3,3′-Dihydr­oxy-5,5,5′,5′-tetra­methyl-2,2′-thio­dicyclo­hex-2-en-1-one

Mol­ecules of the title compound, C₁₆H₂₂O₄S, have twofold crystallographic symmetry and are stabilized by strong intra­molecular O—H...O hydrogen bonds and very weak inter­molecular C—H...O hydrogen bonds, forming layers normal to the c axis. The mol­ecular structure is compared with those of the Se- and CH₂-bridged analogues.

S1. Comment

When two dimedone (5,5-dimethylcylohexane-1,3-dione) molecules are bridged at their 2-positions with X (where X = Se, S or CH₂), they are bound with strong intramolecular O—H···O hydrogen bonds in enol forms, (Ia-)-(Ic). It is of interest to determine how their molecular structures and hydrogen bonds depend on the bridge X atoms.

The crystal structures of (Ia) (Kivekäs & Laitalainen, 1983) and (Ic) (Low et al., 2003; Bolte & Scholtyssik, 1997) are reported to be similar to each other, even though the space group for (Ia) is P4₂bc with Z = 4 and that for (Ic) is Pccn with Z = 8. The space group of the title compound, (Ib), is found to be P4₂bc with slightly smaller lattice constants a and c than those for (Ia). Although crystal structures of seven derivatives of structure (Ic) substituted at the methylene bridge with p-substituted phenyl groups have been determined by Bolte et al. (1997, 2001), their molecular structures are not further mentioned here to ensure focus on the structural differences due to unsubstituted bridge X atoms. The mean values for the structure and ring puckering parameters (Cremer & Pople, 1975; Taylor, 1980) of (Ic) are used here unless otherwise specified, since the structures of the two independent molecules in the crystal of (Ic) are similar to each other.

The C—X bond length decreases from 1.916 (10) Å for (Ia), to 1.763 (2) Å for (Ib), to 1.515 (1) Å for (Ic), while the C—X—C bond angle increases from 100.9 (4)° for (Ia), to 104.8 (2)° for (Ib) to 116.1 (1)° for (Ic). The C—X bond lengths are approximately correlated with the covalent radii of X [1.22, 1.02 and 0.68 Å for X = Se, S and CH₂, respectively] (Cambridge Crystallographic Data Center, 2006). The intramolecular O···O hydrogen-bond distance of 2.732 (3) Å for (Ib) (Table 2) is also between the corresponding distances of 2.857 (12) Å for (Ia) and 2.641 (1) Å for (Ic).

The ring-puckering parameters of θ = 61.6 (3)° and ϕ₂ = −2.4 (4)° for the C2—C1—C6—C5—C4—C3 sequence of the cyclohexen-1-one ring in (Ib) are indicative of conformations somewhere between half-boat and envelope for the cyclohexen-1-one ring as observed for (Ia) [θ = 60.9(1.7)° and ϕ₂= −3.6(1.9)°] and (Ic) [θ = 59.0 (3)° and ϕ₂= 178.5 (4)°; θ = 119.8 (3)° and ϕ₂= 0.9 (6)°]. It is interesting that the total puckering amplitude Q decreases slightly but significantly from (Ia) to (Ic) [Q = 0.490 (15), 0.476 (2) and 0.458 (2) Å for (Ia)–(Ic), respectively. The average distance of O1 and O2 from the mean plane of the cyclohexen-1-one ring also decreases from 0.121 Å for (Ia), to 0.099 Å for (Ib) to 0.046 Å for (Ic). The observed dependence of Q on the bridge X atoms could therefore be ascribed to the intramolecular O—H···O hydrogen bonds, which bring about deformation of the cyclohexen-1-one ring by shrinking of the O1···O2' (and O2···O1') distances. The bond distances along the O1—C1—C2—C3—O2 sequence in (Ib) suggest some π conjugation as reported for (Ia) and (Ic), although the degrees of the bond alternation in (Ia)–(Ic) do not seem to be systematic.

In the crystals of (Ia)–(Ic), mirror-image molecules are stacked along the individual C₂ axes passing through the bridge atoms, forming column structures. The C—X—C planes of the upper and lower molecules in these columns relate by ca 60° as displayed in Fig. 2 for (Ib). There are very weak intermolecular C—H···O hydrogen bonds (Desiraju & Steiner, 1999) between columns in the crystal of (Ib) (Fig. 2 and Table 2), forming layers of molecules normal to c. Similar weak intermolecular hydrogen bonds could also be identified in the crystals of (Ia) and (Ic), although Low et al. (2003) doubted their structural significance.

S2. Experimental

Compound (Ib) was prepared from dimedone and sulfur chloride according to the procedure of Gompper or Gommper et al. (1964), and isolated through a silica gel column. Suitable crystals were obtained by evaporation of a benzene–methanol solution (m.p. 504–507 K).

