5,11,11-Trimethyl-11H-benzo[a]fluorene

Li, S.-H.; Xu, C.-H.

doi:10.1107/S1600536807034320

5,11,11-Trimethyl-11H-benzo[a]fluorene

The title compound, C₂₀H₁₈, contains four approximately coplanar fused rings: three six- and one five-membered. In the crystal structure, molecules form columnar stacks along the a axis. Molecules in adjacent stacks along the [010] direction are oriented approximately perpendicular to each other, with a dihedral angle of 81.38 (3)°. There is a short intermolecular C—H

C contact of 2.72 Å between a methyl group and an aromatic ring.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807034320/gk2079sup1.cif Contains datablocks I, global
	Structure factor file (CIF format) https://doi.org/10.1107/S1600536807034320/gk2079Isup2.hkl Contains datablock I

CCDC reference: 657886

checkCIF report

Key indicators

Single-crystal X-ray study
T = 295 K
Mean (C-C) = 0.004 Å
R factor = 0.038
wR factor = 0.067
Data-to-parameter ratio = 9.3

checkCIF/PLATON results

No syntax errors found



Alert level G
REFLT03_ALERT_4_G 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.
           From the CIF: _diffrn_reflns_theta_max           27.48
           From the CIF: _reflns_number_total               1702
           Count of symmetry unique reflns         1718
           Completeness (_total/calc)             99.07%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         0
           Fraction of Friedel pairs measured     0.000
           Are heavy atom types Z>Si present         no

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   0 ALERT level C = Check and explain
   1 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
   0 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

Comment top

During our investigation of new intramolecular reductive cyclization the title compound has been synthesized unexpectedly as the product of an attempted synthesis of 1,2 -bis (2-(2-(bromopropan-2-yl)phenyl)ethyne in the reaction of 2,2'-(2,2'-(ethyne-1,2-diyl)bis(2,1-phenylene)dipropan-2-ol and chlorotrimethylsilane catalyzed by LiBr in refluxed MeCN (Scheme 2). The molecule consists of four fused rings, three six-membered rings and one five-membered ring, which show a nearly planar structure (Fig. 1). Synthesis of a similar benzofluorene derivative has been reported previously (Mitra & Ray, 1981; Bradsher & Burhans, 1940)

In the crystal structure (Fig. 2), the molecules exhibit a T-packing mode with a few intermolecular CH₂—H···π interactions having H···π distances of about 2.7 Å.

Related literature top

For the synthesis of similar compounds, see: Mitra & Ray (1981); Bradsher & Burhans (1940).

Experimental top

The mixture of 135 mg 2,2'-(2,2'-(ethyne-1,2-diyl)bis(2,1-phenylene)dipropan-2-ol, 0.3 ml chlorotrimethylsilane, 163.9 mg LiBr and 7 ml MeCN was refluxed for 34 h under nitrogen atomsphere. The mixture was extracted with Et₂O, the organic layer was washed with brine, dried over MgSO₄, filtered and concentrated under reduced pressure to give 163.7 mg of product in 85% yield. Recrystallization from hexane/ethyl acetate (4:1) gave a single-crystal which was used for X-ray analysis.

Structure description top

In the crystal structure (Fig. 2), the molecules exhibit a T-packing mode with a few intermolecular CH₂—H···π interactions having H···π distances of about 2.7 Å.

For the synthesis of similar compounds, see: Mitra & Ray (1981); Bradsher & Burhans (1940).

Computing details top

Data collection: RAPID-AUTO (Rigaku, 2001); cell refinement: RAPID-AUTO; data reduction: RAPID-AUTO; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL/PC (Sheldrick, 1994) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97.

Figures top

	Fig. 1. The molecular structure of the title compound, with atom labels and 50% probability displacement ellipsoids for non-H atoms.
	Fig. 2. The crystal packing of the title compound, view along the [101] direction.
	Fig. 3. The formation of (I).

