2-[1-(Methyl­sulfan­yl)naphtho[2,1-b]furan-2-yl]acetic acid

The title compound, C₁₅H₁₂O₃S, was prepared by alkaline hydrolysis of ethyl 2-{1-(methyl­sulfan­yl)naphtho[2,1-b]furan-2-yl}acetate. The crystal structure is stabilized by CH₂—H...π inter­actions between the methyl H atoms of the methyl­sulfanyl substituent and the central benzene ring of the naphthofuran system, and by inversion-related inter­molecular O—H...O hydrogen bonds between the carboxyl groups.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.051
• wR factor = 0.224
• Data-to-parameter ratio = 12.7

checkCIF/PLATON results

No syntax errors found



Alert level A
PLAT029_ALERT_3_A _diffrn_measured_fraction_theta_full Low .......       0.92

Author Response: The high angle reflections were not detected because the sensitivity of detector is weak. And we controlled hkl data by < OMIT -3 51 > in ins file to avoid <PLAT022_ALERT_3_C Ratio Unique / Expected Reflections too Low>.

Alert level C
DIFMN02_ALERT_2_C  The minimum difference density is < -0.1*ZMAX*0.75
            _refine_diff_density_min given =     -1.449
            Test value =     -1.200
DIFMN03_ALERT_1_C  The minimum difference density is < -0.1*ZMAX*0.75
            The relevant atom site should be identified.
REFLT03_ALERT_3_C  Reflection count < 95% complete
           From the CIF: _diffrn_reflns_theta_max           25.50
           From the CIF: _diffrn_reflns_theta_full          25.50
           From the CIF: _reflns_number_total               2209
           TEST2: Reflns within _diffrn_reflns_theta_max
           Count of symmetry unique reflns         2412
           Completeness (_total/calc)             91.58%
RINTA01_ALERT_3_C  The value of Rint is greater than 0.10
            Rint given   0.115
PLAT020_ALERT_3_C The value of Rint is greater than 0.10 .........       0.12
PLAT022_ALERT_3_C Ratio Unique / Expected Reflections too Low ....       0.92
PLAT098_ALERT_2_C Minimum (Negative) Residual Density ............      -1.45 e/A   
PLAT230_ALERT_2_C Hirshfeld Test Diff for    O1     -   C11     ..       6.25 su
PLAT230_ALERT_2_C Hirshfeld Test Diff for    O3     -   C14     ..       5.58 su
PLAT230_ALERT_2_C Hirshfeld Test Diff for    C4     -   C5      ..       5.54 su
PLAT340_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...          6

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

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   5 ALERT type 2 Indicator that the structure model may be wrong or deficient
   6 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

As part of our ongoing studies on the synthesis and structure of 1-(methylsulfanyl)naphtho[2,1-b]furan derivatives, we have recently described 7-bromo-1-methylsulfanyl-2-phenylnaphtho[2,1-b]furan (Choi et al., 2006) and 2-(4-bromophenyl)-1-(methylsulfanyl)naphtho[2,1-b]furan (Choi et al., 2007). Herein we report the molecular and crystal structure of the title compound, 2-{1-(methylsulfanyl)naphtho[2,1-b]furan-2-yl}acetic acid (Fig. 1).

The naphthofuran unit is essentially planar, with a mean deviation of 0.017Å from the least-squares plane defined by the thirteen constituent atoms. The crystal packing (Fig. 2) is stabilized by CH₂—H···π interactions, with a C15—H15B···Cg separation of 3.03Å (Cg is the centroid of the C2/C3/C8/C9/C10/C11 benzene ring; symmetry code as in Fig. 2). Classical inversion- related O3–H3···O2ⁱ hydrogen bonds link the carboxyl groups of adjacent molecules (Table and Fig. 2).

Related literature

For the crystal structures of similar 1-(methylsulfanyl)naphtho[2,1-b]furan compounds, see: Choi et al. (2006, 2007).

S2. Experimental

Ethyl 2-{1-(methylsulfanyl)naphtho[2,1-b]furan-2-yl}acetate (600 mg, 2.0 mmol) was added to a solution of potassium hydroxide (561 mg, 10.0 mmol) in water (20 ml) and methanol (20 ml). The mixture was refluxed for 4 h and then cooled. Water was added, and the solution was washed with chloroform. The aqueous layer was acidified to pH 1 with concentrated hydrochloric acid and then extracted with chloroform, dried over magnesium sulfate, filtered and concentrated under vacuum. The residue was purified by column chromatography (hexane/ethyl-acetate, 1:1 v/v) to afford the title compound as a colourless solid [yield 82%, m.p. 436–437 K; R_f = 0.62 (hexane/ethyl-acetate, 1:1 v/v)]. Single crystals suitable for X-ray diffraction were prepared by slow evaporation of a dilute solution of the title compound in diisopropyl ether at room temperature.