S3. Refinement

All H atoms were located in a difference Fourier synthesis. C-bound H atoms were refined with restrained isotropic displacement parameters [U_iso(H) = 1.5U_eq(C_methyl) or 1.2U_eq(C_methylene)] using a riding model, with C—H distances of 0.96 (methyl) or 0.97 Å (methylene). The hydroxy H atom was refined isotropically with a fixed displacement parameter [U_iso(H) = 1.5U_eq(O)].

Computing details

Data collection: MSC/AFC Diffractometer Control Software (Rigaku/MSC & Rigaku, 2001); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: CrystalStructure (Rigaku/MSC & Rigaku, 2001); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. A perspective view of (Ib), showing the non-H (and H1) atom-numbering scheme, with 50% probability displacement ellipsoids. H atoms are shown as small spheres of arbitrary radii. Primed atoms are at the symmetry position (1 − x, −y, z).
	Fig. 2. A stereoview of the molecular packing for (Ib), with intra- and intermolecular hydrogen bonds shown as dashed lines (see Table 2). The non-H atoms of one molecule involved in the hydrogen bonding are labeled. Atoms are drawn as circles of arbitrary radii.

3,3'-Dihydroxy-5,5,5',5'-tetramethyl-2,2'-thiodicyclohex-2-en-1-one

Crystal data

C16H22O4S	Dx = 1.280 Mg m^−3
Mr = 310.41	Melting point = 504–507 K
Tetragonal, P42bc	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: P 4c -2ab	Cell parameters from 25 reflections
a = 13.3426 (14) Å	θ = 13.6–14.9°
c = 9.049 (2) Å	µ = 0.21 mm^−1
V = 1610.9 (4) Å^3	T = 298 K
Z = 4	Rectangular, colorless
F(000) = 664	1.00 × 0.40 × 0.20 mm

Data collection

Rigaku AFC-7S diffractometer	1004 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.000
Graphite monochromator	θmax = 30.0°, θmin = 3.1°
ω–2θ scans	h = 0→18
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996)	k = 0→13
Tmin = 0.815, Tmax = 0.959	l = 0→12
1251 measured reflections	3 standard reflections every 150 reflections
1251 independent reflections	intensity decay: 0.4%

Refinement

Refinement on F^2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F^2 > 2σ(F^2)] = 0.034	w = 1/[σ^2(Fo^2) + (0.0547P)^2 + 0.1022P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.097	(Δ/σ)max < 0.001
S = 1.07	Δρmax = 0.29 e Å^−3
1251 reflections	Δρmin = −0.19 e Å^−3
102 parameters	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
1 restraint	Extinction coefficient: 0.014 (2)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack (1983), ? Friedel pairs
Secondary atom site location: difference Fourier map	Absolute structure parameter: −0.02 (17)

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
S1	0.5000	0.0000	0.49915 (15)	0.04238 (18)
O1	0.64894 (12)	−0.13934 (11)	0.3584 (3)	0.0615 (6)
O2	0.54750 (12)	0.19631 (11)	0.3452 (3)	0.0527 (5)
C1	0.66713 (15)	−0.04862 (14)	0.3349 (3)	0.0427 (5)
C2	0.60061 (14)	0.02907 (13)	0.3803 (2)	0.0349 (4)
C3	0.61346 (15)	0.12553 (14)	0.3283 (2)	0.0380 (4)
C4	0.70493 (14)	0.15521 (14)	0.2436 (3)	0.0421 (4)
C5	0.79513 (15)	0.08584 (15)	0.2671 (3)	0.0417 (5)
C6	0.75876 (16)	−0.02253 (15)	0.2466 (4)	0.0474 (5)
C7	0.83915 (19)	0.10036 (19)	0.4220 (3)	0.0543 (6)
C8	0.8748 (2)	0.1106 (2)	0.1517 (4)	0.0638 (8)
H1	0.498 (3)	0.181 (3)	0.366 (5)	0.079*
H2	0.7237	0.2227	0.2721	0.051*
H3	0.6886	0.1564	0.1391	0.051*
H4	0.7444	−0.0334	0.1427	0.057*
H5	0.8125	−0.0677	0.2743	0.057*
H6	0.8974	0.0587	0.4332	0.081*
H7	0.7900	0.0821	0.4948	0.081*
H8	0.8576	0.1693	0.4352	0.081*
H9	0.9313	0.0669	0.1644	0.096*
H10	0.8959	0.1789	0.1635	0.096*
H11	0.8473	0.1015	0.0545	0.096*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0457 (4)	0.0454 (4)	0.0361 (3)	−0.0045 (3)	0.000	0.000
O1	0.0492 (8)	0.0294 (6)	0.1059 (16)	0.0036 (6)	0.0056 (11)	0.0058 (10)
O2	0.0438 (8)	0.0309 (7)	0.0835 (13)	0.0040 (5)	−0.0009 (9)	−0.0017 (9)
C1	0.0393 (9)	0.0331 (8)	0.0558 (12)	−0.0012 (8)	−0.0052 (10)	−0.0020 (9)
C2	0.0348 (9)	0.0303 (8)	0.0397 (9)	−0.0010 (7)	−0.0036 (8)	−0.0011 (7)
C3	0.0386 (9)	0.0339 (9)	0.0415 (10)	−0.0010 (6)	−0.0070 (9)	−0.0022 (8)
C4	0.0416 (9)	0.0365 (9)	0.0483 (10)	−0.0025 (7)	−0.0027 (11)	0.0050 (11)
C5	0.0369 (9)	0.0371 (9)	0.0513 (12)	−0.0025 (7)	−0.0001 (10)	0.0010 (10)
C6	0.0405 (10)	0.0390 (9)	0.0629 (12)	0.0005 (7)	0.0036 (13)	−0.0086 (12)
C7	0.0473 (13)	0.0500 (12)	0.0655 (16)	−0.0053 (10)	−0.0179 (12)	0.0061 (12)
C8	0.0474 (13)	0.0707 (17)	0.073 (2)	−0.0040 (12)	0.0131 (13)	0.0069 (15)

