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Acta Cryst. (2008). E64, o686    [ doi:10.1107/S1600536808006016 ]

1,3-Diphenylisobenzofuran

R. T. Boeré, P. W. Dibble and K. E. Fischer

Abstract top

The structure of the title compound, 1,3-diphenyl-2-benzofuran, C20H14O, exhibits a distinct alternation of short [mean 1.361 (3) Å] and long [mean 1.431 (3) Å] C-C bonds around the benzofuran ring system, indicating a predominantly polyene character. Over 60 Diels-Alder adducts of this commercially available furan have been structurally characterized, but this is the first report of the structure of the parent compound.

Comment top

Isobenzofuran is a ten π-electron system exhibiting very high reactivity in Diels-Alder reactions (Wege, 1998; Friedrichsen, 1999). The commercially available 1,3-diphenyl-2-benzofuran, (I), is a molecule with many interesting features (Friedrichsen, 1980) and unlike the parent compound is stable in the solid state. It is brightly fluorescent, electroluminescent and, despite its stability relative to isobenzofuran is still highly reactive in Diels-Alder reactions. Its reactivity is exploited in the quantitative kinetic investigations of biological singlet oxygen generation and in the in situ trapping of transient olefin intermediates. With respect to this latter application, the high reactivity of (I) and the crystallinity of its adducts account for the sixty-eight X-ray structures of diphenylisobenzofuran adducts that appear in the Cambridge Crystallographic Database (Allen, 2002). Surprisingly, an X-ray structure of (I) has not appeared in the literature.

Calculations have suggested that isobenzofuran has a low resonance energy (Yang & Duan, 1991) and mainly polyene character. The structures of isobenzofurans are of interest since the degree of bond length alternation serves to indicate the balance between aromatic and polyene character. Only three structures of isobenzofurans have been published previously: 1-cyano-4,5-methylenedioxyisobenzofuran (Rodrigo et al., 1986); 3,6-dimethoxyisobenzofuran (Lynch et al., 1995) and the highly strained 9,10,12,13-tetraphenyl-11-oxacyclopenta[b]triphenylene (Lu et al., 2006). All three structures show that the isobenzofuran core is essentially polyene in character with the structure of the furan ring very similar to that of furan itself.

The structure of (I) (Fig. 1) is very closely comparable to those of the three previously published examples. There is no significant evidence of bond length averaging indicating that it has predominantly polyene character. Of the three published structures, the bond lengths of (I) are closest to those calculated for the parent compound using the MP2/6–31G* basis set (Friedrichsen, 1980). The only noticeable difference is in the C1—C2, C7—C87 bonds which are slightly longer, perhaps the effect of conjugation to the phenyl substitutents. While the most recent structure (Lu et al., 2006) contains the diphenylisobenzofuran substructure, extensive peri interactions throughout the molecule lead to significant deviations from planarity making direct structural comparisons less meaningfull.

Strong steric interactions between the phenyl substituents of (I) and the peri H atoms (H3 and H6) are indicated by a 25° torsional twist of the phenyl rings out of the plane of the isobenzofuran ring and wide 135.3 (2)° and 135.5 (2)° bond angles for C2—C1—C9, C7—C8—C15.

Related literature top

For related literature, see: Wege (1998); Friedrichsen (1980); Friedrichsen (1999); Allen (2002); Yang & Duan (1991); Rodrigo et al. (1986); Lynch et al. (1995): Lu et al. (2006).

Experimental top

Commercial 1,3-diphenyl-2-benzofuran [CAS-5471–66–6] (Aldrich) was recrystallized from ethanol.

Refinement top

The space group was determined by trial and error and confirmed by a sucessful refinement. The alternative choice, Pc, gave unrealistic geometrical parameters. H-atoms were included at geometrically idealized positions with C—H distance 0.95 Å and Uiso = 1.2 times Ueq of the C-atoms to which they were bonded. The model was refined to convergence, and there were no chemically significant features on the final difference Fourier map.

Computing details top

Data collection: APEX2 (Bruker, 2006); cell refinement: APEX2 (Bruker, 2006); data reduction: SAINT (Bruker, 2006); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: publCIF (Westrip, 2008).

