6,6-Di­methyl-2-phenyl-4,5,6,7-tetra­hydro­benzo­furan-4-one

In the title compound, C₁₆H₁₆O₂, the tetra­hydro­benzene ring adopts a half-chair conformation. The phenyl substituent is almost coplanar with the furan ring.

Key indicators

• Single-crystal X-ray study
• T = 213 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.069
• wR factor = 0.172
• Data-to-parameter ratio = 18.8

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

The strong one-electron oxidant ceric ammonium nitrate (CAN) has been established as an efficient reagent in generating α-carbonylalkyl radicals from enolizable ketones and the addition of these carbon-centered radicals to alkenes have been successfully used in organic synthesis in various C—C bond-formation reactions (Nair et al., 1997). We have recently investigated CAN-mediated reactions of 1,3-dicarbonyl compounds with phenylacetylene (Li & Xu, 2002), and we report here the crystal structure of the title compound, (I), which is one of the products in the reaction of 5,5-dimethylcyclohexa-1,3-dione with phenylacetylene.

The bond lengths and angles in (I) (Fig. 1) are within normal ranges (Allen et al., 1987). In the tetrahydrobenzofuran moiety (O1/C1—C8), the furan ring is planar, while the tetrahydrobenzene ring is not planar and adopts a half-chair conformation. Atoms C3 and C4 are displaced by −0.536 (2) and 0.166 (2) Å, respectively, from the C1/C2/C5/C6 plane. This conformation is also confirmed by its puckering parameters [Q₂ = 0.377 (2) Å, Q₃ = −0.283 (2) Å, Q_T = 0.471 (2) Å, ϕ = 46.5 (3)° and θ = 53.1 (2)°; Cremer & Pople, 1975]. The two ring planes are nearly coplanar, corresponding to the dihedral angle of 7.7 (1)°. The attached ketone atom O2 deviates by 0.231 (1) Å from the tetrahydrobenzene ring plane, and the configurations of the two methyl groups, C15 and C16, are conditioned by the sp³ state of the C3 atom, with the average angle subtended at the C3 atom being 109.5°.

The C9–C14 phenyl ring and the furan ring are almost coplanar, with a dihedral angle of 7.0 (1)°. This enhances the π-conjugation interactions between the two rings and slightly shorten the C8—C9 bond length [1.460 (2) Å, cf. C_sp2—C_ar 1.470 (Allen et al., 1987)].

S2. Experimental

The title compound, (I), was isolated from the reaction of 5,5-dimethylcyclohexa-1,3-dione with ceric ammonium nitrate (CAN) in the presence of an excess amount of phenylacetylene in acetonitrile by column chromatography on silica gel. Single crystals of (I) suitable for X-ray crystallographic measurements were prepared by slow evaporation of the solvent from a petroleum ether–ethyl acetate solution (4:1 v/v).

S3. Refinement

The H atoms were fixed geometrically and were treated as riding atoms on the parent C atoms, with C—H distances = 0.93–0.97 Å and U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT and SADABS (Sheldrick, 1996); program(s) used to solve structure: SHELXTL (Sheldrick, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL, PARST (Nardelli, 1995) and PLATON (Spek, 1990).

Figures

Fig. 1. The structure of (I), showing 50% probability displacement ellipsoids and the atom-numbering scheme.

6,6-Dimethyl-2-phenyl-4,5,6,7-tetrahydrobenzofuran-4-one

Crystal data

C16H16O2	F(000) = 512
Mr = 240.29	Dx = 1.237 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 5.9261 (3) Å	Cell parameters from 5717 reflections
b = 11.1029 (6) Å	θ = 2.8–28.3°
c = 19.6978 (11) Å	µ = 0.08 mm^−1
β = 95.521 (1)°	T = 213 K
V = 1290.0 (1) Å^3	Block, colorless
Z = 4	0.44 × 0.38 × 0.28 mm

