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Logo of actae2this articlesearchopen accesssubmitActa Crystallographica Section E: Crystallographic CommunicationsActa Crystallographica Section E: Crystallographic Communications
 
Acta Crystallogr E Crystallogr Commun. 2017 October 1; 73(Pt 10): 1576–1579.
Published online 2017 September 29. doi:  10.1107/S2056989017013962
PMCID: PMC5730322

Crystal structure and identification of resonance forms of diethyl 2-(3-oxoiso-1,3-di­hydro­benzo­furan-1-yl­idene)malonate

Abstract

The reaction of diethyl malonate with phthaloyl chloride in aceto­nitrile in the presence of tri­ethyl­amine and magnesium chloride results in the formation of the title compound, diethyl 2-(3-oxo-1,3-di­hydro-2-benzo­furan-1-yl­idene)propane­dioate, C15H14O6. One of the ester groups of the diethyl malonate fragment is almost coplanar with the isobenzo­furan unit, while the plane of the other group is perpendicular to it [dihedral angles = 5.45 (3) and 83.30 (3)°, respectively]. The C—C and C—O distances both in the heterocyclic furan ring and the diethyl malonate fragment are indicative of the dipolar delocalization occurring within the isobenzo­furan unit. This delocalization is likely to be responsible for the unusual inter­molecular O(...)O contact [2.756 (2) Å], established between the O atom of the furan ring and the carbonyl O atom of the diethyl malonate fragment. In the crystal, weak C—H(...)O inter­actions are observed, which link the mol­ecules into [100] chains.

Keywords: crystal structure, 3-alkyl­idene-3H-isobenzo­furan-1-ones, delocalization, enolate

Chemical context  

The structural analysis of diethyl 2-(3-oxoisobenzo­furan-1(3H)-yl­idene)malonate (I) was undertaken as part of a study into the synthesis of new reagents for the recovery of trivalent lanthanide metal ions by liquid–liquid extraction. We intended to prepare 2,2′-phthaloylbis(N,N,N′,N′-tetra­butyl­malon­amide) (II), which is similar to the reported earlier 2,2′-[1,2-phenyl­enebis(methyl­ene)]bis­(N,N,N′,N′-tetra­butyl­malon­amide) (III) (Tyumentsev et al., 2016  ), from the respective tetra­ethyl 2,2′-phthaloyldimalonate (IV). In turn (IV) was to be made by the reaction of diethyl malonate with phthaloyl chloride. It is already known that acid chlorides react with diethyl malonate when treated with a combination of tri­ethyl­amine and a mild Lewis acid (magnesium chloride) in aceto­nitrile (Rathke & Cowan, 1985  ). Instead of (IV), an organic product, which contained two ethyl groups in different electronic environments, was obtained in this reaction. Crystals of this compound were grown and examined with single-crystal X-ray diffractometry, and the product was found to be the title compound, (I). The formation of (I) can be rationalized by the nucleophilic attack of the oxygen atom (in an enol form) of the keto-di­ethyl­malonate group on the carbon atom of the unreacted acid chloride group. The mechanism of the formation of (I) was proposed by Naik et al. (1988  ), who obtained this compound by another reaction.

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Object name is e-73-01576-scheme1.jpg

Structural commentary  

Compound (I) crystallizes with one mol­ecule in the asymmetric unit (Fig. 1  ). Atoms C8, C9, C10, C11, C12, O9 and O10 are almost coplanar with the isobenzo­furan unit (r.m.s. deviation = 0.024 Å), as shown by the dihedral angle of 5.45 (3)° between these groupings. This mean plane is inter­cepted nearly perpendicularly by the mean plane of the other ester group (O12, C12, O13, C13, and C14), with a dihedral angle of 83.30 (3)° and the torsion angles C9—C8—C12—O12 and C9—C8—C12—O13 of 90.2 (1)° and −89.6 (1)°, respectively. The bond lengths in the carbocyclic ring of the isobenzo­furan unit range from 1.386 (2) Å to 1.398 (2) Å. In the heterocyclic furan ring the distances C2—C2A = 1.469 (2) Å and C6A—C7 = 1.472 (2) Å are very similar, while the C2—O1 and C7—O1 distances are significantly different. The C2—O1 bond distance of 1.394 (1) Å perfectly matches the corresponding distances in phthalic anhydride [1.396 (5) Å and 1.393 (6) Å (Bates & Cutler, 1977  )]. The shorter C7—O1 distance of 1.385 (1) Å strongly suggests that the bond between the endocyclic oxygen atom O1 and the non-carbonyl carbon atom C7 has an order greater than 1. In the diethyl malonate fragment the distances C8—C9 [1.489 (2) Å] and C8—C12 [1.507 (1) Å] are different most likely due to the particular conformation adopted by the mol­ecule. The bond lengths for the atoms, associated with both the furan ring of the isobenzo­furan unit and the diethyl malonate fragment, indicate that the dipolar resonance form (Ia) of (I) makes a considerable contribution to its overall mol­ecular electronic structure (Fig. 2  ).

