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The title compound, C21H18O4, has a molecular structure with a rigid polycyclic nucleus, in which an acid anhydride ring bridges the two CH positions of the central ring of anthracene. The 1-methoxy­ethyl substituent, by contrast, has conform­ational freedom and adopts an orientation minimizing steric and electronic repulsions with the anhydride group.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536802021311/ob6195sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536802021311/ob6195Isup2.hkl
Contains datablock I

CCDC reference: 202344

Key indicators

  • Single-crystal X-ray study
  • T = 160 K
  • Mean [sigma](C-C) = 0.004 Å
  • R factor = 0.051
  • wR factor = 0.112
  • Data-to-parameter ratio = 12.6

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry








Comment top

The title compound, (I), was prepared as part of a study of diastereoselective Diels–Alder addition reactions of chiral anthracene derivatives substituted at one of the central ring C atoms (Atherton & Jones, 2002). The primary purpose of the structure determination was to confirm the relative stereochemistry, as evidence for the proposed mechanism of the reaction. Both the starting material and the product, (I), of the Diels–Alder reaction are racemic; (I) crystallizes in a centrosymmetric space group.

Detailed examination of the molecular structure of (I) (Fig. 1) shows further points of interest in addition to the qualitative identification required for the mechanistic study. Most of the molecule is relatively rigid, but there is conformational freedom for the 1-methoxyethyl group. Torsion angles for this group are given in Table 1. The antiperiplanar arrangement of the methyl group relative to the ring system and the orientation of the anhydride ring away from the methoxy group are in accord with expected steric and electronic interactions in the starting material and during the course of the reaction, and almost ideal staggering of the substituents around the C10—C19 bond is retained in the solid state, apparently with no significant crystal-packing effects. There are only van der Waals interactions between molecules.

A search of the Cambridge Structural Database (CSD, Version 5.23 of April 2002, and 3 updates; Allen, 2002) reveals 232 structures in which a bridge of two C atoms is added across the opposite CH groups of the central ring of anthracene. Of these, almost one-half are triptycene derivatives, in which the two-atom bridge is part of a third benzene ring. In six structures, the bridge is the C—C bond of an acid anhydride, as in (I) (Bulgarovskaya et al., 1979; Schwartz et al., 1992; Plummer et al., 1997; Weber et al., 1993; Díaz de Dalgado et al., 2002). The rigidity of the polycyclic core of these molecules is demonstrated by the small range of dihedral angles found between pairs of mean planes defined as follows: plane 1 is the anhydride group; plane 2 is C9/C10/C15/C16 (using the atom numbering for the title compound; see Fig. 1); plane 3 is C9/C10/C13/C14; plane 4 is C9/C10/C11/C12. Dihedral angles for the previously reported anhydride structures (defined as hinge angles, such that 180° corresponds to exact coplanarity, as in anthracene itself) lie in the ranges: 118.8–122.3° for planes 1–2; 117.4–119.8° for planes 2–3 and 2–4; 121.7–124.6° for planes 3—4. The corresponding values for (I) are: 120.12 (9) (1–2), 117.69 (11) (2–3), 116.57 (12) (2–4) and 125.74 (10) (3–4), each of them within or marginally outside the range for the other structures. There is no systematic difference between the dihedral angles 2–3 and 2–4, the C9/C15/C16/C10 bridge lying essentially symmetrically above the anthracene nucleus, despite the orientation of the anhydride group to one side. The dihedral angle 3–4 is increased, and both 2–3 and 2–4 are decreased from the 120° of a symmetrical triptycene structure. The differences are small, but systematic, and are probably a consequence of the longer bonds from C9 and C10 to the anhydride group than to the benzene rings, leading to a slightly lower steric demand by the anhydride group.

In (I), as in the other anhydride structures, and also generally in bridged anthracene derivatives, the two benzene rings are essentially coplanar with planes 3 and 4; the respective dihedral (hinge) angles in (I) are 175.26 (19) and 177.42 (18)°.

Experimental top

The synthesis has been described by Atherton & Jones (2002).

Refinement top

H atoms were placed geometrically and refined with a riding model (including free rotation about C—C bonds), and with Uiso constrained to be 1.2 (1.5 for methyl groups) times Ueq of the carrier atom.

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2001); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and local programs.

