1-Acetyl-3-(2-chloro-2,3-di­hydro­benzo­furan-3-yl)-1,2-di­hydro-3-hydroxy-2-oxo-3H-indole

In the title compound, C₁₈H₁₄ClNO₄, the indole moiety is planar, whereas the tetra­hydro­furan ring of the benzo­furan moiety adopts an envelope conformation. The dihedral angle between the benzo­furan and indole moieties is 58.7 (1)°. In the solid state, the mol­ecules are linked by O—H...O hydrogen bonds to form an infinite one-dimensional chain along the a axis.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.072
• wR factor = 0.194
• Data-to-parameter ratio = 15.0

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

The photoinduced cycloaddition reactions of 1H-indole-2,3-dione (isatin) with alkenes give the corresponding spirooxetane derivatives (Xue et al., 2000). These spiroxetanes undergoes acid-catalyzed ring-opening reactions giving 3-hydroxy-2-indole derivatives in which one of their structures having benzofuran has been confirmed by an X-ray crystal structure analysis (Usman et al., 2001a). As an extension of such ring-opening reaction of spirooxetane derivatives, we have prepared the title compound, (I), which was obtained from the hydrochloric acid catalyzed ring-opening of syn-1-acetyl-7,7'a-dihydrospiro[1H-indole-3,2'(2a'H)-oxeto[2,3-b] benzofuran-2(3H)-one (see Scheme). An X-ray crystal structure analysis of (I) was undertaken to elucidate its molecular conformation.

The bond lengths and angles in (I) show normal values (Allen et al., 1987). These values within the indole and benzofuran moieties also agree with those of the related structure previously studied, 1-acetyl-7a'-phenylspiro[3H-indole-3,2'(2a'H)-oxeto[2,3-b]benzofuran]-2(1H)-one (Usman et al., 2001b), except the bond distances involving the C11 atom and O4—C18 bond. The differences are mostly due to the absence of oxetane ring in the title compound. Though the indole moiety is almost planar with a maximum deviation of 0.078 (3) Å at C7, there is an angle of 4.0 (2)° between the pyrrolidine and benzene rings. The ketone O2 atom deviates from the indole plane by 0.161 (3) Å and the acetyl group attached at N1 is twisted out of the indole plane by 2.2 (4)°. The planarity of this indole moiety is due to the conjugation of the N—C and C═O bonds.

In the benzofuran moiety, the tetrahydrofuran ring adopts an envelope conformation with C18 deviating by 0.138 (3) Å from the mean plane through that ring. This furan ring forms a dihedral angle of 6.9 (2)° with the benzene ring. The mean plane through the benzofuran moiety makes a dihedral angle of 58.7 (1)° with respect to the indole moiety. The relative conformation about the bond joining the two moieties is defined by the torsion angle C1—C8—C11—C12 - 44.5 (3)°, which is (-)synclinal. When comparison is made with the related structure having the oxetane ring (Usman et al., 2001b), the value of this angle is smaller by 4.0 (1)°.

In the crystal of the title molecule, the OH group and the O atom of the acetyl group are involved in an intermolecular O—H···O hydrogen bond [O3···O1ⁱ 2.867 (4) Å, O3—H3B 0.78 (4) Å, H3B···O1ⁱ 2.13 (4) Å and O3—H3B···O1ⁱ 158 (4); symmetry code: (i) x - 1, y, z] which links the molecules translated along the a-cell direction to form an infinite one-dimensional chain.

S2. Experimental

The title compound was prepared by hydrochloric acid-catalysed ring-opening reaction of syn-1-acetyl-7,7'a-dihydrospiro[3H-indole-3,2'-(2a'H)oxeto[2,3-b]benzofuran- 2(1H)-one in benzene solution. Single crystals suitable for the X-ray diffraction study were obtained by slow evaporation from a mixture of petroleum ether (b.p. 308–333 K) and acetone solution.

S3. Refinement

After checking their presence in a difference map, the H atoms attached to the C atoms were geometrically fixed (C—H = 0.93–0.98 Å) and allowed to ride on the parent atoms. The hydroxyl H3A atom was isotropically refined. Due to a large fraction of weak data at higher angles, the 2θ maximum was limited to 54°.

