meso-2-Methyl-5-[2-(4-methyl­furan-2-yl)-1,2-bis­(prop-2-yn­yloxy)eth­yl]furan

The title compound, C₁₈H₁₈O₄, crystallizes with half a mol­ecule in the asymmetric unit. The mol­ecule is centrosymmetric and the inversion centre is located in the middle of the furylic C—C bond. The furan rings show an exactly parallel orientation and the alkynyl groups have a parallel orientation with respect to the furan ring systems. Inter­molecular C—H...O hydrogen bonds are present in the crystal structure.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.048
• wR factor = 0.129
• Data-to-parameter ratio = 13.7

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT027_ALERT_3_B _diffrn_reflns_theta_full (too) Low ............      24.99 Deg.
PLAT063_ALERT_3_B Crystal Probably too Large for Beam Size .......       0.90 mm

Alert level C
PLAT480_ALERT_4_C Long H...A H-Bond Reported H3     ..  O1      ..       2.87 Ang.

Alert level G
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K
PLAT793_ALERT_1_G Check the Absolute Configuration of C6     = ...          S

   0 ALERT level A = In general: serious problem
   2 ALERT level B = Potentially serious problem
   1 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
   2 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

In the course of the investigation of the synthetic potential of fufural derivatives as renewable feedstocks (Hashmi et al., 2006; Hashmi, Ata et al., 2007) we investigated their possible transformation into bis-phenols in the gold-catalyzed phenol synthesis (Hashmi et al., 2000), one of the numerous gold-catalyzed cycloisomerization reactions known today (Hashmi, 2004; Hashmi & Hutchings, 2006a,b; Hashmi, 2007). This crystal structure analyis now allows a unambiguous assignment of the different diastereomers formed in previous step, the organo-catalyzed benzoin condensation of fufurals, and in the subsequent step, the gold-catalyzed synthesis of the benzoid arene ring.

The molecule crystallizes with a half of the molecule in the asymmetric unit (Fig. 1). The inversion centre located in the midd of C6—C6A (-x + 2, -y + 1, -z + 1) generates the molecule having the chiral centres of opposite chirality, characteristic of a meso-form. The perfect coplanar orientation of the two symmetry-related furan rings is indicated by the angle of their best planes of 0.00 (12)°. The alkynyl moieties shows a parallel orientation to the best plane of the furan moieties with an angle of 2.48 (19)°. The triple bond C8≡C9 is clearly characterized by the distance of 1.174 (3) A°. The packing diagram (Fig. 2) shows a linear intermolecular C9—H9···O2 contact with a H9···O2 distance of 2.39 Å between the alkynyl moiety and the ether function. A weak intermolecular C3—H3···O1 interaction with a H3···O1 distance of 2.87 Å between neighboring furan moieties along the direction of the c axis is observed.

Related literature

For related literature, see: Hashmi (2004, 2007); Hashmi & Hutchings (2006a, 2006b); Hashmi et al. (2000); Hashmi, Ata et al. (2007); Hashmi et al. (2006); Hashmi, Wölfle et al. (2007).

S2. Experimental

The compound was prepared by the reduction of 2-hydroxy-1,2-bis(5-methylfuran-2-yl)ethanone to the corresponding 1,2-diol and propargylation of the latter with propargyl bromide in the presence of a base as described in the literature (Hashmi, Wölfle et al., 2007). The two diastereomers were separated by column chromatography on silica gel (PE–EtOAc–CH2Cl2, 30:1:2) as described there, the diastereomer eluting first crystallized by slow evaporation from a chloroform solution. 1H NMR spectroscopic data of the pure diastereomer: 1H NMR (300 MHz, CDCl3): d = 2.30 (d, J = 1.0 Hz, 6 H), 2.36 (t, J = 2.4 Hz, 2 H), 3.93 (dd, J = 15.9, 2.4 Hz, 2 H), 4.08 (dd, J = 15.9, 2.4 Hz, 2 H), 4.91 (s, 2 H), 5.95 (dq, J = 3.1, 1.0 Hz, 2 H), 6.33 (d, J = 3.1 Hz, 2 H).

