(1R,4S)-(-)-3,3-Ethyl­enedi­oxy-1,7,7-trimethyl­bicyclo­[2.2.1]heptan-2-one

The title compound, C₁₂H₁₈O₃, was synthesized from camphorquinone and ethyl­ene glycol, with the stereochemistry assumed to be unchanged during the reaction. The mol­ecule exhibits several C-C bond lengths that differ significantly from the expected value of 1.54 Å.

Key indicators

• Single-crystal X-ray study
• T = 223 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.039
• wR factor = 0.112
• Data-to-parameter ratio = 11.4

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........          4

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           27.99
           From the CIF: _reflns_number_total               1589
           Count of symmetry unique reflns         1588
           Completeness (_total/calc)            100.06%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         1
           Fraction of Friedel pairs measured     0.001
           Are heavy atom types Z>Si present         no
PLAT791_ALERT_1_G Confirm the Absolute Configuration of C1     = .          R
PLAT791_ALERT_1_G Confirm the Absolute Configuration of C4     = .          S

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

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 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
   2 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The title compound was synthesized as an intermediate in an ongoing investigation into the synthesis of novel camphor-derived ligands for applications in asymmetric catalysis. The compound was first synthesized in 1968 (Fleming & Woodward, 1968) but the crystal structure has not been reported until now.

The reaction of camphorquinone with ethylene glycol is known to give consistently a 3:1 ratio of the title compound with (1R,4S)-(-)-1,7,7-Trimethyl-2,2-ethylenedioxybicyclo-[2.2.1] heptan-3-one (Lachance et al., 2005). The crystal analysed contains only the title molecule, with no indication of the other in the structure.

The molecule (Fig. 1) exhibits some C—C bonds that differ significantly from the expected C—C bond length of 1.54 Å (Table 1). The shortest bond is 1.502 (3) Å between C2' and C3'. The camphor skeleton also contains several bonds that are both shorter (e.g. 1.520 (3) Å for C1—C2) and longer (1.562 (3) Å for C1—C7) than the expected value. There are numerous short C—H···O and H···H contacts in the structure (Fig. 2): atom O1 interacts with the hydrogen of C4 of one molecule while C2' and C3' interact with O1 of a different neighbouring molecule (Fig. 3). The exo hydrogen on C2' interacts with the hydrogen on C5 of a neighbouring molecule and O3' interacts with one of the hydrogen atoms on C10 of a different molecule.

Related literature

For related literature, see: Fleming & Woodward (1968); Lachance et al. (2005).

S2. Experimental

A solution of camphorquinone (1 mol eq.), ethylene glycol (1 mol eq.) and p-toluenesulphonic acid (catalytic amount) in benzene was refluxed in a Dean-Stark apparatus with water removed azeotropically. When TLC indicated the absence of the starting quinone, the reaction mixture was allowed to cool gradually to ambient temperature and washed sequentially with 10% aqueous NaHCO₃ (100 ml), water (100 ml) and brine (100 ml). The organic layer was dried (Na₂SO₄) and filtered, and the filtrate was concentrated in vacuo. The residue was purified via column chromatography on silica gel by eluting with EtOAc-hexane (5:95). The title compound was obtained in 80% yield as a colourless oil which crystallized on standing at room temperature overnight.

S3. Refinement

All H atoms were visible in difference Fourier maps but were positioned geometrically with C—H = 0.97–0.99 Å and allowed to ride during refinement with U_iso(H) = 1.2U_eq(C). In the absence of significant anomalous scattering effects, Friedel pairs have been merged as equivalent data.

Computing details

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

Figures

	Fig. 1. The molecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level for non-H atoms
	Fig. 2. Packing diagram viewed along the a axis. H atoms have been omitted.
	Fig. 3. Some intermolecular interactions involving O1.