Figures top
[Figure 1] Fig. 1. The molecular structure of (I) with atom labels and 50% probability ellipsoids for non-H atoms.
(11SR,15SR)-9,10,11,15-Tetrahydro-9-[(1SR)-1-methoxyethyl]- 9,10-[3',4']furanoanthracene-12,14-dione top
Crystal data top
C21H18O4Z = 2
Mr = 334.35F(000) = 352
Triclinic, P1Dx = 1.340 Mg m3
a = 9.5923 (8) ÅMo Kα radiation, λ = 0.71073 Å
b = 10.1129 (8) ÅCell parameters from 4879 reflections
c = 10.9661 (9) Åθ = 2.4–28.3°
α = 112.886 (2)°µ = 0.09 mm1
β = 94.278 (2)°T = 160 K
γ = 117.285 (2)°Plate, colourless
V = 828.41 (12) Å30.70 × 0.35 × 0.08 mm
Data collection top
Bruker SMART 1K CCD
diffractometer
2332 reflections with I > 2σ(I)
Radiation source: sealed tubeRint = 0.023
Graphite monochromatorθmax = 25.0°, θmin = 2.1°
Detector resolution: 8.192 pixels mm-1h = 1111
ω rotation with narrow frames scansk = 1211
5885 measured reflectionsl = 1313
2885 independent reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.051H-atom parameters constrained
wR(F2) = 0.112 w = 1/[σ2(Fo2) + (0.0388P)2 + 0.5015P]
where P = (Fo2 + 2Fc2)/3
S = 1.13(Δ/σ)max < 0.001
2885 reflectionsΔρmax = 0.28 e Å3
229 parametersΔρmin = 0.20 e Å3
0 restraintsExtinction correction: SHELXTL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.013 (3)
Crystal data top
C21H18O4γ = 117.285 (2)°
Mr = 334.35V = 828.41 (12) Å3
Triclinic, P1Z = 2
a = 9.5923 (8) ÅMo Kα radiation
b = 10.1129 (8) ŵ = 0.09 mm1
c = 10.9661 (9) ÅT = 160 K
α = 112.886 (2)°0.70 × 0.35 × 0.08 mm
β = 94.278 (2)°
Data collection top
Bruker SMART 1K CCD
diffractometer
2332 reflections with I > 2σ(I)
5885 measured reflectionsRint = 0.023
2885 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0510 restraints
wR(F2) = 0.112H-atom parameters constrained
S = 1.13Δρmax = 0.28 e Å3
2885 reflectionsΔρmin = 0.20 e Å3
229 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C10.2543 (3)0.0219 (3)0.1484 (2)0.0249 (5)
H10.16810.04000.08300.030*
C20.2237 (3)0.1400 (3)0.1945 (3)0.0309 (6)
H20.11590.23730.16160.037*
C30.3487 (3)0.1168 (3)0.2876 (3)0.0333 (6)
H30.32660.19790.31870.040*
C40.5065 (3)0.0250 (3)0.3358 (2)0.0277 (5)
H40.59310.04050.39870.033*
C50.7915 (3)0.6040 (3)0.5022 (2)0.0280 (5)
H50.87430.61430.56490.034*
C60.7729 (3)0.7403 (3)0.5310 (2)0.0320 (6)
H60.84250.84410.61430.038*
C70.6537 (3)0.7255 (3)0.4391 (2)0.0295 (5)
H70.64280.81990.45930.035*
C80.5493 (3)0.5745 (3)0.3173 (2)0.0228 (5)
H80.46830.56600.25420.027*
C90.7034 (3)0.2992 (3)0.3298 (2)0.0225 (5)
H90.79040.31360.39890.027*
C100.4673 (2)0.2630 (3)0.1559 (2)0.0195 (5)
