(1RS,4SR)-3-Dichloro­methyl­ene-1,4-dimethyl-2-oxabicyclo­[2.2.2]oct-5-ene

Tyrrell, A.J.; Feast, G.C.; Robertson, J.

doi:10.1107/S1600536808017248

organic compounds

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ISSN: 2056-9890

Volume 64| Part 7| July 2008| Page o1261

doi:10.1107/S1600536808017248

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(1RS,4SR)-3-Dichloromethylene-1,4-dimethyl-2-oxabicyclo[2.2.2]oct-5-ene

Andrew J. Tyrrell,^a ^* George C. Feast ^a and Jeremy Robertson ^a

^aDepartment of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, England
^*Correspondence e-mail: andrew.tyrrell@chem.ox.ac.uk

(Received 28 May 2008; accepted 8 June 2008; online 13 June 2008)

X-ray crystallography was used to confirm the structure of the enantio-enriched title compound, C₁₀H₁₂Cl₂O, a bicylic enol ether. A bridged boat-like structure is adopted and the dichloromethylene C atom is positioned significantly removed from the core bicyclic unit. In the crystal structure, molecules pack to form sheets approximately perpendicular to the a and c axes.

Related literature

For related literature, see: Yamabe et al. (1996 ); Machiguchi et al. (1999 ); Khanjin et al. (1999 ); Ussing et al. (2006 ); Robertson & Fowler (2006 ).

Experimental

Crystal data

C₁₀H₁₂Cl₂O
M_r = 219.11
Monoclinic, P 2₁ /c
a = 9.3365 (1) Å
b = 9.6327 (2) Å
c = 11.4259 (2) Å
β = 92.7347 (11)°
V = 1026.43 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.59 mm⁻¹
T = 150 K
0.44 × 0.32 × 0.18 mm

Data collection

Nonius KappaCCD diffractometer
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997 ) T_min = 0.83, T_max = 0.90
4320 measured reflections
2321 independent reflections
2094 reflections with I > 2σ(I)
R_int = 0.021

Refinement

R[F² > 2σ(F²)] = 0.034
wR(F²) = 0.093
S = 1.01
2321 reflections
118 parameters
2 restraints
H-atom parameters constrained
Δρ_max = 0.36 e Å⁻³
Δρ_min = −0.38 e Å⁻³

Data collection: COLLECT (Nonius, 2001 ); cell refinement: DENZO/SCALEPACK (Otwinowski & Minor, 1997); data reduction: Görbitz (1999 ) and DENZO/SCALEPACK; program(s) used to solve structure: SIR92 (Altomare et al., 1994 ); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003 ); molecular graphics: CAMERON (Watkin et al., 1996 ); software used to prepare material for publication: CRYSTALS.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808017248/lh2637sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808017248/lh2637Isup2.hkl

checkCIF report

Comment top

The reaction between dienes and ketenes to produce cyclobutanones was long considered to be a textbook example of a [2 + 2] cycloaddition that could be understood in terms of a π2_s + π2_aWoodward–Hoffmann formalism. More recently, evidence has been presented for a stepwise hetero-Diels–Alder/Claisen rearrangement pathway (Yamabe et al., 1996) and it was reported that the periselectivity of these cycloadditions is responsive to the nature of the diene (Machiguchi et al., 1999). The situation is, however, more complex and a combined theoretical and experimental study of the reaction of cyclopentadiene with either dichloro- or diphenylketene revealed that both [4 + 2] and [2 + 2] adducts may be produced directly through parallel reaction pathways traversing a bifurcating energy surface (Ussing et al. 2006). Our studies sought to address certain mechanistic aspects of the Claisen rearrangement of bicyclic enol ethers structurally analogous to those produced in diene/ketene [4 + 2] cycloadditions (Robertson & Fowler, 2006); within this study, although crystals were obtained as a racemate, the title compound was prepared in an enantioenriched form in order to determine if access to non-racemic cyclobutanones could be achieved.

The relationship between computed distances of reacting termini and activation energies has been discussed for structurally similar Claisen precursors in the context of the mechanism of chorismate mutase (Khanjin et al., 1999). The molecular stucture (Fig. 1) shows the dichloromethylene carbon to be significantly removed from the carbon at C5 (3.5523 Å) and yet the title compound can be induced to undergo the Claisen rearrangement under mild thermal conditions to yield (1RS, 6SR)-8,8-dichloro-3,6-dimethylbicyclo[4.2.0]oct-3-en-7-one. Also of note are the sheets of molecules which form approximatedly perpendicular to the a- and c-axes as shown in Fig. 2 and Fig. 3.

Related literature top

For related literature, see: Yamabe et al. (1996), Machiguchi et al. (1999), Khanjin et al. (1999), Ussing et al. (2006) and Robertson & Fowler (2006).

Experimental top

The title compound was crystallized by concentration of a sample dissolved in petroleum ether. [α]_D²⁵-36.1 (CHCl₃, c = 1.0).

Computing details top

Data collection: COLLECT (Nonius, 2001); cell refinement: DENZO/SCALEPACK (Otwinowski & Minor, 1997); data reduction: Görbitz (1999) and DENZO/SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS (Betteridge et al., 2003).

