(6bR,10aS)-6b,10a-Di­methyl-10,10a-di­hydro-9H-fluoranthene

The crystal structure of the title compound, C₁₈H₂₀, contains mol­ecules which are separated by normal van der Waals distances. The methyl groups attached at the junction of the ace­naphthyl­ene and cyclo­hexyl rings are cis with respect to each other. The naphthalene ring in the ace­naphthyl­ene moiety is essentially planar, with the remaining two C atoms lying 0.206 (6) and 0.253 (6) Å on opposite sides of the plane of the naphthalene ring. The five-membered ring adopts an envelope conformation and the cyclo­hexyl ring is in a slightly flattened chair conformation. The molecular dimensions are as expected.

Key indicators

• Single-crystal X-ray study
• T = 200 K
• Mean [sigma](C-C) = 0.007 Å
• R factor = 0.054
• wR factor = 0.214
• Data-to-parameter ratio = 11.0

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level B:



ABSMU_01  Alert B The ratio of given/expected absorption coefficient lies
          outside the range 0.95 <> 1.05
          Calculated value of mu =     0.064
          Value of mu given      =     0.060

General Notes



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           27.50
         From the CIF: _reflns_number_total               1819
         Count of symmetry unique reflns         1818
         Completeness (_total/calc)            100.06%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured         1
         Fraction of Friedel pairs measured     0.001
         Are heavy atom types Z>Si present           no
          Please check that the estimate of the number of Friedel pairs is
          correct. If it is not, please give the correct count in the
          _publ_section_exptl_refinement section of the submitted CIF.


 0 Alert Level A = Potentially serious problem

 1 Alert Level B = Potential problem

 0 Alert Level C = Please check

---

S1. Comment

In order to simplify the number of possible Cr(CO)₃ isomers of a chiral naphthalene and to maximize the chiral environment for the subsequent Cr(CO)₃ transfer, it was desirable to use a C₂-axially symmetric naphthalene, and the trans isomer of (III) appeared to be an ideal target for the subsequent preparation of a homochiral Cr(CO)₃ complex (Simion, 1996). The conjugate addition of lithium dimethylcuprate to the partially resolved enone (I) produced the ketone (II) as a single isomer that upon Wolff–Kishner reduction led to the formation of the title compound, (III), as a cis-isomer, instead of the target trans-isomer. NMR spectroscopy was not decisive in establishing the cis- or trans- ring junction in (III). Therefore, an X-ray structure determination was carried out to investigate the nature of the ring junction. The high cis-stereoselectivity observed in this kinetically controlled conjugate addition of organocuprate reagents to the enone (I) is similar to the one observed in bicyclo[4.4.0]enones which form mainly the corresponding cis-decalin products (Posner, 1972).

Compound (III), while having no chirality in a C_s boat conformation (III-a), may adopt two chiral chair conformations in the crystal (III-b and III-c). Selection of a single-crystal is then equivalent to a spontaneous resolution (Jacques et al., 1981). This is the case with the crystal selected for this study in which compound (III) crystallizes in the non-centrosymmetric space group P2₁2₁2₁ in a chiral chair conformation, (III-b), with a P 6bR, 10aS specified stereochemistry. The stereochemistry for the two chair conformations may be specified as P 6bR, 10aS for (III-b) and M 6bR, 10aS for (III-c); a view down the C6b—C10a bond and clockwise rotation of the front groups to the equivalent back-groups = P, and anticlockwise rotation = M. However, the occurrence of a spontaneous resolution is not demonstrable through the measurement of optical activity since the conformers interconvert very rapidly in solution.

The asymmetric unit of (III) is composed of molecules separated by normal van der Waals distances wherein an acenaphthylene has been fused with a cis-cyclohexyl ring (Fig. 1). The molecular dimensions are as expected with mean bond distances: Csp³—Csp³ 1.54 (2), Csp³—Csp² 1.523 (1), and C—C_aromatic 1.40 (2) Å. The C6b—C10a distance at the junction of the cyclohexyl and acenaphthylene rings is significantly longer than expected for a Csp³—Csp³ single bond at a value of 1.586 (6) Å; the corresponding distance in similar structures, acenaphthoquinone diketal (Parvez et al., 2001a) and a naphthalene derivative of a bicyclooctane diketal (Parvez et al., 2001b) have been reported to be 1.585 (8) and 1.613 (12) Å, respectively.