Computing details

Data collection: SMART (Siemens, 1996a); cell refinement: SAINT (Siemens, 1996b); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL, PARST (Nardelli, 1995) and PLATON (Spek, 1990).

Figures

	Fig. 1. The structure of (I) showing 50% probability displacement ellipsoids and the atom-numbering scheme.
	Fig. 2. The molecular packing of (I) viewed down the b axis.

1-Acetyl-1,2-dihydro-2-oxo-3-hydroxy-3-(2-chloro-2,3- dihydrobenzofuran-3-yl)-(3H)indole

Crystal data

C18H14ClNO4	F(000) = 356
Mr = 343.75	Dx = 1.450 Mg m^−3
Triclinic, P1	Melting point: 406K K
a = 7.8675 (1) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.0796 (2) Å	Cell parameters from 4019 reflections
c = 12.4097 (2) Å	θ = 1.8–28.3°
α = 109.541 (1)°	µ = 0.27 mm^−1
β = 97.227 (1)°	T = 293 K
γ = 104.427 (1)°	Block, colorless
V = 787.54 (2) Å^3	0.48 × 0.16 × 0.14 mm
Z = 2

Data collection

Siemens SMART CCD area-detector diffractometer	3338 independent reflections
Radiation source: fine-focus sealed tube	2171 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.068
Detector resolution: 8.33 pixels mm^-1	θmax = 27.0°, θmin = 1.8°
ω scans	h = −9→10
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996)	k = −11→11
Tmin = 0.883, Tmax = 0.964	l = −15→12
5179 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)] = 0.072	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.194	H atoms treated by a mixture of independent and constrained refinement
S = 0.92	w = 1/[σ^2(Fo^2) + (0.0688P)^2] where P = (Fo^2 + 2Fc^2)/3
3338 reflections	(Δ/σ)max < 0.001
222 parameters	Δρmax = 0.41 e Å^−3
0 restraints	Δρmin = −0.47 e Å^−3

Special details

Experimental. The data collection covered over a hemisphere of reciprocal space by a combination of three sets of exposures; each set had a different ϕ angle (0,88 and 180°) for the crystal and each exposure of 10 s covered 0.3° inω. The crystal-to-detector distance was 4 cm and the detector swing angle was -35°. Crystal decay was monitored by repeating fifty initial frames at the end of data collection and analysing the intensity of duplicate reflections, and was found to be negligible.

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.

