6-Bromo-2,2-diphenyl-2H-1-benzopyran

2H-Benzopyrans (chromenes) and their analogues are the subject of considerable current inter­est due to their highly desirable photochromic properties. Although the benzopyran fragment in the title compound, C₂₁H₁₅BrO, is roughly planar, the pyran ring may be regarded as having a half-chair conformation.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.044
• wR factor = 0.115
• Data-to-parameter ratio = 22.4

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT062_ALERT_4_C Rescale T(min) & T(max) by .....................       1.09
PLAT154_ALERT_1_C The su's on the Cell Angles are Equal  (x 10000)        300 Deg.

Alert level G
ABSTM02_ALERT_3_G  When printed, the submitted absorption T values will be
            replaced by the scaled T values. Since the ratio of scaled T's
            is identical to the ratio of reported T values, the scaling
            does not imply a change to the absorption corrections used in
            the study.
            Ratio of Tmax expected/reported      1.088
            Tmax scaled      0.686 Tmin scaled      0.566
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K

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

   3 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

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S1. Comment

During the last years extensive research has been directed towards the functionalization of chromenes. This interest was justified by the wide range of potential practical applications of these materials in opto-electronic and photonic technologies (Pozzo et al., 1996; Pozzo et al., 1997; Gemert et al., 1999; Crano et al., 1996). Bromine-substituted 2H-benzopyrans (Bougdid et al., 2007) are attractive building blocks for the design of various photochromic molecules for many targets (Shilova et al., 2007). Missing any thorough study of their X-ray structure has motivated us to investigate this type of compounds more detailed.

The pyrane ring in compound (I) has an half-chair conformation with puckering amplitude (Q) = 0.348 (2) Å, θ = 66.6 (5) °, φ = 31.4 (5) ° (Cremer & Pople, 1975) but the benzopyran fragment is nearly planar with the largest deviation from the plane being 0.390 (2) Å at C7 (Fig. 1).

Related literature

For related literature, see: Bougdid et al. (2007); Crano et al. (1996); Cremer & Pople (1975); Gemert (1999); Pozzo et al. (1996, 1997); Shilova et al. (2007).

S2. Experimental

Diagram 1

6-Bromo-2,2-diphenyl-2H-1-benzopyran. 3,3-diphenylprop-1-yn-3-ol (11 mmol), 4-bromophenol (10 mmol), a catalytic amount of p-toluene sulfonic acid (PTSA) and dry dichloromethane (20 ml) purged with argon and stirred at room temperature for 6–10 h. The progress of the reaction was monitored by TLC (pentane/Et₂O, 1:1). After complete disappearance of the bromophenol, the reaction mixture was washed with brine (3x20 ml). The organic layer was dried with MgSO₄, filtered and concentrated to dryness under reduced pressure. Purification by column chromatography (SiO₂; cyclohexane/dichloromethane gradient 100:0 to 50:50) afforded the pure compound as a light yellow solid (yield 74%). Crystals appropriate for data collection were obtained by slow evaporation from acetonitrile solution at 277 K. M.p.125–126 ^oC. FT—IR (KBr): ν= 3055, 3026, 2968, 2924, 1629, 1597, 1472, 1446, 1416, 1265, 1242, 1212, 1163, 1128, 1053, 993, 945, 915, 876, 816, 767, 752, 701, 558 cm^-1 _. ¹H NMR (250 MHz, CDCl₃): δ = 6.13 (d, J = 10.0 Hz, 1 H), 6.47 (d, J = 10.0 Hz, 1 H), 6.72 (d, J = 7.5 Hz, 1 H), 7.04 (d, J = 2.5 Hz, 1 H), 7.12 (dd, J = 2.5, 7.5 Hz, 1 H), 7.15–7.35 (m, 10 H). ¹³C NMR (62.5 MHz, CDCl₃): δ= 82.9 (OC), 113.2 (C), 118.3 (CH=), 122.4 (CH=), 123.0 (C), 127.0 (4 x CH=), 127.7 (2 x CH=), 128.2 (4 x CH=), 129.0 (CH=), 130.2 (CH=), 132.0 (CH=), 144.4 (2 x C), 151.6 (C). Anal. Calcd. for C₂₁H₁₅BrO: C, 69.43; H, 4.16; Br, 21.99. Found: C, 69.52; H, 4.23; Br, 22.01.

