(1RS,4RS)-1-Methoxyspiro[bi­cyclo­[2.2.2]­oct-5-ene-2,2'-[1',3']di­thiol­ane]

The title compound, C₁₁H₁₆OS₂, consists of a five-membered di­thiol­ane ring with a methoxy­bi­cyclo­octene spiro-fused at the 2-position. A few interatomic close contacts seem to influence the geometry of the di­thiol­ane ring.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.054
• wR factor = 0.127
• Data-to-parameter ratio = 13.5

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level B:



PLAT_360  Alert B Short  C(sp3)-C(sp3) Bond  C10    -   C11      =       1.32 Ang.


 Alert Level C:



PLAT_320  Alert C Check Hybridisation of  C3     in Main Residue .          ?

PLAT_320  Alert C Check Hybridisation of  C4     in Main Residue .          ?

PLAT_320  Alert C Check Hybridisation of  C5     in Main Residue .          ?


 0 Alert Level A = Potentially serious problem

 1 Alert Level B = Potential problem

 3 Alert Level C = Please check

---

S1. Comment

Ketene equivalents have found widespread use as partners in Diels-Alder reactions for the construction of cyclic, fused and bridged unsaturated ketones (Ranganathan et al., 1977; Aggarwal et al., 1999). The C₂-symmetric ketene equivalent has been prepared in racemic and enantiomerically pure forms in four steps, and found to be highly reactive and highly diastereoselective (>97:3) in Diels-Alder reactions (Aggarwal et al., 1995). The advantage of this chiral ketene equivalent is that it requires only two steps to remove the chiral auxilary from the cycloadduct (Aggarwal et al., 1995).

Ketene equivalents have also been used in the synthesis of terpenes (Subba Rao & Kalliappan, 1996; Mirrington & Gregson, 1973; Monti & Yang, 1979). 1-Methoxycyclohexa-1,3-diene has been used as a diene in the Diels-Alder reaction (Evans et al., 1972) and it is also a useful diene in the synthesis of terpenoids (Subba Rao & Kalliappan, 1996; Monti & Yang, 1979).

The C₂ symmetric ketene equivalent (Aggarwal et al., 1995) has been investigated with 1-methoxycyclohexa-1,3-diene, under a range of conditions (Aggarwal et al., 1998), giving >97:3 diastereoselectivity in 95% yield.

The title compound, (I), was obtained by reduction of the cycloadduct, according to a literature method (Oea & Drabowicz, 1977). It is a useful starting material for the synthesis of terpenes. The structure determination of (I) was undertaken to understand the effects of the methoxybicyclooctene system and to compare the results with those found in 1,2,3,4-tetrahydrocarbazole-1-spiro-2'-[1,3]dithiolane, (II) (Hökelek et al., 1994), spiro[carbazole-1(2H),2'-[1,3]dithiolan]-4(3H)-one, (III) (Hökelek et al., 1998) and 9-acetonyl-3-ethylidene- 1,2,3,4-tetrahydrospiro[carbazole-1,2'-[1,3]dithiolan]-4-one, (IV) (Hökelek et al., 1999).

The title compound, (I), (Fig. 1) consists of a five-membered dithiolane ring with a methoxybicyclooctene spiro-fused at the 2-position; the dithiolane ring adopts a twist conformation. The S atoms of the dithiolane ring have electron-releasing properties, but the O atom of the methoxy group is electron-withdrawing, thereby influencing the bond lengths and angles of the dithiolane ring (Table 1). Some significant changes in the geometry of the dithiolane ring are evident when a few bond angles are compared with the values found in compounds (II)-(IV) (Table 2).

The structure reveals a number of close contacts: S1···H31(C3) 2.562 (38), O1···H31(C3) 2.403 (31), S2···H61(C6) 2.621 (28), S1···H62(C6) 2.602 (48), O1···H7A(C7) 2.639 (3), S2···H10B(C10) 2.556 (2), O1ⁱ···H11A(C11) 2.813 (3) and Oⁱⁱ···H9A(C9) 2.869 (3) Å [symmetry codes: (i) x − 1, y, z; (ii) −x + 1, −y + 2, −z + 1]. These interactions may have an influence on the bond lengths and angles and also the shape of the molecule.

