Penta­cyclo­[5.4.0.0^2,6.0^3,10.0^5,9]undecane-8,11-dione ethyl­ene acetal

The title mol­ecule, C₁₃H₁₄O₃, is a chiral mol­ecule which exhibits C-C single-bond lengths that deviate from the expected value. Both enanti­omers are present in the crystal structure.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.062
• wR factor = 0.172
• Data-to-parameter ratio = 16.5

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT094_ALERT_2_C Ratio of Maximum / Minimum Residual Density ....       2.19

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   1 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion

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S1. Comment

The structure of the title compound, (I), was determined as part of an ongoing investigation of the chemical reactivity and crystal structures of polycyclic pentacycloundecane (PCU) cage derivatives. Previous studies indicated that PCU cages and derivatives often display C—C bond lengths that deviate from the expected value of 1.54 Å (Flippen-Anderson et al., 1991; Linden et al., 2005; Kruger et al., 2005). It is typically found that bonds involving atoms C4, C8 and C11 are shorter than normal, and that the C9—C10 bond is longer than expected.

The title compound is unsymmetrically substituted at the mouth of the cage, with a ketone substituent at atom C8 and a ketal substituent at atom C11 (Fig. 1). The asymmetric unit is comprised of one chiral molecule, with eight molecules (four of each enantiomer) in the unit cell (Fig. 2). This compound exhibits the shortening and elongation of certain C—C single bonds, as reported for related PCU derivatives (Table 1). The longest C—C single bond is the C9—C10 bond [1.581 (3) Å], with the C3—C10, C6—C7, C5—C9, C2—C6, C5—C6 and C1—C7 bonds also exceeding the expected value of 1.54 Å. The bonds involving the bridgehead atom C4 are shorter than expected; C3—C4 and C4—C5 exhibit values of 1.525 (3) and 1.521 (3) Å, respectively. The shortest bond is the C7—C8 bond [1.509 (3) Å], with the C10—C11, C8—C9 and C12—C13 bonds also exhibiting short C—C single-bond lengths. The unsymmetrical substitution at the mouth of the cage results in corresponding bonds in the molecule displaying different bond lengths, for example, the C1—C11 bond [1.536 (3) Å] is longer than the corresponding C7—C8 bond.

The five-membered rings, C2–C6 and C3–C5/C9/C10, are in the envelope conformation (envelope on C4), and the acetal ring, O1/C11/O2/C13/C12, also adopts the envelope conformation (envelope on C1). The rings, C1–C3/C10/C11 and C5–C9, are twisted on C10—C11 and C8—C9, respectively.

S2. Experimental

The synthetic procedure reported by Dekker & Oliver (1979) was followed to prepare the title compound, (I). In this procedure, a mixture of pentacycloundecane dione (Cookson et al., 1964) (183 g, 1.05 mol), ethylene glycol (81.2 ml, 1.45 mol) and p-toluenesulfonic acid (6.11 g, 3.21 × 10⁻² mol) in benzene (600 ml) was refluxed (Dean–Stark trap) with stirring for 4 d. The reaction mixture was cooled to room temperature and slowly poured into ice-cold 10% (v/v) aqueous Na₂CO₃ (1000 ml), extracted with dichloromethane (3 × 500 ml) and the combined extracts were dried over anhydrous Na₂SO₄. Evaporation of the solvent followed by recrystallization of the crude residue yielded the mono-acetal as colourless crystals (170.04 g, 74%). IR (KBr) max 1747 cm⁻¹ (C═O); ¹H NMR (CDCl₃, 300 MHz): δ 1.51–1.84 (2H, methylene bridge protons), 2.35–2.92 (8H, methine protons), 3.78–3.91 (4H, ketal protons); ¹³C NMR (CDCl₃, 75 MHz): δ 36.35 (d), 38.74 (t), 41.33–53.02 (d), 64.52–65.71 (t, ketal carbons), 113.92 (s), 215.14 (s). The MS spectra was identical to an authentic sample.

S3. Refinement

All H atoms were placed in calculated positions, with methylene C—H distances of 0.99 Å and methine C—H distances of 1.00 Å, and refined using a riding model, with U_iso(H) = 1.2U_eq(parent atom)·The maximum and minimum electron-density peaks were 1.07 Å from atom C3 and 0.59 Å from atom C2, respectively.

Computing details

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Bruker, 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997) and Mercury (Bruno et al., 2002); software used to prepare material for publication: WinGX (Farrugia, 1999) and PLATON (Spek, 2003).