S3. Refinement

All H atoms were fixed geometrically and treated as riding with C—H = 0.93 Å with U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: KappaCCD Reference Manual (Nonius, 1998); cell refinement: DENZO and SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Burnett & Johnson, 1996) and ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: PLATON (Spek, 2003).

Figures

Fig. 1. Molecular view of compound (I) with the atom-labelling scheme. Ellipsoids are drawn at the 50% propability level. H atoms are represented as small sphers of arbitrary radii.

6-Bromo-2,2-diphenyl-2H-1-benzopyran

Crystal data

C21H15BrO	F(000) = 368
Mr = 363.24	Dx = 1.476 Mg m^−3
Triclinic, P1	Melting point: 399(1) K
a = 8.9633 (4) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.4284 (4) Å	Cell parameters from 17241 reflections
c = 10.5524 (5) Å	θ = 2.3–29.9°
α = 72.461 (3)°	µ = 2.52 mm^−1
β = 79.150 (3)°	T = 293 K
γ = 75.594 (3)°	Prism, light yellow
V = 817.37 (7) Å^3	0.20 × 0.20 × 0.15 mm
Z = 2

Data collection

Nonius KappaCCD area-detector diffractometer	4665 independent reflections
Radiation source: fine-focus sealed tube	3473 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.040
φ scans	θmax = 29.9°, θmin = 2.3°
Absorption correction: multi-scan (Blessing & Langs, 1987)	h = −9→12
Tmin = 0.52, Tmax = 0.63	k = −13→12
17241 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)] = 0.044	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.115	H-atom parameters constrained
S = 1.10	w = 1/[σ^2(Fo^2) + (0.0375P)^2 + 0.5037P] where P = (Fo^2 + 2Fc^2)/3
4665 reflections	(Δ/σ)max < 0.001
208 parameters	Δρmax = 0.54 e Å^−3
0 restraints	Δρmin = −0.66 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
C1	−0.2030 (3)	0.5056 (3)	0.7994 (2)	0.0455 (5)
H1	−0.1481	0.4083	0.8355	0.055*
C2	−0.3641 (3)	0.5354 (4)	0.8156 (3)	0.0566 (7)
H2	−0.4161	0.4580	0.8639	0.068*
C3	−0.4478 (3)	0.6772 (4)	0.7614 (3)	0.0578 (7)
H3	−0.5557	0.6966	0.7732	0.069*
C4	−0.3699 (3)	0.7901 (4)	0.6895 (3)	0.0624 (7)
H4	−0.4254	0.8861	0.6505	0.075*
C5	−0.2086 (3)	0.7623 (3)	0.6744 (3)	0.0504 (6)
H5	−0.1574	0.8403	0.6264	0.061*
C6	−0.1237 (2)	0.6198 (3)	0.7299 (2)	0.0361 (4)
C7	0.0536 (2)	0.5925 (3)	0.7133 (2)	0.0347 (4)
C8	0.1046 (2)	0.7238 (3)	0.7401 (2)	0.0349 (4)
C9	0.1586 (3)	0.8380 (3)	0.6386 (2)	0.0481 (6)
H9	0.1703	0.8344	0.5501	0.058*
C10	0.1955 (4)	0.9587 (3)	0.6686 (3)	0.0610 (7)
H10	0.2312	1.0356	0.5998	0.073*
C11	0.1795 (4)	0.9647 (3)	0.7991 (3)	0.0604 (7)
H11	0.2049	1.0450	0.8186	0.073*
C12	0.1260 (4)	0.8525 (3)	0.8999 (3)	0.0569 (7)
