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The title compound, C23H28O2, was obtained from the reaction of acetone with meta-cresol. The molecular structure consists of two identical subunits which are nearly perpendicular to each other. The oxygen-containing rings are not planar and the molecule is chiral. The crystal structure consists of chains of molecules of the same chirality arranged along the [010] axis.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270199013190/gd1069sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270199013190/gd1069Isup2.hkl
Contains datablock I

CCDC reference: 140963

Comment top

4,4,4',4',7,7'-Hexamethyl-2,2'-spirobichroman, (I), belongs to the large and structurally diverse family of the condensation products of carbonyl compounds with phenols. In particular, the acid-catalysed reaction between meta-cresol and acetone can provide any of the compounds presented in the Scheme below. The preponderance of a particular compound in any reaction is dependent on the reaction conditions. Compound (I) was obtained in high yield from (IV) under the influence of boiling hydriodic acid (Baker & Besly, 1939). Another method for its preparation involves the heating (10 h at 423 K) of bisphenol-A with an excess of meta-cresol in the presence of methanesulfonic acid (Caruso & Lee, 1997).

The molecule of (I) is chiral, as are all dissymmetric spiranes. In the proton NMR spectrum, the geminal protons at C3 give two doublets with coupling constants of 14 Hz. Analogously, the methyl C atoms on C4 give two separated signals. Another interesting property of (I) is its dimorphism. According to differential scanning calorimetry (DSC) analyses, the crystals melt at 132.9°, solidify and melt again at 138.1°. Such behaviour seems to be a common feature of structurally related spirobichromans (Baker & Besly, 1939).

The molecule of (I) consists of two identical subunits, which are nearly perpendicular to each other (Fig. 1). The dihedral angle between the O1—C2—C3 and O1i—C2—C3i [symmetry code: (i) 3/2 − x, 1/2 − y, z] planes is 87.2 (1)°. The oxygen-containing ring is not planar, and the C2 and C3 atoms are displaced from the plane defined by the benzene ring by 0.393 (4) and −0.299 (4) Å, respectively. The O1 and C4 atoms are nearly coplanar, with deviations from the ring plane of 0.060 (3) and −0.065 (3) Å, respectively. The analogous half-chair conformation of the pyran ring was observed in (IV) (MacNicol & Mallinson, 1983). The connection of the subunits through the spirane carbon has no significant influence on the geometry of the pyran ring. The bond lengths are the same, within 0.01 Å, as those observed in (IV) (McNicol & Mallinson, 1983) and (V) (Dianin's compound; Flippen et al., 1970). The non-planar conformation of the pyran ring makes the environment of the H atoms on C3 different. The H31 atom occupies a quasi-axial position with a deviation of 1.26 (2) Å from the mean plane of pyran ring. The H32 atom lies in the plane and is situated on the same side of the ring as the O1i atom belonging to the second ring. Consequently, the distance between H32 and O1i [2.55 (2) Å] exceeds the sum of van der Waals radii by 0.05 Å. The difference in the chemical shifts of the methyl groups on C4 is only 0.02 p.p.m. The C41 and C42 atoms are the same distance from the parent aromatic ring, but their displacements from the C3—C4—C10 plane are different [1.207 (5) versus 1.275 (5) Å] because the C41 methyl group is directed outwards while the second methyl group approaches another chroman subunit. The molecule is rigid, hence it can be concluded that the different chemical shifts of C41 and C42 result from non-valence intramolecular interactions.

The crystals of (I) are racemic, i.e. they are built from both enantiomers, as in (IV) and (V). In the crystal structure of the latter, six molecules form the structural unit which consists of three pairs of enantiomers. The molecules of the same chirality are placed on one side of the O—H···O ring (Goldup & Smith, 1970). In clathrates of (IV), the enantiomers are arranged in pairs connected by hydrogen bonds with the guest molecules (Gall et al., 1985).

At the present stage of our investigations, we cannot formulate any convincing explanation of the nature and driving force of the transformation of (I) into its high-temperature polymorph.