The naphthalene ring in the acenaphthylene moiety is essentially planar, with C6b and C10a 0.206 (6) and 0.253 (6) Å, respectively, on opposite sides of the plane of the naphthalene ring atoms; the maximum deviation of any atom from the mean plane of the naphthal ene ring is 0.034 (3) Å. The five-membered ring fused to the naphthalene ring exhibits a C6b-envelope conformation, with C6b 0.385 (6) Å, out of the least-squares plane of the remaining ring atoms. The cyclohexyl ring adopts a slightly distorted chair conformation caused by the fusion of the acenaphthylene and cyclohexyl rings, with torsion angles in the range ±-41.0 (5)–62.5 (5)°.

S2. Experimental

Preparation of (I): enone (I) was prepared (Simion, 1996) from (±)-2-methyl-1-acenaphthenone according to a general protocol reported for the enantioselective elaboration of quaternary carbon centers through Michael-type alkylation of chiral imines (Revial & Pfau, 1992).

Preparation of (II): a solution of (I) (2.34 g, 10 mmol) in 75 ml dry ether was added to a solution of lithium dimethylcuprate prepared from CuI (9.40 g, 48.2 mmol) and MeLi (1.5 M in ether) (66.7 ml, 100 mmol) and cooled to 195 K. After completion of the addition, the reaction mixture was warmed to 253 K and stirred for 1 h, and quenched with saturated NH₄Cl. The organic layer was washed with brine and dried (MgSO₄). Evaporation, followed by recrystallization (pentane) gave 2.22 g, m.p. 382–384 K, [α]²³_D = 114.14° (c = 0.079, CHCl₃), ee = 47% [(+)-diethyl tartrate ketal, GC].

Preparation of (III): a mixture of (II) (2.50 g, 0.01 mol), 80% hydrazine hydrate (26.40 g, 0.66 mol), hydrazine dihydrochloride (8.40 g, 0.80 mol) and triethylene glycol, 225 g, was heated at 403 K for 2.5 h. After adding KOH pellets (85%) (14.5 g, 0.22 mol), the temperature was gradually raised to 483 K by distilling out the low-boiling material, and the reaction mixture was heated at this temperature for 2.5 h. After cooling, the reaction mixture was diluted with water and extracted with ether. The organic layer was washed with 1 N HCl, and then with brine, and dried (MgSO₄). Evaporation of the solvent, followed by recrystallization (hexane) gave 1.88 g (yield 80%), m.p. 393–395 K. Spectroscopic data for (I), (II), and (III) are available (Simion, 1996).

S3. Refinement

The space group, P2₁2₁2₁, was uniquely determined from the systematic absences. The H atoms were located from difference maps and were included at geometrically idealized positions with C—H = 0.95–0.99 Å, in a riding mode with isotropic displacement parameters equal to 1.2 (non-methyl) and 1.5 (methyl) times the thermal displacement parameters of the atoms to which they were attached. As the compound has only C and H atoms, we did not measure any Friedel pairs of reflections; our analysis only determines the relative stereochemistry.

Computing details

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1988); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: TEXSAN (Molecular Structure Corporation, 1994); program(s) used to solve structure: SAPI91 (Fan, 1991); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: TEXSAN; software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

Fig. 1. ORTEPII (Johnson, 1976) drawing of (III). Displacement ellipsoids have been plotted at the 30% probability level.

(6bR,10aS)-6 b,10a-Dimethyl-10,10a-dihydro-9H-fluoranthene

Crystal data

C18H20	Dx = 1.148 Mg m^−3
Mr = 236.34	Mo Kα radiation, λ = 0.71069 Å
Orthorhombic, P212121	Cell parameters from 25 reflections
a = 13.332 (3) Å	θ = 10.0–15.0°
b = 13.791 (3) Å	µ = 0.06 mm^−1
c = 7.440 (2) Å	T = 200 K
V = 1367.9 (6) Å^3	Prism, colourless
Z = 4	0.60 × 0.47 × 0.38 mm
F(000) = 512

Data collection

Rigaku AFC-6S diffractometer	Rint = 0.00
Radiation source: fine-focus sealed tube	θmax = 27.5°, θmin = 2.5°
Graphite monochromator	h = 0→17
ω/2θ scans	k = 0→17
1819 measured reflections	l = 0→9
1819 independent reflections	3 standard reflections every 200 reflections
1073 reflections with I > 2σ(I)	intensity decay: <0.1%

