5,5-Dimethyl-3,4-di-p-tolyl­cyclo­pent-2-enone

In the title compound, C₂₁H₂₂O, the five-membered non-aromatic cyclo­pentenone ring is approximately planar and the two p-tolyl rings form dihedral angles of 28.6 (2) and 66.9 (1)° with this plane. Inter­molecular C—H...O and C—H...π inter­actions are observed. The C—H...π distance (measured to the centroid of the benzene ring) is 2.86 Å and the C—H...π angle is 123°.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.033
• wR factor = 0.086
• Data-to-parameter ratio = 11.7

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           30.05
           From the CIF: _reflns_number_total               2365
           Count of symmetry unique reflns         2400
           Completeness (_total/calc)             98.54%
           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
PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints .......          2

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   0 ALERT level C = Check and explain
   2 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
   1 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

---

S1. Comment

Cyclopentenones are of interest for their anti-viral (Sanatoro & Roberts, 1999; Roberts et al., 1999; Akella & Vince 1996), anti-tumor and anti-diabetes (Akella & Vince, 1996; Shiosaki et al.,1993), pesticide and bactericide (Kyoshi et al., 1994) properties. They are also used in labeling materials for commercial goods (Heller & Vincent, 1999) on account of their photochemical properties. The structure determination of title compound was undertaken as part of our studies on cyclopentenone derivatives.

The title compound consists of two aromatic phenyl rings and a central non aromatic cyclopentenone ring. The five-membered ring C1–C5 is almost planar and has internal angles ranging from 103.58 (10) to 112.52 (11)°. The distortion from a regular five-membered homocyclic ring is due to different hybridization of the ring atoms and different substituents bonded to them. The bond distances range from 1.3500 (17) to 1.5640 (17) Å. Two sp³ carbon atoms of this ring, C4 and C5, have distorted tetrahedral geometries, with angles ranging from 104.62 (10) to 115.49 (10)° for C4 and 103.58 (10) to 115.12 (11) for C5. The phenyl ring bonded to C3 is rotated from the plane of the cylopentenone ring with a dihedral angle of 28.6 (2)° (Figure 1). The other phenyl ring makes an angle of 66.9 (1)° with the cyclopentenone ring.

Intermolecular C—H···O interactions exist between H12B and O1 (Figure 2 and Table 1), and C—H···π interactions are formed between C17 and the phenyl ring C6–C11 (Figure 3).

Related literature

For related literature, see: Akella & Vince (1996); Heller & Vincent (1999); Kyoshi et al. (1994); Roberts et al. (1999); Sanatoro & Roberts (1999); Shiosaki et al. (1993).

S2. Experimental

The title compound was synthesized in three steps:

a) To a solution of NaOH (1 g, 25 mmol) in methanol (10 ml) was added 4,4-dimethylbenzil (1 g, 4.2 mmol) and isopropylmethylketone (2 ml, 18.6 mmol). The mixture was refluxed for 1.5 h then water (20 ml) was added. The resulting precipitate was filtered and dried in vacuo to give 4-hydroxy-5,5-dimethyl-3,4-di-p-tolyl-cyclopent-2-enone (0.85 g, 2.9 mmol) in 85% yield; m.p. 419–421 K.

b) To a solution of 4-hydroxy-5,5-dimethyl-3,4-di-p-tolyl-cyclopent-2-enone (1 g, 3.3 mmol) in MeOH (30 ml) was added a solution of NaBH₄ (1 g, 26.4 mmol) in water (0.2 ml). The mixture was stirred for 3 h at room temperature, then diethylether (30 ml) was added. The ether solution was washed three times with water (30 ml) and dried over Na₂SO₄, then the solvent was evaporated to give 2,2-dimethyl-1,5-di-p-tolyl-cylopent-4-ene-1,3-diol (0.80 g, 2.6 mmol) in 80% yield.

c) To a stirred solution of 2,2-dimethyl-1,5-di-p-tolyl-cylopent-4-ene-1,3-diol (1 g, 3.2 mmol) in EtOH (20 ml), was added HCl (5 ml). The mixture was refluxed for 3 h, then diethylether (30 ml) was added. The ether solution was washed with water (30 ml) and dried over Na₂SO₄, then the solvent was evaporated to give 5,5-dimethyl-3,4-di-p-tolyl-cyclopent-2-enone (0.65 g, 2.2 mmol) in 65% yield; m.p. 375–377 K.