S2. Experimental

The title compound, (I), was prepared according to a literature method (Oea & Drabowicz, 1977), from (1S,1'R,3'R)-1-methoxyspiro[(bicyclo[2.2.2]oct-2-ene)-6,2'- (1,3-dithiolane)]-1',3'-dioxide (compound 29a in Aggarwal et al., 1998) (0.127 g, 0.49 mmol) in acetone (3 cm³), sodium iodide (0.366 g, 2.44 mmol) and TFAA (trifluoroacetic anhydride; 0.4 cm³, 2.94 mmol) at 195 K for 7 h. The crude sulfide was subjected to flash chromatography, eluting with acetone/petrol (50:50) and yielded the title compound, (I), as a white solid. It was crystallized from petrol ether (yield 0.035 g, 32%), m.p. 331 K.

S3. Refinement

Atoms H31, H41, H51, H61 and H62 were located in a difference synthesis and refined isotropically [C—H = 0.87 (4)–1.09 (7) Å]. The remaining H atoms were positioned geometrically at distances of 0.97 Å (CH₂) and 0.96 Å (CH₃) from the parent C atoms; a riding model was used during the refinement process.

Computing details

Data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS; data reduction: SHELXTL (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX publication routines (Farrugia, 1999).

Figures

Fig. 1. An ORTEP-3 (Farrugia, 1997) drawing of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

(I)

Crystal data

C11H16OS2	Z = 2
Mr = 228.36	F(000) = 244
Triclinic, P1	Dx = 1.342 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.748 (4) Å	Cell parameters from 25 reflections
b = 7.870 (4) Å	θ = 12–20°
c = 11.474 (7) Å	µ = 0.44 mm^−1
α = 99.23 (4)°	T = 293 K
β = 103.00 (5)°	Block, colourless
γ = 102.69 (3)°	0.55 × 0.34 × 0.28 mm
V = 564.9 (6) Å^3

Data collection

Siemens P4 diffractometer	Rint = 0.037
Radiation source: fine-focus sealed tube	θmax = 25.0°, θmin = 2.7°
Graphite monochromator	h = −1→8
non–profiled ω scans	k = −9→9
2493 measured reflections	l = −13→13
1983 independent reflections	3 standard reflections every 100 reflections
1040 reflections with I > 2σ(I)	intensity decay: 1%