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)] = 0.054	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.214	H-atom parameters constrained
S = 1.11	w = 1/[σ^2(Fo^2) + (0.113P)^2 + 0.398P] where P = (Fo^2 + 2Fc^2)/3
1819 reflections	(Δ/σ)max < 0.001
165 parameters	Δρmax = 0.31 e Å^−3
0 restraints	Δρmin = −0.27 e Å^−3

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.4412 (4)	0.1819 (3)	0.4497 (6)	0.0480 (12)
H1	0.4739	0.2356	0.5040	0.058*
C2	0.3581 (4)	0.1963 (4)	0.3357 (7)	0.0551 (13)
H2	0.3356	0.2607	0.3150	0.066*
C3	0.3082 (4)	0.1215 (4)	0.2533 (6)	0.0500 (13)
H3	0.2537	0.1347	0.1750	0.060*
C3a	0.3385 (3)	0.0239 (4)	0.2856 (5)	0.0402 (11)
C4	0.2958 (3)	−0.0617 (4)	0.2152 (6)	0.0518 (13)
H4	0.2398	−0.0579	0.1365	0.062*
C5	0.3349 (4)	−0.1501 (4)	0.2599 (7)	0.0548 (13)
H5	0.3063	−0.2067	0.2082	0.066*
C6	0.4162 (4)	−0.1604 (3)	0.3803 (7)	0.0503 (12)
H6	0.4409	−0.2229	0.4112	0.060*
C6a	0.4588 (3)	−0.0789 (3)	0.4514 (5)	0.0330 (9)
C6b	0.5375 (3)	−0.0635 (3)	0.5972 (5)	0.0352 (9)
C7	0.4799 (3)	−0.0765 (3)	0.7778 (5)	0.0406 (10)
H7A	0.4130	−0.0460	0.7664	0.049*
H7B	0.4696	−0.1466	0.7994	0.049*
C8	0.5328 (4)	−0.0333 (4)	0.9388 (6)	0.0477 (12)
H8A	0.6004	−0.0622	0.9519	0.057*
H8B	0.4942	−0.0468	1.0497	0.057*
C9	0.5412 (5)	0.0750 (4)	0.9099 (6)	0.0590 (14)
H9A	0.5730	0.1053	1.0163	0.071*
H9B	0.4734	0.1032	0.8957	0.071*
C10	0.6037 (4)	0.0970 (4)	0.7427 (6)	0.0534 (13)
H10A	0.6038	0.1679	0.7225	0.064*
H10B	0.6739	0.0768	0.7655	0.064*
C10a	0.5669 (3)	0.0471 (3)	0.5719 (5)	0.0395 (10)
C10b	0.4742 (3)	0.0889 (3)	0.4813 (5)	0.0340 (9)
C10c	0.4204 (3)	0.0114 (3)	0.4021 (5)	0.0309 (8)
C11	0.6243 (4)	−0.1348 (4)	0.5907 (7)	0.0548 (13)
H11A	0.5990	−0.2007	0.6094	0.082*
H11B	0.6727	−0.1189	0.6853	0.082*
H11C	0.6573	−0.1308	0.4731	0.082*
C12	0.6523 (4)	0.0571 (4)	0.4302 (7)	0.0587 (14)
H12A	0.6357	0.0183	0.3239	0.088*
H12B	0.7155	0.0339	0.4819	0.088*
H12C	0.6594	0.1253	0.3956	0.088*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.066 (3)	0.034 (2)	0.044 (2)	−0.003 (2)	−0.001 (2)	0.005 (2)
C2	0.072 (3)	0.046 (3)	0.048 (3)	0.017 (3)	0.002 (3)	0.018 (2)
C3	0.044 (2)	0.075 (3)	0.031 (2)	0.019 (2)	−0.007 (2)	0.014 (2)
C3a	0.032 (2)	0.066 (3)	0.0227 (18)	0.001 (2)	−0.0003 (17)	0.0022 (19)
C4	0.038 (2)	0.081 (4)	0.036 (2)	−0.004 (3)	−0.011 (2)	−0.012 (3)
C5	0.055 (3)	0.057 (3)	0.052 (3)	−0.014 (2)	−0.011 (3)	−0.018 (3)
C6	0.064 (3)	0.037 (2)	0.050 (3)	0.003 (2)	−0.002 (3)	−0.009 (2)
C6a	0.0320 (19)	0.038 (2)	0.0288 (17)	0.0027 (18)	−0.0001 (17)	−0.0029 (17)
C6b	0.041 (2)	0.038 (2)	0.0269 (17)	0.0026 (19)	−0.0041 (18)	−0.0014 (17)
C7	0.043 (2)	0.042 (2)	0.036 (2)	−0.002 (2)	−0.0049 (19)	0.0097 (19)
C8	0.056 (3)	0.061 (3)	0.0262 (19)	0.003 (2)	−0.002 (2)	0.002 (2)
C9	0.079 (3)	0.062 (3)	0.036 (2)	0.003 (3)	−0.014 (3)	−0.017 (2)
C10	0.064 (3)	0.046 (3)	0.050 (3)	−0.010 (2)	−0.023 (3)	0.005 (2)
C10a	0.047 (2)	0.041 (2)	0.0307 (19)	−0.009 (2)	−0.0019 (19)	0.0053 (18)
C10b	0.041 (2)	0.036 (2)	0.0253 (17)	0.0018 (18)	0.0038 (18)	0.0010 (16)
C10c	0.0310 (19)	0.040 (2)	0.0220 (16)	0.0009 (17)	0.0027 (16)	0.0011 (17)
C11	0.058 (3)	0.055 (3)	0.051 (3)	0.017 (3)	−0.009 (3)	−0.007 (3)
C12	0.041 (2)	0.082 (4)	0.052 (3)	−0.005 (3)	0.009 (2)	0.014 (3)