H12	0.1145	0.8569	0.9882	0.068*
C13	0.0888 (3)	0.7321 (3)	0.8714 (2)	0.0444 (5)
H13	0.0529	0.6561	0.9409	0.053*
O14	0.10089 (18)	0.45443 (18)	0.81754 (15)	0.0392 (3)
C15	0.2510 (2)	0.3768 (2)	0.8033 (2)	0.0353 (4)
C16	0.3325 (3)	0.3782 (3)	0.6767 (2)	0.0378 (5)
C17	0.2525 (3)	0.4684 (3)	0.5611 (2)	0.0433 (5)
H17	0.2933	0.4561	0.4764	0.052*
C18	0.1215 (3)	0.5682 (3)	0.5767 (2)	0.0404 (5)
H18	0.0706	0.6242	0.5026	0.049*
C19	0.3154 (3)	0.2885 (3)	0.9189 (2)	0.0406 (5)
H19	0.2586	0.2864	1.0026	0.049*
C20	0.4657 (3)	0.2032 (3)	0.9082 (2)	0.0438 (5)
H20	0.5105	0.1436	0.9847	0.053*
C21	0.5477 (3)	0.2079 (3)	0.7829 (3)	0.0443 (5)
C22	0.4828 (3)	0.2917 (3)	0.6675 (2)	0.0449 (5)
H22	0.5390	0.2904	0.5841	0.054*
Br23	0.75853 (3)	0.10283 (4)	0.77031 (3)	0.06376 (13)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0412 (12)	0.0520 (14)	0.0471 (13)	−0.0164 (10)	−0.0043 (10)	−0.0143 (11)
C2	0.0449 (14)	0.0749 (19)	0.0608 (16)	−0.0297 (14)	0.0021 (12)	−0.0251 (14)
C3	0.0302 (12)	0.082 (2)	0.0717 (18)	−0.0139 (12)	−0.0017 (11)	−0.0365 (16)
C4	0.0355 (13)	0.0635 (17)	0.088 (2)	−0.0017 (12)	−0.0165 (13)	−0.0215 (16)
C5	0.0341 (12)	0.0518 (14)	0.0621 (16)	−0.0093 (10)	−0.0091 (10)	−0.0081 (12)
C6	0.0306 (10)	0.0476 (12)	0.0343 (10)	−0.0106 (9)	−0.0034 (8)	−0.0154 (9)
C7	0.0314 (10)	0.0431 (11)	0.0278 (9)	−0.0074 (8)	−0.0027 (7)	−0.0076 (8)
C8	0.0255 (9)	0.0455 (12)	0.0332 (10)	−0.0059 (8)	−0.0048 (7)	−0.0100 (9)
C9	0.0506 (14)	0.0567 (15)	0.0373 (12)	−0.0187 (12)	−0.0073 (10)	−0.0054 (11)
C10	0.0639 (18)	0.0525 (16)	0.0650 (18)	−0.0227 (14)	−0.0153 (14)	−0.0004 (13)
C11	0.0584 (17)	0.0527 (15)	0.080 (2)	−0.0148 (13)	−0.0191 (14)	−0.0225 (14)
C12	0.0592 (17)	0.0668 (17)	0.0536 (15)	−0.0121 (14)	−0.0115 (12)	−0.0271 (14)
C13	0.0437 (13)	0.0562 (14)	0.0361 (11)	−0.0141 (11)	−0.0015 (9)	−0.0152 (10)
O14	0.0324 (8)	0.0455 (8)	0.0334 (7)	−0.0038 (6)	−0.0009 (6)	−0.0067 (6)
C15	0.0331 (10)	0.0375 (11)	0.0365 (11)	−0.0068 (8)	−0.0030 (8)	−0.0125 (9)
C16	0.0358 (11)	0.0452 (12)	0.0350 (11)	−0.0078 (9)	−0.0027 (8)	−0.0159 (9)
C17	0.0413 (12)	0.0607 (14)	0.0309 (11)	−0.0088 (10)	−0.0023 (8)	−0.0190 (10)
C18	0.0381 (11)	0.0554 (13)	0.0285 (10)	−0.0089 (10)	−0.0063 (8)	−0.0114 (9)
C19	0.0427 (12)	0.0406 (11)	0.0361 (11)	−0.0078 (9)	−0.0028 (9)	−0.0083 (9)
C20	0.0439 (13)	0.0404 (12)	0.0458 (13)	−0.0034 (10)	−0.0108 (10)	−0.0108 (10)
C21	0.0376 (12)	0.0436 (12)	0.0541 (14)	0.0005 (9)	−0.0091 (10)	−0.0217 (11)
C22	0.0395 (12)	0.0549 (14)	0.0433 (12)	−0.0039 (10)	−0.0024 (9)	−0.0237 (11)
Br23	0.04440 (17)	0.0739 (2)	0.0716 (2)	0.01358 (13)	−0.01355 (13)	−0.03444 (16)

