3-(3-Oxo-1,3-dihydro­isobenzofuran-1-yl­idene)pentane-2,4-dione

In the title compound, C₁₃H₁₀O₄, prepared by the condensation reaction between phthalic anhydride and pentane-2,4-dione, one of the acetyl groups in the pentane-2,4-dione fragment is almost coplanar with the isobenzofuran ring system, while the other group is twisted out of this plane by almost 80°. The corresponding C-C and C-O distances in the two acetyl units are consistent with dipolar delocalization into the coplanar unit only. There is no supra­molecular aggregation of the mol­ecules, but a number of rather short inter­molecular contacts of C-H...O, O...O and O...C types occur.

S1. Comment

As part of a programme for the synthesis of new fused heterocyclic systems of potential biological interest, we have evaluated the use of 3-(3-oxo-1,3-dihydroisobenzofuran-1-ylidene)pentane-2,4-dione, (I), as a new α,β-unsaturated ketone derivative. Here we report the structure of compound (I), which was prepared by condensation of phthalic anhydride and pentane-2,4-dione.

The bond lengths within the carbocyclic ring span the very narrow range 1.387 (2)–1.394 (2) Å, indicative of unperturbed aromatic delocalization; in the heterocyclic ring, the C31—C37A and C33—C33A distances are very similar (Table 1), as are the C31—O32 and C33—O32 distances. However, in the pentane-2,4-dione fragment, the two C═O distances are significantly different, as are the distances C2—C3 and C3—C4. These differences in bond lengths are associated with the conformations adopted by the two acetyl groups. Atoms C2, C3, C4, O4 and C5 are almost coplanar with the isobenzofuran unit, as shown by the key torsion angles (Table 1). However, the acetyl group C1/C2/O2 is twisted out of this plane by almost 80° (Table 1 and Fig. 1); the dihedral angles between the mean planes C1–C3/O2 and C2/C3/C4/C31/O32 is 79.7 (2)°. The bond distances in the pentane-2,4-dione fragment are thus consistent with the dipolar form (Ia) as a significant contributor to the overall molecular electronic structure, but the close similarity of the C—O distances in the furan ring effectively rules out any contribution from the dipolar form (Ib).

There are two direction-specific intermolecular interactions of possible significance in the structure of (I). The first is a C—H···O interaction (Table 2) where the H···O distances is probably too long and the C—H···O angle is probably too small for this contact to be described as a significant hydrogen bond. Since both the C and the O atoms involved are located in the isobenzofuran ring, it is not possible to find in this interaction any explanation for the differing conformations of the two acetyl units. The second interaction involves rather short contacts between the acetyl atom O2 in the molecule at (x, y, z) and the sequence of atoms C31, O32, C33 in the molecule at (-x, 1 - y, 1 - z); the interatomic distances to C31, O32 and C33 are, respectively, 2.994 (2), 2.831 (2) and 3.005 (2) Å, associated with C—H···X angles of 126.5 (2), 153.6 (2) and 144.0 (2)° for X = C31, O32 and C33, respectively. The expected polarization of the O and C atoms involved suggests that the O2···O32ⁱ interaction [symmetry code: (i) -x, -y + 1, -z + 1] is repulsive, while the interactions O2···C31ⁱ and O2···C33ⁱ are both attractive. As with the intermolecular C—H.·O contact, it is not easy to see in these O···O and O···C contacts any simple explanation for the molecular conformation of (I).

In contrast to the molecular conformation adopted by compound (I), in 3-(triphenylphosphoranylidene)pentane-2,4-dione, (II), the entire pentane-2,4-dione unit is close to planarity in the syn–anti conformation with only modest differences between the corresponding bond distances in the two acetyl units (Castañeda et al., 2005). However in the closely-related compound diethyl 2-(triphenylphosphoranyidene)malonate (III), both ester units are twisted out of the plane of the central PC₃ unit (Castañeda et al., 2005).

Related literature

For related literature, see: Castañeda, Aliaga, Bunton, Garland & Baggio (2005).