Experimental top

A mixture of acetone (14.7 ml, 0.2 mol) meta-cresol (324 g, 3 mol) and methanesulfonic acid (1 ml) was left for 120 h at room temperature and then heated for 9 h to 413–423 K. The unreacted meta-cresol was distilled off in a vacuum. The residue was dissolved in benzene and extracted with water until neutral. The solvent was evaporated and a brown residue containing (I), (III) and (IV) was chromatographed using hexane as the eluent. 4,4,4',4',7,7'-Hexamethyl-2,2'-spirobichroman (5.04 g, 23%) was isolated from the last fractions as a white powder. Crystals suitable for X-ray diffraction studies were obtained by crystallization from methanol. MS, m/z (integration): 336 (4), 321 (35), 281 (13), 265 (21), 174 (14), 173 (100), 149 (71), 121 (11), 105 (12); 1H NMR (DMSO-d6): 7.23 (d, 3J = 7.3 Hz, 2H) and 6.71 (d, 3J = 7.3 Hz, 2H) (aromatic protons at C5, C5i, C6 and C6i), 6.36 (s, 2H, H8 and H8i), 2.11 (s, 6H, Ar-methyl groups), 2.07 (d, 1H) and 1.92 (d, 2J = 13.9 Hz, 1H) (methylene CH2 protons of the pyran ring), 1.51 (s, 6H) and 1.26 (s, 6H) (methyl protons of the isopropenyl bridge); 13C NMR (CDCl3): 150.3 (C9, C9i), 136.8 (C10, C10i); 128.5 (C7, C7i), 126.1, 122.4 and 118.1 (remaining aromatic carbons); 97.7 (spirane carbon, C2); 46.8 (methylene groups, C3, C3i); 32.5, 32.3 (methyl groups on C4 and C4i); 30.6 (C4, C4i); 20.8 (methyl groups at C7 and C7i).

Refinement top

H-atom positions were refined by the full-matrix least-squares method. The C—H distances were in the range 0.97 (2)–1.02 (3) Å for H atoms attached to phenyl rings and in the range 0.91 (5)–1.09 (3) Å range for methyl H atoms.