C110.4112 (3)0.1228 (3)0.1981 (2)0.0207 (5)
C120.5370 (3)0.1440 (3)0.2914 (2)0.0221 (5)
C130.6880 (3)0.4528 (3)0.3811 (2)0.0218 (5)
C140.5644 (2)0.4356 (3)0.2886 (2)0.0192 (5)
C150.7413 (3)0.2735 (3)0.1889 (2)0.0213 (5)
H150.75180.17250.14800.026*
C160.6041 (2)0.2521 (3)0.0863 (2)0.0196 (5)
H160.55260.14080.00020.023*
C170.8969 (3)0.4296 (3)0.2093 (2)0.0266 (5)
C180.6950 (3)0.3958 (3)0.0531 (2)0.0219 (5)
C190.3322 (3)0.2472 (3)0.0561 (2)0.0222 (5)
H190.38550.34340.03480.027*
C200.1922 (3)0.2526 (3)0.1128 (2)0.0271 (5)
H20A0.13810.28720.06310.041*
H20B0.23760.33420.21230.041*
H20C0.11150.14000.09920.041*
C210.2061 (3)0.0984 (3)0.1889 (2)0.0357 (6)
H21A0.11410.11520.17830.054*
H21B0.16760.00830.27300.054*
H21C0.29350.19250.19700.054*
O11.0334 (2)0.4979 (2)0.28256 (19)0.0394 (5)
O20.86159 (18)0.49271 (19)0.12776 (16)0.0284 (4)
O30.6443 (2)0.4314 (2)0.02372 (17)0.0313 (4)
O40.26869 (18)0.09254 (18)0.07118 (15)0.0262 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0248 (12)0.0221 (11)0.0287 (12)0.0124 (10)0.0125 (10)0.0123 (10)
C20.0333 (13)0.0202 (12)0.0396 (14)0.0113 (10)0.0209 (11)0.0165 (11)
C30.0508 (16)0.0277 (13)0.0377 (14)0.0229 (12)0.0258 (12)0.0253 (12)
C40.0384 (14)0.0317 (13)0.0286 (13)0.0241 (11)0.0156 (11)0.0205 (11)
C50.0254 (12)0.0316 (13)0.0220 (12)0.0136 (11)0.0042 (10)0.0109 (11)
C60.0332 (13)0.0227 (12)0.0228 (12)0.0094 (11)0.0033 (10)0.0032 (10)
C70.0346 (13)0.0212 (12)0.0319 (13)0.0157 (11)0.0128 (11)0.0107 (11)
C80.0252 (12)0.0237 (11)0.0248 (12)0.0148 (10)0.0089 (9)0.0138 (10)
C90.0222 (11)0.0249 (12)0.0235 (12)0.0132 (10)0.0052 (9)0.0138 (10)
C100.0200 (11)0.0180 (11)0.0203 (11)0.0091 (9)0.0067 (9)0.0100 (9)
C110.0238 (11)0.0176 (11)0.0229 (11)0.0115 (9)0.0121 (9)0.0103 (9)
C120.0272 (12)0.0225 (11)0.0245 (12)0.0159 (10)0.0126 (10)0.0140 (10)
C130.0222 (11)0.0232 (11)0.0216 (11)0.0109 (9)0.0088 (9)0.0131 (10)
C140.0183 (11)0.0176 (11)0.0201 (11)0.0073 (9)0.0073 (9)0.0101 (9)
C150.0222 (11)0.0198 (11)0.0273 (12)0.0135 (9)0.0098 (9)0.0128 (10)
C160.0227 (11)0.0159 (10)0.0211 (11)0.0105 (9)0.0074 (9)0.0092 (9)
C170.0254 (13)0.0267 (12)0.0298 (13)0.0149 (10)0.0114 (10)0.0135 (11)
C180.0238 (12)0.0219 (11)0.0245 (12)0.0138 (10)0.0100 (9)0.0127 (10)
C190.0226 (11)0.0168 (11)0.0230 (11)0.0089 (9)0.0035 (9)0.0083 (9)
C200.0227 (12)0.0274 (12)0.0301 (13)0.0139 (10)0.0053 (10)0.0127 (11)
C210.0367 (14)0.0374 (14)0.0250 (13)0.0171 (12)0.0005 (11)0.0124 (11)
O10.0213 (9)0.0441 (11)0.0500 (11)0.0128 (8)0.0063 (8)0.0264 (9)
O20.0237 (8)0.0258 (9)0.0373 (9)0.0094 (7)0.0095 (7)0.0209 (8)