S3. Refinement

H atoms were placed in calculated positions and refined as riding with C—H = 0.95–1.00 Å and with U_iso(H) = 1.2U_eq(C) or 1.5U_eq(C). The methyl groups were allowed to rotate about their local threefold axes. In the absence of significant anomalous scattering effects, Friedel pairs have been merged as equivalent data.

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Sheldrick, 2001); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The molecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level for non-H atoms.
	Fig. 2. The unit-cell contents of the title compound. C—H···O interactions are shown as dashed lines.
	Fig. 3. C—H···π interaction between C17 and the aromatic ring C6–C11. The C—H···π distance (measured to the centroid of the phenyl ring) is 2.86 Å and the C—H···π angle is 123°.

5,5-Dimethyl-3,4-di-p-tolylcyclopent-2-enone

Crystal data

C21H22O	F(000) = 624
Mr = 290.39	Dx = 1.179 Mg m^−3
Monoclinic, Cc	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: C -2yc	Cell parameters from 6448 reflections
a = 14.8886 (8) Å	θ = 2.3–30.1°
b = 13.8910 (8) Å	µ = 0.07 mm^−1
c = 10.3902 (6) Å	T = 100 K
β = 130.426 (5)°	Prism, colourless
V = 1635.8 (2) Å^3	0.30 × 0.20 × 0.20 mm
Z = 4

Data collection

Bruker SMART APEXII CCD area-detector diffractometer	2365 independent reflections
Radiation source: fine-focus sealed tube	2318 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.023
φ and ω scans	θmax = 30.1°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 2003)	h = −20→20
Tmin = 0.979, Tmax = 0.989	k = −19→19
10447 measured reflections	l = −14→14