Spectroscopic analysis: ¹H NMR (CDCl₃, 400 MHz) δ 2.39 (s, 3H), 4.17 (s, 2H), 7.49–7.54 (m, 1H), 7.60–7.67 (m, 2H), 7.74 (d, J = 9.16 Hz, 1H), 7.95 (d, J = 7.68 Hz, 1H), 9.18 (d, J = 8.44 Hz, 1H), 11.02 (s, 1H); EI—MS 272 [M⁺].

S3. Refinement

All H atoms were positioned geometrically and refined using a riding model, with C–H = 0.93 Å for aromatic H atoms, C–H = 0.96 Å for methyl H atoms, C–H = 0.97 Å for methylene H atoms, and O–H = 0.82 Å, respectively, and with U_iso(H) = 1.2U_eq(C) for aromatic and methylene H atoms, U_iso(H) = 1.5U_eq(C) for methyl H atoms and U_iso(H) = 1.5U_eq(O) for caroxylic H atom.

The highest peak (1.088 e^.Å^-3) in the difference map is 0.97Å from S and the largest hole (-1.449 e^.Å^-3) is 0.21Å from S.

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and DIAMOND (Brandenburg, 1998); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoides are drawn at the 30% probability level. H atoms are presented as a small spheres of arbitrary radius.
	Fig. 2. The C–H···π interaction and O–H···O hydrogen bond (dotted lines) in the title compound. Cg denotes ring centroids. [Symmetry code: (i) -x + 2, -y + 1, -z; (ii) -x + 3/2, y + 1/2, -z + 1/2; (iii) -x + 3/2, y - 1/2, -z + 1/2.]

2-{1-(Methylsulfanyl)naphtho[2,1-b]furan-2-yl}acetic acid

Crystal data

C15H12O3S	F(000) = 568
Mr = 272.32	Dx = 1.385 Mg m^−3
Monoclinic, P21/n	Melting point = 436–437 K
Hall symbol: -P 2yn	Mo Kα radiation, λ = 0.71073 Å
a = 4.989 (2) Å	Cell parameters from 3886 reflections
b = 14.265 (5) Å	θ = 2.2–27.9°
c = 18.344 (7) Å	µ = 0.25 mm^−1
β = 90.18 (2)°	T = 296 K
V = 1305.5 (9) Å^3	Plate, silver
Z = 4	0.45 × 0.28 × 0.09 mm

Data collection

Bruker SMART CCD diffractometer	1130 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.115
Graphite monochromator	θmax = 25.5°, θmin = 1.8°
Detector resolution: 10.0 pixels mm^-1	h = −6→4
ϕ and ω scans	k = −17→17
8459 measured reflections	l = −22→21
2209 independent 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)] = 0.051	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.224	H-atom parameters constrained
S = 1.24	w = 1/[σ^2(Fo^2) + (0.1148P)^2] where P = (Fo^2 + 2Fc^2)/3
2209 reflections	(Δ/σ)max < 0.001
174 parameters	Δρmax = 1.09 e Å^−3
0 restraints	Δρmin = −1.45 e Å^−3

