(2RS,4aRS,8aRS)-6-Oxoperhydro­naphthalene-2-acetic acid: catemeric hydrogen bonding in a bicyclic keto acid

The title racemate, C₁₂H₁₈O₃, aggregates in the solid as translational acid-to-ketone hydrogen-bonding catemers [O...O = 2.6816 (17) Å and O—H...O = 169°]. The stereochemistry obtained for the side chain arises spontaneously during the synthesis, prior to the hydrogenation that produces the cis ring juncture. Three inter­molecular C—H...O close contacts were found.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.037
• wR factor = 0.102
• Data-to-parameter ratio = 13.5

checkCIF/PLATON results

No syntax errors found



Alert level A
PLAT027_ALERT_3_A _diffrn_reflns_theta_full (too) Low ............      64.84 Deg.

Author Response: diffrn reflns theta full (too) Low...64.84\%. (Alert level A) and resolution (too) Low [sin\q/\l < 0.6] (Alert level C): this problem has arisen because initially we were told by the manufacturer of our newly-installed Bruker Smart Apex II unit that we could collect our small-molecule data to only 0.85\%A resolution (with copper K\a radiation). This yields a \q max. of ca. 64.84\%, less than the current 67\% required by Acta. However, since the crystals of this compound are no longer available (or are of such small size as to preclude collecting a new data set), we can only rely on the current data set.

Alert level C
THETM01_ALERT_3_C  The value of sine(theta_max)/wavelength is less than 0.590
            Calculated sin(theta_max)/wavelength =    0.5871
PLAT023_ALERT_3_C Resolution (too) Low [sin(th)/Lambda < 0.6].....      64.84 Deg.
PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low .......       0.98
PLAT152_ALERT_1_C Supplied and Calc Volume s.u. Inconsistent .....          ?
PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........          2

Alert level G
PLAT793_ALERT_1_G Check the Absolute Configuration of C2     = ...          R
PLAT793_ALERT_1_G Check the Absolute Configuration of C4A    = ...          R
PLAT793_ALERT_1_G Check the Absolute Configuration of C8A    = ...          R

   1 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   5 ALERT level C = Check and explain
   3 ALERT level G = General alerts; check

   4 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
   4 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

Among the five H-bonding modes known for ketocarboxylic acids, dimers are found most often. However, we have shown that acid-to-ketone catemers occur more frequently when centrosymmetry is thwarted or disfavored, as well as among conformationally constrained molecules. The latter is the case for the title compound.

Fig. 1 shows the asymmetric unit with its numbering. In principle, the flexibility of the cis-decalin system permits either of two double-chair conformations. However, the disfavored arrangement would place the side-chain on an axial bond on the inside of the system's curvature, resulting in serious steric interference with an axial H at C8. The C2—C9 staggering requires that C10 have a gauche interaction with an equatorial hydrogen either at C1 or C3. Such gauche arrangements are less serious here than in systems where all centers are tetrahedral, because the carboxyl's sp² hybridization diminishes the steric repulsions involved. The observed C2—C9 conformation has torsion angle C3—C2—C9—C10 = -174.51 (13)°). Within the asymmetric unit, any energy advantage for this arrangement appears so slight that the choice is likely dictated by packing considerations. The remaining available rotation yields a C2—C9—C10—O3 torsion angle of 41.98 (19)° for the carboxyl group.

The averaging of C—O bond lengths and C—C—O angles by disorder often found in carboxyl dimers it is not seen in H-bonding modes whose geometries exclude the averaging mechanisms responsible. Because the title compound's aggregation is not dimeric, these bond lengths and angles are typical of those in highly ordered dimeric carboxyls.

Fig. 2 shows the packing of the cell, with extra molecules included to illustrate the acid-to-ketone H-bonding scheme. Each carboxylic acid is linked to the ketone in a molecule translationally related in the b direction [O···O = 2.6816 (17) Å; O—H···O = 169°], with each of the cell's eight molecules participating in a separate H-bonding chain. These eight parallel chains appear as four counterdirectional pairs arrayed centrosymmetrically about 1/2,1/2,1/2.

We characterize the geometry of H bonding to carbonyls using a combination of the H···O=C angle and the H···O=C—C torsional angle. These describe the approach of the H atom to the O in terms of its deviation from, respectively, C=O axiality (ideal = 120°) and planarity with the carbonyl (ideal = 0°). Here, these angles are 125 & -7.5°.

Three intermolecular close contacts were found within the 2.6 Å range we standardly survey for non-bonded C—H···O packing interactions (Table 1).

Related literature

For related literature, see: House et al. (1965); Malak et al. (2007).