Figures top
[Figure 1] Fig. 1. Thermal ellipsoid plot of the structure of (I) drawn at 50% probability level showing the atom numbering scheme.
1,3-diphenyl-2-benzofuran top
Crystal data top
C20H14OF000 = 568
Mr = 270.31Dx = 1.325 Mg m−3
Monoclinic, P2/cMelting point: 128 K
Hall symbol: -P 2ycMo Kα radiation
λ = 0.71073 Å
a = 12.8198 (17) ÅCell parameters from 2945 reflections
b = 5.5273 (8) Åθ = 2.3–24.1º
c = 19.945 (3) ŵ = 0.08 mm−1
β = 106.480 (2)ºT = 173 (2) K
V = 1355.2 (3) Å3Plate, green
Z = 40.28 × 0.13 × 0.04 mm
Data collection top
Bruker APEXII CCD area-detector
diffractometer		2854 independent reflections
Monochromator: graphite1664 reflections with I > 2σ(I)
T = 173(2) KRint = 0.085
P = 95 kPaθmax = 26.7º
φ and ω scansθmin = 2.1º
Absorption correction: multi-scan
(SADABS; Sheldrick, 2004)		h = −16→16
Tmin = 0.977, Tmax = 0.998k = −6→6
13976 measured reflectionsl = −25→25
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.047  w = 1/[σ2(Fo2) + (0.0358P)2 + 0.3395P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.105(Δ/σ)max < 0.001
S = 1.03Δρmax = 0.20 e Å−3
2854 reflectionsΔρmin = −0.21 e Å−3
191 parametersExtinction correction: SHELXTL (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0103 (12)
Secondary atom site location: difference Fourier map
Crystal data top
C20H14OV = 1355.2 (3) Å3
Mr = 270.31Z = 4
Monoclinic, P2/cMo Kα
a = 12.8198 (17) ŵ = 0.08 mm−1
b = 5.5273 (8) ÅT = 173 (2) K
c = 19.945 (3) Å0.28 × 0.13 × 0.04 mm
β = 106.480 (2)º
Data collection top
Bruker APEXII CCD area-detector
diffractometer		2854 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 2004)		1664 reflections with I > 2σ(I)
Tmin = 0.977, Tmax = 0.998Rint = 0.085
13976 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.047191 parameters
wR(F2) = 0.105H-atom parameters constrained
S = 1.03Δρmax = 0.20 e Å−3
2854 reflectionsΔρmin = −0.21 e Å−3
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. 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.29644 (11)0.9505 (2)0.35614 (7)0.0205 (4)
C10.21954 (16)0.8022 (4)0.31456 (11)0.0202 (5)
C20.20930 (16)0.8560 (4)0.24577 (11)0.0196 (5)
C30.14208 (17)0.7650 (4)0.18104 (11)0.0218 (5)
H30.09050.64060.18010.026*
C40.15333 (17)0.8597 (4)0.12105 (12)0.0240 (5)
H40.10890.80020.07760.029*
C50.23051 (17)1.0476 (4)0.12106 (11)0.0245 (5)
H50.23631.10870.07770.029*
C60.29489 (17)1.1392 (4)0.18114 (11)0.0234 (5)
H60.34611.26280.18040.028*
C70.28490 (16)1.0474 (4)0.24591 (11)0.0191 (5)
C80.33653 (16)1.0998 (4)0.31456 (11)0.0203 (5)
C90.16786 (16)0.6343 (4)0.35090 (11)0.0187 (5)
C100.16433 (16)0.6805 (4)0.41877 (11)0.0236 (5)
H100.19660.82400.44180.028*
C110.11450 (17)0.5203 (4)0.45328 (12)0.0256 (5)
H110.11400.55270.50000.031*
C120.06547 (17)0.3130 (4)0.41987 (11)0.0265 (6)
H120.03000.20460.44320.032*