Geometric parameters (Å, º)

C1—C10b	1.376 (6)	C7—H7A	0.9900
C1—C2	1.410 (7)	C7—H7B	0.9900
C1—H1	0.9500	C8—C9	1.514 (7)
C2—C3	1.372 (7)	C8—H8A	0.9900
C2—H2	0.9500	C8—H8B	0.9900
C3—C3a	1.425 (7)	C9—C10	1.527 (7)
C3—H3	0.9500	C9—H9A	0.9900
C3a—C10c	1.405 (6)	C9—H9B	0.9900
C3a—C4	1.411 (7)	C10—C10a	1.526 (6)
C4—C5	1.367 (8)	C10—H10A	0.9900
C4—H4	0.9500	C10—H10B	0.9900
C5—C6	1.414 (7)	C10a—C10b	1.522 (6)
C5—H5	0.9500	C10a—C12	1.558 (6)
C6—C6a	1.366 (6)	C10b—C10c	1.415 (6)
C6—H6	0.9500	C11—H11A	0.9800
C6a—C10c	1.395 (6)	C11—H11B	0.9800
C6a—C6b	1.524 (5)	C11—H11C	0.9800
C6b—C11	1.520 (6)	C12—H12A	0.9800
C6b—C7	1.558 (6)	C12—H12B	0.9800
C6b—C10a	1.586 (6)	C12—H12C	0.9800
C7—C8	1.512 (6)
C10b—C1—C2	119.1 (4)	C7—C8—H8B	110.1
C10b—C1—H1	120.5	C9—C8—H8B	110.1
C2—C1—H1	120.5	H8A—C8—H8B	108.4
C3—C2—C1	122.9 (4)	C8—C9—C10	110.6 (4)
C3—C2—H2	118.5	C8—C9—H9A	109.5
C1—C2—H2	118.5	C10—C9—H9A	109.5
C2—C3—C3a	119.8 (4)	C8—C9—H9B	109.5
C2—C3—H3	120.1	C10—C9—H9B	109.5
C3a—C3—H3	120.1	H9A—C9—H9B	108.1
C10c—C3a—C4	116.1 (4)	C10a—C10—C9	114.4 (4)
C10c—C3a—C3	116.1 (4)	C10a—C10—H10A	108.7
C4—C3a—C3	127.8 (4)	C9—C10—H10A	108.7
C5—C4—C3a	120.1 (4)	C10a—C10—H10B	108.7
C5—C4—H4	119.9	C9—C10—H10B	108.7
C3a—C4—H4	119.9	H10A—C10—H10B	107.6
C4—C5—C6	122.5 (4)	C10b—C10a—C10	117.3 (4)
C4—C5—H5	118.8	C10b—C10a—C12	105.1 (3)
C6—C5—H5	118.8	C10—C10a—C12	106.8 (4)
C6a—C6—C5	118.7 (4)	C10b—C10a—C6b	102.4 (3)
C6a—C6—H6	120.6	C10—C10a—C6b	114.5 (3)
C5—C6—H6	120.6	C12—C10a—C6b	110.3 (4)
C6—C6a—C10c	118.7 (4)	C1—C10b—C10c	118.1 (4)
C6—C6a—C6b	132.6 (4)	C1—C10b—C10a	133.5 (4)
C10c—C6a—C6b	108.4 (3)	C10c—C10b—C10a	108.1 (3)
C11—C6b—C6a	114.3 (4)	C6a—C10c—C3a	123.8 (4)
C11—C6b—C7	109.1 (4)	C6a—C10c—C10b	112.2 (3)
C6a—C6b—C7	105.0 (3)	C3a—C10c—C10b	123.9 (4)
C11—C6b—C10a	115.5 (4)	C6b—C11—H11A	109.5