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)] = 0.033	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.087	H-atom parameters constrained
S = 1.01	w = 1/[σ^2(Fo^2) + (0.068P)^2 + 0.2P] where P = (Fo^2 + 2Fc^2)/3
2365 reflections	(Δ/σ)max < 0.001
203 parameters	Δρmax = 0.30 e Å^−3
2 restraints	Δρmin = −0.22 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
O1	0.29633 (12)	0.50200 (8)	0.22848 (18)	0.0343 (3)
C1	0.27003 (12)	0.42152 (10)	0.16715 (19)	0.0227 (3)
C2	0.25295 (12)	0.39032 (9)	0.01826 (18)	0.0212 (2)
H2A	0.2673	0.4290	−0.0422	0.025*
C3	0.21383 (10)	0.29855 (9)	−0.02097 (15)	0.0161 (2)
C4	0.20845 (10)	0.25363 (8)	0.10639 (15)	0.0149 (2)
H4A	0.1242	0.2374	0.0467	0.018*
C5	0.24629 (11)	0.33618 (9)	0.23522 (16)	0.0183 (2)
C6	0.17742 (11)	0.24495 (9)	−0.16999 (15)	0.0160 (2)
C7	0.22584 (12)	0.26583 (9)	−0.24578 (16)	0.0193 (2)
H7A	0.2835	0.3151	−0.2002	0.023*
C8	0.18999 (13)	0.21489 (11)	−0.38715 (17)	0.0220 (3)
H8A	0.2249	0.2289	−0.4357	0.026*
C9	0.10359 (12)	0.14339 (10)	−0.45960 (16)	0.0213 (2)
C10	0.05415 (12)	0.12320 (10)	−0.38551 (16)	0.0200 (2)
H10A	−0.0057	0.0756	−0.4341	0.024*
C11	0.09185 (11)	0.17215 (9)	−0.24115 (16)	0.0178 (2)
H11A	0.0592	0.1561	−0.1900	0.021*
C12	0.06775 (16)	0.08719 (14)	−0.6102 (2)	0.0316 (3)
H12A	0.0531	0.1316	−0.6953	0.047*
H12B	−0.0043	0.0508	−0.6586	0.047*
H12C	0.1311	0.0425	−0.5749	0.047*
C13	0.28004 (10)	0.16155 (8)	0.18249 (14)	0.0144 (2)
C14	0.37655 (10)	0.14336 (9)	0.19216 (15)	0.0158 (2)
H14A	0.3982	0.1893	0.1488	0.019*
C15	0.44137 (10)	0.05868 (9)	0.26474 (15)	0.0171 (2)
H15A	0.5054	0.0469	0.2674	0.021*
C16	0.41375 (11)	−0.00923 (9)	0.33366 (16)	0.0180 (2)
C17	0.31813 (12)	0.00912 (10)	0.32504 (16)	0.0200 (2)
H17A	0.2981	−0.0358	0.3719	0.024*
C18	0.25136 (11)	0.09263 (9)	0.24840 (16)	0.0184 (2)
H18A	0.1850	0.1028	0.2409	0.022*
C19	0.48622 (13)	−0.09959 (11)	0.4148 (2)	0.0274 (3)
H19A	0.4690	−0.1299	0.4819	0.041*
H19B	0.5703	−0.0833	0.4884	0.041*
H19C	0.4665	−0.1443	0.3267	0.041*
C20	0.14578 (12)	0.36188 (10)	0.23427 (18)	0.0230 (3)
H20A	0.1690	0.4173	0.3085	0.034*
H20B	0.1292	0.3068	0.2749	0.034*
H20C	0.0749	0.3780	0.1189	0.034*
C21	0.35969 (13)	0.31701 (12)	0.41703 (19)	0.0299 (3)
H21A	0.3807	0.3746	0.4860	0.045*
H21B	0.4239	0.3013	0.4171	0.045*
H21C	0.3470	0.2629	0.4641	0.045*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0359 (6)	0.0203 (5)	0.0508 (7)	−0.0077 (4)	0.0300 (6)	−0.0128 (5)
C1	0.0175 (5)	0.0175 (5)	0.0314 (6)	−0.0010 (4)	0.0152 (5)	−0.0035 (5)
C2	0.0192 (6)	0.0153 (5)	0.0287 (6)	0.0007 (4)	0.0154 (5)	0.0013 (5)
C3	0.0135 (5)	0.0145 (5)	0.0190 (5)	0.0027 (4)	0.0100 (5)	0.0025 (4)
C4	0.0139 (5)	0.0130 (5)	0.0171 (5)	0.0015 (4)	0.0098 (4)	−0.0007 (4)
C5	0.0154 (5)	0.0165 (5)	0.0195 (5)	0.0009 (4)	0.0097 (5)	−0.0042 (4)
C6	0.0152 (5)	0.0157 (5)	0.0172 (5)	0.0037 (4)	0.0106 (5)	0.0046 (4)
C7	0.0177 (5)	0.0196 (5)	0.0204 (6)	0.0016 (4)	0.0123 (5)	0.0060 (4)
C8	0.0224 (6)	0.0273 (6)	0.0202 (6)	0.0022 (5)	0.0156 (5)	0.0060 (5)
C9	0.0194 (6)	0.0276 (6)	0.0168 (5)	0.0024 (5)	0.0117 (5)	0.0021 (5)
C10	0.0190 (6)	0.0229 (6)	0.0193 (5)	−0.0007 (5)	0.0130 (5)	−0.0004 (5)
C11	0.0174 (5)	0.0188 (5)	0.0194 (5)	0.0005 (4)	0.0129 (5)	0.0010 (4)
C12	0.0326 (7)	0.0450 (9)	0.0234 (6)	−0.0059 (7)	0.0209 (6)	−0.0072 (6)
C13	0.0136 (5)	0.0137 (5)	0.0151 (5)	0.0003 (4)	0.0090 (4)	−0.0002 (4)
C14	0.0147 (5)	0.0154 (5)	0.0184 (5)	0.0013 (4)	0.0112 (4)	0.0019 (4)
C15	0.0145 (5)	0.0167 (5)	0.0200 (5)	0.0018 (4)	0.0112 (5)	0.0011 (4)
C16	0.0164 (5)	0.0150 (5)	0.0174 (5)	0.0011 (4)	0.0087 (4)	0.0011 (4)
C17	0.0216 (6)	0.0186 (5)	0.0216 (6)	−0.0002 (4)	0.0148 (5)	0.0035 (4)
C18	0.0183 (5)	0.0198 (6)	0.0218 (6)	0.0012 (4)	0.0151 (5)	0.0018 (4)
C19	0.0234 (7)	0.0192 (6)	0.0338 (7)	0.0066 (5)	0.0159 (6)	0.0097 (5)
C20	0.0232 (6)	0.0230 (6)	0.0275 (6)	0.0023 (5)	0.0185 (6)	−0.0040 (5)
C21	0.0208 (6)	0.0284 (7)	0.0220 (6)	0.0032 (5)	0.0057 (5)	−0.0078 (5)

