
C1—C6 | 1.517 (5) | C4—H4 | 0.9800 |
O8—C7 | 1.197 (4) | C5—H5 | 0.9800 |
O9—C7 | 1.338 (4) | C6—H6a | 0.9700 |
O9—C10 | 1.447 (4) | C6—H6b | 0.9700 |
O12—C11 | 1.191 (4) | C10—H10a | 0.9600 |
O13—C11 | 1.337 (4) | C10—H10b | 0.9600 |
O13—C14 | 1.446 (4) | C10—H10c | 0.9600 |
O16—C15 | 1.201 (4) | C14—H14a | 0.9600 |
O17—C15 | 1.332 (4) | C14—H14b | 0.9600 |
O17—C18 | 1.444 (4) | C14—H14c | 0.9600 |
O20—C19 | 1.197 (4) | C18—H18a | 0.9600 |
O21—C19 | 1.343 (4) | C18—H18b | 0.9600 |
O21—C22 | 1.445 (4) | C18—H18c | 0.9600 |
C1—C7 | 1.506 (5) | C22—H22a | 0.9600 |
C2—C11 | 1.527 (5) | C22—H22b | 0.9600 |
C4—C15 | 1.499 (5) | C22—H22c | 0.9600 |
C2—C1—C6 | 110.9 (3) | C2—C3—H3b | 108.6 |
C1—C2—C3 | 108.9 (3) | C4—C3—H3b | 108.6 |
C2—C3—C4 | 114.6 (3) | H3a—C3—H3b | 107.6 |
C3—C4—C5 | 110.7 (3) | C15—C4—H4 | 107.4 |
C4—C5—C6 | 114.1 (3) | C5—C4—H4 | 107.4 |
C1—C6—C5 | 112.4 (3) | C3—C4—H4 | 107.4 |
C7—O9—C10 | 116.3 (3) | C19—C5—H5 | 106.3 |
C11—O13—C14 | 115.5 (3) | C6—C5—H5 | 106.3 |
C15—O17—C18 | 116.9 (3) | C4—C5—H5 | 106.3 |
C19—O21—C22 | 115.8 (3) | C1—C6—H6a | 109.1 |
C7—C1—C6 | 111.0 (3) | C5—C6—H6a | 109.1 |
C7—C1—C2 | 116.0 (3) | C1—C6—H6b | 109.1 |
C11—C2—C3 | 115.8 (3) | C5—C6—H6b | 109.1 |
C11—C2—C1 | 110.5 (3) | H6a—C6—H6b | 107.9 |
C15—C4—C5 | 113.5 (3) | O9—C10—H10a | 109.5 |
C15—C4—C3 | 110.1 (3) | O9—C10—H10b | 109.5 |
C19—C5—C6 | 109.4 (3) | H10a—C10—H10b | 109.5 |
C19—C5—C4 | 113.9 (3) | O9—C10—H10c | 109.5 |
O8—C7—O9 | 123.4 (4) | H10a—C10—H10c | 109.5 |
O8—C7—C1 | 125.0 (4) | H10b—C10—H10c | 109.5 |
O12—C11—O13 | 124.1 (3) | O13—C14—H14a | 109.5 |
O12—C11—C2 | 124.6 (3) | O13—C14—H14b | 109.5 |
O13—C11—C2 | 111.3 (3) | H14a—C14—H14b | 109.5 |
O9—C7—C1 | 111.6 (3) | O13—C14—H14c | 109.5 |
O16—C15—O17 | 123.3 (3) | H14a—C14—H14c | 109.5 |
O16—C15—C4 | 125.4 (3) | H14b—C14—H14c | 109.5 |
O17—C15—C4 | 111.3 (3) | O17—C18—H18a | 109.5 |
O20—C19—O21 | 122.5 (4) | O17—C18—H18b | 109.5 |
O20—C19—C5 | 125.2 (4) | H18a—C18—H18b | 109.5 |
O21—C19—C5 | 112.3 (3) | O17—C18—H18c | 109.5 |
C7—C1—H1 | 106.1 | H18a—C18—H18c | 109.5 |
C6—C1—H1 | 106.1 | H18b—C18—H18c | 109.5 |
C2—C1—H1 | 106.1 | O21—C22—H22a | 109.5 |
C11—C2—H2 | 107.1 | O21—C22—H22b | 109.5 |
C3—C2—H2 | 107.1 | H22a—C22—H22b | 109.5 |
