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Acta Cryst. (2010). E66, o2880    [ doi:10.1107/S1600536810041565 ]

syn-Dispiro[1,3-dioxolane-2,17'-pentacyclo[12.2.1.16,9.02,13.05,10]octadecane-18',2''-[1,3]dioxolane]-7',15'-diene

R. M. Kachlan, M. C. Ruble, J. C. Timmerman, M. Etzkorn and D. S. Jones

Abstract top

The title compound, C22H28O4, is composed of a central octadecane ring and two spiro[bicyclo[2.2.1]hept[2]ene-7,2'-[1,3]dioxolane] units. This polycycle has pseudo twofold symmetry and the central cyclooctane ring has a distorted boat configuration.

Comment top

The title compound is of interest as a non-chlorinated tether unit for syn-bisquinoxaline molecular tweezers. The non-chlorinated compounds are anticipated to display higher solubility in common organic solvents, thus facilitating the quantitative investigation of host–guest chemistry in solution. The title polycyclic molecule, 3, presented here was obtained by a twofold Diels-Alder reaction of cyclooctadiene and a cyclopentadieneone derivative, 1, followed by subsequent dehalogenation (Fig. 1). Larger molecular frameworks that incorporate scaffold 2a can be found in syn-bisquinoxalines that have previously been investigated for their luminescent properties (Chou et al., 2005) and for their behavior as molecular tweezers (Etzkorn et al., 2010). Compound 3 stems from the chlorinated derivative 2a, which was separated from its anti-isomer 2b via repeated recrystallization from diethyl ether, i.e., the ether solution becomes more enriched in syn-isomer 2a. To improve the solubility of any molecular framework that is derived from scaffold 2a, we reduced the latter with sodium metal in ethanol and liquid ammonia to furnish 3 in good yield. The fully dechlorinated compound 3 did indeed show improved solubility in common organic solvents and, upon further functionalization to tweezer scaffolds, is expected to improve overall solubility.

The title molecule, 3, has pseudo 2-fold symmetry. The central cyclooctane has a distorted boat configuration (Fig. 2). The dioxalane ring (O1,C13,O2,C20,C19) has an envelope configuration with atom O2 at the flap, while ring (O3,C18,O4,C22,C21) has a half-chair configuration being twised about bond O4-C22.

A literature search revealed three related crystal structures. The first (Garcia et al., 1991a) is similar to 3, but has the anti-orientation and an open ketal structure on each of the bridgehead carbon atoms. The second (Tenbusch et al., 2010) is an octachloro derivative with the anti-orientation. The third (Garcia et al., 1991b) is an octachloro syn-structure with an open ketal arrangement on each of the bridgehead carbon atoms; this structure assumes the same distorted boat configuration as does compound 3.

Related literature top

For related structures, see: Garcia et al. (1991a,b); Tenbusch et al. (2010). For related chemistry of syn-bisquinoxalines, see: Chou et al. (2005); Etzkorn et al. (2010).

Experimental top

The synthesis of the title compound, 3, is described in Fig. 1. A mixture of cycloocatdiene (3 g, 29 mmol) and spiroketal (1) (15 g, 57 mmol) was refluxed in toluene (3 ml) for three hours. The off-white paste was filtered, washed with methylene chloride (75 ml), dried, and washed again with cold methanol (15 ml) to remove traces of the mono-Diels-Alder adduct. The remaining colorless solid (14.5 g, 83%) was composed of a mixture of 2a and 2 b in a 1:4 ratio, respectively. After repeated recrystallization from diethyl ether, the pure syn-isomer 2a was obtained as colorless platelets (3.7 g, 21%).