Computing details top

Data collection: Kuma Diffraction Software (Kuma, 1998); cell refinement: Kuma Diffraction Software; data reduction: Kuma Diffraction Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997b); molecular graphics: SHELXTL (Sheldrick, 1990); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The olecular structure of (I). Displacement ellipsoids are shown at 50% probability.
(I) top
Crystal data top
C23H28O2F(000) = 716
Mr = 336.45Dx = 1.132 Mg m3
Dm = ?' Mg m3
Dm measured by not measured
Orthorhombic, PccnMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ab 2acCell parameters from 21 reflections
a = 16.613 (3) Åθ = 10–20°
b = 10.557 (2) ŵ = 0.07 mm1
c = 11.259 (2) ÅT = 293 K
V = 1974.6 (6) Å3Plate, colourless
Z = 40.7 × 0.4 × 0.3 mm
Data collection top
Kuma KM-4
diffractometer
Rint = 0.021
Radiation source: fine-focus sealed tubeθmax = 25.1°, θmin = 2.9°
Graphite monochromatorh = 1813
ωθ scansk = 012
9984 measured reflectionsl = 1310
1592 independent reflections2 standard reflections every 50 reflections
1175 reflections with I > 2σ(I) intensity decay: 1.7%
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.046Hydrogen site location: difference Fourier map
wR(F2) = 0.131All H-atom parameters refined
S = 1.16Calculated w = 1/[σ2(Fo2) + (0.0546P)2 + 0.4667P]
where P = (Fo2 + 2Fc2)/3
1592 reflections(Δ/σ)max = 0.001
170 parametersΔρmax = 0.16 e Å3
0 restraintsΔρmin = 0.12 e Å3
Crystal data top
C23H28O2V = 1974.6 (6) Å3
Mr = 336.45Z = 4
Orthorhombic, PccnMo Kα radiation
a = 16.613 (3) ŵ = 0.07 mm1
b = 10.557 (2) ÅT = 293 K
c = 11.259 (2) Å0.7 × 0.4 × 0.3 mm
Data collection top
Kuma KM-4
diffractometer
Rint = 0.021
9984 measured reflections2 standard reflections every 50 reflections
1592 independent reflections intensity decay: 1.7%
1175 reflections with I > 2σ(I)
Refinement top
R[F2 > 2σ(F2)] = 0.0460 restraints
wR(F2) = 0.131All H-atom parameters refined
S = 1.16Δρmax = 0.16 e Å3
1592 reflectionsΔρmin = 0.12 e Å3
170 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.68228 (7)0.22499 (11)0.44239 (12)0.0593 (4)
C20.75000.25000.5162 (2)0.0544 (7)
C30.73624 (15)0.36735 (18)0.5898 (2)0.0625 (6)
C40.71517 (12)0.48733 (18)0.51973 (19)0.0624 (6)
C410.79053 (16)0.5546 (2)0.4738 (3)0.0745 (7)
C420.6714 (2)0.5769 (3)0.6057 (3)0.0908 (9)
C50.62291 (14)0.5425 (2)0.3478 (3)0.0775 (7)
C60.57193 (14)0.5106 (2)0.2563 (3)0.0823 (8)
C70.55599 (12)0.3851 (2)0.2291 (2)0.0724 (7)
C710.5025 (2)0.3496 (4)0.1274 (4)0.1035 (11)
C80.59392 (11)0.2939 (2)0.2961 (2)0.0618 (6)
C90.64672 (11)0.32637 (17)0.38589 (18)0.0547 (5)
C100.66119 (11)0.45148 (17)0.4170 (2)0.0596 (6)
H320.7837 (14)0.382 (2)0.639 (2)0.078 (7)*
H310.6897 (14)0.345 (2)0.642 (2)0.085 (7)*
H4110.7763 (13)0.636 (2)0.431 (2)0.083 (7)*
H4120.8271 (17)0.578 (3)0.541 (3)0.115 (10)*
H4130.8228 (14)0.501 (2)0.415 (2)0.083 (7)*
H4210.6575 (15)0.658 (3)0.565 (2)0.097 (8)*
H4220.7089 (19)0.600 (3)0.682 (3)0.132 (11)*
H4230.6191 (17)0.537 (3)0.629 (2)0.102 (9)*
H50.6348 (14)0.636 (2)0.364 (2)0.092 (7)*
H60.5491 (14)0.580 (2)0.211 (2)0.089 (7)*
H7110.510 (2)0.265 (4)0.095 (4)0.177 (18)*
H7120.488 (3)0.420 (4)0.086 (5)0.20 (2)*
H7130.448 (3)0.344 (4)0.159 (4)0.194 (18)*
H80.5857 (11)0.203 (2)0.2777 (17)0.062 (5)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0570 (7)0.0439 (7)0.0771 (9)0.0001 (6)0.0076 (7)0.0040 (6)
C20.0516 (14)0.0494 (14)0.0621 (16)0.0002 (12)0.0000.000
C30.0702 (15)0.0492 (12)0.0679 (13)0.0003 (10)0.0046 (12)0.0031 (10)
C40.0677 (12)0.0446 (11)0.0749 (13)0.0026 (9)0.0099 (11)0.0050 (10)
C410.0777 (15)0.0522 (13)0.0935 (18)0.0088 (11)0.0040 (15)0.0016 (13)
C420.116 (2)0.0587 (15)0.098 (2)0.0162 (15)0.0247 (18)0.0109 (15)
C50.0707 (14)0.0547 (13)0.1071 (19)0.0140 (11)0.0006 (14)0.0078 (13)
C60.0668 (14)0.0680 (15)0.112 (2)0.0171 (12)0.0031 (15)0.0209 (15)
C70.0463 (11)0.0815 (16)0.0895 (16)0.0050 (10)0.0017 (11)0.0158 (13)
C710.0794 (19)0.107 (3)0.124 (3)0.0023 (17)0.0341 (18)0.028 (2)
C80.0464 (11)0.0599 (13)0.0792 (14)0.0013 (9)0.0026 (11)0.0073 (11)
C90.0441 (10)0.0483 (10)0.0718 (13)0.0046 (8)0.0068 (9)0.0072 (9)
C100.0529 (11)0.0468 (10)0.0790 (14)0.0075 (8)0.0114 (10)0.0022 (10)
Geometric parameters (Å, º) top
O1—C91.378 (2)C4—C421.536 (3)
O1—C21.423 (2)C5—C61.375 (4)
C2—O1i1.423 (2)C5—C101.391 (3)
C2—C31.508 (2)C6—C71.386 (3)
C2—C3i1.508 (2)C7—C81.376 (3)
C3—C41.533 (3)C7—C711.497 (4)
C4—C101.512 (3)C8—C91.381 (3)
C4—C411.529 (3)C9—C101.387 (3)
C9—O1—C2117.7 (1)C3—C4—C42106.99 (19)
O1—C2—O1i108.6 (2)C6—C5—C10122.1 (2)
O1—C2—C3110.7 (1)C5—C6—C7121.2 (2)
O1i—C2—C3106.8 (1)C8—C7—C6117.4 (2)
O1—C2—C3i106.76 (10)C8—C7—C71121.1 (3)
O1i—C2—C3i110.71 (11)C6—C7—C71121.5 (2)
C3—C2—C3i113.3 (2)C7—C8—C9121.2 (2)
C2—C3—C4115.5 (2)O1—C9—C8114.7 (2)
C10—C4—C41110.09 (19)O1—C9—C10123.3 (2)
C10—C4—C3108.82 (16)C8—C9—C10122.1 (2)
C41—C4—C3111.75 (19)C9—C10—C5115.9 (2)
C10—C4—C42110.8 (2)C9—C10—C4122.3 (2)
C41—C4—C42108.3 (2)C5—C10—C4121.8 (2)
C9—O1—C2—O1i74.64 (13)C2—O1—C9—C1014.9 (3)
C9—O1—C2—C342.2 (2)C7—C8—C9—O1177.76 (18)
C9—O1—C2—C3i165.98 (16)C7—C8—C9—C103.2 (3)
O1—C2—C3—C455.4 (2)O1—C9—C10—C5177.48 (18)
O1i—C2—C3—C462.6 (2)C8—C9—C10—C53.6 (3)
C3i—C2—C3—C4175.3 (2)O1—C9—C10—C42.5 (3)
C2—C3—C4—C1037.8 (2)C8—C9—C10—C4176.39 (17)
C2—C3—C4—C4184.0 (2)C6—C5—C10—C91.9 (3)
C2—C3—C4—C42157.6 (2)C6—C5—C10—C4178.1 (2)
C10—C5—C6—C70.3 (4)C41—C4—C10—C9113.4 (2)
C5—C6—C7—C80.8 (4)C3—C4—C10—C99.4 (3)
C5—C6—C7—C71178.1 (3)C42—C4—C10—C9126.8 (2)
C6—C7—C8—C90.9 (3)C41—C4—C10—C566.6 (2)
C71—C7—C8—C9176.4 (2)C3—C4—C10—C5170.59 (19)
C2—O1—C9—C8166.09 (17)C42—C4—C10—C553.2 (3)
Symmetry code: (i) x+3/2, y+1/2, z.