(1R,4S)-(-)-1,7,7-Trimethyl-3,3-ethylenedioxybicyclo- [2.2.1]heptan-2-one

Crystal data

C12H18O3	F(000) = 456
Mr = 210.26	Dx = 1.232 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 1017 reflections
a = 7.2169 (8) Å	θ = 2.8–28.3°
b = 11.8122 (14) Å	µ = 0.09 mm^−1
c = 13.2986 (15) Å	T = 223 K
V = 1133.7 (2) Å^3	Block, colourless
Z = 4	0.40 × 0.33 × 0.32 mm

Data collection

Bruker SMART 1K CCD diffractometer	1469 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.039
Graphite monochromator	θmax = 28.0°, θmin = 2.3°
φ and ω scans	h = −9→9
8262 measured reflections	k = −15→12
1589 independent reflections	l = −17→17

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.039	H-atom parameters constrained
wR(F^2) = 0.112	w = 1/[σ^2(Fo^2) + (0.068P)^2 + 0.1693P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max = 0.003
1589 reflections	Δρmax = 0.20 e Å^−3
139 parameters	Δρmin = −0.18 e Å^−3
0 restraints	Absolute structure: In the absence of significant anomalous scattering effects, Friedel pairs have been merged as equivalent data.
Primary atom site location: structure-invariant direct methods

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
C1	0.8229 (2)	0.77338 (13)	0.19449 (13)	0.0323 (3)
C2	0.9155 (2)	0.76727 (14)	0.29698 (13)	0.0329 (3)
C2'	1.2832 (3)	0.8104 (2)	0.41436 (16)	0.0573 (6)
H2'A	1.4154	0.8226	0.4272	0.069*
H2'B	1.2461	0.7377	0.4436	0.069*
C3'	1.1691 (4)	0.9056 (2)	0.45635 (16)	0.0567 (6)
H3'A	1.1030	0.8809	0.5169	0.068*
H3'B	1.2484	0.9700	0.4739	0.068*
C3	1.0655 (2)	0.86179 (14)	0.29824 (13)	0.0333 (4)
C4	1.0357 (3)	0.91661 (15)	0.19549 (14)	0.0401 (4)
H4	1.0829	0.9950	0.1899	0.048*
C5	1.1148 (3)	0.83379 (19)	0.11663 (14)	0.0459 (5)
H5A	1.2399	0.8091	0.1349	0.055*
H5B	1.1181	0.8685	0.0497	0.055*
C6	0.9764 (3)	0.73396 (16)	0.11993 (13)	0.0369 (4)
H6A	1.0369	0.6649	0.1442	0.044*
H6B	0.9242	0.7194	0.0531	0.044*
C7	0.8224 (3)	0.90443 (15)	0.17886 (16)	0.0427 (4)
C8	0.7617 (5)	0.9401 (2)	0.0724 (2)	0.0728 (9)
H8A	0.6289	0.9301	0.0656	0.109*
H8B	0.8250	0.8937	0.0231	0.109*
H8C	0.7929	1.0191	0.0616	0.109*
C9	0.7022 (3)	0.9669 (2)	0.2549 (2)	0.0650 (7)
H9A	0.7214	1.0478	0.2480	0.097*
H9B	0.7358	0.9434	0.3223	0.097*
H9C	0.5729	0.9492	0.2427	0.097*
C10	0.6429 (3)	0.7079 (2)	0.18675 (19)	0.0533 (5)
H10A	0.6666	0.6282	0.1990	0.080*
H10B	0.5912	0.7174	0.1200	0.080*
H10C	0.5559	0.7361	0.2364	0.080*
O1	0.8851 (3)	0.70281 (13)	0.36499 (10)	0.0561 (4)
O1'	1.24417 (18)	0.81368 (14)	0.30867 (11)	0.0475 (4)
O4'	1.0419 (2)	0.93654 (12)	0.38033 (11)	0.0476 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0302 (7)	0.0312 (7)	0.0356 (8)	−0.0006 (6)	−0.0002 (7)	−0.0049 (7)
C2	0.0372 (8)	0.0313 (7)	0.0301 (7)	0.0029 (6)	0.0059 (7)	−0.0033 (6)
C2'	0.0568 (12)	0.0747 (15)	0.0403 (10)	0.0140 (12)	−0.0162 (10)	−0.0062 (10)
C3'	0.0703 (15)	0.0578 (12)	0.0421 (10)	0.0059 (12)	−0.0205 (11)	−0.0124 (9)
C3	0.0336 (8)	0.0341 (8)	0.0322 (8)	0.0018 (6)	−0.0031 (7)	−0.0029 (7)
C4	0.0474 (10)	0.0336 (8)	0.0393 (9)	−0.0089 (8)	−0.0073 (8)	0.0063 (8)
C5	0.0470 (10)	0.0597 (11)	0.0308 (8)	−0.0130 (10)	0.0050 (8)	0.0043 (8)
C6	0.0399 (8)	0.0416 (9)	0.0291 (7)	−0.0003 (7)	0.0033 (7)	−0.0038 (7)
C7	0.0473 (10)	0.0319 (8)	0.0490 (10)	0.0069 (8)	−0.0173 (9)	−0.0017 (8)
C8	0.098 (2)	0.0494 (12)	0.0709 (16)	0.0102 (14)	−0.0461 (16)	0.0083 (12)
C9	0.0532 (13)	0.0539 (12)	0.0878 (18)	0.0232 (11)	−0.0220 (13)	−0.0287 (13)
C10	0.0382 (9)	0.0609 (12)	0.0607 (13)	−0.0116 (9)	0.0042 (10)	−0.0184 (11)
O1	0.0811 (11)	0.0519 (8)	0.0352 (7)	−0.0124 (8)	0.0127 (7)	0.0070 (6)
O1'	0.0347 (6)	0.0703 (10)	0.0375 (7)	0.0123 (7)	−0.0063 (6)	−0.0071 (7)
O4'	0.0559 (8)	0.0447 (7)	0.0421 (7)	0.0105 (6)	−0.0136 (7)	−0.0155 (6)