Special details

Geometry. The s.u.'s (except the s.u.'s in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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
S	0.7770 (3)	0.81307 (6)	0.19046 (5)	0.0475 (5)
O1	1.1260 (7)	0.57778 (15)	0.25355 (14)	0.0476 (9)
O2	0.8997 (7)	0.5410 (2)	0.08670 (16)	0.0591 (9)
O3	1.2812 (7)	0.5715 (2)	0.02196 (17)	0.0637 (10)
H3	1.2206	0.5315	−0.0056	0.096*
C1	0.8881 (9)	0.7104 (2)	0.23497 (18)	0.0371 (10)
C2	0.8115 (10)	0.6749 (2)	0.30727 (18)	0.0378 (11)
C3	0.6288 (10)	0.7029 (2)	0.36497 (19)	0.0417 (11)
C4	0.4543 (10)	0.7812 (3)	0.3628 (2)	0.0487 (12)
H4	0.4531	0.8190	0.3215	0.058*
C5	0.2867 (13)	0.8034 (3)	0.4195 (3)	0.0629 (15)
H5	0.1742	0.8551	0.4156	0.076*
C6	0.2828 (11)	0.7483 (3)	0.4842 (2)	0.0604 (13)
H6	0.1703	0.7641	0.5226	0.073*
C7	0.4471 (13)	0.6718 (3)	0.4889 (2)	0.0589 (16)
H7	0.4450	0.6353	0.5310	0.071*
C8	0.6247 (11)	0.6465 (2)	0.4295 (2)	0.0459 (12)
C9	0.7927 (11)	0.5650 (2)	0.4337 (2)	0.0529 (13)
H9	0.7865	0.5284	0.4757	0.063*
C10	0.9638 (12)	0.5385 (2)	0.3780 (2)	0.0520 (13)
H10	1.0721	0.4857	0.3820	0.062*
C11	0.9664 (10)	0.5950 (2)	0.31502 (19)	0.0402 (10)
C12	1.0731 (10)	0.6499 (2)	0.20589 (19)	0.0403 (11)
C13	1.2273 (9)	0.6483 (2)	0.1351 (2)	0.0457 (12)
H13A	1.4123	0.6325	0.1458	0.055*
H13B	1.2257	0.7110	0.1146	0.055*
C14	1.1236 (10)	0.5807 (2)	0.0778 (2)	0.0423 (11)
C15	0.9473 (11)	0.9017 (2)	0.2426 (3)	0.0734 (17)
H15A	0.8677	0.9062	0.2900	0.110*
H15B	0.9321	0.9609	0.2181	0.110*
H15C	1.1331	0.8853	0.2475	0.110*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S	0.0597 (9)	0.0476 (5)	0.0353 (6)	0.0031 (6)	−0.0090 (7)	0.0046 (3)
O1	0.0544 (19)	0.0403 (10)	0.0479 (15)	0.0044 (16)	−0.011 (2)	−0.0052 (10)
O2	0.0561 (19)	0.0729 (17)	0.0483 (17)	−0.019 (2)	0.002 (2)	−0.0139 (14)
O3	0.058 (2)	0.0800 (19)	0.0536 (18)	−0.010 (2)	0.000 (2)	−0.0234 (15)
C1	0.041 (2)	0.0385 (13)	0.0316 (16)	−0.001 (2)	−0.005 (2)	−0.0046 (12)
C2	0.041 (3)	0.0375 (14)	0.0344 (19)	−0.004 (2)	−0.009 (3)	−0.0031 (12)
C3	0.046 (3)	0.0429 (14)	0.0355 (18)	−0.009 (2)	−0.012 (3)	−0.0047 (13)
C4	0.048 (3)	0.0574 (18)	0.041 (2)	0.006 (3)	−0.008 (3)	−0.0054 (15)
C5	0.059 (3)	0.069 (2)	0.062 (3)	0.008 (3)	−0.015 (4)	−0.015 (2)
C6	0.053 (3)	0.079 (3)	0.049 (2)	−0.006 (4)	0.008 (3)	−0.019 (2)
C7	0.079 (4)	0.065 (2)	0.0334 (19)	−0.026 (3)	0.006 (3)	−0.0025 (15)
C8	0.052 (3)	0.0489 (16)	0.0368 (18)	−0.015 (2)	−0.008 (3)	−0.0018 (13)
C9	0.072 (4)	0.0483 (16)	0.0379 (19)	−0.008 (3)	−0.012 (3)	0.0079 (13)
C10	0.068 (3)	0.0392 (14)	0.049 (2)	0.003 (2)	−0.016 (3)	0.0025 (14)
C11	0.044 (2)	0.0384 (13)	0.0385 (18)	0.002 (2)	−0.006 (3)	−0.0056 (13)
C12	0.044 (3)	0.0403 (14)	0.0361 (18)	−0.006 (2)	−0.005 (3)	−0.0047 (12)
C13	0.044 (3)	0.0508 (17)	0.042 (2)	−0.008 (2)	0.003 (3)	−0.0109 (14)
C14	0.045 (3)	0.0474 (16)	0.0343 (18)	0.004 (2)	0.000 (3)	−0.0064 (14)
C15	0.082 (4)	0.0414 (16)	0.096 (3)	−0.006 (3)	−0.040 (4)	0.0067 (18)

Geometric parameters (Å, º)