S3. Refinement

H atoms were located in difference Fourier map and refined with fixed individual displacement parameters [U(H) = 1.2U_eq(C) or U(H) = 1.5U_eq (C_methyl)] using a riding model with C—H ranging from 0.93 to 0.97 A°. In addition, the methyl group was allowed to rotate but not to tip.

Computing details

Data collection: P3/PC Data Collection Software (Siemens, 1991); cell refinement: P3/PC Data Collection Software (Siemens, 1991); data reduction: XDISK in SHELXTL-Plus (Sheldrick, 1991); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL-Plus (Sheldrick, 1991); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997) and PLATON (Spek, 2003).

Figures

	Fig. 1. The ORTEP drawing of (I) with atom numbering. Displacement ellipsoids are at the 50% probability level.
	Fig. 2. Packing diagram (I) along the a axis.

meso-2-Methyl-5-[2-(4-methylfuran-2-yl)-1,2-bis(prop-2-ynyloxy)ethyl]furan

Crystal data

C18H18O4	F(000) = 316
Mr = 298.32	Dx = 1.241 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 26 reflections
a = 7.945 (4) Å	θ = 16–18°
b = 9.215 (5) Å	µ = 0.09 mm^−1
c = 11.408 (5) Å	T = 293 K
β = 107.17 (4)°	Block, colourless
V = 798.1 (7) Å^3	0.9 × 0.8 × 0.5 mm
Z = 2

Data collection

Nicolet P3 diffractometer	Rint = 0.048
Radiation source: fine-focus sealed tube	θmax = 25.0°, θmin = 2.7°
Graphite monochromator	h = 0→9
Wyckoff scan	k = 0→10
1506 measured reflections	l = −13→12
1402 independent reflections	3 standard reflections every 50 reflections
1204 reflections with I > 2σ(I)	intensity decay: 3%

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)] = 0.048	H-atom parameters constrained
wR(F^2) = 0.129	w = 1/[σ^2(Fo^2) + (0.07P)^2 + 0.237P] where P = (Fo^2 + 2Fc^2)/3
S = 1.06	(Δ/σ)max < 0.001
1402 reflections	Δρmax = 0.22 e Å^−3
102 parameters	Δρmin = −0.21 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.019 (5)

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	0.83398 (16)	0.25136 (13)	0.46359 (11)	0.0466 (4)
C1	0.7962 (2)	0.1247 (2)	0.39765 (18)	0.0487 (5)
O2	0.78036 (15)	0.56861 (13)	0.46974 (11)	0.0456 (4)
C2	0.8173 (2)	0.1443 (2)	0.28653 (17)	0.0509 (5)
H2	0.8003	0.0751	0.2247	0.061*
C3	0.8704 (2)	0.2904 (2)	0.28085 (16)	0.0485 (5)
H3	0.8947	0.3353	0.2147	0.058*
C4	0.8788 (2)	0.35128 (19)	0.38888 (15)	0.0413 (4)
C5	0.7412 (3)	0.0006 (2)	0.4606 (2)	0.0710 (7)
H5A	0.7008	−0.0772	0.4032	0.107*
H5B	0.6476	0.0307	0.4925	0.107*
H5C	0.8395	−0.0319	0.5267	0.107*
C6	0.9246 (2)	0.49899 (18)	0.44007 (15)	0.0396 (4)
H6	0.9583	0.5583	0.3793	0.048*
C7	0.6267 (2)	0.5851 (2)	0.36739 (17)	0.0502 (5)
H7A	0.5355	0.6319	0.3946	0.060*
H7B	0.5840	0.4897	0.3365	0.060*
C8	0.6578 (2)	0.6704 (2)	0.26747 (17)	0.0496 (5)
C9	0.6892 (3)	0.7371 (2)	0.1888 (2)	0.0602 (6)
H9	0.7140	0.7900	0.1264	0.072*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0517 (8)	0.0455 (7)	0.0437 (7)	−0.0066 (5)	0.0158 (6)	−0.0024 (5)
C1	0.0430 (10)	0.0440 (10)	0.0570 (11)	−0.0058 (8)	0.0117 (8)	−0.0089 (8)
O2	0.0399 (7)	0.0523 (8)	0.0448 (7)	0.0035 (5)	0.0126 (5)	−0.0032 (5)
C2	0.0436 (10)	0.0540 (11)	0.0542 (11)	−0.0057 (8)	0.0128 (8)	−0.0184 (9)
C3	0.0447 (10)	0.0607 (12)	0.0416 (9)	−0.0033 (8)	0.0151 (8)	−0.0047 (8)
C4	0.0368 (9)	0.0472 (10)	0.0398 (9)	−0.0017 (7)	0.0111 (7)	0.0016 (7)
C5	0.0828 (15)	0.0524 (12)	0.0795 (15)	−0.0167 (11)	0.0265 (12)	−0.0043 (11)
C6	0.0382 (9)	0.0420 (9)	0.0401 (9)	−0.0010 (7)	0.0139 (7)	0.0016 (7)
C7	0.0393 (9)	0.0547 (11)	0.0539 (11)	−0.0004 (8)	0.0099 (8)	−0.0017 (8)
C8	0.0455 (10)	0.0491 (10)	0.0497 (10)	0.0056 (8)	0.0071 (8)	−0.0033 (9)
C9	0.0651 (13)	0.0583 (12)	0.0547 (12)	0.0050 (10)	0.0139 (10)	0.0053 (10)

