1,1′-Di­acetyl-3-hydroxy-2,2′,3,3′-tetra­hydro-3,3′-bi(1H-indole)-2,2′-dione

In the title compound, C₂₀H₁₆N₂O₅, both of the 1-acetyl­isatin (1-acetyl-1H-indole-2,3-dione) moieties are planar and form a dihedral angle of 74.1 (1)°. Weak intermolecular hydrogen bonds and C—H...π interactions stabilize the packing in the crystal.

S1. Comment

Derivatives of 1H-indole-2,3-dione (isatin) are of interest due to their biological activities (Bieck et al., 1993) and wide use as synthetic precursors (Popp, 1975; Shvekhgeimer, 1996). Xue's group has intensively investigated the photoinduced reactions of the isatin derivatives in order to further explore the scope of their photochemistry (Xue et al., 2000; 2001). The title compound, (I), is the sole product of the photoreaction of 1-acetylisatin and dibenzoylmethane. We have undertaken an X-ray crystal structure analysis of (I) to confirm the biindole structure and to establish the steric configuration of the two chiral carbon atoms.

Scheme I

The bond lengths and bond angles observed in (I) are within normal values (Table 1). The values for the two 1-acetylisatin moieties agree with each other and are comparable with those of the previously studied related structure (Zukerman-Schpector et al., 1992). Each of the 1-acetylisatin moieties are almost planar, with maximum deviations of 0.028 (2) Å (C7) and -0.066 (1) Å (C9). The dihedral angles between the heterocyclic and benzene rings are 1.7 (1) and 4.1 (1)°. The two acetyl groups are twisted by 8.3 (1) and 14.7 (1)° from their attached isatin planes, and the two 1-acetylisatin moieties form a dihedral angle of 74.1 (1)°. The ketone atoms O2 and O3 are essentially coplanar with their attached isatin groups, with maximum deviations of 0.032 (1) and 0.127 (1) Å, respectively. Atoms C8 and C9 are chiral centers.

Although intramolecular interactions between the acetyl O1 and O4 atoms and the indole-H atoms [H5A···O4 2.3295, C5···O4 2.863 (2) Å, C5A—H5A···O4 116°; H12A···O1 2.3095, C12···O1 2.855 (2) Å, C12—H12A···O1 117°] can be viewed as closed six-membered rings of O4—C17—N1—C6—C5—H5A and O1—C19—N2—C11—C12—H12A, the planarity of both of the 1-acetylisatin moieties is mostly due to conjugation of N—C and C=O bonds. Atom O4 is also involved in a weak intermolecular O—H···O hydrogen bond, and atom O2 facilitates a bifurcated intermolecular weak C—H···O hydrogen bond (Table 2). These intermolecular hydrogen bonds interconnect the molecules into a three dimensional molecular arrangement (Fig. 2). Intermolecular C—H···π interactions are observed for C18—H18A···π(A)ⁱ [(i) 2 - x,2 - y,-z, H···π 2.785 Å, C···π 3.570 (2) Å, C—H···π 139°] and C18—H18A···π(B)ⁱⁱ [(ii) 1 - x,2 - y,-z, H···π 3.187 Å, C···π 3.846 (2) Å, C—H···π 127°], where A and B denote the center of gravity of the two benzene rings of the isatin moieties. The intermolecular hydrogen bonds and C—H···π interactions stabilize the molecular packing.

S2. Experimental

The title compound was prepared by the photoinduced reaction of a benzene solution (40 ml) of 1-acetylisatin (0.05 M) in an excess of dibenzoylmethane with Pyrex-filtered light from a medium-pressure mercury lamp. The reaction was carried out under a constant nitrogen purge. After irradiation, the solvent was removed in vacuo and the residue was separated by column chromatography with petroleum spirit/ethyl acetate as eluent. The title compound was obtained as the sole product and was recrystallized from an acetone/petroleum ether mixture.