Figures top

	Fig. 1. The title compound with displacement ellipsoids drawn at the 50% probability level. H atoms are shown as spheres of arbitary radius.
	Fig. 2. The title compound viewed along the a-axis with H atoms omitted.
	Fig. 3. The title compound viewed along the b-axis with H atoms omitted.

(1RS,4SR)-3-Dichloromethylene-1,4-dimethyl-2- oxabicyclo[2.2.2]oct-5-ene top

Crystal data top

C₁₀H₁₂Cl₂O	F(000) = 456
M_r = 219.11	D_x = 1.418 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 15784 reflections
a = 9.3365 (1) Å	θ = 5–27°
b = 9.6327 (2) Å	µ = 0.59 mm⁻¹
c = 11.4259 (2) Å	T = 150 K
β = 92.7347 (11)°	Prism, colourless
V = 1026.43 (3) Å³	0.44 × 0.32 × 0.18 mm
Z = 4

Data collection top

Nonius KappaCCD diffractometer	2094 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.021
ω scans	θ_max = 27.4°, θ_min = 5.1°
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997)	h = −12→12
T_min = 0.83, T_max = 0.90	k = −12→12
4320 measured reflections	l = −14→14
2321 independent reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.034	H-atom parameters constrained
wR(F²) = 0.093	Method = Modified Sheldrick w = 1/[σ²(F²) + (0.05P)² + 0.71P], where P = [max(F_o²,0) + 2F_c²]/3
S = 1.01	(Δ/σ)_max = 0.001
2321 reflections	Δρ_max = 0.36 e Å⁻³
118 parameters	Δρ_min = −0.38 e Å⁻³
2 restraints

Crystal data top

C₁₀H₁₂Cl₂O	V = 1026.43 (3) Å³
M_r = 219.11	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 9.3365 (1) Å	µ = 0.59 mm⁻¹
b = 9.6327 (2) Å	T = 150 K
c = 11.4259 (2) Å	0.44 × 0.32 × 0.18 mm
β = 92.7347 (11)°

Data collection top

Nonius KappaCCD diffractometer	2321 independent reflections
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997)	2094 reflections with I > 2σ(I)
T_min = 0.83, T_max = 0.90	R_int = 0.021
4320 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.034	2 restraints
wR(F²) = 0.093	H-atom parameters constrained
S = 1.01	Δρ_max = 0.36 e Å⁻³
2321 reflections	Δρ_min = −0.38 e Å⁻³
118 parameters

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.02322 (16)	0.72676 (17)	0.56170 (14)	0.0234
O2	0.12271 (11)	0.62312 (12)	0.61475 (10)	0.0217
C3	0.26458 (15)	0.64956 (16)	0.59821 (13)	0.0192
C4	0.28716 (17)	0.77747 (17)	0.52291 (14)	0.0230
C5	0.21390 (19)	0.89526 (18)	0.58719 (15)	0.0293
C6	0.07027 (19)	0.86685 (17)	0.60962 (15)	0.0274
C7	0.04601 (18)	0.72396 (18)	0.43089 (14)	0.0280
C8	0.19575 (18)	0.75082 (18)	0.40893 (14)	0.0267
C9	−0.12456 (17)	0.6806 (2)	0.59357 (17)	0.0326
C10	0.44060 (19)	0.8143 (2)	0.49372 (17)	0.0339
C11	0.35800 (16)	0.56064 (17)	0.64983 (14)	0.0215
Cl12	0.29697 (4)	0.42007 (4)	0.72783 (4)	0.0295
Cl13	0.54194 (4)	0.56859 (5)	0.64989 (4)	0.0320
H51	0.2631	0.9775	0.6123	0.0403*
H61	0.0073	0.9265	0.6509	0.0362*
H71	−0.0214	0.7925	0.3907	0.0397*
H72	0.0158	0.6344	0.3998	0.0386*
H81	0.1990	0.8293	0.3587	0.0379*
H82	0.2347	0.6712	0.3675	0.0381*
H91	−0.1917	0.7492	0.5652	0.0477*
H92	−0.1261	0.6724	0.6804	0.0498*
H93	−0.1529	0.5941	0.5590	0.0483*
H101	0.4319	0.8976	0.4440	0.0529*
H102	0.5032	0.8374	0.5608	0.0543*
H103	0.4864	0.7409	0.4472	0.0531*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0213 (7)	0.0229 (7)	0.0254 (8)	0.0045 (6)	−0.0044 (6)	−0.0009 (6)
O2	0.0175 (5)	0.0225 (6)	0.0251 (5)	0.0016 (4)	0.0005 (4)	0.0041 (4)
C3	0.0188 (7)	0.0205 (7)	0.0183 (7)	−0.0023 (5)	0.0005 (5)	−0.0019 (6)
C4	0.0257 (7)	0.0220 (7)	0.0209 (7)	−0.0043 (6)	−0.0022 (5)	0.0018 (6)
C5	0.0373 (8)	0.0221 (8)	0.0275 (8)	0.0009 (7)	−0.0073 (7)	−0.0031 (7)
C6	0.0339 (8)	0.0229 (8)	0.0251 (8)	0.0055 (7)	−0.0030 (6)	−0.0032 (6)
C7	0.0347 (8)	0.0264 (8)	0.0223 (8)	0.0014 (7)	−0.0067 (6)	−0.0013 (6)
C8	0.0352 (8)	0.0268 (8)	0.0178 (7)	−0.0025 (7)	−0.0026 (6)	0.0010 (6)
C9	0.0212 (8)	0.0328 (9)	0.0435 (10)	0.0028 (7)	−0.0005 (7)	−0.0031 (8)
C10	0.0309 (9)	0.0345 (10)	0.0360 (9)	−0.0126 (7)	−0.0013 (7)	0.0072 (8)
C11	0.0189 (7)	0.0234 (7)	0.0222 (7)	−0.0011 (6)	0.0001 (5)	0.0004 (6)
Cl12	0.0292 (2)	0.0261 (2)	0.0329 (2)	−0.00012 (15)	−0.00257 (16)	0.01006 (16)
Cl13	0.0183 (2)	0.0372 (3)	0.0401 (3)	0.00107 (15)	−0.00273 (16)	0.00256 (18)