Geometric parameters (Å, º)

O1—C4	1.371 (2)	C5—H5A	0.9600
O1—C1	1.373 (2)	C5—H5B	0.9600
C1—C2	1.339 (3)	C5—H5C	0.9600
C1—C5	1.483 (3)	C6—C6^i	1.529 (3)
O2—C7	1.427 (2)	C6—H6	0.9800
O2—C6	1.438 (2)	C7—C8	1.464 (3)
C2—C3	1.418 (3)	C7—H7A	0.9700
C2—H2	0.9300	C7—H7B	0.9700
C3—C4	1.338 (2)	C8—C9	1.174 (3)
C3—H3	0.9300	C9—H9	0.9300
C4—C6	1.484 (2)
C4—O1—C1	106.57 (14)	C1—C5—H5C	109.5
C2—C1—O1	109.62 (17)	H5A—C5—H5C	109.5
C2—C1—C5	134.38 (19)	H5B—C5—H5C	109.5
O1—C1—C5	115.99 (17)	O2—C6—C4	112.45 (14)
C7—O2—C6	113.80 (13)	O2—C6—C6^i	104.63 (16)
C1—C2—C3	107.06 (16)	C4—C6—C6^i	113.56 (17)
C1—C2—H2	126.5	O2—C6—H6	108.7
C3—C2—H2	126.5	C4—C6—H6	108.7
C4—C3—C2	106.91 (16)	C6^i—C6—H6	108.7
C4—C3—H3	126.5	O2—C7—C8	113.20 (15)
C2—C3—H3	126.5	O2—C7—H7A	108.9
C3—C4—O1	109.85 (16)	C8—C7—H7A	108.9
C3—C4—C6	133.41 (16)	O2—C7—H7B	108.9
O1—C4—C6	116.74 (14)	C8—C7—H7B	108.9
C1—C5—H5A	109.5	H7A—C7—H7B	107.8
C1—C5—H5B	109.5	C9—C8—C7	177.5 (2)
H5A—C5—H5B	109.5	C8—C9—H9	180.0
C4—O1—C1—C2	0.27 (19)	C1—O1—C4—C6	179.62 (14)
C4—O1—C1—C5	−179.11 (17)	C7—O2—C6—C4	−59.43 (18)
O1—C1—C2—C3	−0.2 (2)	C7—O2—C6—C6^i	176.88 (15)
C5—C1—C2—C3	179.0 (2)	C3—C4—C6—O2	118.0 (2)
C1—C2—C3—C4	0.1 (2)	O1—C4—C6—O2	−61.82 (19)
C2—C3—C4—O1	0.1 (2)	C3—C4—C6—C6^i	−123.5 (2)
C2—C3—C4—C6	−179.71 (18)	O1—C4—C6—C6^i	56.7 (2)
C1—O1—C4—C3	−0.22 (19)	C6—O2—C7—C8	−59.1 (2)

Symmetry code: (i) −x+2, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C9—H9···O2^ii	0.93	2.39	3.323 (3)	179
C3—H3···O1^iii	0.93	2.87	3.566 (3)	132

Symmetry codes: (ii) x, −y+3/2, z−1/2; (iii) x, −y+1/2, z−1/2.