Experimental details

Crystal data
Chemical formulaC23H28O2
Mr336.45
Crystal system, space groupOrthorhombic, Pccn
Temperature (K)293
a, b, c (Å)16.613 (3), 10.557 (2), 11.259 (2)
V3)1974.6 (6)
Z4
Radiation typeMo Kα
µ (mm1)0.07
Crystal size (mm)0.7 × 0.4 × 0.3
Data collection
DiffractometerKuma KM-4
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
9984, 1592, 1175
Rint0.021
(sin θ/λ)max1)0.596
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.046, 0.131, 1.16
No. of reflections1592
No. of parameters170
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.16, 0.12

Computer programs: Kuma Diffraction Software (Kuma, 1998), Kuma Diffraction Software, SHELXS97 (Sheldrick, 1997a), SHELXL97 (Sheldrick, 1997b), SHELXTL (Sheldrick, 1990), SHELXL97.

Selected geometric parameters (Å, º) top
O1—C91.378 (2)C3—C41.533 (3)
O1—C21.423 (2)C4—C101.512 (3)
C2—C31.508 (2)C9—C101.387 (3)
C9—O1—C2117.7 (1)C2—C3—C4115.5 (2)
O1—C2—O1i108.6 (2)O1—C9—C8114.7 (2)
O1—C2—C3110.7 (1)O1—C9—C10123.3 (2)
O1i—C2—C3106.8 (1)C8—C9—C10122.1 (2)
C3—C2—C3i113.3 (2)C9—C10—C4122.3 (2)
Symmetry code: (i) x+3/2, y+1/2, z.
 

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