Methyl 6-acetyl-1,4-benzodioxine-2-carboxyl­ate

The title compound, C₁₂H₁₀O₅, was prepared as part of our study on obtaining pure regioselective Friedel–Crafts acetyl­ation products. The mol­ecule is planar with no hydrogen bonds found in the crystal structure. The mol­ecules are stacked together through π–π inter­actions (centroid–centroid distance = 3.655 Å), with the stacks of mol­ecules forming a zigzag packing arrangement stabilized by van der Waals forces.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.052
• wR factor = 0.132
• Data-to-parameter ratio = 11.1

checkCIF/PLATON results

No syntax errors found



Alert level C
ABSTM02_ALERT_3_C  The ratio of expected to reported Tmax/Tmin(RR') is < 0.90
            Tmin and Tmax reported:      0.757     1.000
            Tmin(prime) and Tmax expected:      0.941     0.979
            RR(prime) =      0.787
            Please check that your absorption correction is appropriate.
PLAT061_ALERT_3_C Tmax/Tmin Range Test RR' too Large .............       0.79
PLAT062_ALERT_4_C Rescale T(min) & T(max) by .....................       0.98
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .......          ?

Alert level G
ABSTM02_ALERT_3_G  When printed, the submitted absorption T values will be
            replaced by the scaled T values. Since the ratio of scaled T's
            is identical to the ratio of reported T values, the scaling
            does not imply a change to the absorption corrections used in
            the study.
            Ratio of Tmax expected/reported      0.979
            Tmax scaled      0.979 Tmin scaled      0.741
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   4 ALERT level C = Check and explain
   3 ALERT level G = General alerts; check

   2 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
   3 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The title compound was first obtained as a mixture with 7-acetyl-l,4-benzodioxin-2-carboxylic acid methyl ester nisomer in a ratio of 85:15 with total yield of 85%-87% by Friedel-Crafts actylation (Mata & Suárez, 1997). In order to get pure regioselective acylation products, we tried to use AlCl₃—CS₂ as reagent (Thiéry et al., 1995) in the reaction and did obtain a pure acetylation product. In order to determine the location of the acetyl group, an X-ray structure determination of the title compound (I) has been carried out and the results are presented here (Fig.1).

As seen from Fig. 1, the acetyl group was located on C2 of phenyl ring, which confirms the acetylation position is at C-6 of 1,4-benzodioxin-2-carboxylic acid methyl ester and the acetylation product is the title compound (I). The 1,4-dioxin plane defined by O1/O2/C5/C6/C7/C8 and the phenyl ring defined by C1/C2/C3/C4/C5/C6 are coplanar with each other with a dihedral angle between their mean planes of 0.65 (0.06)°. These groups are also planar with the acetyl group and the ester group, forming torsion angles of C1—C2—C11—O5 [-3.2 (3)°] and C3—C2—C11—C12 [-4.2 (3)°], C7—C8—C9—O4 [9.3 (3)°] and O1—C8—C9—O3 [8.7 (2)°], respectively. Three other structures contining the 1,4-Benzodioxin-2-yl moiety have been published (Leger et al., 1983).

No suitable hydrogen bonds are found in the crystal structure. In the crystal cell packing diagram (Fig. 2), the molecules are stacked together through π ··· π interactions, and stacks of molecules form a zigzag packing arrangement stabilized by van de Waals forces.

Related literature

For regioselective Friedel–Crafts acetylation reactions, see: Mata & Suárez (1997); Thiéry et al. (1995). For related structures, see: Leger et al. (1983).

S2. Experimental

The title compound was synthesized as described by Thiéry et al. (1995) from l,4-benzodioxin-2-carboxylic acid ethyl ester, acyl chloride and anhydrous AlCl₃ in CS₂(Fig. 3). The title compound was obtained as colorless needles, yields: 94%, mp 393 K. ¹H-NMR (CDC1₃): δ 2.50 (s, 3H, CH₃CO), 3.83 (s, 3H, OCH₃), 6.87 (d, J = 8.5 Hz, 1H, H-8), 6.98 (s, 1H, H-3), 7.31(d, J = 2.0 Hz, 1H, H-5), 7.53 (dd, J = 8.5, 2.0 Hz, 1H, H-7). Single crystals of (I) suitable for X-ray diffraction were obtained by slow evaporation of a MeOH-CHCl₃ solution.