S3. Refinement

After checking their presence in the difference map, all H atoms were geometrically fixed and allowed to ride on the parent C atoms.

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); 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. Packing diagram of the title structure (I) viewed down the b axis. The dashed lines denote the weak intermolecular hydrogen bonds.

1,1'-diacetyl-3-hydroxy-1,1',3,3'-tetrahydro-3,3'-bisindole-2,2'-dione

Crystal data

C20H16N2O5	Dx = 1.383 Mg m^−3
Mr = 364.35	Melting point: 425K K
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 10.2447 (1) Å	Cell parameters from 8056 reflections
b = 10.3416 (1) Å	θ = 2.1–28.3°
c = 16.9848 (2) Å	µ = 0.10 mm^−1
β = 103.482 (1)°	T = 293 K
V = 1749.89 (3) Å^3	Block, colourless
Z = 4	0.40 × 0.36 × 0.32 mm
F(000) = 760

Data collection

Siemens SMART CCD area detector diffractometer	4186 independent reflections
Radiation source: fine-focus sealed tube	2872 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.071
Detector resolution: 8.33 pixels mm^-1	θmax = 28.2°, θmin = 2.1°
ω scans	h = −13→13
Absorption correction: empirical (using intensity measurements) SADABS (Sheldrick, 1996)	k = −13→10
Tmin = 0.961, Tmax = 0.968	l = −22→22
11650 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)] = 0.053	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.138	H-atom parameters constrained
S = 0.92	w = 1/[σ^2(Fo^2) + (0.0647P)^2] where P = (Fo^2 + 2Fc^2)/3
4186 reflections	(Δ/σ)max < 0.001
246 parameters	Δρmax = 0.21 e Å^−3
0 restraints	Δρmin = −0.30 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° in ω. 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. 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	0.31295 (14)	0.52762 (14)	−0.03210 (8)	0.0632 (4)
O2	0.60067 (11)	0.80810 (12)	0.05176 (6)	0.0452 (3)
O3	0.72325 (12)	1.08574 (12)	0.01751 (8)	0.0500 (3)
O4	1.06736 (12)	0.88071 (13)	0.12001 (7)	0.0539 (4)
O5	0.67471 (11)	1.01219 (12)	−0.15358 (7)	0.0441 (3)
H5A	0.7488	1.0421	−0.1537	0.066*
N1	0.87171 (12)	0.91177 (13)	0.02826 (7)	0.0334 (3)
N2	0.43969 (12)	0.70124 (12)	−0.04652 (7)	0.0316 (3)
C1	0.77762 (14)	0.80929 (15)	−0.09308 (9)	0.0344 (3)
C2	0.76833 (18)	0.71839 (18)	−0.15415 (11)	0.0478 (4)
H2A	0.6980	0.7210	−0.2000	0.057*
C3	0.8667 (2)	0.6231 (2)	−0.14517 (12)	0.0579 (5)
H3A	0.8625	0.5613	−0.1854	0.069*
C4	0.97040 (19)	0.61993 (19)	−0.07692 (12)	0.0557 (5)
H4A	1.0351	0.5554	−0.0720	0.067*
C5	0.98113 (17)	0.71046 (18)	−0.01507 (11)	0.0467 (4)