Figure 1
The mol­ecular structure of (I), showing displacement ellipsoids drawn at the 50% probability level.
Figure 2
Chemical diagram of a mol­ecule (I) and its possible resonance forms (Ia) and (Ib).

According to the structure of the resonance form (Ia) a partial positive charge is localized on the oxygen atom of the heterocyclic furan ring, and one of the carbonyl oxygen atoms of the diethyl malonate fragment carries a partial negative charge, which should lead to an electrostatic attraction of these two oxygen atoms. In the structure of (I) the O1 and O9 atoms are nearly coplanar (the torsion angles C7—C8—C9—O9 and C9—C8—C7—O1 equal to −10.6 (2)° and 0.7 (2)°, respectively), and the distance O1(...)O9 is 2.756 (2) Å. It can be argued that simple electrostatic attraction is responsible for this close contact.

Supra­molecular features  

The possible non van der Waals contact in the crystal of (I) is a very weak C—H(...)O inter­action (Table 1  ), which links the mol­ecules into [100] C(8) chains. A parallel-displaced π–π stacking inter­action between mol­ecules of (I) is observed with an inter­planar distance of 3.423 Å (Fig. 3  ) and inter­molecular furan–benzene and benzene–benzene centroid-to-centroid distances of 3.5379 (13) and 3.7859 (14) Å, respectively.

Figure 3
Mol­ecules of (I) inter­acting via parallel-displaced π–π stacking.
Table 1
Hydrogen-bond geometry (Å, °)

Database survey  

In the structure of 3-(3-oxo-1,3-di­hydro­isobenzo­furan-1-yl­idene)pentane-2,4-dione (HIFQUJ; Portilla et al., 2007  ) the dominant resonance form resembles (Ib). No contact was observed between the endocyclic oxygen atom and the carbonyl oxygen atom of the acetyl group (the distance between these atoms exceeds 4 Å). In 2-meth­oxy­ethyl 3-oxo-2-(3-oxo-2-benzo­furan-1(3H)-yl­idene)butano­ate (UBAVIE; Mkrtchyan et al., 2011  ), no close contacts exist between the endocyclic oxygen atom and any other oxygen atoms.

In methyl 4,4-dimethyl-3-oxo-2-(3-oxo-2-benzo­furan-1(3H)-yl­idene)penta­noate (UBAVEA; Mkrtchyan et al., 2011  ), neither of the two carbonyl oxygen atoms of the methyl 4,4-dimethyl-3-oxo­penta­noate fragment are within the same plane as the isobenzo­furan unit. The shortest inter­molecular O(...)O contact is 3.161 Å, which occurs between the endocyclic oxygen atom and that carbonyl oxygen atom, which is closest to the plane of the isobenzo­furan unit. The torsion angle O4—C15—C9—C8 in UBAVEA is 26.81°, while the corresponding torsion angle in (I), C7—C8—C9—O9, is 10.6 (2)°.

Synthesis and crystallization  

The title compound was prepared by the reaction of diethyl malonate with phthaloyl chloride in aceto­nitrile in the presence of tri­ethyl­amine and magnesium chloride (Rathke & Cowan, 1985  ). The reagents for the synthesis were purchased from Aldrich and were used as supplied. The crude product was washed with petroleum ether on filter paper and recrystallized from cyclo­hexane solution as colorless crystals (69% yield); m.p. 345–346 K. 1H NMR (400 MHz, CDCl3) δ 1.38 (m, 6H), 4.39 (m, 4H), 7.72 (t, J = 6.7 Hz, 1H), 7.80 (t, J = 7.4 Hz, 1H), 7.99 (d, J = 7.8 Hz, 1H), 8.65 (d, J = 8.2 Hz, 1H). 13C NMR (400 MHz, CDCl3) δ 135.36; 132.93; 127.58; 126.11; 125.84; 62.18; 62.06; 14.04; 14.01. Found: C, 62.08; H, 4.94%. C15H14O6 Theoretical: C, 62.07; H, 4.86%. The crystalline product was found to be stable to air, water and brief exposure to 1 M hydro­chloric acid.