A solution of 2a (1 g, 1.58 mmol) and THF (20 ml) was added to a mixture of liquid ammonia (250 ml) and ethanol (1.5 ml). Pieces of sodium metal (0.8 g, 29.6 mmol) were slowly added over two hours; the reaction mixture was then stirred for an additional hour. The reaction was quenched with solid ammonium chloride, and the ammonia was allowed to evaporate. The residue was taken up in water (75 ml) and the aqueous phase was extracted with methylene chloride (4 x 50 ml) to yield 3 as light-brown crystals (0.490 g). Purification of 3 by column chromatography (cyclohexane: ethyl acetate [4:1], Rf = 0.11) afforded colorless crystals (0.439 g, 78%); Mp.>568 K. IR (KBr): ~ν = 2955, 2856 (CH2), 1649 (C═C), 1473 (CH2 bend), 1303, 1290 (C—O—C), 1243, 1224, 1084, 1046, 819, 725 cm-1; 1H NMR (CDCl3; 300 MHz):δ = 6.18 (m, 4H, H-7',-8',-15',-16'), 3.98–3.90 (m, 4H, H-4,-4"), 3.85–3.76 (m, 4H, H-5,-5"), 2.86–2.72 (m, 4H, H-2',-5',-10'-13'), 2.46–2.4 (m, 4H, H-1',-6',-9',-13'); 13C NMR (CDCl3; 75.6 MHz):δ = 133.7 (C-7',-8',-15',-16'), 124.8 (C-17',-18'), 64.8 (C-4,-4"), 64.1 (C-5,-5"), 53.6 (C-2',-5',-10',-13'), 37.4 (C-1',-6', -9',-14'), 25.3 (C-3',-4',-11',-10').

Refinement top

The H-atoms were included in calculated positions and constrained using a riding model: C—H = 0.97 Å for methylene, 0.98 Å for methine, and 0.93 Å for olefinic H-atoms, with Uiso(H) = 1.2Ueq(C).

Computing details top

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS (Enraf–Nonius, 1994); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae, et al., 2006); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. Synthesis scheme.
[Figure 2] Fig. 2. A view of the molecular structure of compound 3, with 50% probability displacement ellipsoids.
syn-Dispiro[1,3-dioxolane-2,17'-pentacyclo [12.2.1.16,9.02,13.05,\10]octadecane-18',2''-[1,3]dioxolane]-7',15'-diene top
Crystal data top
C22H28O4F(000) = 768
Mr = 356.44Dx = 1.309 Mg m−3
Monoclinic, P21/nCu Kα radiation, λ = 1.54184 Å
Hall symbol: -P 2ynCell parameters from 25 reflections
a = 11.4167 (11) Åθ = 15.3–42.6°
b = 6.7354 (7) ŵ = 0.71 mm−1
c = 24.185 (2) ÅT = 295 K
β = 103.521 (9)°Prism, colorless
V = 1808.2 (3) Å30.35 × 0.20 × 0.20 mm
Z = 4
Data collection top
Enraf–Nonius CAD-4
diffractometer		θmax = 67.5°, θmin = 3.8°
Non–profiled ω/2θ scansh = −13→0
8422 measured reflectionsk = −8→8
3248 independent reflectionsl = −28→28
2693 reflections with I > 2σ(I)3 standard reflections every 79 reflections
Rint = 0.045 intensity decay: 2%
Refinement top
Refinement on F2H-atom parameters constrained
Least-squares matrix: full w = 1/[σ2(Fo2) + (0.0414P)2 + 0.4578P]
where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.039(Δ/σ)max < 0.001
wR(F2) = 0.106Δρmax = 0.24 e Å−3
S = 1.05Δρmin = −0.19 e Å−3
3248 reflectionsExtinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
236 parametersExtinction coefficient: 0.0117 (6)
0 restraints
Crystal data top
C22H28O4V = 1808.2 (3) Å3
Mr = 356.44Z = 4
Monoclinic, P21/nCu Kα radiation
a = 11.4167 (11) ŵ = 0.71 mm−1
b = 6.7354 (7) ÅT = 295 K
c = 24.185 (2) Å0.35 × 0.20 × 0.20 mm
β = 103.521 (9)°
Data collection top
Enraf–Nonius CAD-4
diffractometer		Rint = 0.045
8422 measured reflectionsθmax = 67.5°
3248 independent reflections3 standard reflections every 79 reflections
2693 reflections with I > 2σ(I) intensity decay: 2%
Refinement top
R[F2 > 2σ(F2)] = 0.039H-atom parameters constrained
wR(F2) = 0.106Δρmax = 0.24 e Å−3
S = 1.05Δρmin = −0.19 e Å−3
3248 reflectionsAbsolute structure: ?
236 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
Special details top

