2-Methoxy­methyl-1,3-dithiepane 1,1,3,3-tetraoxide

The title compound, C₇H₁₄O₅S₂, consists of a seven-membered dithiepane ring with two O atoms bonded to each S atom and a methoxy­methyl group at the 2-position. A few close contacts seem to influence the geometry of the dithiepane ring.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.035
• wR factor = 0.068
• Data-to-parameter ratio = 10.5

checkCIF/PLATON results

No syntax errors found



Alert level B
REFLT03_ALERT_3_B  Reflection count < 90% complete (theta max?)
           From the CIF: _diffrn_reflns_theta_max           26.01
           From the CIF: _diffrn_reflns_theta_full           0.00
           From the CIF: _reflns_number_total               1800
           TEST2: Reflns within _diffrn_reflns_theta_max
           Count of symmetry unique reflns         2050
           Completeness (_total/calc)             87.80%
PLAT022_ALERT_3_B Ratio Unique / Expected Reflections too Low ..       0.88

   0 ALERT level A = In general: serious problem
   2 ALERT level B = Potentially serious problem
   0 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
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 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

During the last decade, compounds having two geminal sulfones have been shown to be useful dienophiles, and they have reveived considerable attention. A number of aryl-substituted ketenedithioacetal tetraoxides have been shown to be good dienophiles (De Lucchi et al., 1992) in Diels–Alder reactions. The cycloadducts desulfonylate to the corresponding norbornenes.

Similarly, bis(phenylsulfonyl)ethene has been reported (De Lucchi, Fabbri, Cossu & Valle, 1991) and the bis-sulfone undergoes highly diastereoselective cycloadditions with unsymmetrical dienes. The bis-sulfone has been shown to be a useful acetylene equivalent in cycloaddition reactions (De Lucchi, Fabbri & Lucchini, 1991).

Recently, a sulfone-containing dienophile, benzenesulfonylallene, has been reported (Trudell et al., 1997), and found to undergo a Diels–Alder reaction with N-Boc-pyrrole. The cycloadduct transformed into the epibatidine precursor in three steps. The sulfonyl group has versatile functionality in organic synthesis and can be conveniently eliminated, resulting in an alkene (Little & Myong, 1980; Lopez & Carretero, 1991). Moreover, the sulfonyl group may undergo desulfonylation and oxidative desulfonylation with the formation of the corresponding ketones (Leon & Carretero, 1991).

Racemic 2-methoxymethyl-1,3-dithiolane 1,3-dioxide has been shown to be a useful starting material for the preparation of (1R,3R)-2-methylene-1,3-dithiolane 1,3-dioxide (Aggarwal et al., 1998). The crystal structure of the five-membered ring analogue of the title compound, (I), viz. 2-methoxymethyl-1,3-dithiolane 1,1,3,3-tetraoxide has been reported previously (Özcan et al., 2003). Compound (I) may also prove to be a useful starting material for the preparation of a new sulfone-containing dienophile.

The title compound, (I) (Fig. 1), consists of a seven-membered dithiepane ring with two O atoms bonded to each S atom and a methoxymethyl group attached at the 2-position. The S atoms of the dithiepane ring have electron-releasing properties, but the O atoms bonded to the S atoms have electron-withdrawing properties, thereby influencing the bond lengths and angles of the dithiepane ring (Table 1). The dithiepane ring is, of course, not planar.