Refinement  

Crystal data, data collection and structure refinement details are summarized in Table 2  . H atoms were refined using the riding model with C—H = 0.95–0.99 Å and U iso(H) = 1.2U eq(C).

Table 2
Experimental details

Supplementary Material

Crystal structure: contains datablock(s) I. DOI: 10.1107/S2056989017013962/hb7700sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989017013962/hb7700Isup3.hkl

CCDC reference: 1543053

Additional supporting information: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Crystal data

C15H14O6Z = 2
Mr = 290.27F(000) = 304.00
Triclinic, P1Dx = 1.428 Mg m3
a = 7.942 (2) ÅMo Kα radiation, λ = 0.71075 Å
b = 9.453 (3) ÅCell parameters from 2290 reflections
c = 10.226 (2) Åθ = 2.3–27.5°
α = 67.706 (15)°µ = 0.11 mm1
β = 72.228 (16)°T = 93 K
γ = 86.41 (2)°Prism, colorless
V = 675.2 (3) Å30.30 × 0.20 × 0.15 mm

Data collection

Rigaku XtaLAB P200 diffractometer2278 reflections with F2 > 2.0σ(F2)
Detector resolution: 5.814 pixels mm-1Rint = 0.031
ω scansθmax = 25.3°, θmin = 2.3°
Absorption correction: multi-scan (REQAB; Rigaku, 1998)h = −9→9
Tmin = 0.829, Tmax = 0.983k = −11→11
9890 measured reflectionsl = −12→12
2466 independent reflections

Refinement

Refinement on F2Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.028Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.078H-atom parameters constrained
S = 1.07w = 1/[σ2(Fo2) + (0.0425P)2 + 0.0953P] where P = (Fo2 + 2Fc2)/3
2466 reflections(Δ/σ)max < 0.001
192 parametersΔρmax = 0.25 e Å3
0 restraintsΔρmin = −0.18 e Å3
Primary atom site location: structure-invariant direct methods

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement was performed using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F2. R-factor (gt) are based on F. The threshold expression of F2 > 2.0 sigma(F2) is used only for calculating R-factor (gt).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