C6a—C6b—C10a	102.7 (3)	C6b—C11—H11B	109.5
C7—C6b—C10a	109.6 (3)	H11A—C11—H11B	109.5
C8—C7—C6b	114.1 (3)	C6b—C11—H11C	109.5
C8—C7—H7A	108.7	H11A—C11—H11C	109.5
C6b—C7—H7A	108.7	H11B—C11—H11C	109.5
C8—C7—H7B	108.7	C10a—C12—H12A	109.5
C6b—C7—H7B	108.7	C10a—C12—H12B	109.5
H7A—C7—H7B	107.6	H12A—C12—H12B	109.5
C7—C8—C9	108.1 (4)	C10a—C12—H12C	109.5
C7—C8—H8A	110.1	H12A—C12—H12C	109.5
C9—C8—H8A	110.1	H12B—C12—H12C	109.5
C10b—C1—C2—C3	−0.3 (7)	C7—C6b—C10a—C10b	−87.1 (4)
C1—C2—C3—C3a	1.7 (7)	C11—C6b—C10a—C10	−82.7 (5)
C2—C3—C3a—C10c	−0.5 (6)	C6a—C6b—C10a—C10	152.2 (4)
C2—C3—C3a—C4	179.2 (5)	C7—C6b—C10a—C10	41.0 (5)
C10c—C3a—C4—C5	−0.6 (6)	C11—C6b—C10a—C12	37.8 (5)
C3—C3a—C4—C5	179.7 (5)	C6a—C6b—C10a—C12	−87.3 (4)
C3a—C4—C5—C6	1.9 (8)	C7—C6b—C10a—C12	161.4 (3)
C4—C5—C6—C6a	−1.5 (7)	C2—C1—C10b—C10c	−2.2 (6)
C5—C6—C6a—C10c	−0.1 (6)	C2—C1—C10b—C10a	170.0 (4)
C5—C6—C6a—C6b	172.1 (4)	C10—C10a—C10b—C1	40.3 (6)
C6—C6a—C6b—C11	40.9 (7)	C12—C10a—C10b—C1	−78.2 (6)
C10c—C6a—C6b—C11	−146.2 (4)	C6b—C10a—C10b—C1	166.6 (4)
C6—C6a—C6b—C7	−78.6 (6)	C10—C10a—C10b—C10c	−146.9 (4)
C10c—C6a—C6b—C7	94.2 (4)	C12—C10a—C10b—C10c	94.7 (4)
C6—C6a—C6b—C10a	166.8 (5)	C6b—C10a—C10b—C10c	−20.6 (4)
C10c—C6a—C6b—C10a	−20.4 (4)	C6—C6a—C10c—C3a	1.4 (6)
C11—C6b—C7—C8	76.0 (5)	C6b—C6a—C10c—C3a	−172.6 (4)
C6a—C6b—C7—C8	−161.1 (4)	C6—C6a—C10c—C10b	−177.9 (4)
C10a—C6b—C7—C8	−51.3 (5)	C6b—C6a—C10c—C10b	8.1 (4)
C6b—C7—C8—C9	62.5 (5)	C4—C3a—C10c—C6a	−1.0 (6)
C7—C8—C9—C10	−61.7 (5)	C3—C3a—C10c—C6a	178.7 (4)
C8—C9—C10—C10a	54.4 (6)	C4—C3a—C10c—C10b	178.2 (4)
C9—C10—C10a—C10b	75.9 (5)	C3—C3a—C10c—C10b	−2.1 (6)
C9—C10—C10a—C12	−166.6 (4)	C1—C10b—C10c—C6a	−177.2 (4)
C9—C10—C10a—C6b	−44.3 (6)	C10a—C10b—C10c—C6a	8.7 (4)
C11—C6b—C10a—C10b	149.2 (4)	C1—C10b—C10c—C3a	3.5 (6)
C6a—C6b—C10a—C10b	24.1 (4)	C10a—C10b—C10c—C3a	−170.6 (4)