cis-9,10-Bis(bromo­meth­yl)-1,4,5,8-tetra­oxadeca­lin

The title compound, C₈H₁₂Br₂O₄, is a bicyclic ketal in which the two six-membered rings are cis to one another and assume a double-chair conformation. A crystallographic twofold axis bisects the molecule.

Related literature

A determination of this structure has been previously attempted (Fuchs et al., 1972), but the authors did not publish or deposit any atomic coordinates. The same paper gives detailed information for a related structure which has H atoms in place of the bromo­methyl groups of the title compound. A search of the Cambridge Structural Database [Version 5.29; (Allen, 2002); CONQUEST (Bruno et al., 2002)] did not yield any other closely related structures. See also: Fuchs (1970).

Experimental

Crystal data

• C₈H₁₂Br₂O₄

• M_r = 332

• Orthorhombic, P n c a

• a = 8.5314 (14) Å

• b = 9.5295 (7) Å

• c = 13.1348 (13) Å

• V = 1067.9 (2) ų

• Z = 4

• Cu Kα radiation

• μ = 9.57 mm⁻¹

• T = 295 (2) K

• 0.5 × 0.3 × 0.15 mm

Data collection

• Enra–Nonius CAD4 diffractometer

• Absorption correction: multi-scan (Blessing, 1995) T_min = 0.039, T_max = 0.486 (expected range = 0.019–0.238)

• 4584 measured reflections

• 968 independent reflections

• 915 reflections with I > 2σ(I)

• R_int = 0.063

• 3 standard reflections every 67 reflections intensity decay: 3%

Refinement

• R[F² > 2σ(F²)] = 0.036

• wR(F²) = 0.101

• S = 1.10

• 968 reflections

• 65 parameters

• H-atom parameters constrained

• Δρ_max = 0.45 e Å⁻³

• Δρ_min = −0.43 e Å⁻³

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

Supporting information

S1. Comment

The title compound is a bicyclic ketal in which the two six-membered rings are cis to one another and assume a doublechair conformation. A crystallographic twofold axis relates one of the fused rings to the other.

A determination of this structure has been previously attempted (Fuchs et al., 1972), but the authors did not publish or deposit any atomic coordinates. They halted their study after three cycles of isotropic refinement because "···the accuracy of the atomic parameters was relatively low." They did present the Fourier map resulting from the isotropic refinement, and it shows an overall structure in agreement with that presented here. The space group and unit-cell parameters which they obtained are also in agreement with those of the present study.

The authors of this prior study attributed the "relatively low" accuracy of their atomic parameters to the domination of the scattering by the Br atoms. Our present study suggests that the importance of absorption corrections probably played a part as well.

The same paper (Fuchs et al., 1972) gives detailed structural information for a related compound which has hydrogen atoms in place of the bromomethyl groups of the title compound. That structure is similar to the one reported here, in that the two six-membered rings are cis to one another and assume a doublechair conformation.

Related literature

A determination of this structure has been previously attempted (Fuchs et al., 1972), but the authors did not publish or deposit any atomic coordinates. The same paper gives detailed information for a related structure which has H atoms in place of the bromomethyl groups of the title compound. A search of the Cambridge Structural Database [Version 5.29; (Allen, 2002); CONQUEST (Bruno et al., 2002)] did not yield any other closely related structures. See also: Fuchs (1970).

S2. Experimental

The title compound 3 has been described as the major reaction product in the acid-catalyzed reaction of diketone 1 with ethylene glycol (Fuchs, 1970). Since the dispiro derivative 2 was needed for one of our projects, literature procedures (Fuchs et al., 1972) were followed to yield a product mixture from which only the bicyclic title compound 3 could be isolated, as colorless crystals. The NMR data obtained for 3 deviated from the published data (Fuchs, 1970), and the X-ray structure was therefore determined to ultimately confirm the formation of 3.

¹H NMR (CDCl₃, 500 MHz): δ = 4.14 (m_c, 4H), 3.75 (m_c, 4H), 3.69 (s, 4H) p.p.m..

¹³C NMR (CDCl₃, 125.7 MHz): δ = 92.3, 61.1, 31.6 p.p.m..

S3. Refinement

All H atoms were constrained using a riding model. C — H bond lengths were fixed at 0.97 Å, with U_iso(H) = 1.2 U_eq. (C).