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.49270 (9)0.9050 (2)−0.18532 (5)0.0544 (4)
O20.56491 (10)1.0106 (2)−0.25975 (4)0.0545 (4)
O30.58431 (10)0.6331 (2)0.05326 (5)0.0597 (4)
O40.68575 (10)0.66022 (19)0.14523 (4)0.0534 (4)
C10.68153 (12)1.0631 (2)−0.10437 (6)0.0351 (4)
C20.72139 (12)0.8459 (2)−0.11521 (6)0.0360 (4)
C30.84705 (13)0.7735 (2)−0.08405 (6)0.0419 (5)
C40.87904 (12)0.7689 (2)−0.01860 (6)0.0413 (5)
C50.77291 (12)0.7502 (2)0.00928 (6)0.0348 (4)
C60.70386 (12)0.9466 (2)0.01680 (6)0.0362 (4)
C70.75302 (14)1.1468 (2)0.00213 (6)0.0423 (5)
C80.76760 (13)1.1811 (2)−0.05857 (6)0.0399 (5)
C90.65659 (13)1.1569 (2)−0.16468 (6)0.0416 (5)
C100.80267 (14)0.9816 (3)−0.19355 (7)0.0535 (6)
C110.77312 (14)1.1653 (3)−0.18360 (6)0.0509 (6)
C120.70828 (13)0.8439 (3)−0.18100 (6)0.0445 (5)
C130.59793 (13)0.9774 (3)−0.20041 (6)0.0430 (5)
C140.80596 (13)0.6639 (2)0.07062 (6)0.0408 (5)
C150.89060 (14)0.8058 (3)0.10824 (6)0.0484 (5)
C160.82908 (15)0.9654 (3)0.11512 (6)0.0500 (5)
C170.70117 (14)0.9382 (2)0.08140 (6)0.0428 (5)
C180.68912 (13)0.7153 (2)0.08916 (6)0.0419 (5)
C190.39160 (16)0.9459 (4)−0.23040 (8)0.0676 (7)
C200.44134 (16)1.0615 (3)−0.27232 (8)0.0645 (7)
C210.53301 (14)0.4946 (3)0.08401 (7)0.0488 (5)
C220.62046 (16)0.4807 (3)0.14092 (8)0.0564 (6)
H10.604401.05420−0.093300.0420*
H20.661800.75390−0.106400.0430*
H3A0.905900.85690−0.096000.0500*
H3B0.857300.64010−0.097300.0500*
H4A0.933200.65830−0.006200.0500*
H4B0.922500.88970−0.004900.0500*
H50.714600.65960−0.014100.0420*
H60.620900.93370−0.005700.0430*
H7C0.700301.249800.010500.0510*
H7D0.831201.166200.027800.0510*
H8C0.756101.32130−0.067400.0480*
H8D0.849501.14760−0.059900.0480*
H90.609001.27950−0.169700.0500*
H100.870300.94370−0.206200.0640*
H110.816401.27930−0.187600.0610*
H120.703400.71250−0.198800.0530*
H140.829800.523800.073800.0490*
H150.972100.784500.123900.0580*
H160.859201.075800.137000.0600*
H170.640401.021400.092800.0510*
H19G0.332101.02310−0.217000.0810*
H19H0.354500.82380−0.247200.0810*
H20E0.402101.02430−0.311000.0770*
H20F0.430901.20290−0.267600.0770*
H21A0.523500.366700.065100.0590*
H21B0.454800.539800.088200.0590*
H22C0.578400.469400.171300.0680*
H22D0.673400.367300.142400.0680*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0405 (6)0.0779 (9)0.0398 (6)−0.0133 (5)−0.0009 (4)0.0090 (6)
O20.0556 (6)0.0750 (9)0.0288 (5)0.0006 (6)0.0017 (5)0.0037 (5)
O30.0506 (6)0.0824 (9)0.0389 (6)−0.0342 (6)−0.0039 (5)0.0101 (6)