Geometric parameters (Å, º)

S1—C2	1.763 (2)	C5—C8	1.526 (4)
S1—C2^i	1.763 (2)	C5—C7	1.532 (4)
O1—C1	1.253 (2)	C5—C6	1.537 (3)
O2—C3	1.300 (2)	C6—H4	0.9700
O2—H1	0.72 (4)	C6—H5	0.9700
C1—C2	1.425 (3)	C7—H6	0.9600
C1—C6	1.502 (3)	C7—H7	0.9600
C2—C3	1.381 (3)	C7—H8	0.9600
C3—C4	1.495 (3)	C8—H9	0.9600
C4—C5	1.533 (3)	C8—H10	0.9600
C4—H2	0.9700	C8—H11	0.9600
C4—H3	0.9700
C2—S1—C2^i	104.82 (15)	C7—C5—C6	110.5 (2)
C3—O2—H1	116 (3)	C4—C5—C6	107.66 (16)
O1—C1—C2	122.2 (2)	C1—C6—C5	114.27 (19)
O1—C1—C6	118.2 (2)	C1—C6—H4	108.7
C2—C1—C6	119.46 (17)	C5—C6—H4	108.7
C3—C2—C1	120.16 (19)	C1—C6—H5	108.7
C3—C2—S1	120.48 (15)	C5—C6—H5	108.7
C1—C2—S1	119.33 (14)	H4—C6—H5	107.6
O2—C3—C2	123.6 (2)	C5—C7—H6	109.5
O2—C3—C4	114.88 (18)	C5—C7—H7	109.5
C2—C3—C4	121.53 (18)	H6—C7—H7	109.5
C3—C4—C5	114.21 (18)	C5—C7—H8	109.5
C3—C4—H2	108.7	H6—C7—H8	109.5
C5—C4—H2	108.7	H7—C7—H8	109.5
C3—C4—H3	108.7	C5—C8—H9	109.5
C5—C4—H3	108.7	C5—C8—H10	109.5
H2—C4—H3	107.6	H9—C8—H10	109.5
C8—C5—C7	109.4 (2)	C5—C8—H11	109.5
C8—C5—C4	108.8 (2)	H9—C8—H11	109.5
C7—C5—C4	110.6 (2)	H10—C8—H11	109.5
C8—C5—C6	109.9 (2)
O1—C1—C2—C3	−167.6 (3)	O2—C3—C4—C5	160.8 (2)
C6—C1—C2—C3	8.0 (3)	C2—C3—C4—C5	−20.8 (3)
O1—C1—C2—S1	10.6 (3)	C3—C4—C5—C8	168.1 (2)
C6—C1—C2—S1	−173.8 (2)	C3—C4—C5—C7	−71.8 (2)
C2^i—S1—C2—C3	87.38 (17)	C3—C4—C5—C6	49.0 (3)
C2^i—S1—C2—C1	−90.89 (17)	O1—C1—C6—C5	−160.2 (2)
C1—C2—C3—O2	168.6 (2)	C2—C1—C6—C5	24.1 (4)
S1—C2—C3—O2	−9.7 (3)	C8—C5—C6—C1	−169.0 (2)
C1—C2—C3—C4	−9.7 (3)	C7—C5—C6—C1	70.2 (3)
S1—C2—C3—C4	172.02 (17)	C4—C5—C6—C1	−50.7 (3)

Symmetry code: (i) −x+1, −y, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1···O1^i	0.72 (4)	2.04 (4)	2.732 (2)	163 (5)
C4—H2···O1^ii	0.97	2.62	3.521 (3)	154
C7—H8···O1^ii	0.96	2.65	3.524 (3)	152

Symmetry codes: (i) −x+1, −y, z; (ii) −x+3/2, y+1/2, z.