S2. Experimental

To a solution of phthalic anhydride (20 mmol) and 2,4-pentanedione (20 mmol) in acetic anhydride (11.3 ml) at 298 K, triethylamine (40 mmol) was added dropwise, and the mixture was then stirred for 30 min. The reaction was quenched by the addition of aqueous hydrochloric acid (45 ml of 1 mol dm^-3 solution). The resulting solid was collected by filtration, and washed with diethyl ether (two aliquots of 25 ml) and then with hexane (two aliquots of 25 ml) to give (I) as colourless crystals, which were suitable for single-crystal X-ray diffraction (yield 90%, m.p. 406–408 K). MS (70 eV) m/z (%) 230 (5, M⁺), 187 (39), 172 (100), 104 (39), 89 (74), 76 (38), 43 (66), 42 (96) 15 (44).

S3. Refinement

The space group P2₁/c was uniquely assigned from the systematic absences. All H atoms were located in difference maps and then treated as riding atoms in geometrically idealized positions with C—H distances of 0.95 Å (aromatic) or 0.98 Å (methyl), and with U_iso(H) = kU_eq(C), where k = 1.2 for the aromatic ring and k = 1.5 for the methyl groups.

Computing details

Data collection: COLLECT (Hooft, 1999); cell refinement: DIRAX/LSQ (Duisenberg et al., 2000); data reduction: EVALCCD (Duisenberg et al., 2003); program(s) used to solve structure: SIR2004 (Burla et al., 2005) and WinGX (Farrugia, 1999); program(s) used to refine structure: OSCAIL (McArdle, 2003) and SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97 and PRPKAPPA (Ferguson, 1999).

Figures

Fig. 1. The molecular structure of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level.

3-(3-Oxo-1,3-dihydroisobenzofuran-1-ylidene)pentane-2,4-dione

Crystal data

C13H10O4	F(000) = 480
Mr = 230.21	Dx = 1.447 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 2426 reflections
a = 8.2779 (3) Å	θ = 3.5–27.5°
b = 8.4719 (6) Å	µ = 0.11 mm^−1
c = 15.1413 (12) Å	T = 120 K
β = 95.534 (6)°	Block, colourless
V = 1056.90 (12) Å^3	0.52 × 0.31 × 0.08 mm
Z = 4

Data collection

Bruker–Nonius KappaCCD diffractometer	2426 independent reflections
Radiation source: Bruker-Nonius FR591 rotating anode	1813 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.043
Detector resolution: 9.091 pixels mm^-1	θmax = 27.5°, θmin = 3.5°
ϕ and ω scans	h = −10→10
Absorption correction: multi-scan (SADABS; Sheldrick, 2003)	k = −10→10
Tmin = 0.964, Tmax = 0.991	l = −19→19
25118 measured reflections

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)] = 0.048	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.139	H-atom parameters constrained
S = 1.08	w = 1/[σ^2(Fo^2) + (0.07P)^2 + 0.6226P] where P = (Fo^2 + 2Fc^2)/3
2426 reflections	(Δ/σ)max < 0.001
156 parameters	Δρmax = 0.27 e Å^−3
0 restraints	Δρmin = −0.24 e Å^−3