Figures

	Fig. 1. The molecular structure of (I), showing the atom-numbering scheme and displacement ellipsoids drawn at the 50% probability level (ORTEP-3; Farrugia, 1997).
	Fig. 2. Packing diagram (Mercury; Bruno et al., 2002) of (I), viewed along the b axis.

Pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane-8–11-dione ethylene acetal

Crystal data

C13H14O3	F(000) = 928
Mr = 218.24	Dx = 1.455 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 3784 reflections
a = 24.7387 (10) Å	θ = 3.2–28.2°
b = 6.6340 (3) Å	µ = 0.10 mm^−1
c = 12.7631 (5) Å	T = 173 K
β = 107.914 (2)°	Plate, colourless
V = 1993.09 (14) Å^3	0.37 × 0.22 × 0.11 mm
Z = 8

Data collection

Bruker SMART CCD area-detector diffractometer	1984 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.026
Graphite monochromator	θmax = 28.0°, θmin = 1.7°
ϕ and ω scans	h = −32→32
10114 measured reflections	k = −8→8
2394 independent reflections	l = −16→11

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.062	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.172	H-atom parameters constrained
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0769P)^2 + 5.0276P] where P = (Fo^2 + 2Fc^2)/3
2394 reflections	(Δ/σ)max < 0.001
145 parameters	Δρmax = 0.58 e Å^−3
0 restraints	Δρmin = −0.27 e Å^−3

Special details

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.37708 (7)	0.2153 (3)	0.49972 (13)	0.0337 (4)
O2	0.42588 (7)	0.1357 (2)	0.67591 (12)	0.0281 (4)
O3	0.43301 (7)	0.3342 (3)	0.90396 (13)	0.0346 (4)
C11	0.38698 (9)	0.2763 (3)	0.61014 (17)	0.0246 (4)
C10	0.33147 (9)	0.2869 (4)	0.6361 (2)	0.0312 (5)
H10	0.3082	0.1615	0.6157	0.037*
C3	0.30253 (9)	0.4749 (4)	0.56919 (19)	0.0333 (5)
H3	0.2814	0.4493	0.4900	0.040*
C4	0.26712 (10)	0.5617 (5)	0.6374 (2)	0.0409 (6)
H4A	0.2516	0.6967	0.6117	0.049*
H4B	0.2362	0.4701	0.6413	0.049*
C5	0.31574 (10)	0.5697 (4)	0.74473 (19)	0.0337 (5)
H5	0.3058	0.6245	0.8095	0.040*
C9	0.34154 (9)	0.3535 (4)	0.75962 (19)	0.0307 (5)
H9	0.3241	0.2607	0.8019	0.037*
C8	0.40359 (9)	0.3992 (3)	0.81707 (17)	0.0244 (4)
C7	0.41823 (9)	0.5648 (3)	0.74936 (17)	0.0266 (5)
H7	0.4539	0.6419	0.7848	0.032*
C6	0.36223 (10)	0.6893 (3)	0.71134 (19)	0.0302 (5)
H6	0.3650	0.8374	0.7267	0.036*
C2	0.35290 (9)	0.6213 (3)	0.59021 (18)	0.0287 (5)
H2	0.3505	0.7292	0.5342	0.034*
C1	0.40826 (9)	0.4949 (3)	0.62745 (16)	0.0249 (4)
H1	0.4385	0.5323	0.5939	0.030*
C12	0.43072 (11)	0.1416 (4)	0.49494 (19)	0.0342 (5)
H12A	0.4548	0.2528	0.4828	0.041*
H12B	0.4256	0.0403	0.4358	0.041*
C13	0.45626 (9)	0.0469 (3)	0.60825 (18)	0.0282 (5)
H13A	0.4511	−0.1012	0.6045	0.034*
H13B	0.4973	0.0775	0.6377	0.034*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0349 (9)	0.0390 (9)	0.0226 (8)	0.0069 (7)	0.0020 (6)	−0.0081 (7)
O2	0.0320 (8)	0.0282 (8)	0.0247 (8)	0.0087 (6)	0.0096 (6)	0.0036 (6)
O3	0.0423 (9)	0.0408 (9)	0.0201 (8)	0.0147 (7)	0.0088 (7)	0.0052 (7)
C11	0.0259 (10)	0.0260 (10)	0.0195 (10)	0.0023 (8)	0.0037 (8)	−0.0017 (8)
C10	0.0232 (10)	0.0337 (12)	0.0354 (12)	−0.0033 (9)	0.0071 (9)	−0.0049 (9)
C3	0.0226 (9)	0.0450 (13)	0.0279 (11)	0.0070 (9)	0.0013 (8)	−0.0035 (10)
C4	0.0258 (11)	0.0516 (15)	0.0449 (14)	0.0077 (10)	0.0100 (10)	0.0023 (12)
C5	0.0309 (11)	0.0434 (13)	0.0297 (11)	0.0119 (10)	0.0135 (9)	0.0027 (10)
C9	0.0266 (10)	0.0355 (12)	0.0339 (12)	−0.0008 (9)	0.0150 (9)	0.0033 (9)
C8	0.0284 (10)	0.0257 (10)	0.0208 (9)	0.0050 (8)	0.0103 (8)	−0.0002 (8)
C7	0.0321 (11)	0.0258 (10)	0.0215 (10)	−0.0036 (8)	0.0073 (8)	−0.0013 (8)
C6	0.0365 (12)	0.0253 (10)	0.0272 (11)	0.0045 (9)	0.0072 (9)	0.0004 (8)
C2	0.0320 (11)	0.0288 (11)	0.0246 (10)	0.0043 (9)	0.0075 (9)	0.0049 (8)
C1	0.0278 (10)	0.0264 (10)	0.0210 (9)	−0.0013 (8)	0.0083 (8)	0.0017 (8)
C12	0.0408 (13)	0.0349 (12)	0.0279 (11)	0.0063 (10)	0.0121 (10)	−0.0051 (9)
C13	0.0297 (10)	0.0260 (10)	0.0302 (11)	0.0016 (8)	0.0110 (9)	−0.0019 (8)