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)] = 0.055	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.127	H atoms treated by a mixture of independent and constrained refinement
S = 1.00	w = 1/[σ^2(Fo^2) + (0.0676P)^2] where P = (Fo^2 + 2Fc^2)/3
1983 reflections	(Δ/σ)max = 0.002
147 parameters	Δρmax = 0.30 e Å^−3
0 restraints	Δρmin = −0.17 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
H41	−0.307 (9)	0.320 (8)	0.268 (5)	0.14 (2)*
H31	0.103 (6)	0.526 (4)	0.241 (3)	0.063 (10)*
H61	−0.334 (5)	0.734 (4)	0.101 (3)	0.054 (9)*
H62	−0.253 (8)	0.582 (7)	0.036 (5)	0.120 (16)*
H51	−0.516 (9)	0.458 (7)	0.197 (5)	0.128 (18)*
S1	0.14523 (13)	0.75242 (11)	0.10461 (7)	0.0537 (3)
S2	−0.02942 (15)	1.01505 (11)	0.22952 (10)	0.0674 (4)
O1	0.2272 (3)	0.8104 (3)	0.38379 (19)	0.0608 (6)
C2	−0.0373 (4)	0.7751 (3)	0.1983 (2)	0.0386 (6)
C1	0.0184 (4)	0.7118 (3)	0.3202 (2)	0.0408 (6)
C4	−0.2288 (6)	0.4076 (5)	0.2180 (4)	0.0676 (10)
C11	−0.3429 (5)	0.6548 (5)	0.3202 (3)	0.0655 (9)
H11A	−0.4261	0.7395	0.3068	0.079*
H11B	−0.4031	0.5800	0.3697	0.079*
C3	−0.0032 (5)	0.5118 (4)	0.2862 (3)	0.0552 (8)
C5	−0.3623 (5)	0.5404 (5)	0.1995 (3)	0.0597 (9)
C6	−0.2620 (5)	0.6598 (5)	0.1219 (3)	0.0588 (9)
C7	0.3251 (6)	0.9731 (5)	0.1657 (4)	0.0767 (11)
H7A	0.4237	0.9746	0.2420	0.092*
H7B	0.4048	1.0042	0.1081	0.092*
C9	0.2998 (6)	0.7914 (5)	0.5060 (3)	0.0674 (10)
H9A	0.4429	0.8625	0.5407	0.101*
H9B	0.2935	0.6683	0.5057	0.101*
H9C	0.2122	0.8306	0.5541	0.101*
C8	0.2045 (6)	1.1028 (5)	0.1873 (5)	0.0822 (12)
H8A	0.1663	1.1467	0.1133	0.099*
H8B	0.2939	1.2035	0.2518	0.099*
C10	−0.1484 (4)	0.7441 (4)	0.3825 (3)	0.0508 (7)
H10A	−0.1179	0.7120	0.4615	0.061*
H10B	−0.1399	0.8707	0.3974	0.061*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0521 (5)	0.0628 (5)	0.0466 (4)	0.0145 (4)	0.0171 (3)	0.0089 (3)
S2	0.0737 (6)	0.0474 (5)	0.0923 (7)	0.0230 (4)	0.0369 (5)	0.0175 (4)
O1	0.0430 (13)	0.0799 (15)	0.0403 (10)	−0.0090 (10)	−0.0036 (9)	0.0158 (10)
C2	0.0326 (14)	0.0447 (13)	0.0353 (12)	0.0104 (11)	0.0044 (11)	0.0065 (11)
C1	0.0274 (13)	0.0508 (14)	0.0359 (13)	0.0056 (11)	−0.0008 (11)	0.0060 (11)
C4	0.071 (2)	0.0519 (17)	0.064 (2)	0.0037 (16)	0.0072 (18)	0.0001 (16)
C11	0.0481 (19)	0.088 (2)	0.070 (2)	0.0251 (17)	0.0239 (16)	0.0225 (19)
C3	0.0444 (18)	0.0631 (19)	0.0613 (18)	0.0217 (14)	0.0108 (15)	0.0179 (15)
C5	0.0381 (17)	0.069 (2)	0.0549 (17)	−0.0026 (14)	0.0025 (14)	0.0035 (15)
C6	0.0398 (18)	0.0579 (18)	0.0588 (19)	0.0077 (14)	−0.0142 (15)	0.0036 (15)
C7	0.060 (2)	0.067 (2)	0.096 (3)	−0.0007 (17)	0.030 (2)	0.0106 (19)
C9	0.061 (2)	0.090 (2)	0.0336 (14)	0.0000 (18)	−0.0036 (14)	0.0126 (16)
C8	0.068 (3)	0.064 (2)	0.094 (3)	0.0073 (18)	−0.004 (2)	0.011 (2)
C10	0.0422 (17)	0.0527 (16)	0.0507 (16)	0.0089 (13)	0.0088 (13)	0.0028 (14)

Geometric parameters (Å, º)

