Dimethyl 4,5-di­chloro­phthalate

Hickstein, D.D.; Reinheimer, E.W.; Johnson, A.R.; O'Leary, D.J.

doi:10.1107/S2414314621010439

organic compounds

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ISSN: 2414-3146

Volume 6| Part 10| October 2021| x211043

https://doi.org/10.1107/S2414314621010439

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Dimethyl 4,5-dichlorophthalate

Daniel D. Hickstein,^a Eric W. Reinheimer,^b Adam R. Johnson ^c and Daniel J. O'Leary ^a ^*

^aDepartment of Chemistry, Pomona College, 645 N. College Ave., Claremont, CA 91711, USA, ^bDepartment of Chemistry and Biochemistry, W.M. Keck Foundation Center for Molecular Structure, California State University San Marcos, 333. S. Twin Oaks Valley Road, San Marcos, CA 92096, USA, and ^cDepartment of Chemistry, Harvey Mudd College, 301 Platt Blvd., Claremont, CA 91711, USA
^*Correspondence e-mail: Daniel_OLeary@pomona.edu

Edited by R. J. Butcher, Howard University, USA (Received 3 August 2021; accepted 7 October 2021; online 13 October 2021)

While endeavoring to synthesize new chlorinated ligands for ruthenium-based metathesis catalysts, the title compound dimethyl 4,5-dichlorophthalate, C₁₀H₈Cl₂O₄, was prepared from commercially available 4,5-dichlorophthalic acid in ∼77% yield. The title molecule, which also finds utility as a precursor molecule for the synthesis of drugs used in the treatment of Alzheimer's disease, shows one carbonyl-containing methyl ester moiety lying nearly co-planar with the chlorine-derivatized aromatic ring while the second methyl ester shows a significant deviation of 101.05 (12)° from the least-squares plane of the aromatic ring. Within the crystal, structural integrity is maintained by the concerted effects of electrostatic interactions involving the electron-deficient carbonyl carbon atom and the electron-rich aromatic ring along the a-axis direction and C—H⋯O hydrogen bonds between neighboring molecules parallel to b.

Keywords: crystal structure; carbonyl; ester; metathesis; catalyst.

CCDC reference: 720360

Structure description

While endeavoring to synthesize new chlorinated ligands for ruthenium-based metathesis catalysts (Anderson et al., 2006 ), the title compound, 1, was prepared from commercially available 4,5-dichlorophthalic acid in ∼77% yield. The title molecule also finds utility as a precursor molecule for the synthesis of drugs used in the treatment of Alzheimer's disease (Hennessy & Buchwald, 2005 ).

Compound 1 crystallizes in the centrosymmetric triclinic space group P $[\overline{1}]$ with a full molecule of the title compound as the contents of asymmetric unit (Fig. 1, Table 1). Within the structure of 1, one of the carbonyl-containing ester groups is nearly co-planar with the aromatic ring demonstrating a deviation of 3.41 (12)° from the least-squares plane of the chlorine-derivatized aromatic ring. The second ester group reveals a much larger deviation from planarity as the dihedral angle involving the second carbonyl group is 101.05 (12)°.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C5—H5⋯O1ⁱ	0.95	2.33	3.2327 (15)	159
C10—H10B⋯O3ⁱⁱ	0.98	2.68	3.5380 (16)	147
Symmetry codes: (i) ; (ii) .

Figure 1
Anisotropic displacement ellipsoid plot of 1 with ellipsoids set to the 50% probability level.

Looking down the a-axis, and involving a second molecule of 1 related by inversion, the centroid of the electron-rich, chlorine-derivatized aromatic ring of the first molecule lies above the electron-deficient carbonyl carbon atom of the second at a distance of 3.4600 (12) Å, suggesting the presence of electrostatic interactions (Fig. 2). In addition to the electrostatic interactions, when looking into the bc-plane, between H5 on the aromatic ring and O1 from the carbonyl that is nearly co-planar with the aromatic ring, a C—H⋯O [d(C5⋯O1) = 3.23 Å; Θ(C5—H5—O1) = 159°] hydrogen bond was observed (Fig. 3, Table 2). A one-dimensional array of symmetry-equivalent molecules of 1 linked by C—H⋯O hydrogen bonds results along the b-axis direction when looking into the bc-plane (Fig. 3). While there are no additional interactions between neighboring, co-planar one-dimensional arrays parallel to one another along c, weak C—H⋯O [d(C10⋯O3) = 3.54 Å; Θ(C10—H10B—O3) = 147°] interactions with a neighboring layer having the symmetry code (1 − x, −y, −z) yielded a centrosymmetric dimer (Fig. 4, Table 2) having the R₂²(10) graph-set notation (Bernstein et al., 1995 ).