C1—C2—H2 | 107.1 | O21—C22—H22c | 109.5 |
C2—C3—H3a | 108.6 | H22a—C22—H22c | 109.5 |
C4—C3—H3a | 108.6 | H22b—C22—H22c | 109.5 |
C7—C1—C2—C11 | 58.2 (4) | C6—C1—C7—O9 | 170.0 (3) |
C15—C4—C5—C19 | −47.9 (4) | C2—C1—C7—O9 | 42.3 (4) |
C2—C3—C4—C5 | 49.4 (4) | C14—O13—C11—O12 | 1.3 (5) |
C2—C1—C6—C5 | −57.2 (4) | C14—O13—C11—C2 | 178.5 (3) |
C3—C4—C5—C6 | −45.6 (4) | C3—C2—C11—O12 | −144.1 (3) |
C6—C1—C2—C3 | 58.7 (4) | C1—C2—C11—O12 | −19.7 (5) |
C1—C2—C3—C4 | −56.1 (4) | C3—C2—C11—O13 | 38.7 (4) |
C11—C2—C3—C4 | 69.1 (4) | C1—C2—C11—O13 | 163.0 (3) |
C2—C3—C4—C15 | −76.9 (3) | C18—O17—C15—O16 | −4.2 (5) |
C19—C5—C6—C1 | 179.9 (3) | C18—O17—C15—C4 | 174.6 (3) |
C7—C1—C6—C5 | 172.3 (3) | C5—C4—C15—O16 | −25.5 (5) |
C4—C5—C6—C1 | 50.9 (4) | C3—C4—C15—O16 | 99.2 (4) |
C6—C1—C2—C11 | −69.5 (4) | C5—C4—C15—O17 | 155.7 (3) |
C7—C1—C2—C3 | −173.5 (3) | C3—C4—C15—O17 | −79.5 (3) |
C3—C4—C5—C19 | −172.3 (3) | C22—O21—C19—O20 | −1.4 (5) |
C15—C4—C5—C6 | 78.8 (4) | C22—O21—C19—C5 | −179.8 (3) |
C10—O9—C7—O8 | −1.1 (5) | C6—C5—C19—O20 | 21.2 (5) |
C10—O9—C7—C1 | 176.0 (3) | C4—C5—C19—O20 | 150.3 (4) |
C6—C1—C7—O8 | −13.0 (5) | C6—C5—C19—O21 | −160.4 (3) |
C2—C1—C7—O8 | −140.7 (4) | C4—C5—C19—O21 | −31.3 (4) |
Experimental details
Crystal data | |
Chemical formula | C14H20O8 |
Mr | 316.3 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 296 |
a, b, c (Å) | 18.6901 (19), 10.031 (2), 17.781 (2) |
β (°) | 109.910 (8) |
V (Å3) | 3134.3 (9) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.11 |
Crystal size (mm) | 0.49 × 0.30 × 0.05 |
Data collection | |
Diffractometer | Rigaku AFC-5S diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2864, 2766, 1039 |
Rint | 0.027 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.040, 0.128, 0.96 |
No. of reflections | 2766 |
No. of parameters | 203 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.17, −0.15 |
Computer programs: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1996), MSC/AFC Diffractometer Control Software, PROCESS in TEXSAN (Molecular Structure Corporation, 1997), SIR92 (Burla et al., 1989), LS in TEXSAN and SHELXL97 (Sheldrick, 1997), ORTEP in TEXSAN (Johnson, 1965), TEXSAN, SHELXL97, and PLATON (Spek, 2000).