O40.0637 (7)0.0621 (8)0.0314 (6)−0.0194 (6)0.0048 (5)0.0056 (5)
C10.0343 (7)0.0386 (8)0.0312 (7)−0.0020 (6)0.0055 (5)0.0016 (6)
C20.0367 (7)0.0384 (8)0.0319 (7)−0.0039 (6)0.0061 (5)0.0006 (6)
C30.0398 (7)0.0443 (9)0.0424 (8)0.0042 (6)0.0113 (6)0.0030 (7)
C40.0342 (7)0.0452 (9)0.0412 (8)0.0014 (6)0.0021 (6)0.0035 (7)
C50.0355 (7)0.0340 (8)0.0311 (7)−0.0065 (6)0.0000 (5)−0.0010 (6)
C60.0367 (7)0.0375 (8)0.0315 (7)−0.0043 (6)0.0021 (5)−0.0010 (6)
C70.0535 (8)0.0346 (8)0.0363 (8)−0.0053 (6)0.0055 (6)−0.0029 (6)
C80.0460 (8)0.0331 (8)0.0382 (8)−0.0057 (6)0.0051 (6)0.0018 (6)
C90.0464 (8)0.0421 (9)0.0339 (8)0.0000 (6)0.0046 (6)0.0049 (7)
C100.0456 (8)0.0806 (13)0.0365 (8)0.0042 (8)0.0143 (7)0.0091 (9)
C110.0487 (9)0.0662 (12)0.0355 (8)−0.0129 (8)0.0052 (7)0.0122 (8)
C120.0518 (9)0.0470 (10)0.0338 (8)0.0015 (7)0.0084 (6)−0.0043 (7)
C130.0442 (8)0.0543 (10)0.0283 (7)−0.0047 (7)0.0041 (6)0.0033 (7)
C140.0444 (8)0.0380 (8)0.0346 (8)−0.0049 (6)−0.0017 (6)0.0030 (6)
C150.0410 (8)0.0607 (11)0.0358 (8)−0.0132 (7)−0.0063 (6)0.0049 (8)
C160.0623 (10)0.0507 (10)0.0313 (8)−0.0204 (8)−0.0006 (7)−0.0055 (7)
C170.0493 (8)0.0454 (9)0.0328 (8)−0.0034 (7)0.0079 (6)−0.0024 (7)
C180.0427 (8)0.0517 (9)0.0265 (7)−0.0136 (7)−0.0017 (6)0.0020 (7)
C190.0475 (9)0.0934 (16)0.0524 (11)−0.0054 (10)−0.0072 (8)0.0120 (10)
C200.0559 (10)0.0827 (15)0.0455 (10)0.0009 (9)−0.0074 (8)0.0076 (10)
C210.0448 (8)0.0518 (10)0.0501 (9)−0.0117 (7)0.0118 (7)0.0008 (8)
C220.0569 (10)0.0599 (11)0.0510 (10)−0.0133 (8)0.0099 (8)0.0112 (9)
Geometric parameters (Å, °) top
O1—C131.4210 (19)C19—C201.492 (3)
O1—C191.417 (2)C21—C221.503 (3)
O2—C131.4138 (17)C1—H10.9800
O2—C201.414 (2)C2—H20.9800
O3—C181.4165 (19)C3—H3A0.9700
O3—C211.404 (2)C3—H3B0.9700
O4—C181.4151 (17)C4—H4A0.9700
O4—C221.411 (2)C4—H4B0.9700
C1—C21.5722 (19)C5—H50.9800
C1—C81.522 (2)C6—H60.9800
C1—C91.554 (2)C7—H7C0.9700
C2—C31.536 (2)C7—H7D0.9700
C2—C121.563 (2)C8—H8C0.9700
C3—C41.539 (2)C8—H8D0.9700
C4—C51.523 (2)C9—H90.9800
C5—C61.5721 (19)C10—H100.9300
C5—C141.555 (2)C11—H110.9300
C6—C71.534 (2)C12—H120.9800
C6—C171.571 (2)C14—H140.9800
C7—C81.533 (2)C15—H150.9300
C9—C111.506 (2)C16—H160.9300
C9—C131.545 (2)C17—H170.9800
C10—C111.319 (3)C19—H19G0.9700
C10—C121.506 (2)C19—H19H0.9700
C12—C131.530 (2)C20—H20E0.9700
C14—C151.505 (2)C20—H20F0.9700
C14—C181.543 (2)C21—H21A0.9700
C15—C161.316 (3)C21—H21B0.9700
C16—C171.508 (2)C22—H22C0.9700