Geometric parameters (Å, º)

C1—C10	1.515 (2)	C4—H4	0.990
C1—C2	1.520 (2)	C5—C6	1.546 (3)
C1—C6	1.558 (2)	C5—H5A	0.980
C1—C7	1.562 (2)	C5—H5B	0.980
C2—O1	1.202 (2)	C6—H6A	0.980
C2—C3	1.555 (2)	C6—H6B	0.980
C2'—O1'	1.434 (3)	C7—C9	1.522 (3)
C2'—C3'	1.502 (3)	C7—C8	1.540 (3)
C2'—H2'A	0.980	C8—H8A	0.970
C2'—H2'B	0.980	C8—H8B	0.970
C3'—O4'	1.413 (3)	C8—H8C	0.970
C3'—H3'A	0.980	C9—H9A	0.970
C3'—H3'B	0.980	C9—H9B	0.970
C3—O4'	1.414 (2)	C9—H9C	0.970
C3—O1'	1.416 (2)	C10—H10A	0.970
C3—C4	1.527 (3)	C10—H10B	0.970
C4—C5	1.544 (3)	C10—H10C	0.970
C4—C7	1.562 (3)
C10—C1—C2	114.44 (16)	C4—C5—H5B	111.2
C10—C1—C6	114.42 (15)	C6—C5—H5B	111.2
C2—C1—C6	104.10 (13)	H5A—C5—H5B	109.1
C10—C1—C7	119.68 (16)	C5—C6—C1	104.45 (14)
C2—C1—C7	99.64 (13)	C5—C6—H6A	110.9
C6—C1—C7	102.31 (15)	C1—C6—H6A	110.9
O1—C2—C1	128.63 (17)	C5—C6—H6B	110.9
O1—C2—C3	125.01 (17)	C1—C6—H6B	110.9
C1—C2—C3	106.36 (14)	H6A—C6—H6B	108.9
O1'—C2'—C3'	103.67 (18)	C9—C7—C8	108.39 (19)
O1'—C2'—H2'A	111.0	C9—C7—C4	115.01 (17)
C3'—C2'—H2'A	111.0	C8—C7—C4	112.7 (2)
O1'—C2'—H2'B	111.0	C9—C7—C1	113.15 (19)
C3'—C2'—H2'B	111.0	C8—C7—C1	113.22 (17)
H2'A—C2'—H2'B	109.0	C4—C7—C1	94.02 (14)
O4'—C3'—C2'	106.49 (16)	C7—C8—H8A	109.5
O4'—C3'—H3'A	110.4	C7—C8—H8B	109.5
C2'—C3'—H3'A	110.4	H8A—C8—H8B	109.5
O4'—C3'—H3'B	110.4	C7—C8—H8C	109.5
C2'—C3'—H3'B	110.4	H8A—C8—H8C	109.5
H3'A—C3'—H3'B	108.6	H8B—C8—H8C	109.5
O4'—C3—O1'	106.51 (14)	C7—C9—H9A	109.5
O4'—C3—C4	114.15 (14)	C7—C9—H9B	109.5
O1'—C3—C4	112.71 (16)	H9A—C9—H9B	109.5
O4'—C3—C2	111.90 (15)	C7—C9—H9C	109.5