Refinement. Refinement of F² against all reflections within the 2θ maximum of 54°, excepting 15 inconsistent equivalents. 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
Cl1	0.15018 (10)	0.45538 (11)	0.18958 (8)	0.0527 (3)
O1	1.2326 (3)	0.9055 (4)	0.2714 (2)	0.0627 (7)
O2	0.7094 (3)	0.9129 (3)	0.1841 (2)	0.0551 (7)
O3	0.5619 (3)	0.8896 (3)	0.3883 (2)	0.0443 (6)
H3B	0.483 (5)	0.885 (4)	0.341 (3)	0.040 (10)*
O4	0.4294 (3)	0.4021 (3)	0.29140 (18)	0.0428 (5)
N1	0.9435 (3)	0.8656 (3)	0.2887 (2)	0.0310 (5)
C1	0.7844 (3)	0.7563 (3)	0.4039 (2)	0.0296 (6)
C2	0.7651 (4)	0.7039 (4)	0.4943 (3)	0.0431 (7)
H2A	0.6532	0.6774	0.5125	0.052*
C3	0.9147 (5)	0.6907 (4)	0.5588 (3)	0.0526 (9)
H3A	0.9022	0.6508	0.6182	0.063*
C4	1.0811 (4)	0.7368 (4)	0.5342 (3)	0.0480 (8)
H4A	1.1800	0.7275	0.5780	0.058*
C5	1.1059 (4)	0.7965 (3)	0.4468 (2)	0.0368 (7)
H5A	1.2197	0.8309	0.4328	0.044*
C6	0.9552 (4)	0.8031 (3)	0.3808 (2)	0.0285 (6)
C7	0.7660 (4)	0.8651 (3)	0.2562 (3)	0.0332 (6)
C8	0.6484 (3)	0.7825 (3)	0.3225 (2)	0.0311 (6)
C9	1.0879 (4)	0.9188 (4)	0.2399 (3)	0.0377 (7)
C10	1.0544 (5)	0.9821 (5)	0.1469 (3)	0.0571 (9)
H10A	0.9487	0.9067	0.0882	0.086*
H10B	1.1562	0.9935	0.1116	0.086*
H10C	1.0365	1.0874	0.1804	0.086*
C11	0.5070 (3)	0.6266 (3)	0.2298 (2)	0.0296 (6)
H11A	0.4407	0.6557	0.1718	0.036*
C12	0.5808 (4)	0.4907 (3)	0.1676 (2)	0.0317 (6)
C13	0.6819 (4)	0.4727 (4)	0.0829 (2)	0.0372 (7)
H13A	0.7168	0.5546	0.0536	0.045*
C14	0.7301 (4)	0.3299 (4)	0.0427 (3)	0.0486 (8)
H14A	0.7975	0.3155	−0.0143	0.058*
C15	0.6785 (5)	0.2109 (4)	0.0866 (3)	0.0525 (9)
H15A	0.7122	0.1163	0.0588	0.063*
C16	0.5778 (5)	0.2260 (4)	0.1712 (3)	0.0501 (9)
H16A	0.5433	0.1444	0.2008	0.060*
C17	0.5315 (4)	0.3680 (4)	0.2091 (3)	0.0373 (7)
C18	0.3736 (4)	0.5357 (4)	0.2845 (3)	0.0375 (7)
H18A	0.3734	0.6096	0.3628	0.045*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0277 (4)	0.0624 (6)	0.0610 (6)	0.0016 (4)	0.0046 (4)	0.0259 (5)
O1	0.0295 (12)	0.105 (2)	0.0755 (17)	0.0299 (13)	0.0240 (12)	0.0503 (16)
O2	0.0368 (12)	0.0653 (15)	0.0806 (17)	0.0159 (11)	0.0058 (12)	0.0521 (15)
O3	0.0299 (11)	0.0405 (13)	0.0540 (14)	0.0169 (10)	0.0114 (11)	0.0024 (11)
O4	0.0430 (12)	0.0450 (13)	0.0483 (13)	0.0125 (10)	0.0163 (10)	0.0262 (11)
N1	0.0225 (11)	0.0352 (13)	0.0360 (13)	0.0093 (10)	0.0077 (9)	0.0139 (11)
C1	0.0281 (13)	0.0256 (13)	0.0304 (14)	0.0078 (11)	0.0078 (11)	0.0051 (12)
C2	0.0399 (17)	0.0502 (19)	0.0338 (16)	0.0059 (14)	0.0097 (13)	0.0148 (14)
C3	0.055 (2)	0.063 (2)	0.0377 (17)	0.0094 (18)	0.0054 (16)	0.0242 (17)
C4	0.0442 (18)	0.062 (2)	0.0392 (17)	0.0217 (16)	0.0001 (14)	0.0207 (16)
C5	0.0310 (15)	0.0362 (16)	0.0390 (16)	0.0127 (12)	0.0034 (12)	0.0092 (13)
C6	0.0285 (13)	0.0239 (13)	0.0293 (13)	0.0085 (10)	0.0076 (11)	0.0047 (11)
C7	0.0256 (13)	0.0274 (14)	0.0470 (16)	0.0091 (11)	0.0073 (12)	0.0145 (13)
C8	0.0232 (13)	0.0352 (15)	0.0356 (15)	0.0124 (11)	0.0098 (11)	0.0109 (13)
C9	0.0318 (15)	0.0380 (16)	0.0430 (17)	0.0100 (12)	0.0147 (13)	0.0135 (14)
C10	0.0465 (19)	0.075 (2)	0.067 (2)	0.0172 (18)	0.0263 (18)	0.045 (2)
C11	0.0246 (13)	0.0301 (14)	0.0337 (14)	0.0069 (11)	0.0069 (11)	0.0127 (12)
C12	0.0278 (13)	0.0340 (15)	0.0296 (14)	0.0083 (11)	0.0026 (11)	0.0099 (12)
C13	0.0341 (15)	0.0400 (17)	0.0334 (15)	0.0112 (13)	0.0075 (12)	0.0093 (13)
C14	0.0380 (17)	0.067 (2)	0.0384 (17)	0.0259 (16)	0.0082 (14)	0.0100 (16)
C15	0.052 (2)	0.047 (2)	0.056 (2)	0.0268 (16)	0.0036 (17)	0.0104 (17)
C16	0.056 (2)	0.0327 (17)	0.057 (2)	0.0135 (15)	0.0005 (17)	0.0165 (16)
C17	0.0299 (14)	0.0415 (17)	0.0375 (16)	0.0080 (13)	0.0022 (12)	0.0158 (14)
C18	0.0258 (14)	0.0463 (18)	0.0378 (15)	0.0082 (13)	0.0085 (12)	0.0146 (14)