Geometric parameters (Å, º)

O1—C1	1.2189 (17)	C12—H12A	0.980
C1—C2	1.461 (2)	C12—H12B	0.980
C1—C5	1.5344 (19)	C12—H12C	0.980
C2—C3	1.3500 (17)	C13—C18	1.3954 (16)
C2—H2A	0.950	C13—C14	1.3970 (16)
C3—C6	1.4687 (17)	C14—C15	1.3927 (16)
C3—C4	1.5113 (17)	C14—H14A	0.950
C4—C13	1.5179 (16)	C15—C16	1.3978 (17)
C4—C5	1.5640 (17)	C15—H15A	0.950
C4—H4A	1.000	C16—C17	1.3908 (18)
C5—C20	1.5322 (18)	C16—C19	1.5067 (18)
C5—C21	1.5342 (19)	C17—C18	1.3933 (17)
C6—C7	1.4001 (17)	C17—H17A	0.950
C6—C11	1.4037 (17)	C18—H18A	0.950
C7—C8	1.388 (2)	C19—H19A	0.980
C7—H7A	0.950	C19—H19B	0.980
C8—C9	1.397 (2)	C19—H19C	0.980
C8—H8A	0.950	C20—H20A	0.980
C9—C10	1.3957 (18)	C20—H20B	0.980
C9—C12	1.503 (2)	C20—H20C	0.980
C10—C11	1.3912 (18)	C21—H21A	0.980
C10—H10A	0.950	C21—H21B	0.980
C11—H11A	0.950	C21—H21C	0.980
O1—C1—C2	127.00 (14)	H12A—C12—H12B	109.5
O1—C1—C5	124.03 (14)	C9—C12—H12C	109.5
C2—C1—C5	108.96 (11)	H12A—C12—H12C	109.5
C3—C2—C1	110.15 (12)	H12B—C12—H12C	109.5
C3—C2—H2A	124.9	C18—C13—C14	117.93 (11)
C1—C2—H2A	124.9	C18—C13—C4	119.93 (11)
C2—C3—C6	126.09 (12)	C14—C13—C4	122.13 (11)
C2—C3—C4	112.52 (11)	C15—C14—C13	120.73 (11)
C6—C3—C4	121.38 (10)	C15—C14—H14A	119.6
C3—C4—C13	112.71 (10)	C13—C14—H14A	119.6
C3—C4—C5	104.62 (10)	C14—C15—C16	121.11 (11)
C13—C4—C5	115.49 (10)	C14—C15—H15A	119.4
C3—C4—H4A	107.9	C16—C15—H15A	119.4
C13—C4—H4A	107.9	C17—C16—C15	118.17 (11)
C5—C4—H4A	107.9	C17—C16—C19	121.37 (12)
C20—C5—C21	109.80 (12)	C15—C16—C19	120.45 (12)
C20—C5—C1	109.45 (10)	C16—C17—C18	120.70 (11)
C21—C5—C1	107.65 (12)	C16—C17—H17A	119.6
C20—C5—C4	110.92 (10)	C18—C17—H17A	119.6
C21—C5—C4	115.12 (11)	C17—C18—C13	121.32 (11)
C1—C5—C4	103.58 (10)	C17—C18—H18A	119.3
C7—C6—C11	118.39 (11)	C13—C18—H18A	119.3
C7—C6—C3	121.01 (12)	C16—C19—H19A	109.5
C11—C6—C3	120.60 (11)	C16—C19—H19B	109.5
C8—C7—C6	120.31 (12)	H19A—C19—H19B	109.5
C8—C7—H7A	119.8	C16—C19—H19C	109.5
C6—C7—H7A	119.8	H19A—C19—H19C	109.5