5,11,11-Trimethyl-11H-benzo[a]fluorene top

Crystal data top

C₂₀H₁₈	F(000) = 552
M_r = 258.34	D_x = 1.190 Mg m⁻³
Orthorhombic, Pca2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2ac	Cell parameters from 3084 reflections
a = 9.5632 (19) Å	θ = 2.2–27.5°
b = 9.3715 (19) Å	µ = 0.07 mm⁻¹
c = 16.089 (3) Å	T = 295 K
V = 1441.9 (5) Å³	Platelet, colorless
Z = 4	0.31 × 0.26 × 0.22 mm

Data collection top

Rigaku R-AXIS RAPID diffractometer	1216 reflections with I > 2σ(I)
Radiation source: Rotating anode	R_int = 0.019
Graphite monochromator	θ_max = 27.5°, θ_min = 2.2°
ω scans	h = −12→12
3084 measured reflections	k = −12→12
1702 independent reflections	l = −20→20

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.038	H-atom parameters constrained
wR(F²) = 0.067	w = 1/[σ²(F_o²) + (0.007P)² + 0.2P] where P = (F_o² + 2F_c²)/3
S = 1.07	(Δ/σ)_max < 0.001
1702 reflections	Δρ_max = 0.12 e Å⁻³
183 parameters	Δρ_min = −0.11 e Å⁻³
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0309 (11)

Crystal data top

C₂₀H₁₈	V = 1441.9 (5) Å³
M_r = 258.34	Z = 4
Orthorhombic, Pca2₁	Mo Kα radiation
a = 9.5632 (19) Å	µ = 0.07 mm⁻¹
b = 9.3715 (19) Å	T = 295 K
c = 16.089 (3) Å	0.31 × 0.26 × 0.22 mm

Data collection top

Rigaku R-AXIS RAPID diffractometer	1216 reflections with I > 2σ(I)
3084 measured reflections	R_int = 0.019
1702 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.038	0 restraints
wR(F²) = 0.067	H-atom parameters constrained
S = 1.07	Δρ_max = 0.12 e Å⁻³
1702 reflections	Δρ_min = −0.11 e Å⁻³
183 parameters