S3. Refinement

H atoms were refined with fixed individual displacement parameters [U_iso(H) = 1.2U_eq(C) for CH and or U_iso(H) = 1.5U_eq(C) for CH₃] using a riding model with C—H distances ranging from 0.93 to 1.01 Å.

Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT and SHETXL (Bruker, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2000) and ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXTL (Bruker, 2000).

Figures

	Fig. 1. The molecular structure of (I), showing the atom-labelling scheme and 50% probability displacement ellipsoids.
	Fig. 2. The packing view of the title compound (I) along c axis.
	Fig. 3. The reaction scheme.

Methyl 6-acetyl-l,4-benzodioxine-2-carboxylate

Crystal data

C12H10O5	Dx = 1.476 Mg m^−3
Mr = 234.20	Melting point: 393 K
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.2282 (11) Å	Cell parameters from 1401 reflections
b = 25.147 (4) Å	θ = 5.8–49.6°
c = 5.9639 (9) Å	µ = 0.12 mm^−1
β = 103.598 (3)°	T = 293 K
V = 1053.6 (3) Å^3	Block, colorless
Z = 4	0.52 × 0.23 × 0.18 mm
F(000) = 488

Data collection

Bruker SMART CCD area-detector diffractometer	2172 independent reflections
Radiation source: fine-focus sealed tube	1409 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.079
phi and ω scans	θmax = 26.5°, θmin = 1.6°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −9→8
Tmin = 0.757, Tmax = 1.000	k = −31→29
5915 measured reflections	l = −6→7

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)] = 0.052	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.132	w = 1/[σ^2(Fo^2) + (0.0666P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.92	(Δ/σ)max = 0.006
2172 reflections	Δρmax = 0.22 e Å^−3
195 parameters	Δρmin = −0.21 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.017 (3)

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.

Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

6.9022 (0.0019) x + 6.9493 (0.0175) y - 1.9684 (0.0042) z = 4.2331 (0.0098)

* 0.0008 (0.0013) C1 * 0.0003 (0.0013) C2 * -0.0033 (0.0013) C3 * 0.0053 (0.0013) C4 * -0.0042 (0.0013) C5 * 0.0012 (0.0013) C6

Rms deviation of fitted atoms = 0.0031

6.9132 (0.0018) x + 6.9225 (0.0179) y - 1.9054 (0.0035) z = 4.2516 (0.0085)

Angle to previous plane (with approximate e.s.d.) = 0.65 (0.06)

* -0.0012 (0.0011) O1 * 0.0013 (0.0011) O2 * 0.0052 (0.0012) C5 * -0.0052 (0.0012) C6 * 0.0027 (0.0013) C7 * -0.0028 (0.0012) C8