C17—C181.5232 (19)C22—H22D0.9700
C13—O1—C19108.73 (13)H3A—C3—H3B107.00
C13—O2—C20105.81 (12)C3—C4—H4A108.00
C18—O3—C21109.41 (12)C3—C4—H4B108.00
C18—O4—C22106.62 (12)C5—C4—H4A108.00
C2—C1—C8116.40 (12)C5—C4—H4B108.00
C2—C1—C9102.62 (11)H4A—C4—H4B107.00
C8—C1—C9114.61 (11)C4—C5—H5107.00
C1—C2—C3119.16 (11)C6—C5—H5107.00
C1—C2—C12102.43 (12)C14—C5—H5107.00
C3—C2—C12110.67 (12)C5—C6—H6108.00
C2—C3—C4118.74 (12)C7—C6—H6108.00
C3—C4—C5115.77 (12)C17—C6—H6108.00
C4—C5—C6116.99 (11)C6—C7—H7C108.00
C4—C5—C14114.35 (12)C6—C7—H7D108.00
C6—C5—C14102.74 (11)C8—C7—H7C108.00
C5—C6—C7119.51 (12)C8—C7—H7D108.00
C5—C6—C17102.22 (11)H7C—C7—H7D107.00
C7—C6—C17110.80 (11)C1—C8—H8C108.00
C6—C7—C8118.79 (12)C1—C8—H8D109.00
C1—C8—C7114.97 (12)C7—C8—H8C109.00
C1—C9—C11108.64 (12)C7—C8—H8D109.00
C1—C9—C1399.63 (11)H8C—C8—H8D108.00
C11—C9—C1399.07 (12)C1—C9—H9116.00
C11—C10—C12108.38 (15)C11—C9—H9116.00
C9—C11—C10107.58 (15)C13—C9—H9116.00
C2—C12—C10107.29 (13)C11—C10—H10126.00
C2—C12—C13100.56 (12)C12—C10—H10126.00
C10—C12—C1398.80 (15)C9—C11—H11126.00
O1—C13—O2105.91 (12)C10—C11—H11126.00
O1—C13—C9114.01 (13)C2—C12—H12116.00
O1—C13—C12113.87 (15)C10—C12—H12116.00
O2—C13—C9114.95 (15)C13—C12—H12116.00
O2—C13—C12114.18 (13)C5—C14—H14116.00
C9—C13—C1294.02 (12)C15—C14—H14116.00
C5—C14—C15108.52 (12)C18—C14—H14116.00
C5—C14—C1899.20 (11)C14—C15—H15126.00
C15—C14—C1899.11 (11)C16—C15—H15126.00
C14—C15—C16108.01 (14)C15—C16—H16126.00
C15—C16—C17108.08 (15)C17—C16—H16126.00
C6—C17—C16106.97 (12)C6—C17—H17116.00
C6—C17—C18100.45 (11)C16—C17—H17116.00
C16—C17—C1899.04 (13)C18—C17—H17116.00
O3—C18—O4106.06 (12)O1—C19—H19G111.00
O3—C18—C14113.46 (12)O1—C19—H19H111.00
O3—C18—C17113.42 (12)C20—C19—H19G111.00
O4—C18—C14116.03 (12)C20—C19—H19H111.00
O4—C18—C17113.58 (12)H19G—C19—H19H109.00
C14—C18—C1794.37 (11)O2—C20—H20E111.00
O1—C19—C20104.67 (15)O2—C20—H20F111.00
O2—C20—C19104.27 (15)C19—C20—H20E111.00
O3—C21—C22104.87 (14)C19—C20—H20F111.00
O4—C22—C21103.92 (15)H20E—C20—H20F109.00
C2—C1—H1108.00O3—C21—H21A111.00
C8—C1—H1108.00O3—C21—H21B111.00
C9—C1—H1108.00C22—C21—H21A111.00
C1—C2—H2108.00C22—C21—H21B111.00
C3—C2—H2108.00H21A—C21—H21B109.00
C12—C2—H2108.00O4—C22—H22C111.00
C2—C3—H3A108.00O4—C22—H22D111.00
C2—C3—H3B108.00C21—C22—H22C111.00
C4—C3—H3A108.00C21—C22—H22D111.00
C4—C3—H3B108.00H22C—C22—H22D109.00
C19—O1—C13—O2−16.0 (2)C5—C6—C7—C859.18 (18)
C19—O1—C13—C9111.44 (16)C17—C6—C7—C8177.55 (13)