xyzUiso*/Ueq
O10.78603 (9)0.26223 (8)−0.08336 (8)0.01823 (18)
O20.88520 (10)0.18829 (9)−0.27766 (9)0.0250 (2)
O90.92060 (10)0.33329 (10)0.10424 (10)0.0292 (2)
O100.71494 (9)0.40999 (9)0.26677 (8)0.02015 (19)
O120.34235 (10)0.41829 (8)0.23018 (8)0.02202 (19)
O130.39408 (9)0.17091 (8)0.34225 (8)0.01784 (18)
C20.76082 (14)0.20746 (12)−0.18525 (12)0.0188 (2)
C2A0.56886 (14)0.18300 (12)−0.15155 (12)0.0176 (2)
C30.47681 (14)0.12685 (12)−0.21879 (12)0.0203 (2)
H30.53670.0970−0.29920.024*
C40.29321 (14)0.11623 (12)−0.16343 (12)0.0209 (2)
H40.22550.0764−0.20530.025*
C50.20674 (14)0.16332 (12)−0.04692 (12)0.0199 (2)
H50.08090.1570−0.01260.024*
C60.30017 (13)0.21919 (12)0.02009 (12)0.0181 (2)
H60.24060.25130.09900.022*
C6A0.48425 (14)0.22634 (11)−0.03286 (11)0.0164 (2)
C70.62379 (13)0.27243 (11)0.01279 (11)0.0164 (2)
C80.61249 (13)0.31329 (11)0.12678 (12)0.0170 (2)
C90.76891 (13)0.35264 (12)0.16046 (12)0.0182 (2)
C100.85459 (14)0.45643 (13)0.30998 (13)0.0233 (3)
H10A0.92770.54520.22710.028*
H10B0.93230.37120.33710.028*
C110.76446 (15)0.49876 (14)0.44073 (13)0.0267 (3)
H11A0.69540.40910.52280.032*
H11B0.68530.58100.41310.032*
H11C0.85370.53380.47180.032*
C120.43443 (13)0.31193 (12)0.23574 (11)0.0162 (2)
C130.22714 (13)0.15072 (12)0.46014 (12)0.0202 (2)
H13A0.12830.18460.41750.024*
H13B0.23270.21160.51920.024*
C140.19989 (14)−0.01740 (12)0.55625 (12)0.0220 (2)
H14A0.1880−0.07570.49780.026*
H14B0.0921−0.03530.64040.026*
H14C0.3018−0.05060.59310.026*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
O10.0135 (4)0.0209 (4)0.0182 (4)0.0008 (3)−0.0019 (3)−0.0076 (3)
O20.0191 (4)0.0308 (5)0.0227 (4)0.0033 (3)−0.0006 (3)−0.0122 (4)
O90.0152 (4)0.0410 (5)0.0386 (5)0.0039 (3)−0.0071 (4)−0.0241 (4)
O100.0160 (4)0.0236 (4)0.0251 (4)0.0010 (3)−0.0078 (3)−0.0125 (3)
O120.0203 (4)0.0195 (4)0.0236 (4)0.0050 (3)−0.0050 (3)−0.0073 (3)
O130.0145 (4)0.0173 (4)0.0184 (4)0.0013 (3)−0.0019 (3)−0.0056 (3)
C20.0194 (5)0.0169 (5)0.0174 (5)0.0022 (4)−0.0042 (4)−0.0048 (4)
C2A0.0175 (5)0.0155 (5)0.0167 (5)0.0024 (4)−0.0038 (4)−0.0040 (4)
C30.0233 (6)0.0199 (5)0.0179 (5)0.0036 (4)−0.0061 (4)−0.0080 (4)
C40.0226 (5)0.0202 (6)0.0220 (6)0.0018 (4)−0.0103 (5)−0.0075 (5)
C50.0165 (5)0.0203 (5)0.0215 (6)0.0022 (4)−0.0066 (4)−0.0060 (4)
C60.0171 (5)0.0188 (5)0.0174 (5)0.0027 (4)−0.0044 (4)−0.0066 (4)
C6A0.0174 (5)0.0136 (5)0.0162 (5)0.0015 (4)−0.0055 (4)−0.0033 (4)
C70.0134 (5)0.0140 (5)0.0176 (5)0.0012 (4)−0.0028 (4)−0.0032 (4)
C80.0153 (5)0.0146 (5)0.0188 (5)0.0012 (4)−0.0047 (4)−0.0043 (4)
C90.0173 (5)0.0157 (5)0.0201 (5)0.0007 (4)−0.0051 (4)−0.0055 (4)
C100.0190 (5)0.0230 (6)0.0338 (7)0.0014 (4)−0.0136 (5)−0.0126 (5)
C110.0286 (6)0.0274 (6)0.0314 (7)0.0030 (5)−0.0162 (5)−0.0137 (5)
C120.0164 (5)0.0176 (5)0.0169 (5)0.0001 (4)−0.0071 (4)−0.0073 (4)
C130.0153 (5)0.0220 (6)0.0198 (6)0.0009 (4)−0.0003 (4)−0.0081 (5)
C140.0188 (5)0.0213 (6)0.0217 (6)−0.0005 (4)−0.0023 (4)−0.0064 (5)

Geometric parameters (Å, º)