S1—C7	1.811 (4)	C11—H11B	0.9700
S1—C2	1.826 (3)	C3—H31	0.97 (4)
S2—C8	1.782 (5)	C5—C6	1.547 (6)
S2—C2	1.852 (3)	C5—H51	1.09 (6)
O1—C1	1.412 (3)	C6—H61	0.87 (4)
O1—C9	1.421 (4)	C6—H62	1.09 (5)
C2—C1	1.554 (4)	C7—C8	1.462 (6)
C2—C6	1.560 (4)	C7—H7A	0.9700
C1—C10	1.507 (4)	C7—H7B	0.9700
C1—C3	1.526 (4)	C9—H9A	0.9600
C4—C3	1.521 (5)	C9—H9B	0.9600
C4—C5	1.532 (5)	C9—H9C	0.9600
C4—H41	1.09 (7)	C8—H8A	0.9700
C11—C10	1.319 (4)	C8—H8B	0.9700
C11—C5	1.488 (5)	C10—H10A	0.9700
C11—H11A	0.9700	C10—H10B	0.9700
C7—S1—C2	97.42 (16)	C6—C5—H51	139 (3)
C8—S2—C2	99.37 (16)	C5—C6—C2	109.8 (3)
C1—O1—C9	116.0 (2)	C5—C6—H61	112 (2)
C1—C2—C6	108.0 (2)	C2—C6—H61	106 (2)
C1—C2—S1	113.79 (18)	C5—C6—H62	112 (3)
C6—C2—S1	108.1 (2)	C2—C6—H62	110 (3)
C1—C2—S2	110.58 (17)	H61—C6—H62	106 (4)
C6—C2—S2	110.6 (2)	C8—C7—S1	109.3 (3)
S1—C2—S2	105.72 (15)	C8—C7—H7A	109.8
O1—C1—C10	115.5 (2)	S1—C7—H7A	109.8
O1—C1—C3	112.3 (2)	C8—C7—H7B	109.8
C10—C1—C3	109.7 (2)	S1—C7—H7B	109.8
O1—C1—C2	106.8 (2)	H7A—C7—H7B	108.3
C10—C1—C2	104.8 (2)	O1—C9—H9A	109.5
C3—C1—C2	107.1 (2)	O1—C9—H9B	109.5
C3—C4—C5	108.5 (3)	H9A—C9—H9B	109.5
C3—C4—H41	114 (3)	O1—C9—H9C	109.5
C5—C4—H41	104 (3)	H9A—C9—H9C	109.5
C10—C11—C5	114.9 (3)	H9B—C9—H9C	109.5
C10—C11—H11A	108.6	C7—C8—S2	113.9 (3)
C5—C11—H11A	108.6	C7—C8—H8A	108.8
C10—C11—H11B	108.6	S2—C8—H8A	108.8
C5—C11—H11B	108.6	C7—C8—H8B	108.8
H11A—C11—H11B	107.5	S2—C8—H8B	108.8
C4—C3—C1	111.7 (3)	H8A—C8—H8B	107.7
C4—C3—H31	119 (2)	C11—C10—C1	114.6 (3)
C1—C3—H31	93.6 (19)	C11—C10—H10A	108.6
C11—C5—C4	109.6 (3)	C1—C10—H10A	108.6
C11—C5—C6	108.3 (3)	C11—C10—H10B	108.6
C4—C5—C6	105.3 (3)	C1—C10—H10B	108.6
C11—C5—H51	92 (3)	H10A—C10—H10B	107.6
C4—C5—H51	100 (3)
C7—S1—C2—C1	−91.5 (2)	O1—C1—C3—C4	179.9 (3)
C7—S1—C2—C6	148.5 (2)	C10—C1—C3—C4	50.1 (3)
C7—S1—C2—S2	30.1 (2)	C2—C1—C3—C4	−63.1 (3)
C8—S2—C2—C1	108.3 (2)	C10—C11—C5—C4	57.2 (5)
C8—S2—C2—C6	−132.0 (2)	C10—C11—C5—C6	−57.1 (4)
C8—S2—C2—S1	−15.3 (2)	C3—C4—C5—C11	−55.5 (4)
C9—O1—C1—C10	55.4 (4)	C3—C4—C5—C6	60.8 (3)
C9—O1—C1—C3	−71.4 (3)	C11—C5—C6—C2	50.3 (4)
C9—O1—C1—C2	171.5 (3)	C4—C5—C6—C2	−66.8 (3)
C6—C2—C1—O1	176.4 (2)	C1—C2—C6—C5	7.1 (3)
S1—C2—C1—O1	56.4 (2)	S1—C2—C6—C5	130.6 (3)
S2—C2—C1—O1	−62.4 (2)	S2—C2—C6—C5	−114.1 (3)
C6—C2—C1—C10	−60.7 (3)	C2—S1—C7—C8	−38.6 (4)
S1—C2—C1—C10	179.34 (17)	S1—C7—C8—S2	32.1 (4)
S2—C2—C1—C10	60.5 (2)	C2—S2—C8—C7	−10.1 (4)
C6—C2—C1—C3	55.8 (3)	C5—C11—C10—C1	−0.6 (5)
S1—C2—C1—C3	−64.2 (2)	O1—C1—C10—C11	178.2 (3)
S2—C2—C1—C3	177.04 (19)	C3—C1—C10—C11	−53.7 (4)
C5—C4—C3—C1	2.8 (4)	C2—C1—C10—C11	61.0 (4)