S—C1	1.766 (3)	C6—C7	1.368 (7)
S—C15	1.797 (4)	C6—H6	0.9300
O1—C12	1.375 (4)	C7—C8	1.453 (7)
O1—C11	1.404 (5)	C7—H7	0.9300
O2—C14	1.263 (5)	C8—C9	1.435 (6)
O3—C14	1.300 (5)	C9—C10	1.386 (7)
O3—H3	0.8200	C9—H9	0.9300
C1—C12	1.372 (6)	C10—C11	1.410 (5)
C1—C2	1.471 (5)	C10—H10	0.9300
C2—C11	1.384 (5)	C12—C13	1.512 (6)
C2—C3	1.455 (6)	C13—C14	1.516 (4)
C3—C4	1.417 (6)	C13—H13A	0.9700
C3—C8	1.431 (5)	C13—H13B	0.9700
C4—C5	1.373 (7)	C15—H15A	0.9600
C4—H4	0.9300	C15—H15B	0.9600
C5—C6	1.423 (7)	C15—H15C	0.9600
C5—H5	0.9300
C1—S—C15	100.99 (18)	C10—C9—C8	122.8 (3)
C12—O1—C11	105.7 (3)	C10—C9—H9	118.6
C14—O3—H3	109.5	C8—C9—H9	118.6
C12—C1—C2	108.2 (3)	C9—C10—C11	117.1 (4)
C12—C1—S	123.5 (3)	C9—C10—H10	121.4
C2—C1—S	128.3 (3)	C11—C10—H10	121.4
C11—C2—C3	120.1 (3)	C2—C11—O1	112.3 (3)
C11—C2—C1	103.2 (4)	C2—C11—C10	123.3 (4)
C3—C2—C1	136.7 (3)	O1—C11—C10	124.4 (4)
C4—C3—C8	117.1 (4)	C1—C12—O1	110.6 (4)
C4—C3—C2	125.6 (3)	C1—C12—C13	133.5 (3)
C8—C3—C2	117.3 (4)	O1—C12—C13	115.9 (3)
C5—C4—C3	122.4 (4)	C12—C13—C14	115.6 (4)
C5—C4—H4	118.8	C12—C13—H13A	108.4
C3—C4—H4	118.8	C14—C13—H13A	108.4
C4—C5—C6	121.0 (5)	C12—C13—H13B	108.4
C4—C5—H5	119.5	C14—C13—H13B	108.4
C6—C5—H5	119.5	H13A—C13—H13B	107.4
C7—C6—C5	118.9 (5)	O2—C14—O3	126.5 (3)
C7—C6—H6	120.5	O2—C14—C13	119.7 (4)
C5—C6—H6	120.5	O3—C14—C13	113.8 (4)
C6—C7—C8	121.2 (4)	S—C15—H15A	109.5
C6—C7—H7	119.4	S—C15—H15B	109.5
C8—C7—H7	119.4	H15A—C15—H15B	109.5
C3—C8—C9	119.4 (4)	S—C15—H15C	109.5
C3—C8—C7	119.4 (4)	H15A—C15—H15C	109.5
C9—C8—C7	121.2 (4)	H15B—C15—H15C	109.5
C15—S—C1—C12	−106.1 (4)	C3—C8—C9—C10	0.9 (6)
C15—S—C1—C2	72.4 (4)	C7—C8—C9—C10	179.8 (4)
C12—C1—C2—C11	1.0 (4)	C8—C9—C10—C11	−0.5 (6)
S—C1—C2—C11	−177.7 (3)	C3—C2—C11—O1	178.7 (3)
C12—C1—C2—C3	−178.8 (4)	C1—C2—C11—O1	−1.1 (4)
S—C1—C2—C3	2.5 (7)	C3—C2—C11—C10	−1.8 (6)
C11—C2—C3—C4	−178.0 (4)	C1—C2—C11—C10	178.4 (4)
C1—C2—C3—C4	1.7 (7)	C12—O1—C11—C2	0.9 (4)
C11—C2—C3—C8	2.0 (5)	C12—O1—C11—C10	−178.6 (4)
C1—C2—C3—C8	−178.3 (4)	C9—C10—C11—C2	1.0 (6)
C8—C3—C4—C5	0.0 (6)	C9—C10—C11—O1	−179.5 (3)
C2—C3—C4—C5	180.0 (4)	C2—C1—C12—O1	−0.5 (4)
C3—C4—C5—C6	0.6 (6)	S—C1—C12—O1	178.3 (3)
C4—C5—C6—C7	−0.7 (7)	C2—C1—C12—C13	−179.2 (4)
C5—C6—C7—C8	0.3 (7)	S—C1—C12—C13	−0.4 (6)
C4—C3—C8—C9	178.5 (4)	C11—O1—C12—C1	−0.2 (4)
C2—C3—C8—C9	−1.5 (5)	C11—O1—C12—C13	178.7 (3)
C4—C3—C8—C7	−0.4 (5)	C1—C12—C13—C14	−102.7 (5)
C2—C3—C8—C7	179.6 (4)	O1—C12—C13—C14	78.6 (4)
C6—C7—C8—C3	0.3 (6)	C12—C13—C14—O2	10.5 (5)
C6—C7—C8—C9	−178.6 (4)	C12—C13—C14—O3	−170.9 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3···O2^i	0.82	1.91	2.711 (4)	167
C15—H15B···Cg^ii	0.96	3.03	3.949 (3)	161

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