C130.06827 (17)0.2643 (4)0.35262 (12)0.0246 (5)
H130.03490.12160.32970.030*
C140.11927 (16)0.4218 (4)0.31841 (11)0.0214 (5)
H140.12140.38560.27230.026*
C150.42170 (17)1.2651 (4)0.35097 (11)0.0204 (5)
C160.48555 (17)1.2125 (4)0.41833 (11)0.0241 (5)
H160.47221.06920.44090.029*
C170.56847 (17)1.3671 (4)0.45278 (12)0.0273 (6)
H170.61131.33020.49890.033*
C180.58898 (18)1.5752 (4)0.42018 (12)0.0285 (6)
H180.64641.68030.44360.034*
C190.52636 (17)1.6294 (4)0.35396 (12)0.0281 (6)
H190.54071.77210.33160.034*
C200.44235 (17)1.4777 (4)0.31940 (12)0.0243 (5)
H200.39851.51890.27390.029*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0184 (8)0.0201 (8)0.0231 (8)−0.0025 (6)0.0062 (7)0.0010 (7)
C10.0161 (11)0.0185 (12)0.0258 (13)−0.0009 (9)0.0058 (10)−0.0030 (10)
C20.0163 (11)0.0172 (11)0.0257 (13)0.0014 (9)0.0065 (10)−0.0009 (9)
C30.0190 (12)0.0185 (11)0.0272 (13)0.0002 (9)0.0055 (10)−0.0018 (10)
C40.0213 (12)0.0256 (13)0.0248 (13)0.0016 (10)0.0059 (10)−0.0023 (10)
C50.0231 (12)0.0249 (12)0.0266 (13)0.0033 (10)0.0090 (10)0.0046 (10)
C60.0207 (12)0.0219 (12)0.0281 (13)0.0003 (10)0.0076 (10)0.0023 (10)
C70.0185 (11)0.0179 (11)0.0228 (12)0.0027 (9)0.0089 (10)0.0002 (9)
C80.0209 (12)0.0173 (12)0.0252 (13)0.0020 (9)0.0105 (10)0.0040 (9)
C90.0145 (10)0.0178 (11)0.0233 (12)0.0027 (9)0.0046 (9)0.0032 (9)
C100.0203 (12)0.0226 (12)0.0265 (13)−0.0024 (9)0.0045 (10)−0.0001 (10)
C110.0258 (12)0.0276 (13)0.0235 (12)−0.0004 (10)0.0071 (10)0.0019 (10)
C120.0254 (13)0.0249 (13)0.0308 (14)−0.0011 (10)0.0107 (11)0.0064 (11)
C130.0196 (12)0.0196 (12)0.0342 (14)0.0005 (10)0.0067 (11)0.0020 (10)
C140.0183 (11)0.0211 (12)0.0239 (12)0.0038 (9)0.0045 (10)0.0019 (10)
C150.0168 (11)0.0196 (12)0.0265 (13)0.0014 (9)0.0092 (10)−0.0031 (10)
C160.0228 (12)0.0232 (13)0.0271 (13)−0.0021 (10)0.0084 (10)−0.0038 (10)
C170.0203 (12)0.0334 (14)0.0277 (13)0.0002 (10)0.0060 (10)−0.0088 (11)
C180.0216 (12)0.0260 (14)0.0397 (15)−0.0069 (10)0.0119 (11)−0.0146 (11)
C190.0275 (13)0.0188 (13)0.0428 (16)−0.0005 (10)0.0178 (12)−0.0031 (11)
C200.0228 (12)0.0211 (12)0.0313 (13)0.0025 (10)0.0113 (10)−0.0001 (10)
Geometric parameters (Å, °) top
O1—C11.366 (2)C10—H100.9500
O1—C81.369 (2)C11—C121.384 (3)
C1—C21.373 (3)C11—H110.9500
C1—C91.449 (3)C12—C131.379 (3)
C2—C31.425 (3)C12—H120.9500
C2—C71.435 (3)C13—C141.380 (3)
C3—C41.351 (3)C13—H130.9500
C3—H30.9500C14—H140.9500
C4—C51.435 (3)C15—C161.391 (3)
C4—H40.9500C15—C201.394 (3)
C5—C61.346 (3)C16—C171.385 (3)
C5—H50.9500C16—H160.9500
C6—C71.427 (3)C17—C181.383 (3)
C6—H60.9500C17—H170.9500
C7—C81.372 (3)C18—C191.370 (3)
C8—C151.451 (3)C18—H180.9500
C9—C101.391 (3)C19—C201.384 (3)
C9—C141.399 (3)C19—H190.9500
C10—C111.384 (3)C20—H200.9500
C1—O1—C8108.91 (16)C12—C11—C10120.1 (2)
O1—C1—C2108.95 (18)C12—C11—H11120.0