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.3492 (3)	0.6555 (3)	0.74283 (17)	0.0494 (6)
C2	0.3398 (3)	0.7348 (3)	0.82441 (17)	0.0479 (6)
C3	0.2341 (3)	0.7335 (3)	0.88295 (17)	0.0604 (8)
H3A	0.1547	0.6778	0.8750	0.072*
C4	0.2484 (4)	0.8161 (3)	0.9532 (2)	0.0683 (8)
H4A	0.1783	0.8144	0.9933	0.082*
C5	0.3630 (3)	0.9005 (3)	0.9655 (2)	0.0710 (9)
H5A	0.3700	0.9562	1.0131	0.085*
C6	0.4688 (3)	0.9028 (3)	0.90671 (19)	0.0632 (8)
H6A	0.5471	0.9601	0.9143	0.076*
C7	0.4563 (3)	0.8193 (3)	0.83708 (17)	0.0493 (7)
C8	0.5481 (2)	0.8018 (3)	0.76460 (15)	0.0468 (6)
C9	0.6766 (2)	0.8676 (3)	0.74735 (19)	0.0543 (7)
H9A	0.7160	0.9291	0.7862	0.065*
C10	0.7438 (3)	0.8426 (2)	0.67483 (18)	0.0530 (7)
C11	0.6831 (3)	0.7487 (3)	0.61546 (17)	0.0486 (6)
C12	0.7497 (4)	0.7194 (3)	0.5390 (2)	0.0621 (7)
H12A	0.8336	0.7647	0.5264	0.075*
C13	0.6939 (3)	0.6266 (4)	0.4837 (2)	0.0734 (9)
H13A	0.7390	0.6099	0.4335	0.088*
C14	0.5699 (3)	0.5561 (4)	0.50155 (19)	0.0684 (9)
H14A	0.5338	0.4903	0.4639	0.082*
C15	0.5011 (3)	0.5827 (3)	0.57354 (18)	0.0576 (7)
H15A	0.4169	0.5363	0.5840	0.069*
C16	0.5541 (3)	0.6789 (3)	0.63294 (16)	0.0473 (6)
C17	0.4877 (2)	0.7098 (2)	0.70901 (16)	0.0433 (6)
C18	0.2245 (3)	0.6957 (3)	0.68713 (18)	0.0633 (8)
H18A	0.2254	0.7966	0.6769	0.095*
H18B	0.1389	0.6699	0.7144	0.095*
H18C	0.2314	0.6455	0.6353	0.095*
C19	0.3511 (3)	0.4956 (3)	0.75899 (18)	0.0643 (8)
H19A	0.2629	0.4667	0.7820	0.096*
H19B	0.4246	0.4733	0.7975	0.096*
H19C	0.3670	0.4458	0.7077	0.096*
C20	0.8835 (3)	0.9111 (3)	0.6573 (2)	0.0769 (10)
H20A	0.9137	0.9633	0.7054	0.115*
H20B	0.8747	0.9751	0.6110	0.115*
H20C	0.9509	0.8385	0.6444	0.115*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0484 (14)	0.0450 (14)	0.0547 (16)	−0.0066 (11)	−0.0079 (13)	0.0020 (13)
C2	0.0528 (14)	0.0417 (13)	0.0491 (14)	0.0040 (12)	−0.0030 (13)	0.0052 (13)
C3	0.0603 (18)	0.0589 (17)	0.0620 (18)	0.0018 (15)	0.0006 (15)	0.0069 (17)
C4	0.078 (2)	0.0657 (17)	0.0608 (17)	0.0128 (19)	0.0070 (16)	0.0010 (17)
C5	0.087 (2)	0.0637 (19)	0.0619 (19)	0.0132 (18)	−0.0064 (19)	−0.0148 (17)
C6	0.0653 (19)	0.0585 (18)	0.0660 (19)	0.0021 (15)	−0.0086 (16)	−0.0107 (16)
C7	0.0539 (15)	0.0404 (13)	0.0537 (16)	0.0041 (12)	−0.0081 (14)	−0.0004 (14)
C8	0.0463 (13)	0.0389 (13)	0.0553 (17)	0.0026 (11)	−0.0093 (13)	0.0006 (13)
C9	0.0502 (15)	0.0397 (14)	0.0730 (19)	−0.0017 (11)	−0.0102 (15)	−0.0076 (14)
C10	0.0452 (14)	0.0392 (13)	0.075 (2)	0.0031 (13)	−0.0024 (14)	0.0029 (14)
C11	0.0494 (14)	0.0383 (13)	0.0580 (16)	0.0053 (11)	−0.0028 (13)	0.0057 (13)
C12	0.0584 (16)	0.0615 (18)	0.0664 (17)	0.0051 (16)	0.0034 (15)	0.0059 (17)
C13	0.076 (2)	0.086 (2)	0.059 (2)	0.0133 (19)	0.0049 (17)	−0.0053 (19)
C14	0.075 (2)	0.074 (2)	0.0560 (18)	0.0074 (19)	−0.0087 (17)	−0.0119 (16)
C15	0.0607 (16)	0.0585 (16)	0.0535 (16)	−0.0005 (15)	−0.0084 (14)	−0.0052 (15)
C16	0.0485 (14)	0.0424 (13)	0.0510 (16)	0.0040 (12)	−0.0097 (13)	0.0028 (13)
C17	0.0453 (13)	0.0359 (12)	0.0488 (14)	0.0014 (11)	−0.0078 (12)	0.0030 (13)
C18	0.0505 (15)	0.0747 (18)	0.065 (2)	−0.0061 (14)	−0.0101 (14)	0.0042 (17)
C19	0.0790 (18)	0.0483 (14)	0.0657 (19)	−0.0099 (14)	0.0001 (16)	0.0009 (16)
C20	0.0545 (17)	0.0645 (19)	0.112 (3)	−0.0106 (15)	0.0074 (18)	−0.007 (2)

Geometric parameters (Å, º) top

C1—C2	1.511 (3)	C11—C12	1.412 (4)
C1—C17	1.519 (3)	C11—C16	1.424 (3)
C1—C19	1.522 (4)	C12—C13	1.353 (4)
C1—C18	1.539 (3)	C12—H12A	0.9300
C2—C7	1.382 (4)	C13—C14	1.387 (4)
C2—C3	1.382 (4)	C13—H13A	0.9300
C3—C4	1.377 (4)	C14—C15	1.355 (4)
C3—H3A	0.9300	C14—H14A	0.9300
C4—C5	1.366 (4)	C15—C16	1.409 (4)
C4—H4A	0.9300	C15—H15A	0.9300
C5—C6	1.385 (4)	C16—C17	1.409 (3)
C5—H5A	0.9300	C18—H18A	0.9600
C6—C7	1.372 (4)	C18—H18B	0.9600
C6—H6A	0.9300	C18—H18C	0.9600
C7—C8	1.469 (3)	C19—H19A	0.9600
C8—C17	1.370 (3)	C19—H19B	0.9600
C8—C9	1.402 (3)	C19—H19C	0.9600
C9—C10	1.353 (4)	C20—H20A	0.9600
C9—H9A	0.9300	C20—H20B	0.9600
C10—C11	1.422 (4)	C20—H20C	0.9600
C10—C20	1.509 (3)