O30.0371 (10)0.0354 (10)0.0367 (10)0.0220 (8)0.0155 (8)0.0265 (8)
O40.0287 (8)0.0217 (8)0.0215 (8)0.0123 (7)0.0002 (7)0.0071 (7)
Geometric parameters (Å, º) top
C1—H10.950C10—C161.591 (3)
C1—C21.392 (3)C10—C191.538 (3)
C1—C111.394 (3)C11—C121.398 (3)
C2—H20.950C13—C141.401 (3)
C2—C31.382 (3)C15—H151.000
C3—H30.950C15—C161.541 (3)
C3—C41.389 (3)C15—C171.511 (3)
C4—H40.950C16—H161.000
C4—C121.387 (3)C16—C181.517 (3)
C5—H50.950C17—O11.192 (3)
C5—C61.388 (3)C17—O21.385 (3)
C5—C131.385 (3)C18—O21.389 (3)
C6—H60.950C18—O31.188 (3)
C6—C71.378 (3)C19—H191.000
C7—H70.950C19—C201.536 (3)
C7—C81.389 (3)C19—O41.438 (2)
C8—H80.950C20—H20A0.980
C8—C141.393 (3)C20—H20B0.980
C9—H91.000C20—H20C0.980
C9—C121.509 (3)C21—H21A0.980
C9—C131.514 (3)C21—H21B0.980
C9—C151.564 (3)C21—H21C0.980
C10—C111.537 (3)C21—O41.417 (3)
C10—C141.537 (3)
H1—C1—C2119.9C5—C13—C14120.8 (2)
H1—C1—C11119.9C9—C13—C14113.81 (18)
C2—C1—C11120.1 (2)C8—C14—C10126.63 (19)
C1—C2—H2119.7C8—C14—C13119.20 (19)
C1—C2—C3120.5 (2)C10—C14—C13113.95 (18)
H2—C2—C3119.7C9—C15—H15110.3
C2—C3—H3120.0C9—C15—C16110.15 (16)
C2—C3—C4120.0 (2)C9—C15—C17110.74 (17)
H3—C3—C4120.0H15—C15—C16110.3
C3—C4—H4120.2H15—C15—C17110.3
C3—C4—C12119.6 (2)C16—C15—C17104.95 (16)
H4—C4—C12120.2C10—C16—C15110.47 (16)
H5—C5—C6120.3C10—C16—H16109.9
H5—C5—C13120.3C10—C16—C18112.74 (16)
C6—C5—C13119.4 (2)C15—C16—H16109.9
C5—C6—H6119.9C15—C16—C18103.70 (16)
C5—C6—C7120.1 (2)H16—C16—C18109.9
H6—C6—C7119.9C15—C17—O1129.3 (2)
C6—C7—H7119.5C15—C17—O2109.79 (18)
C6—C7—C8121.0 (2)O1—C17—O2120.9 (2)
H7—C7—C8119.5C16—C18—O2110.25 (17)
C7—C8—H8120.3C16—C18—O3129.9 (2)
C7—C8—C14119.5 (2)O2—C18—O3119.89 (19)
H8—C8—C14120.3C10—C19—H19107.8
H9—C9—C12112.2C10—C19—C20114.98 (18)
H9—C9—C13112.2C10—C19—O4107.25 (16)
H9—C9—C15112.2H19—C19—C20107.8
C12—C9—C13109.15 (17)H19—C19—O4107.8
C12—C9—C15104.93 (17)C20—C19—O4110.87 (17)
C13—C9—C15105.85 (16)C19—C20—H20A109.5
C11—C10—C14108.56 (16)C19—C20—H20B109.5
C11—C10—C16103.10 (15)C19—C20—H20C109.5
C11—C10—C19116.06 (17)H20A—C20—H20B109.5
C14—C10—C16104.05 (16)H20A—C20—H20C109.5
C14—C10—C19112.95 (17)H20B—C20—H20C109.5
C16—C10—C19111.01 (16)H21A—C21—H21B109.5
C1—C11—C10126.91 (19)H21A—C21—H21C109.5
C1—C11—C12118.79 (19)H21A—C21—O4109.5
C10—C11—C12114.22 (18)H21B—C21—H21C109.5
C4—C12—C9125.3 (2)H21B—C21—O4109.5
C4—C12—C11120.9 (2)H21C—C21—O4109.5
C9—C12—C11113.72 (18)C17—O2—C18111.28 (16)
C5—C13—C9125.2 (2)C19—O4—C21112.70 (17)
C11—C1—C2—C31.2 (3)C16—C10—C14—C8114.8 (2)
C1—C2—C3—C40.2 (3)C16—C10—C14—C1359.6 (2)
C2—C3—C4—C121.0 (3)C19—C10—C14—C85.7 (3)
C13—C5—C6—C70.7 (3)C19—C10—C14—C13179.93 (17)