Geometric parameters (Å, º)

C1—C6	1.382 (3)	C11—C12	1.365 (4)
C1—C2	1.389 (4)	C11—H11	0.9300
C1—H1	0.9300	C12—C13	1.386 (4)
C2—C3	1.371 (5)	C12—H12	0.9300
C2—H2	0.9300	C13—H13	0.9300
C3—C4	1.370 (4)	O14—C15	1.367 (3)
C3—H3	0.9300	C15—C19	1.388 (3)
C4—C5	1.391 (4)	C15—C16	1.395 (3)
C4—H4	0.9300	C16—C22	1.394 (3)
C5—C6	1.383 (3)	C16—C17	1.458 (3)
C5—H5	0.9300	C17—C18	1.327 (3)
C6—C7	1.530 (3)	C17—H17	0.9300
C7—O14	1.456 (3)	C18—H18	0.9300
C7—C18	1.517 (3)	C19—C20	1.390 (3)
C7—C8	1.537 (3)	C19—H19	0.9300
C8—C9	1.382 (3)	C20—C21	1.381 (4)
C8—C13	1.390 (3)	C20—H20	0.9300
C9—C10	1.396 (4)	C21—C22	1.379 (4)
C9—H9	0.9300	C21—Br23	1.903 (2)
C10—C11	1.374 (4)	C22—H22	0.9300
C10—H10	0.9300
C6—C1—C2	120.4 (3)	C12—C11—H11	120.1
C6—C1—H1	119.8	C10—C11—H11	120.1
C2—C1—H1	119.8	C11—C12—C13	120.4 (3)
C3—C2—C1	121.0 (3)	C11—C12—H12	119.8
C3—C2—H2	119.5	C13—C12—H12	119.8
C1—C2—H2	119.5	C12—C13—C8	120.7 (2)
C4—C3—C2	119.0 (3)	C12—C13—H13	119.6
C4—C3—H3	120.5	C8—C13—H13	119.6
C2—C3—H3	120.5	C15—O14—C7	117.79 (16)
C3—C4—C5	120.6 (3)	O14—C15—C19	117.65 (19)
C3—C4—H4	119.7	O14—C15—C16	120.90 (19)
C5—C4—H4	119.7	C19—C15—C16	121.3 (2)
C6—C5—C4	120.7 (3)	C22—C16—C15	118.7 (2)
C6—C5—H5	119.6	C22—C16—C17	123.9 (2)
C4—C5—H5	119.6	C15—C16—C17	117.4 (2)
C1—C6—C5	118.3 (2)	C18—C17—C16	120.0 (2)
C1—C6—C7	121.9 (2)	C18—C17—H17	120.0
C5—C6—C7	119.8 (2)	C16—C17—H17	120.0
O14—C7—C18	109.85 (18)	C17—C18—C7	121.2 (2)
O14—C7—C6	104.92 (16)	C17—C18—H18	119.4
C18—C7—C6	110.74 (17)	C7—C18—H18	119.4
O14—C7—C8	108.43 (16)	C15—C19—C20	119.3 (2)
C18—C7—C8	112.69 (18)	C15—C19—H19	120.3
C6—C7—C8	109.90 (18)	C20—C19—H19	120.3
C9—C8—C13	118.5 (2)	C21—C20—C19	119.3 (2)
C9—C8—C7	122.7 (2)	C21—C20—H20	120.3
C13—C8—C7	118.66 (19)	C19—C20—H20	120.3
C8—C9—C10	120.2 (2)	C22—C21—C20	121.7 (2)
C8—C9—H9	119.9	C22—C21—Br23	119.49 (18)
C10—C9—H9	119.9	C20—C21—Br23	118.78 (18)
C11—C10—C9	120.4 (3)	C21—C22—C16	119.6 (2)
C11—C10—H10	119.8	C21—C22—H22	120.2
C9—C10—H10	119.8	C16—C22—H22	120.2
C12—C11—C10	119.8 (3)
O14—C7—C8—C9	142.9 (2)	O14—C7—C6—C5	161.2 (2)