Geometric parameters (Å, º)

O1—C11	1.413 (2)	C5—H5	1.0000
O1—C12	1.433 (3)	C9—C8	1.514 (3)
O2—C11	1.416 (2)	C9—H9	1.0000
O2—C13	1.434 (3)	C8—C7	1.509 (3)
O3—C8	1.204 (3)	C7—C6	1.557 (3)
C11—C10	1.510 (3)	C7—C1	1.569 (3)
C11—C1	1.536 (3)	C7—H7	1.0000
C10—C3	1.556 (3)	C6—C2	1.558 (3)
C10—C9	1.581 (3)	C6—H6	1.0000
C10—H10	1.0000	C2—C1	1.550 (3)
C3—C4	1.525 (3)	C2—H2	1.0000
C3—C2	1.537 (3)	C1—H1	1.0000
C3—H3	1.0000	C12—C13	1.524 (3)
C4—C5	1.521 (3)	C12—H12A	0.9900
C4—H4A	0.9900	C12—H12B	0.9900
C4—H4B	0.9900	C13—H13A	0.9900
C5—C9	1.557 (3)	C13—H13B	0.9900
C5—C6	1.560 (3)
C11—O1—C12	105.16 (16)	O3—C8—C9	127.6 (2)
C11—O2—C13	107.47 (15)	C7—C8—C9	104.74 (17)
O1—C11—O2	106.27 (16)	C8—C7—C6	102.55 (17)
O1—C11—C10	110.00 (17)	C8—C7—C1	111.14 (17)
O2—C11—C10	113.50 (18)	C6—C7—C1	89.67 (16)
O1—C11—C1	111.14 (18)	C8—C7—H7	116.6
O2—C11—C1	113.36 (17)	C6—C7—H7	116.6
C10—C11—C1	102.65 (17)	C1—C7—H7	116.6
C11—C10—C3	102.27 (18)	C7—C6—C2	90.09 (16)
C11—C10—C9	110.91 (17)	C7—C6—C5	107.77 (18)
C3—C10—C9	103.20 (18)	C2—C6—C5	103.13 (18)
C11—C10—H10	113.2	C7—C6—H6	117.3
C3—C10—H10	113.2	C2—C6—H6	117.3
C9—C10—H10	113.2	C5—C6—H6	117.3
C4—C3—C2	103.8 (2)	C3—C2—C1	107.72 (18)
C4—C3—C10	103.7 (2)	C3—C2—C6	102.75 (18)
C2—C3—C10	101.49 (17)	C1—C2—C6	90.29 (16)
C4—C3—H3	115.3	C3—C2—H2	117.4
C2—C3—H3	115.3	C1—C2—H2	117.4
C10—C3—H3	115.3	C6—C2—H2	117.4
C5—C4—C3	95.36 (17)	C11—C1—C2	103.59 (16)
C5—C4—H4A	112.7	C11—C1—C7	111.36 (17)
C3—C4—H4A	112.7	C2—C1—C7	89.94 (16)
C5—C4—H4B	112.7	C11—C1—H1	116.2
C3—C4—H4B	112.7	C2—C1—H1	116.2
H4A—C4—H4B	110.2	C7—C1—H1	116.2
C4—C5—C9	105.0 (2)	O1—C12—C13	102.66 (18)
C4—C5—C6	102.53 (19)	O1—C12—H12A	111.2
C9—C5—C6	101.11 (17)	C13—C12—H12A	111.2
C4—C5—H5	115.4	O1—C12—H12B	111.2
C9—C5—H5	115.4	C13—C12—H12B	111.2
C6—C5—H5	115.4	H12A—C12—H12B	109.1
C8—C9—C5	101.02 (18)	O2—C13—C12	105.12 (17)