The structure reveals a number of short contacts: O1···H22(C2) = 2.51 (2), O2···H62(C6) = 2.50 (3), O3···H21(C2) = 2.58 (3), O4···H61(C6) = 2.45 (3), O1ⁱ···H11(C1) = 2.59 (2), O2ⁱⁱ···H42(C4) = 2.52 (3), O3ⁱⁱⁱ···H22(C2) = 2.59 (2), O4^iv···H31(C3) = 2.63 (3) and O5ⁱ···H32(C3) = 2.68 (3) Å [symmetry codes: (i) −x, −y + 1, −z + 1; (ii) x − 1, y, z; (iii) x + 0.5, −y + 0.5, z + 0.5; (iv) −x + 0.5, y − 0.5, −z + 0.5]. 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 (Aggarwal et al., 1998) from 2-methoxymethyl-1,3-dithiepane (3.3 g, 18.5 mmol) in dry ether (40 ml) and purified m-CPBA (m-chloroperoxybenzoic acid; 7.03 g, 40.7 mmol) in diethyl ether (70 ml). The reaction was stirred for 4 h at 273 K, after which the white solid was collected by filtration and purified by column chromatography. Eluting with EtOAc gave racemic (1RS,3RS)-2-methoxymethyl-1,3-dithiepane 1,3-dioxide (yield 0.5 g, 45%) and 2-methoxymethyl-1,3-dithiepane 1,1,3,3-tetraoxide (yield 0.5 g, 13%); the latter was crystallized from EtOAc (m.p. 361 K).

S3. Refinement

Atoms H7A, H7B and H7C were positioned geometrically at a distance of 0.96 Å from C7, and a riding model was used during the refinement process. The U_iso value was set equal to 1.5U_eq(C7). The remaining H atoms were located in a difference synthesis and refined isotropically [C—H = 0.89 (2)–1.01 (3) Å].

Computing details

Data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS; data reduction: SHELXTL (Siemens, 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 (Farrugia, 1999).

Figures

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

(I)

Crystal data

C7H14O5S2	F(000) = 512
Mr = 242.30	Dx = 1.546 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 25 reflections
a = 7.8972 (9) Å	θ = 10–22°
b = 14.627 (2) Å	µ = 0.51 mm^−1
c = 9.5192 (10) Å	T = 293 K
β = 108.739 (8)°	Prism, yellow
V = 1041.3 (2) Å^3	0.35 × 0.20 × 0.15 mm
Z = 4