S2. Experimental

The title compound has not previously been reported. The corresponding Δ^4a,5 keto acid, prepared as described by Malak et al. (2007), was hydrogenated over Pd/C in absolute ethanol solution and yielded material mp 405 when recrystallized from Et₂O/hexane. The stereochemistry obtained for C2 versus C8a arises prior to the hydrogenation, probably as a result of equilibrations during saponification or earlier (House et al., 1965), while the cis ring-juncture stereochemistry obtained in the reduction is typical of results in a variety of octalones.

The solid-state (KBr) infrared spectrum of (I) has C=O absorptions at 1721 & 1678 cm^-1, with a peak separation typical of the shifts seen in catemers, due, respectively, to removal of H bonding from the acid C=O and addition of H bonding to the ketone. In CHCl₃ solution, where dimers predominate, these bands coalesce and appear at 1706 cm^-1.

S3. Refinement

All H atoms for (I) were found in electron-density difference maps. The O—H was constrained to an idealized position with distance fixed at 0.84 Å and U_iso(H) = 1.5U_eq(O). The methylene and methine Hs were placed in geometrically idealized positions and constrained to ride on their parent C atoms with C—H distances of 0.99 and 1.00 Å, respectively, and U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: APEX2 (Bruker, 2006); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2004); program(s) used to refine structure: SHELXTL (Sheldrick, 2004); molecular graphics: SHELXTL (Sheldrick, 2004); software used to prepare material for publication: SHELXTL (Sheldrick, 2004).

Figures

Fig. 1. The asymmetric unit with its numbering. Displacement ellipsoids are set at the 30% probability level.

Fig. 2. A partial packing diagram with extracellular molecules, illustrating four of the eight translational acid-to-ketone H-bonding chains passing through the cell; the remaining four chains are related by centrosymmetry (about 1/2,1/2,1/2) to the ones shown and are therefore counterdirectional to them. All carbon-bound H atoms are removed for clarity. Displacement ellipsoids are set at the 30% probability level. Hydrogen bonds are shown as dashed lines.

'(2RS,4aRS,8aRS)-6-Oxoperhydronaphthalene-2-acetic acid'

Crystal data

C12H18O3	F(000) = 912
Mr = 210.26	Dx = 1.253 Mg m^−3
Monoclinic, C2/c	Melting point: 405 K
Hall symbol: -C 2yc	Cu Kα radiation, λ = 1.54178 Å
a = 21.1804 (4) Å	Cell parameters from 11741 reflections
b = 10.1644 (2) Å	θ = 4.6–64.8°
c = 11.3208 (3) Å	µ = 0.72 mm^−1
β = 113.841 (2)°	T = 100 K
V = 2229.24 (8) Å^3	Parallelepiped, colourless
Z = 8	0.39 × 0.25 × 0.25 mm

Data collection

Bruker SMART CCD APEX II area-detector diffractometer	1848 independent reflections
Radiation source: fine-focus sealed tube	1516 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.057
φ and ω scans	θmax = 64.8°, θmin = 4.6°
Absorption correction: multi-scan (SADABS; Sheldrick, 2001)	h = −24→24
Tmin = 0.767, Tmax = 0.841	k = −11→11
11737 measured reflections	l = −11→12

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.037	H-atom parameters constrained
wR(F^2) = 0.102	w = 1/[σ^2(Fo^2) + (0.0533P)^2 + 1.3738P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max < 0.001
1848 reflections	Δρmax = 0.31 e Å^−3
137 parameters	Δρmin = −0.15 e Å^−3
0 restraints	Extinction correction: SHELXTL (Sheldrick, 2004)
Primary atom site location: structure-invariant direct methods	Extinction coefficient: none

Special details

Experimental. 'crystal mounted on cryoloop using Paratone-N'