Computing details

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: DIRDIF (Beurskens et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. View of the title compound, 3, with 50% probability displacement ellipsoids. [Symmetry code: (') -x + 1/2, -y + 1, z.]
	Fig. 2. Schematic representations of compounds 1–4.

cis-9,10-Bis(bromomethyl)-1,4,5,8-tetraoxadecalin

Crystal data

C8H12Br2O4	F(000) = 648
Mr = 332	Dx = 2.065 Mg m^−3
Orthorhombic, Pnca	Cu Kα radiation, λ = 1.54184 Å
Hall symbol: -P 2a 2n	Cell parameters from 23 reflections
a = 8.5314 (14) Å	θ = 9.7–23.5°
b = 9.5295 (7) Å	µ = 9.57 mm^−1
c = 13.1348 (13) Å	T = 295 K
V = 1067.9 (2) Å^3	Irregular, colorless
Z = 4	0.5 × 0.3 × 0.15 mm

Data collection

Enra–Nonius CAD4 diffractometer	915 reflections with I > 2σ(I)
Radiation source: normal-focus sealed tube	Rint = 0.063
Graphite monochromator	θmax = 67.6°, θmin = 5.7°
Non–profiled ω/2θ scans	h = −10→10
Absorption correction: multi-scan (Blessing, 1995)	k = −11→0
Tmin = 0.039, Tmax = 0.486	l = −15→15
4584 measured reflections	3 standard reflections every 67 reflections
968 independent reflections	intensity decay: 3%

Refinement

Refinement on F^2	H-atom parameters constrained
Least-squares matrix: full	w = 1/[σ^2(Fo^2) + (0.0428P)^2 + 0.7055P] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.036	(Δ/σ)max < 0.001
wR(F^2) = 0.101	Δρmax = 0.45 e Å^−3
S = 1.10	Δρmin = −0.43 e Å^−3
968 reflections	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
65 parameters	Extinction coefficient: 0.0045 (3)
0 restraints

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.

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

	x	y	z	Uiso*/Ueq
Br	0.12607 (5)	0.16873 (4)	0.02778 (4)	0.0766 (3)
O2	0.0390 (2)	0.4700 (2)	0.13501 (17)	0.0603 (6)
O1	0.2328 (3)	0.3492 (2)	0.21071 (17)	0.0605 (6)
C4	0.2152 (4)	0.3552 (3)	0.0252 (2)	0.0588 (8)
H4A	0.3256	0.3483	0.0083	0.071*
H4B	0.1644	0.4092	−0.028	0.071*
C3	0.0090 (4)	0.5542 (4)	0.2241 (3)	0.0672 (9)
H3A	0.0354	0.5012	0.2848	0.081*
H3B	−0.1015	0.5779	0.2273	0.081*
C1	0.1982 (3)	0.4327 (3)	0.1255 (2)	0.0545 (7)
C2	0.3958 (4)	0.3150 (4)	0.2203 (3)	0.0680 (10)
H2A	0.4284	0.2583	0.1628	0.082*
H2B	0.4125	0.2609	0.2819	0.082*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br	0.0951 (5)	0.0623 (4)	0.0725 (4)	−0.00632 (17)	−0.00192 (18)	−0.00707 (17)
O2	0.0530 (11)	0.0674 (14)	0.0606 (12)	0.0026 (10)	0.0035 (10)	−0.0047 (11)
O1	0.0656 (13)	0.0620 (13)	0.0539 (12)	0.0008 (10)	−0.0008 (11)	0.0060 (10)
C4	0.0597 (18)	0.0570 (18)	0.060 (2)	0.0007 (14)	0.0019 (14)	−0.0019 (14)
C3	0.0648 (19)	0.073 (2)	0.064 (2)	0.0056 (16)	0.0107 (17)	−0.0070 (17)
C1	0.0510 (15)	0.0600 (19)	0.0525 (17)	0.0049 (13)	0.0015 (13)	−0.0006 (13)
C2	0.072 (2)	0.069 (2)	0.063 (2)	0.0096 (16)	−0.0108 (17)	0.0074 (17)

Geometric parameters (Å, º)

Br—C4	1.933 (3)	C4—H4B	0.97
O2—C1	1.409 (4)	C3—C2^i	1.489 (5)
O2—C3	1.442 (4)	C3—H3A	0.97
O1—C1	1.404 (4)	C3—H3B	0.97
O1—C2	1.434 (4)	C1—C1^i	1.558 (6)
C4—C1	1.518 (4)	C2—H2A	0.97
C4—H4A	0.97	C2—H2B	0.97
C1—O2—C3	112.5 (2)	H3A—C3—H3B	108.2
C1—O1—C2	113.7 (3)	O1—C1—O2	105.9 (2)
C1—C4—Br	113.2 (2)	O1—C1—C4	113.3 (3)
C1—C4—H4A	108.9	O2—C1—C4	107.0 (3)
Br—C4—H4A	108.9	O1—C1—C1^i	110.3 (2)
C1—C4—H4B	108.9	O2—C1—C1^i	109.8 (3)
Br—C4—H4B	108.9	C4—C1—C1^i	110.3 (2)
H4A—C4—H4B	107.7	O1—C2—C3^i	110.0 (3)
O2—C3—C2^i	110.0 (3)	O1—C2—H2A	109.7
O2—C3—H3A	109.7	C3^i—C2—H2A	109.7
C2^i—C3—H3A	109.7	O1—C2—H2B	109.7
O2—C3—H3B	109.7	C3^i—C2—H2B	109.7
C2^i—C3—H3B	109.7	H2A—C2—H2B	108.2

Symmetry code: (i) −x+1/2, −y+1, z.