O1—C71.3854 (12)C6—C6A1.3916 (15)
O1—C21.3940 (13)C6—H60.9500
O2—C21.1997 (13)C6A—C71.4719 (14)
O9—C91.2019 (13)C7—C81.3377 (15)
O10—C91.3391 (13)C8—C91.4888 (14)
O10—C101.4579 (13)C8—C121.5070 (14)
O12—C121.1995 (13)C10—C111.4986 (16)
O13—C121.3435 (13)C10—H10A0.9900
O13—C131.4591 (12)C10—H10B0.9900
C2—C2A1.4695 (15)C11—H11A0.9800
C2A—C31.3862 (15)C11—H11B0.9800
C2A—C6A1.3919 (15)C11—H11C0.9800
C3—C41.3886 (16)C13—C141.5055 (16)
C3—H30.9500C13—H13A0.9900
C4—C51.3978 (16)C13—H13B0.9900
C4—H40.9500C14—H14A0.9800
C5—C61.3904 (15)C14—H14B0.9800
C5—H50.9500C14—H14C0.9800
C7—O1—C2109.90 (8)O9—C9—O10124.58 (10)
C9—O10—C10115.85 (8)O9—C9—C8125.85 (10)
C12—O13—C13116.01 (8)O10—C9—C8109.55 (9)
O2—C2—O1120.62 (10)O10—C10—C11106.67 (9)
O2—C2—C2A132.18 (11)O10—C10—H10A110.4
O1—C2—C2A107.20 (9)C11—C10—H10A110.4
C3—C2A—C6A122.56 (10)O10—C10—H10B110.4
C3—C2A—C2129.50 (10)C11—C10—H10B110.4
C6A—C2A—C2107.95 (9)H10A—C10—H10B108.6
C2A—C3—C4117.04 (10)C10—C11—H11A109.5
C2A—C3—H3121.5C10—C11—H11B109.5
C4—C3—H3121.5H11A—C11—H11B109.5
C3—C4—C5120.88 (10)C10—C11—H11C109.5
C3—C4—H4119.6H11A—C11—H11C109.5
C5—C4—H4119.6H11B—C11—H11C109.5
C6—C5—C4121.67 (10)O12—C12—O13124.83 (10)
C6—C5—H5119.2O12—C12—C8126.32 (10)
C4—C5—H5119.2O13—C12—C8108.85 (8)
C5—C6—C6A117.49 (10)O13—C13—C14106.78 (8)
C5—C6—H6121.3O13—C13—H13A110.4
C6A—C6—H6121.3C14—C13—H13A110.4
C6—C6A—C2A120.32 (10)O13—C13—H13B110.4
C6—C6A—C7132.70 (10)C14—C13—H13B110.4
C2A—C6A—C7106.98 (9)H13A—C13—H13B108.6
C8—C7—O1121.51 (9)C13—C14—H14A109.5
C8—C7—C6A130.55 (10)C13—C14—H14B109.5
O1—C7—C6A107.90 (9)H14A—C14—H14B109.5
C7—C8—C9123.84 (9)C13—C14—H14C109.5
C7—C8—C12120.08 (9)H14A—C14—H14C109.5
C9—C8—C12115.97 (9)H14B—C14—H14C109.5
C7—O1—C2—O2−179.09 (9)C6—C6A—C7—O1−177.86 (10)
C7—O1—C2—C2A0.60 (11)C2A—C6A—C7—O12.72 (11)
O2—C2—C2A—C31.1 (2)O1—C7—C8—C90.65 (16)
O1—C2—C2A—C3−178.50 (10)C6A—C7—C8—C9178.04 (9)
O2—C2—C2A—C6A−179.21 (11)O1—C7—C8—C12−175.47 (8)
O1—C2—C2A—C6A1.15 (11)C6A—C7—C8—C121.92 (17)
C6A—C2A—C3—C40.54 (15)C10—O10—C9—O92.55 (15)
C2—C2A—C3—C4−179.85 (10)C10—O10—C9—C8−179.01 (8)
C2A—C3—C4—C51.21 (15)C7—C8—C9—O9−10.62 (17)
C3—C4—C5—C6−1.41 (16)C12—C8—C9—O9165.65 (10)
C4—C5—C6—C6A−0.18 (15)C7—C8—C9—O10170.96 (9)
C5—C6—C6A—C2A1.90 (15)C12—C8—C9—O10−12.77 (12)
C5—C6—C6A—C7−177.45 (10)C9—O10—C10—C11−173.45 (9)
C3—C2A—C6A—C6−2.15 (15)C13—O13—C12—O12−1.65 (14)
C2—C2A—C6A—C6178.17 (9)C13—O13—C12—C8178.17 (8)
C3—C2A—C6A—C7177.35 (9)C7—C8—C12—O12−93.36 (14)
C2—C2A—C6A—C7−2.32 (11)C9—C8—C12—O1290.22 (13)
C2—O1—C7—C8175.88 (9)C7—C8—C12—O1386.82 (11)
C2—O1—C7—C6A−2.03 (10)C9—C8—C12—O13−89.60 (10)
C6—C6A—C7—C84.48 (19)C12—O13—C13—C14173.90 (8)
C2A—C6A—C7—C8−174.94 (11)

Hydrogen-bond geometry (Å, º)

D—H···AD—HH···AD···AD—H···A
C5—H5···O9i0.952.483.0689 (18)120

Symmetry code: (i) x−1, y, z.

Funding Statement

This work was funded by the European Community’s Seventh Framework Programme ([FP7/2007-2013]) grant 607411.

This paper was supported by the following grant(s):

the European Community’s Seventh Framework Programme ([FP7/2007-2013]) 607411.

References

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