Rms deviation of fitted atoms = 0.0035

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	0.35476 (17)	0.45094 (4)	0.69473 (18)	0.0474 (4)
O2	0.20608 (19)	0.46719 (5)	0.21300 (19)	0.0529 (4)
O3	0.4490 (2)	0.35620 (5)	0.8458 (2)	0.0554 (4)
O4	0.4360 (2)	0.32251 (5)	0.4951 (2)	0.0674 (5)
O5	0.0113 (3)	0.65702 (6)	0.1407 (3)	0.0841 (5)
C1	0.1371 (3)	0.55620 (7)	0.2935 (3)	0.0437 (5)
C2	0.1378 (2)	0.59835 (6)	0.4449 (3)	0.0427 (4)
C3	0.2126 (3)	0.58992 (7)	0.6794 (3)	0.0455 (5)
C4	0.2862 (3)	0.54074 (7)	0.7596 (3)	0.0441 (5)
C5	0.2828 (2)	0.49959 (6)	0.6071 (3)	0.0383 (4)
C6	0.2086 (2)	0.50773 (6)	0.3728 (3)	0.0391 (4)
C7	0.2794 (3)	0.41997 (7)	0.3069 (3)	0.0468 (5)
C8	0.3480 (2)	0.41189 (6)	0.5290 (3)	0.0410 (4)
C9	0.4162 (3)	0.35916 (7)	0.6169 (3)	0.0449 (5)
C10	0.4945 (5)	0.30349 (9)	0.9420 (4)	0.0731 (8)
C11	0.0631 (3)	0.65106 (7)	0.3482 (3)	0.0519 (5)
C12	0.0555 (4)	0.69607 (9)	0.5089 (5)	0.0681 (7)
H1	0.083 (2)	0.5606 (7)	0.130 (3)	0.056 (5)*
H2	0.217 (3)	0.6176 (8)	0.786 (3)	0.057 (6)*
H3	0.338 (2)	0.5343 (7)	0.927 (3)	0.059 (6)*
H4	0.266 (3)	0.3939 (9)	0.186 (3)	0.067 (6)*
H5	0.501 (3)	0.3071 (11)	1.113 (5)	0.109 (9)*
H6	0.620 (3)	0.2945 (10)	0.922 (4)	0.101 (10)*
H7	0.395 (4)	0.2768 (11)	0.869 (4)	0.112 (10)*
H8	−0.016 (3)	0.7269 (10)	0.427 (4)	0.097 (8)*
H9	0.182 (4)	0.7100 (12)	0.592 (5)	0.106 (11)*
H10	−0.016 (3)	0.6863 (10)	0.625 (5)	0.104 (10)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0722 (9)	0.0322 (6)	0.0347 (7)	0.0072 (6)	0.0066 (6)	−0.0009 (5)
O2	0.0824 (10)	0.0409 (7)	0.0313 (7)	0.0105 (6)	0.0049 (6)	−0.0036 (5)
O3	0.0904 (11)	0.0350 (7)	0.0398 (8)	0.0104 (6)	0.0133 (7)	0.0029 (5)
O4	0.1143 (13)	0.0404 (8)	0.0489 (8)	0.0128 (7)	0.0223 (8)	−0.0059 (6)
O5	0.1253 (14)	0.0571 (10)	0.0602 (10)	0.0223 (9)	0.0023 (9)	0.0156 (8)
C1	0.0509 (11)	0.0436 (10)	0.0352 (10)	0.0012 (8)	0.0075 (8)	0.0040 (8)
C2	0.0477 (11)	0.0356 (9)	0.0460 (10)	−0.0016 (8)	0.0134 (8)	0.0029 (8)
C3	0.0625 (12)	0.0351 (10)	0.0388 (10)	−0.0015 (8)	0.0121 (9)	−0.0046 (8)
C4	0.0595 (12)	0.0395 (10)	0.0330 (9)	0.0001 (8)	0.0105 (8)	−0.0009 (8)
C5	0.0453 (11)	0.0334 (9)	0.0365 (9)	−0.0001 (7)	0.0102 (7)	0.0025 (7)
C6	0.0474 (11)	0.0350 (9)	0.0356 (9)	−0.0014 (7)	0.0109 (8)	−0.0020 (7)
C7	0.0658 (13)	0.0363 (9)	0.0373 (10)	0.0038 (9)	0.0102 (9)	−0.0040 (8)
C8	0.0527 (11)	0.0343 (9)	0.0375 (10)	−0.0015 (8)	0.0134 (8)	−0.0045 (7)
C9	0.0569 (12)	0.0373 (10)	0.0413 (10)	0.0007 (8)	0.0131 (9)	−0.0017 (8)
C10	0.123 (3)	0.0399 (12)	0.0553 (15)	0.0178 (14)	0.0183 (15)	0.0128 (10)
C11	0.0561 (13)	0.0414 (10)	0.0565 (13)	0.0015 (9)	0.0095 (10)	0.0057 (9)
C12	0.0884 (19)	0.0361 (11)	0.0763 (17)	0.0080 (11)	0.0126 (15)	0.0008 (11)

Geometric parameters (Å, º)