C5—C6—C7—C80.7 (4)C12—C9—C15—C1658.0 (2)
C6—C7—C8—C140.7 (3)C12—C9—C15—C17173.66 (17)
C2—C1—C11—C10178.4 (2)C13—C9—C15—C1657.4 (2)
C2—C1—C11—C121.7 (3)C13—C9—C15—C1758.3 (2)
C14—C10—C11—C1133.1 (2)C9—C15—C16—C100.0 (2)
C14—C10—C11—C1250.1 (2)C9—C15—C16—C18121.06 (18)
C16—C10—C11—C1116.9 (2)C17—C15—C16—C10119.22 (17)
C16—C10—C11—C1259.8 (2)C17—C15—C16—C181.8 (2)
C19—C10—C11—C14.7 (3)C11—C10—C16—C1556.8 (2)
C19—C10—C11—C12178.59 (18)C11—C10—C16—C18172.27 (17)
C3—C4—C12—C9177.0 (2)C14—C10—C16—C1556.5 (2)
C3—C4—C12—C110.4 (3)C14—C10—C16—C1859.0 (2)
C1—C11—C12—C41.0 (3)C19—C10—C16—C15178.30 (16)
C1—C11—C12—C9176.04 (19)C19—C10—C16—C1862.8 (2)
C10—C11—C12—C4178.00 (19)C9—C15—C17—O159.0 (3)
C10—C11—C12—C91.0 (3)C9—C15—C17—O2120.40 (19)
C13—C9—C12—C4129.9 (2)C16—C15—C17—O1177.8 (2)
C13—C9—C12—C1153.2 (2)C16—C15—C17—O21.6 (2)
C15—C9—C12—C4117.0 (2)C10—C16—C18—O2117.92 (18)
C15—C9—C12—C1159.8 (2)C10—C16—C18—O362.5 (3)
C6—C5—C13—C9174.2 (2)C15—C16—C18—O21.6 (2)
C6—C5—C13—C140.6 (3)C15—C16—C18—O3178.0 (2)
C12—C9—C13—C5131.3 (2)C11—C10—C19—C2061.5 (2)
C12—C9—C13—C1453.5 (2)C11—C10—C19—O462.2 (2)
C15—C9—C13—C5116.2 (2)C14—C10—C19—C2064.8 (2)
C15—C9—C13—C1458.9 (2)C14—C10—C19—O4171.45 (16)
C7—C8—C14—C10176.1 (2)C16—C10—C19—C20178.81 (17)
C7—C8—C14—C131.9 (3)C16—C10—C19—O455.0 (2)
C5—C13—C14—C81.9 (3)C15—C17—O2—C180.6 (2)
C5—C13—C14—C10176.80 (19)O1—C17—O2—C18178.8 (2)
C9—C13—C14—C8173.46 (18)C16—C18—O2—C170.7 (2)
C9—C13—C14—C101.4 (2)O3—C18—O2—C17179.0 (2)
C11—C10—C14—C8135.9 (2)C10—C19—O4—C21151.95 (18)
C11—C10—C14—C1349.7 (2)C20—C19—O4—C2181.8 (2)

Experimental details

Crystal data
Chemical formulaC21H18O4
Mr334.35
Crystal system, space groupTriclinic, P1
Temperature (K)160
a, b, c (Å)9.5923 (8), 10.1129 (8), 10.9661 (9)
α, β, γ (°)112.886 (2), 94.278 (2), 117.285 (2)
V3)828.41 (12)
Z2
Radiation typeMo Kα
µ (mm1)0.09
Crystal size (mm)0.70 × 0.35 × 0.08
Data collection
DiffractometerBruker SMART 1K CCD
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
5885, 2885, 2332
Rint0.023
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.051, 0.112, 1.13
No. of reflections2885
No. of parameters229
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.28, 0.20

Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2001), SAINT, SHELXTL (Sheldrick, 2001), SHELXTL and local programs.

Selected torsion angles (º) top
C11—C10—C19—C2061.5 (2)C14—C10—C19—O4171.45 (16)
C11—C10—C19—O462.2 (2)C16—C10—C19—C20178.81 (17)
C14—C10—C19—C2064.8 (2)C16—C10—C19—O455.0 (2)
 

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