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
C1	0.12293 (7)	0.55256 (15)	0.08048 (14)	0.0208 (3)
H1A	0.1606	0.6001	0.1498	0.025*
H1B	0.1081	0.4792	0.1208	0.025*
O1	0.10016 (6)	1.02711 (11)	0.15128 (12)	0.0359 (3)
C2	0.15039 (7)	0.49638 (14)	−0.01477 (14)	0.0213 (3)
H2A	0.1128	0.4436	−0.0809	0.026*
O2	0.23668 (6)	0.24042 (12)	0.21637 (11)	0.0348 (3)
C3	0.16989 (8)	0.60852 (15)	−0.08379 (16)	0.0260 (4)
H3A	0.2084	0.6596	−0.0201	0.031*
H3B	0.1858	0.5714	−0.1479	0.031*
O3	0.13891 (6)	0.22685 (11)	0.04077 (11)	0.0324 (3)
H3	0.1322	0.1624	0.0807	0.049*
C4	0.10842 (9)	0.69988 (16)	−0.15210 (15)	0.0285 (4)
H4A	0.1232	0.7730	−0.1928	0.034*
H4B	0.0718	0.6503	−0.2216	0.034*
C4A	0.07856 (8)	0.75706 (15)	−0.06068 (14)	0.0237 (4)
H4AA	0.0343	0.8022	−0.1145	0.028*
C5	0.12764 (8)	0.86090 (16)	0.02976 (15)	0.0254 (4)
H5A	0.1742	0.8220	0.0735	0.030*
H5B	0.1313	0.9363	−0.0226	0.030*
C6	0.10384 (8)	0.90974 (16)	0.12963 (16)	0.0262 (4)
C7	0.08506 (9)	0.80542 (16)	0.20388 (16)	0.0282 (4)
H7A	0.0631	0.8470	0.2569	0.034*
H7B	0.1275	0.7601	0.2629	0.034*
C8	0.03537 (8)	0.70459 (16)	0.11229 (16)	0.0275 (4)
H8A	−0.0098	0.7474	0.0640	0.033*
H8B	0.0281	0.6322	0.1639	0.033*
C8A	0.06196 (7)	0.64682 (15)	0.01577 (14)	0.0222 (3)
H8AA	0.0234	0.5938	−0.0479	0.027*
C9	0.21235 (8)	0.40612 (16)	0.05273 (16)	0.0262 (4)
H9A	0.2308	0.3787	−0.0111	0.031*
H9B	0.2489	0.4574	0.1206	0.031*
C10	0.19796 (7)	0.28470 (15)	0.11360 (15)	0.0229 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0221 (7)	0.0191 (8)	0.0203 (7)	−0.0016 (6)	0.0075 (6)	0.0014 (6)
O1	0.0488 (7)	0.0217 (6)	0.0414 (7)	−0.0043 (5)	0.0228 (6)	−0.0076 (5)
C2	0.0211 (7)	0.0202 (8)	0.0215 (8)	−0.0015 (6)	0.0072 (6)	−0.0014 (6)
O2	0.0273 (6)	0.0412 (8)	0.0292 (7)	0.0041 (5)	0.0043 (5)	0.0073 (5)
C3	0.0324 (8)	0.0242 (8)	0.0264 (9)	−0.0012 (7)	0.0171 (7)	−0.0012 (6)
O3	0.0322 (6)	0.0251 (6)	0.0297 (6)	−0.0043 (5)	0.0020 (5)	0.0036 (5)
C4	0.0396 (9)	0.0248 (8)	0.0230 (8)	0.0010 (7)	0.0146 (7)	0.0030 (6)
C4A	0.0261 (8)	0.0206 (8)	0.0213 (8)	0.0018 (6)	0.0062 (6)	0.0020 (6)
C5	0.0293 (8)	0.0212 (8)	0.0280 (8)	−0.0013 (6)	0.0139 (6)	0.0025 (6)
C6	0.0246 (8)	0.0245 (9)	0.0265 (8)	−0.0019 (6)	0.0072 (6)	−0.0033 (6)
C7	0.0337 (8)	0.0269 (9)	0.0282 (9)	−0.0008 (7)	0.0168 (7)	−0.0032 (7)
C8	0.0260 (8)	0.0249 (9)	0.0342 (9)	−0.0002 (6)	0.0148 (7)	0.0003 (7)
C8A	0.0219 (7)	0.0206 (8)	0.0228 (8)	−0.0010 (6)	0.0076 (6)	0.0001 (6)
C9	0.0208 (7)	0.0258 (8)	0.0314 (9)	0.0023 (6)	0.0098 (6)	0.0007 (7)
C10	0.0209 (7)	0.0229 (8)	0.0246 (8)	0.0065 (6)	0.0090 (6)	−0.0032 (6)

Geometric parameters (Å, º)