Data collection

Siemens P4 diffractometer	Rint = 0.052
Radiation source: fine-focus sealed tube	θmax = 26.0°, θmin = 2.7°
Graphite monochromator	h = 0→9
non–profiled ω scans	k = 0→18
1933 measured reflections	l = −11→11
1800 independent reflections	2 standard reflections every 50 reflections
1255 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)] = 0.035	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.068	H atoms treated by a mixture of independent and constrained refinement
S = 0.99	w = 1/[σ^2(Fo^2) + (0.0236P)^2] where P = (Fo^2 + 2Fc^2)/3
1800 reflections	(Δ/σ)max < 0.001
171 parameters	Δρmax = 0.17 e Å^−3
0 restraints	Δρmin = −0.16 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
H11	−0.078 (3)	0.4823 (16)	0.373 (2)	0.029 (6)*
H31	−0.232 (4)	0.215 (2)	0.421 (3)	0.054 (8)*
H22	0.029 (3)	0.2253 (17)	0.381 (3)	0.034 (7)*
H21	−0.099 (4)	0.250 (2)	0.226 (3)	0.055 (9)*
H32	−0.184 (3)	0.310 (2)	0.465 (3)	0.049 (8)*
H41	−0.401 (3)	0.2644 (18)	0.189 (3)	0.038 (7)*
H51	−0.510 (4)	0.4109 (18)	0.174 (3)	0.044 (8)*
H52	−0.378 (4)	0.4423 (19)	0.322 (3)	0.053 (8)*
H42	−0.483 (4)	0.2896 (19)	0.320 (3)	0.056 (8)*
H62	0.112 (3)	0.5018 (18)	0.170 (3)	0.035 (7)*
H61	0.006 (4)	0.581 (2)	0.224 (3)	0.052 (9)*
S1	0.08885 (8)	0.35681 (4)	0.36062 (7)	0.03741 (18)
S2	−0.25018 (9)	0.44686 (5)	0.14862 (7)	0.03981 (19)
O5	0.2248 (2)	0.54619 (13)	0.37807 (19)	0.0509 (5)
O1	0.1642 (2)	0.36821 (13)	0.5187 (2)	0.0537 (5)
O2	0.2038 (3)	0.34533 (15)	0.2730 (3)	0.0641 (6)
O4	−0.3062 (3)	0.53754 (13)	0.0993 (2)	0.0651 (6)
C5	−0.3996 (4)	0.4030 (2)	0.2351 (3)	0.0438 (7)
C3	−0.2137 (4)	0.2704 (2)	0.3862 (3)	0.0389 (6)
C4	−0.3873 (3)	0.30212 (19)	0.2727 (3)	0.0418 (7)
O3	−0.2256 (3)	0.38244 (13)	0.04372 (19)	0.0513 (5)
C2	−0.0578 (3)	0.26136 (18)	0.3265 (3)	0.0380 (6)
C1	−0.0406 (3)	0.46021 (17)	0.2973 (3)	0.0340 (6)
C7	0.3535 (4)	0.6025 (2)	0.3442 (3)	0.0556 (8)
H7A	0.4535	0.6120	0.4324	0.083*
H7B	0.3003	0.6603	0.3071	0.083*
H7C	0.3935	0.5730	0.2704	0.083*
C6	0.0760 (4)	0.5300 (2)	0.2531 (3)	0.0482 (7)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0260 (3)	0.0363 (4)	0.0469 (4)	0.0022 (3)	0.0074 (3)	0.0038 (3)
S2	0.0414 (4)	0.0351 (4)	0.0313 (3)	−0.0030 (3)	−0.0047 (3)	0.0030 (3)
O5	0.0475 (11)	0.0582 (12)	0.0414 (10)	−0.0216 (10)	0.0064 (8)	−0.0015 (9)
O1	0.0461 (11)	0.0521 (13)	0.0445 (11)	−0.0061 (9)	−0.0110 (8)	0.0123 (9)
O2	0.0506 (12)	0.0562 (13)	0.0985 (17)	0.0013 (10)	0.0422 (12)	−0.0051 (12)
O4	0.0615 (13)	0.0418 (12)	0.0634 (13)	−0.0003 (10)	−0.0195 (10)	0.0169 (10)
C5	0.0312 (14)	0.0485 (16)	0.0432 (15)	0.0110 (13)	0.0005 (12)	0.0013 (13)
C3	0.0386 (15)	0.0317 (15)	0.0478 (16)	−0.0025 (12)	0.0160 (12)	0.0030 (13)
C4	0.0299 (14)	0.0398 (16)	0.0531 (17)	−0.0017 (12)	0.0097 (13)	−0.0058 (13)
O3	0.0589 (12)	0.0580 (13)	0.0333 (10)	−0.0130 (10)	0.0095 (9)	−0.0087 (9)
C2	0.0333 (14)	0.0304 (14)	0.0443 (16)	0.0037 (11)	0.0041 (12)	0.0012 (12)
C1	0.0382 (13)	0.0328 (14)	0.0263 (12)	−0.0005 (11)	0.0039 (10)	−0.0003 (11)
C7	0.0543 (18)	0.0588 (19)	0.0564 (17)	−0.0188 (15)	0.0214 (14)	−0.0093 (16)
C6	0.0505 (17)	0.0413 (17)	0.0440 (17)	−0.0119 (14)	0.0028 (13)	0.0051 (13)

Geometric parameters (Å, º)