C2—C1—C17	101.4 (2)	C13—C12—C11	121.3 (3)
C2—C1—C19	109.7 (2)	C13—C12—H12A	119.4
C17—C1—C19	112.4 (2)	C11—C12—H12A	119.4
C2—C1—C18	109.9 (2)	C12—C13—C14	120.5 (3)
C17—C1—C18	112.7 (2)	C12—C13—H13A	119.7
C19—C1—C18	110.5 (2)	C14—C13—H13A	119.7
C7—C2—C3	119.6 (3)	C15—C14—C13	120.2 (3)
C7—C2—C1	111.2 (2)	C15—C14—H14A	119.9
C3—C2—C1	129.1 (3)	C13—C14—H14A	119.9
C4—C3—C2	118.8 (3)	C14—C15—C16	121.5 (3)
C4—C3—H3A	120.6	C14—C15—H15A	119.2
C2—C3—H3A	120.6	C16—C15—H15A	119.2
C5—C4—C3	121.6 (3)	C17—C16—C15	124.0 (2)
C5—C4—H4A	119.2	C17—C16—C11	117.9 (2)
C3—C4—H4A	119.2	C15—C16—C11	118.2 (2)
C4—C5—C6	119.8 (3)	C8—C17—C16	120.4 (2)
C4—C5—H5A	120.1	C8—C17—C1	110.2 (2)
C6—C5—H5A	120.1	C16—C17—C1	129.4 (2)
C7—C6—C5	119.0 (3)	C1—C18—H18A	109.5
C7—C6—H6A	120.5	C1—C18—H18B	109.5
C5—C6—H6A	120.5	H18A—C18—H18B	109.5
C6—C7—C2	121.2 (3)	C1—C18—H18C	109.5
C6—C7—C8	131.3 (3)	H18A—C18—H18C	109.5
C2—C7—C8	107.5 (2)	H18B—C18—H18C	109.5
C17—C8—C9	121.1 (2)	C1—C19—H19A	109.5
C17—C8—C7	109.7 (2)	C1—C19—H19B	109.5
C9—C8—C7	129.2 (2)	H19A—C19—H19B	109.5
C10—C9—C8	120.7 (3)	C1—C19—H19C	109.5
C10—C9—H9A	119.6	H19A—C19—H19C	109.5
C8—C9—H9A	119.6	H19B—C19—H19C	109.5
C9—C10—C11	119.5 (2)	C10—C20—H20A	109.5
C9—C10—C20	120.5 (3)	C10—C20—H20B	109.5
C11—C10—C20	119.9 (3)	H20A—C20—H20B	109.5
C12—C11—C10	121.4 (3)	C10—C20—H20C	109.5
C12—C11—C16	118.2 (2)	H20A—C20—H20C	109.5
C10—C11—C16	120.3 (2)	H20B—C20—H20C	109.5

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C20—H20A···C8ⁱ	0.96	2.72	3.563 (4)	147

Symmetry code: (i) x+1/2, −y+2, z.

Experimental details

Crystal data
Chemical formula	C₂₀H₁₈
M_r	258.34
Crystal system, space group	Orthorhombic, Pca2₁
Temperature (K)	295
a, b, c (Å)	9.5632 (19), 9.3715 (19), 16.089 (3)
V (Å³)	1441.9 (5)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.07
Crystal size (mm)	0.31 × 0.26 × 0.22

Data collection
Diffractometer	Rigaku R-AXIS RAPID
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	3084, 1702, 1216
R_int	0.019
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.038, 0.067, 1.07
No. of reflections	1702
No. of parameters	183
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.12, −0.11

Computer programs: RAPID-AUTO (Rigaku, 2001), RAPID-AUTO, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL/PC (Sheldrick, 1994) and Mercury (Macrae et al., 2006), SHELXL97.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C20—H20A···C8ⁱ	0.96	2.72	3.563 (4)	147

Symmetry code: (i) x+1/2, −y+2, z.

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