Geometric parameters (Å, º)

Cl1—C18	1.810 (3)	C7—C8	1.534 (4)
O1—C9	1.204 (4)	C8—C11	1.540 (4)
O2—C7	1.201 (3)	C9—C10	1.475 (4)
O3—C8	1.419 (3)	C10—H10A	0.96
O3—H3B	0.78 (3)	C10—H10B	0.96
O4—C17	1.380 (4)	C10—H10C	0.96
O4—C18	1.413 (3)	C11—C12	1.513 (4)
N1—C7	1.403 (4)	C11—C18	1.538 (4)
N1—C9	1.409 (3)	C11—H11A	0.98
N1—C6	1.438 (3)	C12—C17	1.370 (4)
C1—C2	1.369 (4)	C12—C13	1.387 (4)
C1—C6	1.401 (4)	C13—C14	1.391 (4)
C1—C8	1.495 (4)	C13—H13A	0.93
C2—C3	1.391 (5)	C14—C15	1.364 (5)
C2—H2A	0.93	C14—H14A	0.93
C3—C4	1.377 (5)	C15—C16	1.384 (5)
C3—H3A	0.93	C15—H15A	0.93
C4—C5	1.379 (4)	C16—C17	1.373 (4)
C4—H4A	0.93	C16—H16A	0.93
C5—C6	1.380 (4)	C18—H18A	0.98
C5—H5A	0.93
C8—O3—H3B	104 (3)	C9—C10—H10B	109.5
C17—O4—C18	106.7 (2)	H10A—C10—H10B	109.5
C7—N1—C9	126.0 (2)	C9—C10—H10C	109.5
C7—N1—C6	108.9 (2)	H10A—C10—H10C	109.5
C9—N1—C6	125.2 (2)	H10B—C10—H10C	109.5
C2—C1—C6	119.8 (3)	C12—C11—C18	100.0 (2)
C2—C1—C8	130.1 (3)	C12—C11—C8	115.1 (2)
C6—C1—C8	110.0 (2)	C18—C11—C8	112.4 (2)
C1—C2—C3	119.3 (3)	C12—C11—H11A	109.7
C1—C2—H2A	120.3	C18—C11—H11A	109.7
C3—C2—H2A	120.3	C8—C11—H11A	109.7
C4—C3—C2	119.8 (3)	C17—C12—C13	119.3 (3)
C4—C3—H3A	120.1	C17—C12—C11	108.1 (2)
C2—C3—H3A	120.1	C13—C12—C11	132.6 (3)
C3—C4—C5	122.1 (3)	C12—C13—C14	118.7 (3)
C3—C4—H4A	118.9	C12—C13—H13A	120.6
C5—C4—H4A	118.9	C14—C13—H13A	120.6
C4—C5—C6	117.4 (3)	C15—C14—C13	120.1 (3)
C4—C5—H5A	121.3	C15—C14—H14A	120.0
C6—C5—H5A	121.3	C13—C14—H14A	120.0
C5—C6—C1	121.5 (2)	C14—C15—C16	122.3 (3)
C5—C6—N1	128.9 (2)	C14—C15—H15A	118.9
C1—C6—N1	109.5 (2)	C16—C15—H15A	118.9
O2—C7—N1	126.7 (3)	C17—C16—C15	116.5 (3)
O2—C7—C8	124.2 (2)	C17—C16—H16A	121.8
N1—C7—C8	109.0 (2)	C15—C16—H16A	121.8
O3—C8—C1	109.9 (2)	C12—C17—C16	123.1 (3)
O3—C8—C7	110.7 (2)	C12—C17—O4	112.7 (3)