C7—C8—C9	121.37 (12)	H19B—C19—H19C	109.5
C7—C8—H8A	119.3	C5—C20—H20A	109.5
C9—C8—H8A	119.3	C5—C20—H20B	109.5
C10—C9—C8	118.44 (13)	H20A—C20—H20B	109.5
C10—C9—C12	120.77 (13)	C5—C20—H20C	109.5
C8—C9—C12	120.75 (13)	H20A—C20—H20C	109.5
C11—C10—C9	120.54 (12)	H20B—C20—H20C	109.5
C11—C10—H10A	119.7	C5—C21—H21A	109.5
C9—C10—H10A	119.7	C5—C21—H21B	109.5
C10—C11—C6	120.92 (12)	H21A—C21—H21B	109.5
C10—C11—H11A	119.5	C5—C21—H21C	109.5
C6—C11—H11A	119.5	H21A—C21—H21C	109.5
C9—C12—H12A	109.5	H21B—C21—H21C	109.5
C9—C12—H12B	109.5
O1—C1—C2—C3	−174.33 (14)	C11—C6—C7—C8	−0.41 (18)
C5—C1—C2—C3	4.22 (15)	C3—C6—C7—C8	−179.62 (12)
C1—C2—C3—C6	174.66 (12)	C6—C7—C8—C9	1.4 (2)
C1—C2—C3—C4	−4.37 (15)	C7—C8—C9—C10	−0.6 (2)
C2—C3—C4—C13	−123.54 (11)	C7—C8—C9—C12	−178.52 (14)
C6—C3—C4—C13	57.38 (14)	C8—C9—C10—C11	−1.1 (2)
C2—C3—C4—C5	2.71 (14)	C12—C9—C10—C11	176.80 (13)
C6—C3—C4—C5	−176.37 (10)	C9—C10—C11—C6	2.1 (2)
O1—C1—C5—C20	57.90 (18)	C7—C6—C11—C10	−1.31 (18)
C2—C1—C5—C20	−120.70 (11)	C3—C6—C11—C10	177.91 (12)
O1—C1—C5—C21	−61.39 (17)	C3—C4—C13—C18	−155.44 (11)
C2—C1—C5—C21	120.00 (12)	C5—C4—C13—C18	84.38 (14)
O1—C1—C5—C4	176.25 (14)	C3—C4—C13—C14	25.73 (15)
C2—C1—C5—C4	−2.35 (13)	C5—C4—C13—C14	−94.45 (14)
C3—C4—C5—C20	117.27 (11)	C18—C13—C14—C15	0.32 (17)
C13—C4—C5—C20	−118.23 (12)	C4—C13—C14—C15	179.17 (11)
C3—C4—C5—C21	−117.30 (13)	C13—C14—C15—C16	−1.64 (18)
C13—C4—C5—C21	7.20 (17)	C14—C15—C16—C17	1.20 (18)
C3—C4—C5—C1	−0.06 (12)	C14—C15—C16—C19	−178.81 (12)
C13—C4—C5—C1	124.44 (11)	C15—C16—C17—C18	0.54 (19)
C2—C3—C6—C7	28.61 (19)	C19—C16—C17—C18	−179.46 (13)
C4—C3—C6—C7	−152.43 (12)	C16—C17—C18—C13	−1.87 (19)
C2—C3—C6—C11	−150.58 (13)	C14—C13—C18—C17	1.42 (18)
C4—C3—C6—C11	28.37 (17)	C4—C13—C18—C17	−177.46 (11)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C12—H12B···O1^i	0.98	2.48	3.429 (3)	164
C17—H17···Cg^ii	0.95	2.86	3.477 (2)	123

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