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

	x	y	z	Uiso*/Ueq
O2	−0.02595 (16)	0.74009 (16)	0.44235 (9)	0.0306 (3)
O4	0.06268 (17)	0.82367 (16)	0.65971 (9)	0.0324 (3)
O32	0.32107 (14)	0.42453 (14)	0.59930 (8)	0.0212 (3)
O33	0.45158 (15)	0.19081 (15)	0.60270 (8)	0.0262 (3)
C1	0.1922 (2)	0.9184 (2)	0.47907 (12)	0.0255 (4)
C2	0.0981 (2)	0.7696 (2)	0.48845 (12)	0.0225 (4)
C3	0.1665 (2)	0.6540 (2)	0.55897 (11)	0.0214 (4)
C4	0.1304 (2)	0.6971 (2)	0.65039 (12)	0.0240 (4)
C5	0.1689 (2)	0.5891 (2)	0.72776 (12)	0.0292 (4)
C31	0.2478 (2)	0.5254 (2)	0.53509 (11)	0.0205 (4)
C33	0.3873 (2)	0.2961 (2)	0.55893 (11)	0.0213 (4)
C33A	0.3635 (2)	0.3219 (2)	0.46296 (11)	0.0214 (4)
C34	0.4119 (2)	0.2284 (2)	0.39511 (12)	0.0240 (4)
C35	0.3738 (2)	0.2813 (2)	0.30883 (12)	0.0269 (4)
C36	0.2890 (2)	0.4225 (2)	0.29260 (12)	0.0276 (4)
C37	0.2394 (2)	0.5148 (2)	0.36095 (12)	0.0253 (4)
C37A	0.2795 (2)	0.4633 (2)	0.44773 (11)	0.0213 (4)
H1A	0.2954	0.8935	0.4556	0.038*
H1B	0.2134	0.9691	0.5372	0.038*
H1C	0.1293	0.9902	0.4382	0.038*
H34	0.4688	0.1322	0.4072	0.029*
H35	0.4056	0.2210	0.2605	0.032*
H36	0.2646	0.4565	0.2330	0.033*
H37	0.1801	0.6096	0.3489	0.030*
H5A	0.2864	0.5886	0.7442	0.044*
H5B	0.1325	0.4820	0.7116	0.044*
H5C	0.1132	0.6260	0.7781	0.044*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0258 (9)	0.0222 (9)	0.0285 (9)	−0.0014 (7)	0.0021 (7)	0.0018 (7)
C2	0.0239 (8)	0.0214 (9)	0.0225 (8)	0.0018 (7)	0.0044 (7)	−0.0013 (7)
O2	0.0282 (7)	0.0287 (7)	0.0334 (8)	−0.0022 (5)	−0.0047 (6)	0.0032 (6)
C3	0.0202 (8)	0.0219 (9)	0.0219 (9)	−0.0020 (7)	0.0014 (6)	0.0001 (7)
C31	0.0201 (8)	0.0205 (9)	0.0205 (8)	−0.0031 (7)	0.0000 (6)	0.0019 (6)
O32	0.0229 (6)	0.0213 (6)	0.0190 (6)	0.0024 (5)	0.0006 (5)	0.0001 (5)
C33	0.0217 (8)	0.0212 (9)	0.0214 (8)	−0.0013 (7)	0.0044 (7)	−0.0023 (7)
O33	0.0293 (7)	0.0258 (7)	0.0237 (7)	0.0059 (5)	0.0028 (5)	0.0026 (5)
C34	0.0244 (8)	0.0245 (9)	0.0233 (9)	−0.0022 (7)	0.0037 (7)	−0.0007 (7)
C33A	0.0212 (8)	0.0229 (9)	0.0198 (9)	−0.0022 (7)	0.0013 (6)	0.0002 (7)
C35	0.0301 (9)	0.0297 (10)	0.0216 (9)	−0.0021 (8)	0.0055 (7)	−0.0033 (7)
C36	0.0331 (10)	0.0301 (10)	0.0194 (8)	−0.0029 (8)	0.0015 (7)	0.0022 (7)
C37	0.0279 (9)	0.0243 (9)	0.0235 (9)	−0.0009 (7)	0.0017 (7)	0.0029 (7)
C37A	0.0208 (8)	0.0228 (9)	0.0204 (8)	−0.0034 (7)	0.0027 (6)	0.0000 (7)
C4	0.0249 (9)	0.0235 (9)	0.0237 (9)	−0.0024 (7)	0.0034 (7)	−0.0025 (7)
O4	0.0419 (8)	0.0276 (7)	0.0286 (7)	0.0076 (6)	0.0087 (6)	−0.0014 (6)
C5	0.0360 (10)	0.0302 (10)	0.0218 (9)	0.0033 (8)	0.0047 (7)	0.0000 (8)

Geometric parameters (Å, º)