Table 2
Experimental details

Crystal data
Chemical formula	C₁₀H₈Cl₂O₄
M_r	263.06
Crystal system, space group	Triclinic, P $[\overline{1}]$
Temperature (K)	173
a, b, c (Å)	7.0204 (6), 7.7661 (6), 10.5392 (8)
α, β, γ (°)	97.733 (1), 109.293 (1), 90.217 (1)
V (Å³)	536.69 (7)
Z	2
Radiation type	Mo Kα
μ (mm⁻¹)	0.60
Crystal size (mm)	0.35 × 0.29 × 0.28

Data collection
Diffractometer	Bruker APEX CCD area detector
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.838, 0.927
No. of measured, independent and observed [I > 2σ(I)] reflections	5934, 2582, 2417
R_int	0.031
(sin θ/λ)_max (Å⁻¹)	0.668

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.026, 0.073, 1.04
No. of reflections	2582
No. of parameters	147
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.45, −0.21
Computer programs: APEX2 and SAINT (Bruker, 2016 ), SHELXT2014/5 (Sheldrick, 2015a ), SHELXL2014/7 (Sheldrick, 2015b ) and OLEX2 (Dolomanov et al., 2009 ).

Figure 2
Solid-state expansion of 1 showing the superposition of the electron-rich aromatic ring centroid and the electron-deficient carbonyl carbon atom. Anisotropic displacement ellipsoids have been set to the 50% probability level.

Figure 3
Projection of 1 within the bc-plane showing the C—H⋯O hydrogen bonding between neighboring molecules along b to form one-dimensional arrays. Anisotropic displacement ellipsoids have been set to the 50% probability level. Dashed lines represent hydrogen bonds.

Figure 4
Projection of 1 within the ac-plane showing the formation of the R₂²(10) centrosymmetric dimer facilitated by weak C—H⋯O interactions between layers. Anisotropic displacement ellipsoids have been set to the 50% probability level. Dashed lines represent the C—H⋯O interactions.

Synthesis and crystallization

Compound 1 was synthesized by adding 4,5-dichlorophthalic acid (23.68 mmol, 5.566 g) to 70 ml of CH₃OH in a 200 ml flask. While stirring, 1.0 ml H₂SO₄ (98%) was added dropwise and the mixture was allowed to reflux at 70°C overnight. The product was extracted with ethyl acetate, and washed with water, concentrated NaHCO₃, 10% NaHCO₃, and then a saturated solution of NaCl. After filtering through Na₂SO₄ to remove trace moisture, the solvent was removed in vacuo to yield a clear oil, which later crystallized into small rods. Recrystallization from the mixed solvents of isopropyl alcohol and dichloromethane produced X-ray quality crystals of 1 up to 2 mm.

Refinement

Crystal data, data collection and structure refinement details for 1 are summarized in Table 2. The choice of the space group P $[\overline{1}]$ for 1 was unambiguously verified by PLATON (Spek, 2003 ; Spek, 2020 ).

Structural data

CCDC reference: 720360

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314621010439/bv4041sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314621010439/bv4041Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314621010439/bv4041Isup3.cml

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2016); cell refinement: SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016); program(s) used to solve structure: SHELXT2014/5 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

Dimethyl 4,5-dichlorophthalate top

Crystal data top

C₁₀H₈Cl₂O₄	Z = 2
M_r = 263.06	F(000) = 268
Triclinic, P1	D_x = 1.628 Mg m⁻³
a = 7.0204 (6) Å	Mo Kα radiation, λ = 0.71073 Å
b = 7.7661 (6) Å	Cell parameters from 548 reflections
c = 10.5392 (8) Å	θ = 2.4–27.7°
α = 97.733 (1)°	µ = 0.60 mm⁻¹
β = 109.293 (1)°	T = 173 K
γ = 90.217 (1)°	Irregular, colorless
V = 536.69 (7) Å³	0.35 × 0.29 × 0.28 mm

Data collection top

Bruker APEX CCD area detector diffractometer	2582 independent reflections
Radiation source: Fine-focus sealed tube	2417 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.031
phi and ω scans	θ_max = 28.3°, θ_min = 2.1°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	h = −9→9
T_min = 0.838, T_max = 0.927	k = −10→10
5934 measured reflections	l = −14→14

Refinement top

Refinement on F²	Primary atom site location: dual
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.026	H-atom parameters constrained
wR(F²) = 0.073	w = 1/[σ²(F_o²) + (0.0368P)² + 0.1955P] where P = (F_o² + 2F_c²)/3
S = 1.04	(Δ/σ)_max = 0.001
2582 reflections	Δρ_max = 0.45 e Å⁻³
147 parameters	Δρ_min = −0.21 e Å⁻³
0 restraints

Special details top

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. All non-hydrogen atoms were refined anisotropically. H atoms bound to C atoms were constrained to ride on the atoms onto which they are bonded, where C—H = 0.95 (aromatic) or 0.98 Å (methyl) with U_iso(H) = 1.2U_eq(C).