O1'—C3—C2	110.28 (14)	H9A—C9—H9C	109.5
C4—C3—C2	101.35 (14)	H9B—C9—H9C	109.5
C3—C4—C5	106.68 (15)	C1—C10—H10A	109.5
C3—C4—C7	103.09 (16)	C1—C10—H10B	109.5
C5—C4—C7	102.12 (15)	H10A—C10—H10B	109.5
C3—C4—H4	114.5	C1—C10—H10C	109.5
C5—C4—H4	114.5	H10A—C10—H10C	109.5
C7—C4—H4	114.5	H10B—C10—H10C	109.5
C4—C5—C6	103.02 (15)	C3—O1'—C2'	106.62 (15)
C4—C5—H5A	111.2	C3'—O4'—C3	108.23 (15)
C6—C5—H5A	111.2
C10—C1—C2—O1	15.0 (3)	C7—C1—C6—C5	30.94 (18)
C6—C1—C2—O1	−110.6 (2)	C3—C4—C7—C9	62.7 (2)
C7—C1—C2—O1	144.0 (2)	C5—C4—C7—C9	173.32 (18)
C10—C1—C2—C3	−165.94 (15)	C3—C4—C7—C8	−172.37 (16)
C6—C1—C2—C3	68.44 (16)	C5—C4—C7—C8	−61.8 (2)
C7—C1—C2—C3	−36.97 (17)	C3—C4—C7—C1	−55.13 (17)
O1'—C2'—C3'—O4'	14.3 (3)	C5—C4—C7—C1	55.44 (17)
O1—C2—C3—O4'	−56.3 (2)	C10—C1—C7—C9	60.8 (2)
C1—C2—C3—O4'	124.53 (15)	C2—C1—C7—C9	−64.69 (19)
O1—C2—C3—O1'	62.0 (2)	C6—C1—C7—C9	−171.54 (15)
C1—C2—C3—O1'	−117.10 (15)	C10—C1—C7—C8	−63.1 (3)
O1—C2—C3—C4	−178.37 (18)	C2—C1—C7—C8	171.5 (2)
C1—C2—C3—C4	2.50 (17)	C6—C1—C7—C8	64.6 (2)
O4'—C3—C4—C5	165.71 (15)	C10—C1—C7—C4	−179.83 (17)
O1'—C3—C4—C5	44.03 (19)	C2—C1—C7—C4	54.72 (16)
C2—C3—C4—C5	−73.83 (17)	C6—C1—C7—C4	−52.14 (16)
O4'—C3—C4—C7	−87.15 (18)	O4'—C3—O1'—C2'	29.8 (2)
O1'—C3—C4—C7	151.17 (15)	C4—C3—O1'—C2'	155.70 (17)
C2—C3—C4—C7	33.31 (17)	C2—C3—O1'—C2'	−91.8 (2)
C3—C4—C5—C6	69.78 (18)	C3'—C2'—O1'—C3	−26.8 (2)
C7—C4—C5—C6	−38.04 (19)	C2'—C3'—O4'—C3	3.4 (3)
C4—C5—C6—C1	4.21 (19)	O1'—C3—O4'—C3'	−20.3 (2)
C10—C1—C6—C5	161.92 (17)	C4—C3—O4'—C3'	−145.36 (18)
C2—C1—C6—C5	−72.45 (17)	C2—C3—O4'—C3'	100.3 (2)