C1—C2	1.496 (2)	C34—C33A	1.387 (2)
C1—H1A	0.98	C34—C35	1.389 (3)
C1—H1B	0.98	C34—H34	0.95
C1—H1C	0.98	C33A—C37A	1.393 (2)
C2—O2	1.211 (2)	C35—C36	1.396 (3)
C4—O4	1.225 (2)	C35—H35	0.95
C2—C3	1.518 (2)	C36—C37	1.390 (3)
C3—C4	1.489 (2)	C36—H36	0.95
C3—C31	1.348 (3)	C37—C37A	1.394 (2)
C31—C37A	1.470 (2)	C37—H37	0.95
C33—C33A	1.464 (2)	C4—C5	1.496 (3)
O32—C31	1.389 (2)	C5—H5A	0.98
O32—C33	1.387 (2)	C5—H5B	0.98
C33—O33	1.204 (2)	C5—H5C	0.98
C2—C1—H1A	109.5	C34—C33A—C33	128.95 (17)
C2—C1—H1B	109.5	C37A—C33A—C33	108.06 (15)
H1A—C1—H1B	109.5	C34—C35—C36	120.46 (18)
C2—C1—H1C	109.5	C34—C35—H35	119.8
H1A—C1—H1C	109.5	C36—C35—H35	119.8
H1B—C1—H1C	109.5	C37—C36—C35	122.03 (17)
O2—C2—C1	122.67 (16)	C37—C36—H36	119.0
O2—C2—C3	120.70 (16)	C35—C36—H36	119.0
C1—C2—C3	116.62 (15)	C36—C37—C37A	117.73 (17)
C31—C3—C4	126.69 (16)	C36—C37—H37	121.1
C31—C3—C2	119.67 (15)	C37A—C37—H37	121.1
C4—C3—C2	113.63 (15)	C33A—C37A—C37	119.63 (16)
C3—C31—O32	120.34 (15)	C33A—C37A—C31	106.76 (15)
C3—C31—C37A	131.87 (16)	C37—C37A—C31	133.58 (17)
O32—C31—C37A	107.79 (14)	O4—C4—C3	117.18 (16)
C33—O32—C31	109.81 (13)	O4—C4—C5	120.71 (17)
O33—C33—O32	120.74 (15)	C3—C4—C5	122.08 (16)
O33—C33—C33A	131.84 (17)	C4—C5—H5A	109.5
O32—C33—C33A	107.41 (14)	C4—C5—H5B	109.5
C33A—C34—C35	117.15 (17)	H5A—C5—H5B	109.5
C33A—C34—H34	121.4	C4—C5—H5C	109.5
C35—C34—H34	121.4	H5A—C5—H5C	109.5
C34—C33A—C37A	122.98 (16)	H5B—C5—H5C	109.5
O2—C2—C3—C4	−100.7 (2)	O33—C33—C33A—C37A	179.42 (18)
C1—C2—C3—C4	79.82 (19)	O32—C33—C33A—C37A	−1.59 (18)
C2—C3—C31—O32	175.40 (14)	C33A—C34—C35—C36	−0.5 (3)
O2—C2—C3—C31	77.9 (2)	C34—C35—C36—C37	−0.2 (3)
C1—C2—C3—C31	−101.57 (19)	C35—C36—C37—C37A	1.1 (3)
C4—C3—C31—O32	−6.2 (3)	C34—C33A—C37A—C37	0.7 (3)
O4—C4—C3—C31	175.99 (17)	C33—C33A—C37A—C37	−179.28 (16)
C5—C4—C3—C31	−6.1 (3)	C34—C33A—C37A—C31	179.01 (16)
C4—C3—C31—C37A	174.21 (17)	C33—C33A—C37A—C31	−0.98 (18)
C2—C3—C31—C37A	−4.2 (3)	C36—C37—C37A—C33A	−1.3 (3)
C3—C31—O32—C33	176.00 (15)	C36—C37—C37A—C31	−179.09 (18)
C37A—C31—O32—C33	−4.31 (17)	C3—C31—C37A—C33A	−177.14 (18)
C31—O32—C33—O33	−177.18 (15)	O32—C31—C37A—C33A	3.22 (18)
C31—O32—C33—C33A	3.69 (17)	C3—C31—C37A—C37	0.8 (3)
C35—C34—C33A—C37A	0.2 (3)	O32—C31—C37A—C37	−178.83 (18)
C35—C34—C33A—C33	−179.78 (17)	C2—C3—C4—O4	−5.5 (2)
O33—C33—C33A—C34	−0.6 (3)	C2—C3—C4—C5	172.34 (16)
O32—C33—C33A—C34	178.42 (16)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C35—H35···O(33)^i	0.95	2.57	3.256 (2)	130

Symmetry code: (i) x, −y+1/2, z−1/2.