C19—O1—C13—C12−142.24 (16)C5—C6—C17—C1668.32 (14)
C13—O1—C19—C20−4.0 (2)C5—C6—C17—C18−34.58 (14)
C20—O2—C13—O130.52 (18)C7—C6—C17—C16−60.10 (16)
C20—O2—C13—C9−96.31 (16)C7—C6—C17—C18−162.99 (12)
C20—O2—C13—C12156.61 (15)C6—C7—C8—C127.76 (19)
C13—O2—C20—C19−32.55 (19)C1—C9—C11—C1070.25 (15)
C21—O3—C18—O4−13.28 (16)C13—C9—C11—C10−33.20 (15)
C21—O3—C18—C14115.23 (14)C1—C9—C13—O158.67 (16)
C21—O3—C18—C17−138.60 (14)C1—C9—C13—O2−178.77 (12)
C18—O3—C21—C22−5.34 (18)C1—C9—C13—C12−59.72 (12)
C22—O4—C18—O327.73 (16)C11—C9—C13—O1169.48 (13)
C22—O4—C18—C14−99.25 (15)C11—C9—C13—O2−67.95 (15)
C22—O4—C18—C17152.96 (14)C11—C9—C13—C1251.10 (13)
C18—O4—C22—C21−30.43 (17)C12—C10—C11—C9−0.71 (17)
C8—C1—C2—C3−5.80 (18)C11—C10—C12—C2−69.33 (17)
C8—C1—C2—C12−128.27 (13)C11—C10—C12—C1334.70 (16)
C9—C1—C2—C3120.19 (13)C2—C12—C13—O1−60.17 (16)
C9—C1—C2—C12−2.28 (14)C2—C12—C13—O2178.01 (14)
C2—C1—C8—C7−85.21 (15)C2—C12—C13—C958.33 (13)
C9—C1—C8—C7155.07 (12)C10—C12—C13—O1−169.73 (13)
C2—C1—C9—C11−64.62 (14)C10—C12—C13—O268.45 (17)
C2—C1—C9—C1338.44 (13)C10—C12—C13—C9−51.23 (13)
C8—C1—C9—C1162.51 (16)C5—C14—C15—C1670.53 (16)
C8—C1—C9—C13165.58 (12)C18—C14—C15—C16−32.44 (15)
C1—C2—C3—C460.36 (17)C5—C14—C18—O357.69 (14)
C12—C2—C3—C4178.65 (13)C5—C14—C18—O4−179.12 (11)
C1—C2—C12—C1067.63 (15)C5—C14—C18—C17−60.19 (12)
C1—C2—C12—C13−35.14 (15)C15—C14—C18—O3168.29 (12)
C3—C2—C12—C10−60.42 (17)C15—C14—C18—O4−68.52 (15)
C3—C2—C12—C13−163.20 (12)C15—C14—C18—C1750.41 (12)
C2—C3—C4—C525.27 (17)C14—C15—C16—C17−1.07 (17)
C3—C4—C5—C6−82.83 (15)C15—C16—C17—C6−69.25 (16)
C3—C4—C5—C14157.02 (11)C15—C16—C17—C1834.67 (16)
C4—C5—C6—C7−6.45 (18)C6—C17—C18—O3−59.54 (15)
C4—C5—C6—C17−129.14 (13)C6—C17—C18—O4179.28 (12)
C14—C5—C6—C7119.68 (13)C6—C17—C18—C1458.38 (12)
C14—C5—C6—C17−3.01 (13)C16—C17—C18—O3−168.80 (12)
C4—C5—C14—C1563.85 (15)C16—C17—C18—O470.02 (15)
C4—C5—C14—C18166.77 (11)C16—C17—C18—C14−50.88 (12)
C6—C5—C14—C15−63.96 (14)O1—C19—C20—O222.4 (2)
C6—C5—C14—C1838.95 (12)O3—C21—C22—O421.88 (18)
Acknowledgements top

This work was supported in part by funds provided by the University of North Carolina at Charlotte. Support for Research Experience for Undergraduates (REU) participant RMK was provided by the National Science Foundation, award number CHE-0851797. Many helpful discussions with T. Blake Monroe are gratefully acknowledged.

references
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