C1—C8—C7	102.3 (2)	C16—C17—O4	124.2 (3)
O3—C8—C11	110.1 (2)	O4—C18—C11	107.3 (2)
C1—C8—C11	116.3 (2)	O4—C18—Cl1	108.53 (19)
C7—C8—C11	107.0 (2)	C11—C18—Cl1	109.52 (19)
O1—C9—N1	119.6 (3)	O4—C18—H18A	110.5
O1—C9—C10	121.7 (3)	C11—C18—H18A	110.5
N1—C9—C10	118.6 (3)	Cl1—C18—H18A	110.5
C9—C10—H10A	109.5
C6—C1—C2—C3	−3.0 (4)	C6—N1—C9—O1	3.8 (4)
C8—C1—C2—C3	−179.4 (3)	C7—N1—C9—C10	0.8 (4)
C1—C2—C3—C4	2.7 (5)	C6—N1—C9—C10	−179.1 (3)
C2—C3—C4—C5	−0.1 (5)	O3—C8—C11—C12	−170.4 (2)
C3—C4—C5—C6	−2.3 (5)	C1—C8—C11—C12	−44.5 (3)
C4—C5—C6—C1	2.0 (4)	C7—C8—C11—C12	69.1 (3)
C4—C5—C6—N1	177.1 (3)	O3—C8—C11—C18	−56.8 (3)
C2—C1—C6—C5	0.6 (4)	C1—C8—C11—C18	69.1 (3)
C8—C1—C6—C5	177.7 (2)	C7—C8—C11—C18	−177.3 (2)
C2—C1—C6—N1	−175.4 (2)	C18—C11—C12—C17	−13.9 (3)
C8—C1—C6—N1	1.7 (3)	C8—C11—C12—C17	106.8 (3)
C7—N1—C6—C5	−173.1 (3)	C18—C11—C12—C13	166.3 (3)
C9—N1—C6—C5	6.8 (4)	C8—C11—C12—C13	−73.1 (4)
C7—N1—C6—C1	2.4 (3)	C17—C12—C13—C14	0.0 (4)
C9—N1—C6—C1	−177.7 (2)	C11—C12—C13—C14	179.9 (3)
C9—N1—C7—O2	−1.8 (5)	C12—C13—C14—C15	−0.2 (4)
C6—N1—C7—O2	178.0 (3)	C13—C14—C15—C16	0.1 (5)
C9—N1—C7—C8	174.6 (2)	C14—C15—C16—C17	0.1 (5)
C6—N1—C7—C8	−5.5 (3)	C13—C12—C17—C16	0.2 (4)
C2—C1—C8—O3	54.3 (4)	C11—C12—C17—C16	−179.7 (3)
C6—C1—C8—O3	−122.4 (2)	C13—C12—C17—O4	−179.1 (2)
C2—C1—C8—C7	172.0 (3)	C11—C12—C17—O4	1.1 (3)
C6—C1—C8—C7	−4.8 (3)	C15—C16—C17—C12	−0.3 (5)
C2—C1—C8—C11	−71.8 (4)	C15—C16—C17—O4	178.9 (3)
C6—C1—C8—C11	111.5 (3)	C18—O4—C17—C12	13.8 (3)
O2—C7—C8—O3	−60.1 (4)	C18—O4—C17—C16	−165.4 (3)
N1—C7—C8—O3	123.3 (2)	C17—O4—C18—C11	−22.6 (3)
O2—C7—C8—C1	−177.2 (3)	C17—O4—C18—Cl1	95.7 (2)
N1—C7—C8—C1	6.2 (3)	C12—C11—C18—O4	22.0 (3)
O2—C7—C8—C11	60.0 (4)	C8—C11—C18—O4	−100.5 (3)
N1—C7—C8—C11	−116.6 (2)	C12—C11—C18—Cl1	−95.6 (2)
C7—N1—C9—O1	−176.3 (3)	C8—C11—C18—Cl1	141.9 (2)