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

	x	y	z	U_iso*/U_eq
Cl1	0.81953 (5)	0.48342 (4)	0.83259 (3)	0.02349 (9)
Cl2	0.74478 (5)	0.08068 (4)	0.71750 (3)	0.02487 (9)
O1	0.76916 (17)	0.76700 (12)	0.40055 (10)	0.0310 (2)
O2	0.69277 (14)	0.55617 (11)	0.22210 (9)	0.02121 (18)
O3	0.50933 (14)	0.17388 (12)	0.16137 (9)	0.02470 (19)
O4	0.84744 (13)	0.20884 (11)	0.21752 (8)	0.02113 (18)
C1	0.73795 (16)	0.47447 (14)	0.43804 (11)	0.0158 (2)
C2	0.77075 (17)	0.53010 (15)	0.57530 (12)	0.0170 (2)
H2	0.7904	0.6508	0.6094	0.020*
C3	0.77483 (17)	0.41014 (15)	0.66231 (11)	0.0172 (2)
C4	0.74445 (17)	0.23318 (15)	0.61230 (12)	0.0181 (2)
C5	0.71216 (18)	0.17662 (15)	0.47593 (12)	0.0185 (2)
H5	0.6921	0.0558	0.4423	0.022*
C6	0.70903 (17)	0.29623 (14)	0.38820 (11)	0.0159 (2)
C7	0.73570 (17)	0.61539 (15)	0.35369 (12)	0.0179 (2)
C8	0.6829 (2)	0.68909 (17)	0.13612 (13)	0.0247 (3)
H8A	0.6390	0.6352	0.0408	0.037*
H8B	0.8168	0.7473	0.1603	0.037*
H8C	0.5863	0.7746	0.1491	0.037*
C9	0.67274 (18)	0.22206 (14)	0.24202 (12)	0.0175 (2)
C10	0.8297 (2)	0.14662 (17)	0.07783 (12)	0.0249 (3)
H10A	0.7640	0.2330	0.0200	0.037*
H10B	0.7485	0.0365	0.0474	0.037*
H10C	0.9646	0.1283	0.0717	0.037*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl1	0.02835 (16)	0.02741 (16)	0.01490 (15)	−0.00009 (11)	0.00920 (12)	−0.00131 (11)
Cl2	0.03392 (18)	0.02289 (16)	0.01804 (15)	−0.00098 (12)	0.00730 (12)	0.00740 (11)
O1	0.0505 (6)	0.0152 (4)	0.0266 (5)	0.0004 (4)	0.0124 (4)	0.0022 (3)
O2	0.0281 (4)	0.0181 (4)	0.0175 (4)	−0.0002 (3)	0.0066 (3)	0.0052 (3)
O3	0.0253 (5)	0.0269 (4)	0.0174 (4)	−0.0058 (3)	0.0021 (3)	0.0010 (3)
O4	0.0235 (4)	0.0248 (4)	0.0136 (4)	0.0029 (3)	0.0056 (3)	−0.0005 (3)
C1	0.0142 (5)	0.0158 (5)	0.0169 (5)	0.0010 (4)	0.0045 (4)	0.0026 (4)
C2	0.0152 (5)	0.0161 (5)	0.0188 (5)	0.0008 (4)	0.0056 (4)	−0.0004 (4)
C3	0.0156 (5)	0.0217 (5)	0.0139 (5)	0.0011 (4)	0.0052 (4)	0.0000 (4)
C4	0.0183 (5)	0.0196 (5)	0.0164 (5)	0.0003 (4)	0.0049 (4)	0.0050 (4)
C5	0.0216 (5)	0.0155 (5)	0.0171 (5)	−0.0003 (4)	0.0048 (4)	0.0019 (4)
C6	0.0155 (5)	0.0165 (5)	0.0143 (5)	0.0002 (4)	0.0034 (4)	0.0011 (4)
C7	0.0168 (5)	0.0167 (5)	0.0204 (5)	0.0019 (4)	0.0059 (4)	0.0036 (4)
C8	0.0292 (6)	0.0237 (6)	0.0243 (6)	0.0038 (5)	0.0098 (5)	0.0115 (5)
C9	0.0242 (6)	0.0125 (5)	0.0150 (5)	0.0009 (4)	0.0049 (4)	0.0030 (4)
C10	0.0342 (7)	0.0261 (6)	0.0147 (5)	0.0029 (5)	0.0097 (5)	−0.0001 (4)