Data collection

Siemens SMART CCD area-detector diffractometer	2228 reflections with I > 2σ(I)'
Radiation source: fine-focus sealed tube	Rint = 0.093
Graphite monochromator	θmax = 28.3°, θmin = 2.8°
Detector resolution: 8.33 pixels mm^-1	h = −7→7
ω scans	k = −14→14
7600 measured reflections	l = −18→26
3123 independent reflections

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)] = 0.069	H-atom parameters constrained
wR(F^2) = 0.172	w = 1/[σ^2(Fo^2) + (0.0884P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.94	(Δ/σ)max < 0.001
3123 reflections	Δρmax = 0.48 e Å^−3
166 parameters	Δρmin = −0.43 e Å^−3
0 restraints	Extinction correction: SHELXTL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.073 (8)

Special details

Experimental. The data collection covered over a hemisphere of reciprocal space by a combination of three sets of exposures; each set had a different ϕ angle (0, 88 and 180°) for the crystal and each exposure of 30 s covered 0.3° in ω. The crystal-to-detector distance was 5 cm and the detector swing angle was −35°. Crystal decay was monitored by repeating fifty initial frames at the end of data collection and analysing the intensity of duplicate reflections, and was found to be negligible.

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	0.15951 (18)	0.92435 (10)	0.12959 (5)	0.0260 (3)
O2	−0.2391 (2)	1.25676 (10)	0.18815 (6)	0.0389 (3)
C1	0.1602 (3)	1.02093 (14)	0.17239 (7)	0.0246 (4)
C2	0.3476 (3)	1.04185 (16)	0.22640 (8)	0.0298 (4)
H2A	0.4746	1.0791	0.2069	0.036*
H2B	0.3981	0.9657	0.2467	0.036*
C3	0.2631 (3)	1.12510 (14)	0.28160 (8)	0.0271 (4)
C4	0.1331 (3)	1.23240 (14)	0.24656 (8)	0.0309 (4)
H4A	0.0781	1.2833	0.2815	0.037*
H4B	0.2380	1.2798	0.2227	0.037*
C5	−0.0654 (3)	1.19711 (14)	0.19654 (8)	0.0275 (4)
C6	−0.0296 (3)	1.08724 (14)	0.15819 (8)	0.0253 (4)
C7	−0.1630 (3)	1.02746 (14)	0.10399 (8)	0.0280 (4)
H7	−0.3046	1.0510	0.0839	0.034*
C8	−0.0428 (3)	0.93004 (14)	0.08766 (7)	0.0240 (4)
C9	−0.0831 (3)	0.83434 (13)	0.03713 (7)	0.0246 (4)
C10	−0.2926 (3)	0.82647 (16)	−0.00152 (9)	0.0344 (4)