C8—C9—C10	111.35 (17)	O2—C13—H13A	110.7
C5—C9—C10	101.69 (18)	C12—C13—H13A	110.7
C8—C9—H9	113.8	O2—C13—H13B	110.7
C5—C9—H9	113.8	C12—C13—H13B	110.7
C10—C9—H9	113.8	H13A—C13—H13B	108.8
O3—C8—C7	127.2 (2)
C12—O1—C11—O2	−36.8 (2)	C9—C8—C7—C1	−59.5 (2)
C12—O1—C11—C10	−160.01 (19)	C8—C7—C6—C2	−112.19 (17)
C12—O1—C11—C1	87.0 (2)	C1—C7—C6—C2	−0.59 (16)
C13—O2—C11—O1	23.5 (2)	C8—C7—C6—C5	−8.4 (2)
C13—O2—C11—C10	144.49 (18)	C1—C7—C6—C5	103.24 (18)
C13—O2—C11—C1	−98.9 (2)	C4—C5—C6—C7	−128.41 (19)
O1—C11—C10—C3	−70.9 (2)	C9—C5—C6—C7	−20.1 (2)
O2—C11—C10—C3	170.16 (17)	C4—C5—C6—C2	−34.0 (2)
C1—C11—C10—C3	47.4 (2)	C9—C5—C6—C2	74.3 (2)
O1—C11—C10—C9	179.60 (18)	C4—C3—C2—C1	127.62 (19)
O2—C11—C10—C9	60.7 (2)	C10—C3—C2—C1	20.2 (2)
C1—C11—C10—C9	−62.0 (2)	C4—C3—C2—C6	33.2 (2)
C11—C10—C3—C4	−148.97 (19)	C10—C3—C2—C6	−74.3 (2)
C9—C10—C3—C4	−33.7 (2)	C7—C6—C2—C3	108.85 (18)
C11—C10—C3—C2	−41.5 (2)	C5—C6—C2—C3	0.6 (2)
C9—C10—C3—C2	73.8 (2)	C7—C6—C2—C1	0.59 (16)
C2—C3—C4—C5	−53.4 (2)	C5—C6—C2—C1	−107.69 (17)
C10—C3—C4—C5	52.3 (2)	O1—C11—C1—C2	83.6 (2)
C3—C4—C5—C9	−52.3 (2)	O2—C11—C1—C2	−156.80 (17)
C3—C4—C5—C6	53.0 (2)	C10—C11—C1—C2	−34.0 (2)
C4—C5—C9—C8	147.18 (19)	O1—C11—C1—C7	178.94 (16)
C6—C5—C9—C8	40.8 (2)	O2—C11—C1—C7	−61.4 (2)
C4—C5—C9—C10	32.4 (2)	C10—C11—C1—C7	61.4 (2)
C6—C5—C9—C10	−73.94 (19)	C3—C2—C1—C11	7.9 (2)
C11—C10—C9—C8	2.9 (3)	C6—C2—C1—C11	111.40 (17)
C3—C10—C9—C8	−105.9 (2)	C3—C2—C1—C7	−104.09 (18)
C11—C10—C9—C5	109.8 (2)	C6—C2—C1—C7	−0.59 (16)
C3—C10—C9—C5	0.9 (2)	C8—C7—C1—C11	−0.7 (2)
C5—C9—C8—O3	124.0 (2)	C6—C7—C1—C11	−104.00 (18)
C10—C9—C8—O3	−128.7 (2)	C8—C7—C1—C2	103.93 (19)
C5—C9—C8—C7	−48.6 (2)	C6—C7—C1—C2	0.59 (16)
C10—C9—C8—C7	58.7 (2)	C11—O1—C12—C13	34.1 (2)
O3—C8—C7—C6	−137.6 (2)	C11—O2—C13—C12	−1.9 (2)
C9—C8—C7—C6	35.1 (2)	O1—C12—C13—O2	−19.7 (2)
O3—C8—C7—C1	127.9 (2)