Geometric parameters (Å, º) top

Cl1—C3	1.7305 (12)	C2—C3	1.3865 (16)
Cl2—C4	1.7272 (12)	C3—C4	1.3931 (16)
O1—C7	1.2042 (15)	C4—C5	1.3871 (16)
O2—C7	1.3330 (15)	C5—H5	0.9500
O2—C8	1.4500 (14)	C5—C6	1.3915 (15)
O3—C9	1.2022 (15)	C6—C9	1.5069 (16)
O4—C9	1.3359 (15)	C8—H8A	0.9800
O4—C10	1.4503 (14)	C8—H8B	0.9800
C1—C2	1.3940 (16)	C8—H8C	0.9800
C1—C6	1.4018 (15)	C10—H10A	0.9800
C1—C7	1.4969 (15)	C10—H10B	0.9800
C2—H2	0.9500	C10—H10C	0.9800

C7—O2—C8	115.05 (9)	C5—C6—C9	116.26 (10)
C9—O4—C10	115.31 (10)	O1—C7—O2	123.60 (11)
C2—C1—C6	119.63 (10)	O1—C7—C1	123.11 (11)
C2—C1—C7	115.67 (10)	O2—C7—C1	113.29 (9)
C6—C1—C7	124.70 (10)	O2—C8—H8A	109.5
C1—C2—H2	119.8	O2—C8—H8B	109.5
C3—C2—C1	120.33 (10)	O2—C8—H8C	109.5
C3—C2—H2	119.8	H8A—C8—H8B	109.5
C2—C3—Cl1	119.14 (9)	H8A—C8—H8C	109.5
C2—C3—C4	119.92 (10)	H8B—C8—H8C	109.5
C4—C3—Cl1	120.94 (9)	O3—C9—O4	125.21 (11)
C3—C4—Cl2	121.06 (9)	O3—C9—C6	124.09 (11)
C5—C4—Cl2	118.80 (9)	O4—C9—C6	110.60 (10)
C5—C4—C3	120.14 (10)	O4—C10—H10A	109.5
C4—C5—H5	119.9	O4—C10—H10B	109.5
C4—C5—C6	120.23 (10)	O4—C10—H10C	109.5
C6—C5—H5	119.9	H10A—C10—H10B	109.5
C1—C6—C9	124.00 (10)	H10A—C10—H10C	109.5
C5—C6—C1	119.74 (10)	H10B—C10—H10C	109.5

Cl1—C3—C4—Cl2	1.42 (14)	C4—C5—C6—C1	−0.23 (17)
Cl1—C3—C4—C5	−178.93 (9)	C4—C5—C6—C9	−179.96 (10)
Cl2—C4—C5—C6	179.38 (9)	C5—C6—C9—O3	78.67 (15)
C1—C2—C3—Cl1	179.08 (9)	C5—C6—C9—O4	−97.92 (12)
C1—C2—C3—C4	−0.50 (17)	C6—C1—C2—C3	0.00 (17)
C1—C6—C9—O3	−101.05 (14)	C6—C1—C7—O1	−176.90 (12)
C1—C6—C9—O4	82.36 (13)	C6—C1—C7—O2	3.20 (16)
C2—C1—C6—C5	0.37 (17)	C7—C1—C2—C3	179.72 (10)
C2—C1—C6—C9	−179.92 (10)	C7—C1—C6—C5	−179.33 (10)
C2—C1—C7—O1	3.39 (17)	C7—C1—C6—C9	0.38 (18)
C2—C1—C7—O2	−176.51 (10)	C8—O2—C7—O1	−1.71 (17)
C2—C3—C4—Cl2	−179.00 (8)	C8—O2—C7—C1	178.18 (9)
C2—C3—C4—C5	0.65 (17)	C10—O4—C9—O3	6.33 (17)
C3—C4—C5—C6	−0.28 (18)	C10—O4—C9—C6	−177.12 (9)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5···O1ⁱ	0.95	2.33	3.2327 (15)	159
C10—H10B···O3ⁱⁱ	0.98	2.68	3.5380 (16)	147

Symmetry codes: (i) x, y−1, z; (ii) −x+1, −y, −z.

Funding information

Funding for this research was provided by: Pomona College; Harvey Mudd College.

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