H10	−0.4051	0.8823	0.0054	0.041*
C11	−0.3357 (3)	0.73705 (17)	−0.04995 (9)	0.0403 (5)
H11	−0.4754	0.7337	−0.0758	0.048*
C12	−0.1704 (3)	0.65270 (16)	−0.05990 (9)	0.0381 (5)
H12	−0.1992	0.5919	−0.0920	0.046*
C13	0.0375 (3)	0.65922 (15)	−0.02193 (9)	0.0358 (4)
H13	0.1490	0.6027	−0.0287	0.043*
C14	0.0817 (3)	0.74926 (14)	0.02626 (8)	0.0295 (4)
H14	0.2225	0.7528	0.0515	0.035*
C15	0.1062 (3)	1.05533 (16)	0.32505 (9)	0.0364 (4)
H15A	−0.0216	1.0253	0.2964	0.055*
H15B	0.0543	1.1079	0.3590	0.055*
H15C	0.1877	0.9891	0.3470	0.055*
C16	0.4655 (3)	1.17231 (19)	0.32773 (10)	0.0423 (5)
H16A	0.4127	1.2233	0.3622	0.063*
H16B	0.5629	1.2176	0.3010	0.063*
H16C	0.5481	1.1057	0.3489	0.063*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0267 (6)	0.0289 (6)	0.0222 (6)	0.0030 (5)	0.0005 (4)	−0.0047 (4)
O2	0.0422 (8)	0.0299 (7)	0.0437 (7)	0.0095 (6)	−0.0004 (6)	−0.0038 (5)
C1	0.0266 (8)	0.0248 (8)	0.0228 (7)	−0.0027 (6)	0.0048 (6)	−0.0045 (6)
C2	0.0243 (8)	0.0365 (9)	0.0285 (8)	−0.0007 (7)	0.0016 (6)	−0.0096 (6)
C3	0.0253 (8)	0.0302 (8)	0.0257 (8)	−0.0009 (7)	0.0019 (6)	−0.0061 (6)
C4	0.0364 (10)	0.0248 (8)	0.0312 (8)	−0.0026 (7)	0.0023 (7)	−0.0060 (6)
C5	0.0345 (9)	0.0207 (7)	0.0275 (8)	0.0003 (7)	0.0041 (6)	−0.0002 (6)
C6	0.0274 (8)	0.0236 (8)	0.0245 (8)	0.0006 (6)	0.0008 (6)	−0.0001 (6)
C7	0.0285 (8)	0.0284 (8)	0.0259 (8)	0.0041 (7)	−0.0029 (6)	0.0003 (6)
C8	0.0266 (8)	0.0265 (8)	0.0187 (7)	−0.0004 (6)	0.0002 (6)	0.0013 (5)
C9	0.0310 (9)	0.0251 (8)	0.0178 (7)	−0.0010 (6)	0.0024 (6)	0.0016 (5)
C10	0.0359 (10)	0.0361 (9)	0.0301 (9)	0.0038 (8)	−0.0027 (7)	−0.0067 (7)
C11	0.0412 (11)	0.0460 (11)	0.0319 (9)	−0.0038 (9)	−0.0059 (8)	−0.0090 (8)
C12	0.0506 (12)	0.0351 (10)	0.0284 (9)	−0.0053 (8)	0.0023 (8)	−0.0095 (7)
C13	0.0451 (11)	0.0321 (9)	0.0307 (9)	0.0059 (8)	0.0065 (7)	−0.0043 (7)
C14	0.0338 (9)	0.0302 (9)	0.0243 (8)	0.0026 (7)	0.0014 (6)	0.0001 (6)
C15	0.0458 (11)	0.0367 (9)	0.0278 (8)	0.0010 (8)	0.0094 (8)	0.0012 (7)
C16	0.0368 (10)	0.0501 (11)	0.0384 (10)	−0.0004 (9)	−0.0041 (8)	−0.0187 (8)