O1—C5	1.3829 (19)	C3—H2	0.938 (19)
O1—C8	1.3858 (19)	C4—C5	1.374 (2)
O2—C7	1.366 (2)	C4—H3	0.993 (17)
O2—C6	1.3927 (19)	C5—C6	1.389 (2)
O3—C9	1.332 (2)	C7—C8	1.317 (2)
O3—C10	1.451 (2)	C7—H4	0.96 (2)
O4—C9	1.203 (2)	C8—C9	1.468 (2)
O5—C11	1.215 (2)	C10—H5	1.01 (3)
C1—C6	1.364 (2)	C10—H6	0.97 (2)
C1—C2	1.392 (2)	C10—H7	1.00 (3)
C1—H1	0.965 (17)	C11—C12	1.492 (3)
C2—C3	1.392 (2)	C12—H8	0.99 (2)
C2—C11	1.495 (2)	C12—H9	0.99 (3)
C3—C4	1.386 (2)	C12—H10	0.99 (3)
C5—O1—C8	114.21 (12)	O2—C7—H4	109.0 (12)
C7—O2—C6	114.49 (13)	C7—C8—O1	123.37 (15)
C9—O3—C10	115.18 (16)	C7—C8—C9	120.94 (16)
C6—C1—C2	120.80 (16)	O1—C8—C9	115.65 (14)
C6—C1—H1	118.8 (11)	O4—C9—O3	123.97 (16)
C2—C1—H1	120.4 (11)	O4—C9—C8	123.65 (17)
C1—C2—C3	118.50 (16)	O3—C9—C8	112.36 (15)
C1—C2—C11	118.65 (16)	O3—C10—H5	105.6 (15)
C3—C2—C11	122.83 (16)	O3—C10—H6	107.2 (15)
C4—C3—C2	120.62 (16)	H5—C10—H6	109 (2)
C4—C3—H2	118.7 (11)	O3—C10—H7	111.5 (16)
C2—C3—H2	120.7 (11)	H5—C10—H7	111 (2)
C5—C4—C3	119.85 (16)	H6—C10—H7	113 (2)
C5—C4—H3	119.1 (10)	O5—C11—C12	120.76 (18)
C3—C4—H3	121.1 (10)	O5—C11—C2	119.93 (18)
C4—C5—O1	117.99 (15)	C12—C11—C2	119.31 (18)
C4—C5—C6	119.83 (16)	C11—C12—H8	111.6 (14)
O1—C5—C6	122.18 (15)	C11—C12—H9	114.7 (17)
C1—C6—C5	120.38 (16)	H8—C12—H9	106 (2)
C1—C6—O2	118.26 (15)	C11—C12—H10	111.5 (15)
C5—C6—O2	121.36 (15)	H8—C12—H10	104 (2)
C8—C7—O2	124.38 (16)	H9—C12—H10	108 (2)
C8—C7—H4	126.5 (12)
C6—C1—C2—C3	−0.2 (3)	C7—O2—C6—C5	0.7 (2)
C6—C1—C2—C11	178.17 (17)	C6—O2—C7—C8	0.1 (3)
C1—C2—C3—C4	0.6 (3)	O2—C7—C8—O1	−0.5 (3)
C11—C2—C3—C4	−177.70 (18)	O2—C7—C8—C9	177.14 (17)
C2—C3—C4—C5	−1.0 (3)	C5—O1—C8—C7	0.1 (3)
C3—C4—C5—O1	−178.92 (17)	C5—O1—C8—C9	−177.66 (15)
C3—C4—C5—C6	1.1 (3)	C10—O3—C9—O4	−5.6 (3)
C8—O1—C5—C4	−179.24 (15)	C10—O3—C9—C8	172.8 (2)
C8—O1—C5—C6	0.7 (2)	C7—C8—C9—O4	9.3 (3)
C2—C1—C6—C5	0.3 (3)	O1—C8—C9—O4	−172.86 (17)
C2—C1—C6—O2	−179.30 (16)	C7—C8—C9—O3	−169.07 (17)
C4—C5—C6—C1	−0.7 (3)	O1—C8—C9—O3	8.7 (2)
O1—C5—C6—C1	179.31 (15)	C1—C2—C11—O5	−3.2 (3)
C4—C5—C6—O2	178.80 (15)	C3—C2—C11—O5	175.04 (19)
O1—C5—C6—O2	−1.2 (3)	C1—C2—C11—C12	177.5 (2)
C7—O2—C6—C1	−179.73 (17)	C3—C2—C11—C12	−4.2 (3)