S1—O2	1.4259 (19)	C3—C4	1.520 (4)
S1—O1	1.439 (2)	C3—H31	0.91 (3)
S1—C2	1.776 (3)	C3—H32	0.91 (3)
S1—C1	1.816 (3)	C4—H41	0.95 (3)
S2—O4	1.429 (2)	C4—H42	1.01 (3)
S2—O3	1.4308 (19)	C2—H22	0.89 (2)
S2—C5	1.762 (3)	C2—H21	0.92 (3)
S2—C1	1.810 (2)	C1—C6	1.521 (4)
O5—C6	1.398 (3)	C1—H11	0.92 (2)
O5—C7	1.423 (3)	C7—H7A	0.9600
C5—C4	1.515 (4)	C7—H7B	0.9600
C5—H51	0.89 (3)	C7—H7C	0.9600
C5—H52	0.97 (3)	C6—H62	1.01 (2)
C3—C2	1.518 (4)	C6—H61	0.92 (3)
O2—S1—O1	119.86 (13)	C5—C4—H42	106.3 (16)
O2—S1—C2	107.49 (13)	C3—C4—H42	105.1 (15)
O1—S1—C2	107.99 (13)	H41—C4—H42	112 (2)
O2—S1—C1	107.47 (13)	C3—C2—S1	115.0 (2)
O1—S1—C1	104.47 (12)	C3—C2—H22	113.7 (15)
C2—S1—C1	109.24 (12)	S1—C2—H22	91.4 (16)
O4—S2—O3	118.63 (12)	C3—C2—H21	110.2 (17)
O4—S2—C5	107.94 (14)	S1—C2—H21	108.8 (18)
O3—S2—C5	110.34 (13)	H22—C2—H21	117 (2)
O4—S2—C1	105.41 (11)	C6—C1—S2	109.78 (17)
O3—S2—C1	108.78 (12)	C6—C1—S1	108.92 (19)
C5—S2—C1	104.78 (13)	S2—C1—S1	116.44 (14)
C6—O5—C7	111.8 (2)	C6—C1—H11	110.9 (15)
C4—C5—S2	117.6 (2)	S2—C1—H11	101.7 (14)
C4—C5—H51	104.8 (18)	S1—C1—H11	108.9 (14)
S2—C5—H51	108.3 (17)	O5—C7—H7A	109.5
C4—C5—H52	113.2 (16)	O5—C7—H7B	109.5
S2—C5—H52	102.5 (16)	H7A—C7—H7B	109.5
H51—C5—H52	110 (2)	O5—C7—H7C	109.5
C2—C3—C4	114.5 (2)	H7A—C7—H7C	109.5
C2—C3—H31	107.7 (18)	H7B—C7—H7C	109.5
C4—C3—H31	108.4 (18)	O5—C6—C1	107.2 (2)
C2—C3—H32	109.8 (17)	O5—C6—H62	111.4 (14)
C4—C3—H32	109.2 (17)	C1—C6—H62	106.9 (14)
H31—C3—H32	107 (2)	O5—C6—H61	111.9 (17)
C5—C4—C3	116.1 (2)	C1—C6—H61	105.9 (18)
C5—C4—H41	112.7 (15)	H62—C6—H61	113 (2)
C3—C4—H41	104.8 (15)
O4—S2—C5—C4	169.5 (2)	O4—S2—C1—S1	−168.34 (15)
O3—S2—C5—C4	38.5 (2)	O3—S2—C1—S1	−40.11 (18)
C1—S2—C5—C4	−78.5 (2)	C5—S2—C1—S1	77.89 (18)
S2—C5—C4—C3	64.1 (3)	O2—S1—C1—C6	−35.4 (2)
C2—C3—C4—C5	−76.7 (3)	O1—S1—C1—C6	92.93 (19)
C4—C3—C2—S1	97.1 (3)	C2—S1—C1—C6	−151.73 (18)
O2—S1—C2—C3	−168.5 (2)	O2—S1—C1—S2	89.34 (17)
O1—S1—C2—C3	60.9 (2)	O1—S1—C1—S2	−142.32 (14)
C1—S1—C2—C3	−52.1 (2)	C2—S1—C1—S2	−27.0 (2)
O4—S2—C1—C6	−44.0 (2)	C7—O5—C6—C1	173.1 (2)
O3—S2—C1—C6	84.2 (2)	S2—C1—C6—O5	172.5 (2)
C5—S2—C1—C6	−157.8 (2)	S1—C1—C6—O5	−58.9 (3)