C1—C2 | 1.536 (4) | C4—C5 | 1.543 (4) |
C2—C3 | 1.532 (4) | C5—C6 | 1.529 (4) |
C3—C4 | 1.547 (4) | C1—C6 | 1.517 (5) |
C2—C1—C6 | 110.9 (3) | C3—C4—C5 | 110.7 (3) |
C1—C2—C3 | 108.9 (3) | C4—C5—C6 | 114.1 (3) |
C2—C3—C4 | 114.6 (3) | C1—C6—C5 | 112.4 (3) |
C7—C1—C2—C11 | 58.2 (4) | C1—C2—C3—C4 | −56.1 (4) |
C15—C4—C5—C19 | −47.9 (4) | C11—C2—C3—C4 | 69.1 (4) |
C2—C3—C4—C5 | 49.4 (4) | C2—C3—C4—C15 | −76.9 (3) |
C2—C1—C6—C5 | −57.2 (4) | C19—C5—C6—C1 | 179.9 (3) |
C3—C4—C5—C6 | −45.6 (4) | C7—C1—C6—C5 | 172.3 (3) |
C6—C1—C2—C3 | 58.7 (4) | C4—C5—C6—C1 | 50.9 (4) |
In our synthetic studies towards beltenes and cyclacenes (Stoddart, 1989), previously unreported all-cis tetramethyl 1,2,4,5-cyclohexanetetracarboxylate, (I), was required. Although the synthesis of the trans,cis,trans isomer from the hydrogenation of tetrasodium pyromellitate at 423 K with hydrogen at 3000 p.s.i. and W-2 Raney nickel was reported, the stereochemistry was not well established (Longone, 1963; Bailey et al., 1962). We synthesized (I) in 91% yield from the hydrogenation of tetramethyl 1,4-cyclohexadiene-1,2,4,5-tetracarboxylate, (II), with 10% palladium over carbon and 80 p.s.i. of hydrogen in methanol at 298 K (Scheme). While the stereochemistry of (I) could not be determined from elemental and spectral analysis alone, its structure was unambiguously characterized by X-ray crystal structure analysis. Compound (II) was synthesized from the Diels-Alder reaction of dimethyl acetylenedicarboxylate and dimethyl 2,3-di(methylene)-1,4-butanedioate (Hamon & Spurr, 1981) in refluxing toluene. \sch
The molecular structure of (I) with the atom-numbering scheme (Fig. 1) shows it to have a chair conformation, with the methyl ester groups at C2 and C4 axially oriented and those at C1 and C5 equatorially oriented. All four carbonyl (C═O) moieties point in the same direction, towards C6 of the cyclohexane chair, an arrangement which reduces the steric interaction among the four carbomethoxyl groups. The molecule has approximate, non-crystallographic mirror symmetry. It can be seen from Table 1 that all the bond lengths within the ring are similar, with a mean distance of 1.534 (4) Å, which compares favorably with the mean C—C ring bond length [1.529 (4) Å] of trans-1,4-dicyanocyclohexane (Echeverria et al., 1995). The largest endocyclic angle, C2—C3—C4, bearing the cis-diaxial C2- and C4-carbomethoxyl groups, reflects the classic 1,3-diaxial repulsion (Elial & Wilson, 1984), the corresponding angle, C1—C6—C5, bearing these two substituents equatorially on the C1 and C5 atoms, being substantially smaller. The fact that angle C4—C5—C6 is significantly larger than its corresponding angle C2—C1—C6 is a reflection of the asymmetric skeletal distortion associated with the noted above. The mean endocyclic angle [111.9 (3)°] is identical, within error, to the mean value [111.4 (4)°] of those in trans-1,4-cyclohexanedicarboxylic (Dunitz & Strickler, 1966; Von Luger et al., 1972). The structural deformation caused by the 1,3-diaxial carbomethoxyl groups in (I) is also quite evident from a comparison of the related torsion angles, e.g. C7—C1—C2—C11 is much larger than C15—C4—C5—C19, while C3—C4—C5—C6 is much smaller than C6—C1—C2—C3; C1—C2—C3—C4 is much larger than C2—C3—C4—C5; and C2—C1—C6—C5 is substantially larger than C4—C5—C6—C1.