Geometric parameters (Å, º)

O1—C1	1.3638 (17)	C8—C9	1.460 (2)
O1—C8	1.3905 (18)	C9—C14	1.390 (2)
O2—C5	1.222 (2)	C9—C10	1.395 (2)
C1—C6	1.351 (2)	C10—C11	1.384 (2)
C1—C2	1.480 (2)	C10—H10	0.9300
C2—C3	1.546 (2)	C11—C12	1.383 (3)
C2—H2A	0.9700	C11—H11	0.9300
C2—H2B	0.9700	C12—C13	1.380 (3)
C3—C16	1.526 (2)	C12—H12	0.9300
C3—C15	1.533 (2)	C13—C14	1.386 (2)
C3—C4	1.545 (2)	C13—H13	0.9300
C4—C5	1.512 (2)	C14—H14	0.9300
C4—H4A	0.9700	C15—H15A	0.9600
C4—H4B	0.9700	C15—H15B	0.9600
C5—C6	1.461 (2)	C15—H15C	0.9600
C6—C7	1.429 (2)	C16—H16A	0.9600
C7—C8	1.351 (2)	C16—H16B	0.9600
C7—H7	0.9300	C16—H16C	0.9600
C1—O1—C8	106.41 (12)	C7—C8—C9	133.62 (15)
C6—C1—O1	110.35 (14)	O1—C8—C9	116.56 (13)
C6—C1—C2	127.97 (14)	C14—C9—C10	118.35 (15)
O1—C1—C2	121.67 (14)	C14—C9—C8	121.89 (15)
C1—C2—C3	109.15 (13)	C10—C9—C8	119.76 (15)
C1—C2—H2A	109.9	C11—C10—C9	121.11 (17)
C3—C2—H2A	109.8	C11—C10—H10	119.4
C1—C2—H2B	109.8	C9—C10—H10	119.4
C3—C2—H2B	109.8	C12—C11—C10	119.84 (17)
H2A—C2—H2B	108.3	C12—C11—H11	120.1
C16—C3—C15	108.99 (14)	C10—C11—H11	120.1
C16—C3—C4	109.32 (14)	C13—C12—C11	119.68 (16)
C15—C3—C4	109.61 (13)	C13—C12—H12	120.2
C16—C3—C2	109.58 (13)	C11—C12—H12	120.2
C15—C3—C2	110.19 (14)	C12—C13—C14	120.58 (17)
C4—C3—C2	109.14 (13)	C12—C13—H13	119.7
C5—C4—C3	114.51 (13)	C14—C13—H13	119.7
C5—C4—H4A	108.6	C13—C14—C9	120.43 (16)
C3—C4—H4A	108.6	C13—C14—H14	119.8
C5—C4—H4B	108.6	C9—C14—H14	119.8
C3—C4—H4B	108.6	C3—C15—H15A	109.5
H4A—C4—H4B	107.6	C3—C15—H15B	109.5
O2—C5—C6	123.04 (15)	H15A—C15—H15B	109.5
O2—C5—C4	122.70 (14)	C3—C15—H15C	109.5
C6—C5—C4	114.25 (14)	H15A—C15—H15C	109.5
C1—C6—C7	106.93 (13)	H15B—C15—H15C	109.5
C1—C6—C5	120.50 (14)	C3—C16—H16A	109.5
C7—C6—C5	132.57 (15)	C3—C16—H16B	109.5
C8—C7—C6	106.46 (14)	H16A—C16—H16B	109.5
C8—C7—H7	126.8	C3—C16—H16C	109.5
C6—C7—H7	126.8	H16A—C16—H16C	109.5
C7—C8—O1	109.82 (13)	H16B—C16—H16C	109.5
C8—O1—C1—C6	−1.14 (16)	C4—C5—C6—C7	−175.26 (16)
C8—O1—C1—C2	177.72 (14)	C1—C6—C7—C8	−1.42 (18)
C6—C1—C2—C3	19.7 (2)	C5—C6—C7—C8	179.00 (16)
O1—C1—C2—C3	−158.98 (13)	C6—C7—C8—O1	0.75 (18)
C1—C2—C3—C16	−166.11 (15)	C6—C7—C8—C9	−179.45 (16)
C1—C2—C3—C15	73.98 (17)	C1—O1—C8—C7	0.19 (17)
C1—C2—C3—C4	−46.43 (18)	C1—O1—C8—C9	−179.64 (12)
C16—C3—C4—C5	177.08 (14)	C7—C8—C9—C14	173.45 (17)
C15—C3—C4—C5	−63.52 (17)	O1—C8—C9—C14	−6.8 (2)
C2—C3—C4—C5	57.23 (18)	C7—C8—C9—C10	−6.9 (3)
C3—C4—C5—O2	145.61 (16)	O1—C8—C9—C10	172.91 (14)
C3—C4—C5—C6	−35.64 (19)	C14—C9—C10—C11	−0.5 (3)
O1—C1—C6—C7	1.59 (18)	C8—C9—C10—C11	179.79 (16)
C2—C1—C6—C7	−177.18 (15)	C9—C10—C11—C12	0.9 (3)
O1—C1—C6—C5	−178.77 (13)	C10—C11—C12—C13	−0.7 (3)
C2—C1—C6—C5	2.5 (3)	C11—C12—C13—C14	0.3 (3)
O2—C5—C6—C1	−176.04 (15)	C12—C13—C14—C9	0.1 (3)
C4—C5—C6—C1	5.2 (2)	C10—C9—C14—C13	0.0 (2)
O2—C5—C6—C7	3.5 (3)	C8—C9—C14—C13	179.72 (15)