Geometric parameters (Å, º) top

C1—O2	1.4741 (18)	C7—C8	1.455 (2)
C1—C6	1.514 (2)	C7—H71	1.008
C1—C7	1.520 (2)	C7—H72	0.970
C1—C9	1.511 (2)	C8—H81	0.950
O2—C3	1.3707 (17)	C8—H82	0.980
C3—C4	1.523 (2)	C9—H91	0.957
C3—C11	1.339 (2)	C9—H92	0.996
C4—C5	1.531 (2)	C9—H93	0.954
C4—C8	1.544 (2)	C10—H101	0.985
C4—C10	1.528 (2)	C10—H102	0.968
C5—C6	1.404 (3)	C10—H103	0.993
C5—H51	0.953	C11—Cl12	1.7324 (16)
C6—H61	0.962	C11—Cl13	1.7190 (15)

O2—C1—C6	106.78 (12)	C1—C7—H72	108.9
O2—C1—C7	106.10 (12)	C8—C7—H72	111.1
C6—C1—C7	108.65 (14)	H71—C7—H72	104.6
O2—C1—C9	105.44 (13)	C4—C8—C7	112.39 (13)
C6—C1—C9	115.34 (14)	C4—C8—H81	110.2
C7—C1—C9	113.84 (14)	C7—C8—H81	107.7
C1—O2—C3	114.30 (12)	C4—C8—H82	109.5
O2—C3—C4	112.89 (12)	C7—C8—H82	109.0
O2—C3—C11	115.71 (13)	H81—C8—H82	107.9
C4—C3—C11	131.40 (14)	C1—C9—H91	107.8
C3—C4—C5	104.57 (13)	C1—C9—H92	108.7
C3—C4—C8	104.84 (12)	H91—C9—H92	110.5
C5—C4—C8	106.63 (13)	C1—C9—H93	113.3
C3—C4—C10	117.88 (14)	H91—C9—H93	107.4
C5—C4—C10	112.19 (14)	H92—C9—H93	109.1
C8—C4—C10	109.92 (13)	C4—C10—H101	105.3
C4—C5—C6	113.31 (14)	C4—C10—H102	114.7
C4—C5—H51	122.7	H101—C10—H102	107.4
C6—C5—H51	123.9	C4—C10—H103	112.5
C1—C6—C5	111.77 (14)	H101—C10—H103	107.3
C1—C6—H61	122.4	H102—C10—H103	109.2
C5—C6—H61	125.8	C3—C11—Cl12	120.21 (12)
C1—C7—C8	110.31 (13)	C3—C11—Cl13	126.97 (12)
C1—C7—H71	108.8	Cl12—C11—Cl13	112.82 (9)
C8—C7—H71	112.9

Experimental details

Crystal data
Chemical formula	C₁₀H₁₂Cl₂O
M_r	219.11
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	150
a, b, c (Å)	9.3365 (1), 9.6327 (2), 11.4259 (2)
β (°)	92.7347 (11)
V (Å³)	1026.43 (3)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.59
Crystal size (mm)	0.44 × 0.32 × 0.18

Data collection
Diffractometer	Nonius KappaCCD diffractometer
Absorption correction	Multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997)
T_min, T_max	0.83, 0.90
No. of measured, independent and observed [I > 2σ(I)] reflections	4320, 2321, 2094
R_int	0.021
(sin θ/λ)_max (Å⁻¹)	0.648

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.034, 0.093, 1.01
No. of reflections	2321
No. of parameters	118
No. of restraints	2
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.36, −0.38

Computer programs: COLLECT (Nonius, 2001), Görbitz (1999) and DENZO/SCALEPACK (Otwinowski & Minor, 1997), SIR92 (Altomare et al., 1994), CRYSTALS (Betteridge et al., 2003), CAMERON (Watkin et al., 1996).

Acknowledgements

The authors thank the Oxford Chemical Crystallography Service for use of instrumentation and Dr Amber L. Thompson for her advice.

References

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