C1—C2	1.528 (2)	C4A—C8A	1.541 (2)
C1—C8A	1.536 (2)	C4A—C5	1.544 (2)
C1—H1A	0.9900	C4A—H4AA	1.0000
C1—H1B	0.9900	C5—C6	1.496 (2)
O1—C6	1.227 (2)	C5—H5A	0.9900
C2—C9	1.529 (2)	C5—H5B	0.9900
C2—C3	1.530 (2)	C6—C7	1.503 (2)
C2—H2A	1.0000	C7—C8	1.533 (2)
O2—C10	1.207 (2)	C7—H7A	0.9900
C3—C4	1.530 (2)	C7—H7B	0.9900
C3—H3A	0.9900	C8—C8A	1.534 (2)
C3—H3B	0.9900	C8—H8A	0.9900
O3—C10	1.3252 (19)	C8—H8B	0.9900
O3—H3	0.8400	C8A—H8AA	1.0000
C4—C4A	1.529 (2)	C9—C10	1.504 (2)
C4—H4A	0.9900	C9—H9A	0.9900
C4—H4B	0.9900	C9—H9B	0.9900
C2—C1—C8A	112.53 (12)	C6—C5—H5B	109.1
C2—C1—H1A	109.1	C4A—C5—H5B	109.1
C8A—C1—H1A	109.1	H5A—C5—H5B	107.8
C2—C1—H1B	109.1	O1—C6—C5	122.79 (15)
C8A—C1—H1B	109.1	O1—C6—C7	121.45 (15)
H1A—C1—H1B	107.8	C5—C6—C7	115.76 (14)
C1—C2—C9	111.49 (12)	C6—C7—C8	110.96 (13)
C1—C2—C3	109.89 (12)	C6—C7—H7A	109.4
C9—C2—C3	110.36 (12)	C8—C7—H7A	109.4
C1—C2—H2A	108.3	C6—C7—H7B	109.4
C9—C2—H2A	108.3	C8—C7—H7B	109.4
C3—C2—H2A	108.3	H7A—C7—H7B	108.0
C4—C3—C2	111.11 (12)	C7—C8—C8A	112.85 (12)
C4—C3—H3A	109.4	C7—C8—H8A	109.0
C2—C3—H3A	109.4	C8A—C8—H8A	109.0
C4—C3—H3B	109.4	C7—C8—H8B	109.0
C2—C3—H3B	109.4	C8A—C8—H8B	109.0
H3A—C3—H3B	108.0	H8A—C8—H8B	107.8
C10—O3—H3	109.5	C8—C8A—C1	112.28 (12)
C4A—C4—C3	112.88 (13)	C8—C8A—C4A	110.76 (13)
C4A—C4—H4A	109.0	C1—C8A—C4A	112.51 (12)
C3—C4—H4A	109.0	C8—C8A—H8AA	107.0
C4A—C4—H4B	109.0	C1—C8A—H8AA	107.0
C3—C4—H4B	109.0	C4A—C8A—H8AA	107.0
H4A—C4—H4B	107.8	C10—C9—C2	115.43 (12)
C4—C4A—C8A	110.76 (13)	C10—C9—H9A	108.4
C4—C4A—C5	110.91 (13)	C2—C9—H9A	108.4
C8A—C4A—C5	111.72 (12)	C10—C9—H9B	108.4
C4—C4A—H4AA	107.8	C2—C9—H9B	108.4
C8A—C4A—H4AA	107.8	H9A—C9—H9B	107.5
C5—C4A—H4AA	107.8	O2—C10—O3	122.47 (15)
C6—C5—C4A	112.69 (13)	O2—C10—C9	124.27 (14)
C6—C5—H5A	109.1	O3—C10—C9	113.22 (13)
C4A—C5—H5A	109.1
C8A—C1—C2—C9	178.32 (12)	C6—C7—C8—C8A	52.53 (18)
C8A—C1—C2—C3	55.63 (16)	C7—C8—C8A—C1	71.69 (17)
C1—C2—C3—C4	−56.71 (16)	C7—C8—C8A—C4A	−55.02 (17)
C9—C2—C3—C4	179.93 (13)	C2—C1—C8A—C8	−179.09 (12)
C2—C3—C4—C4A	56.59 (17)	C2—C1—C8A—C4A	−53.33 (16)
C3—C4—C4A—C8A	−52.68 (17)	C4—C4A—C8A—C8	177.19 (12)
C3—C4—C4A—C5	71.97 (17)	C5—C4A—C8A—C8	53.01 (16)
C4—C4A—C5—C6	−174.28 (13)	C4—C4A—C8A—C1	50.61 (16)
C8A—C4A—C5—C6	−50.18 (17)	C5—C4A—C8A—C1	−73.58 (16)
C4A—C5—C6—O1	−130.97 (16)	C1—C2—C9—C10	63.15 (17)
C4A—C5—C6—C7	49.60 (19)	C3—C2—C9—C10	−174.43 (13)
O1—C6—C7—C8	130.45 (16)	C2—C9—C10—O2	−140.42 (16)
C5—C6—C7—C8	−50.12 (18)	C2—C9—C10—O3	41.91 (19)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3···O1^i	0.84	1.85	2.6816 (17)	169
C1—H1A···O2^ii	0.99	2.53	3.4997 (18)	167
C5—H5A···O2^ii	0.99	2.51	3.368 (2)	145
C8—H8A···O3^iii	0.99	2.52	3.4559 (19)	158

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