O1—C1—C9115.74 (18)C10—C11—H11120.0
C2—C1—C9135.3 (2)C13—C12—C11119.8 (2)
C1—C2—C3133.7 (2)C13—C12—H12120.1
C1—C2—C7106.53 (18)C11—C12—H12120.1
C3—C2—C7119.77 (19)C12—C13—C14120.3 (2)
C4—C3—C2118.5 (2)C12—C13—H13119.8
C4—C3—H3120.8C14—C13—H13119.8
C2—C3—H3120.8C13—C14—C9120.8 (2)
C3—C4—C5121.8 (2)C13—C14—H14119.6
C3—C4—H4119.1C9—C14—H14119.6
C5—C4—H4119.1C16—C15—C20118.5 (2)
C6—C5—C4121.4 (2)C16—C15—C8120.30 (19)
C6—C5—H5119.3C20—C15—C8121.2 (2)
C4—C5—H5119.3C17—C16—C15120.6 (2)
C5—C6—C7118.8 (2)C17—C16—H16119.7
C5—C6—H6120.6C15—C16—H16119.7
C7—C6—H6120.6C18—C17—C16120.1 (2)
C8—C7—C6133.4 (2)C18—C17—H17119.9
C8—C7—C2106.96 (18)C16—C17—H17119.9
C6—C7—C2119.64 (19)C19—C18—C17119.8 (2)
O1—C8—C7108.65 (18)C19—C18—H18120.1
O1—C8—C15115.80 (18)C17—C18—H18120.1
C7—C8—C15135.5 (2)C18—C19—C20120.5 (2)
C10—C9—C14118.14 (19)C18—C19—H19119.7
C10—C9—C1121.01 (19)C20—C19—H19119.7
C14—C9—C1120.86 (19)C19—C20—C15120.4 (2)
C11—C10—C9120.9 (2)C19—C20—H20119.8
C11—C10—H10119.5C15—C20—H20119.8
C9—C10—H10119.5
C8—O1—C1—C2−0.2 (2)C2—C1—C9—C10−155.0 (2)
C8—O1—C1—C9−179.21 (16)O1—C1—C9—C14−156.91 (17)
O1—C1—C2—C3−178.8 (2)C2—C1—C9—C1424.5 (4)
C9—C1—C2—C3−0.2 (4)C14—C9—C10—C110.2 (3)
O1—C1—C2—C70.2 (2)C1—C9—C10—C11179.72 (19)
C9—C1—C2—C7178.9 (2)C9—C10—C11—C12−1.2 (3)
C1—C2—C3—C4−179.7 (2)C10—C11—C12—C131.3 (3)
C7—C2—C3—C41.4 (3)C11—C12—C13—C14−0.3 (3)
C2—C3—C4—C50.0 (3)C12—C13—C14—C9−0.7 (3)
C3—C4—C5—C6−0.4 (3)C10—C9—C14—C130.7 (3)
C4—C5—C6—C7−0.5 (3)C1—C9—C14—C13−178.76 (19)
C5—C6—C7—C8−179.9 (2)O1—C8—C15—C1623.8 (3)
C5—C6—C7—C21.8 (3)C7—C8—C15—C16−154.2 (2)
C1—C2—C7—C8−0.2 (2)O1—C8—C15—C20−156.92 (18)
C3—C2—C7—C8179.07 (19)C7—C8—C15—C2025.1 (4)
C1—C2—C7—C6178.52 (19)C20—C15—C16—C17−0.7 (3)
C3—C2—C7—C6−2.3 (3)C8—C15—C16—C17178.64 (19)
C1—O1—C8—C70.1 (2)C15—C16—C17—C18−0.4 (3)
C1—O1—C8—C15−178.40 (16)C16—C17—C18—C190.7 (3)
C6—C7—C8—O1−178.4 (2)C17—C18—C19—C200.2 (3)
C2—C7—C8—O10.0 (2)C18—C19—C20—C15−1.3 (3)
C6—C7—C8—C15−0.3 (4)C16—C15—C20—C191.5 (3)
C2—C7—C8—C15178.1 (2)C8—C15—C20—C19−177.77 (19)
O1—C1—C9—C1023.6 (3)
Table 1
Selected geometric parameters (Å, °) top
O1—C11.366 (2)C3—C41.351 (3)
O1—C81.369 (2)C4—C51.435 (3)
C1—C21.373 (3)C5—C61.346 (3)
C1—C91.449 (3)C6—C71.427 (3)
C2—C31.425 (3)C7—C81.372 (3)
C2—C71.435 (3)C8—C151.451 (3)
C1—O1—C8108.91 (16)C8—C7—C2106.96 (18)
O1—C1—C2108.95 (18)C6—C7—C2119.64 (19)
C2—C1—C9135.3 (2)O1—C8—C7108.65 (18)
C1—C2—C7106.53 (18)C7—C8—C15135.5 (2)
Acknowledgements top

The Natural Sciences and Engineering Research Council of Canada is acknowledged for Discovery Grants (RTB & PWD). The diffractometer was purchased with the help of NSERC and the University of Lethbridge. The advice of C. A. Campana of Bruker AXS is also gratefully acknowledged.

references
References top

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