H5B	1.0513	0.7072	0.0308	0.056*
C6	0.88320 (14)	0.80589 (15)	−0.02442 (9)	0.0340 (3)
C7	0.75740 (14)	0.98635 (16)	−0.00787 (9)	0.0334 (3)
C8	0.68700 (14)	0.92212 (15)	−0.08918 (9)	0.0316 (3)
C9	0.54206 (14)	0.88879 (14)	−0.08615 (8)	0.0296 (3)
H9A	0.4987	0.9698	−0.0766	0.036*
C10	0.53475 (14)	0.79807 (15)	−0.01683 (9)	0.0314 (3)
C11	0.38959 (14)	0.71884 (14)	−0.13248 (8)	0.0309 (3)
C12	0.29013 (17)	0.64997 (16)	−0.18539 (10)	0.0433 (4)
H12A	0.2488	0.5789	−0.1680	0.052*
C13	0.25490 (18)	0.69128 (18)	−0.26512 (10)	0.0485 (5)
H13A	0.1874	0.6476	−0.3015	0.058*
C14	0.31670 (18)	0.79519 (17)	−0.29239 (10)	0.0450 (4)
H14A	0.2919	0.8194	−0.3466	0.054*
C15	0.41626 (15)	0.86367 (17)	−0.23860 (9)	0.0379 (4)
H15A	0.4582	0.9341	−0.2563	0.045*
C16	0.45174 (14)	0.82509 (14)	−0.15827 (8)	0.0299 (3)
C17	0.96249 (15)	0.94156 (17)	0.10180 (9)	0.0395 (4)
C18	0.92867 (19)	1.0452 (2)	0.15434 (11)	0.0551 (5)
H18A	0.8390	1.0324	0.1609	0.083*
H18B	0.9346	1.1279	0.1297	0.083*
H18C	0.9905	1.0423	0.2063	0.083*
C19	0.38605 (17)	0.61266 (17)	0.00105 (10)	0.0412 (4)
C20	0.4213 (2)	0.6294 (2)	0.09094 (11)	0.0610 (6)
H20A	0.4045	0.7172	0.1041	0.091*
H20B	0.5146	0.6097	0.1117	0.091*
H20C	0.3676	0.5722	0.1148	0.091*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0673 (9)	0.0564 (9)	0.0606 (9)	−0.0230 (7)	0.0041 (7)	0.0072 (7)
O2	0.0399 (6)	0.0632 (8)	0.0259 (5)	−0.0066 (5)	−0.0059 (5)	0.0002 (5)
O3	0.0392 (7)	0.0468 (7)	0.0579 (8)	0.0062 (5)	−0.0010 (6)	−0.0190 (6)
O4	0.0328 (6)	0.0674 (9)	0.0526 (8)	−0.0023 (6)	−0.0082 (5)	0.0069 (6)
O5	0.0340 (6)	0.0529 (7)	0.0414 (6)	−0.0044 (5)	0.0007 (5)	0.0127 (5)
N1	0.0236 (6)	0.0413 (7)	0.0325 (6)	−0.0009 (5)	0.0004 (5)	0.0001 (6)
N2	0.0312 (6)	0.0311 (7)	0.0289 (6)	0.0012 (5)	−0.0002 (5)	0.0016 (5)
C1	0.0279 (7)	0.0410 (9)	0.0344 (8)	0.0010 (6)	0.0076 (6)	−0.0007 (7)
C2	0.0424 (9)	0.0579 (12)	0.0427 (9)	0.0038 (8)	0.0093 (8)	−0.0128 (8)
C3	0.0585 (12)	0.0559 (12)	0.0630 (12)	0.0088 (9)	0.0218 (10)	−0.0179 (10)
C4	0.0509 (11)	0.0476 (11)	0.0714 (14)	0.0156 (8)	0.0195 (10)	−0.0003 (10)
C5	0.0373 (9)	0.0469 (10)	0.0538 (10)	0.0098 (7)	0.0067 (8)	0.0074 (8)
C6	0.0289 (7)	0.0368 (9)	0.0364 (8)	0.0013 (6)	0.0076 (6)	0.0028 (7)
C7	0.0233 (7)	0.0383 (9)	0.0365 (8)	−0.0014 (6)	0.0026 (6)	−0.0025 (7)
C8	0.0269 (7)	0.0358 (8)	0.0298 (7)	0.0003 (6)	0.0021 (6)	0.0001 (6)
C9	0.0245 (7)	0.0342 (8)	0.0272 (7)	0.0012 (6)	0.0001 (5)	−0.0022 (6)
C10	0.0254 (7)	0.0376 (8)	0.0288 (7)	0.0025 (6)	0.0016 (6)	−0.0028 (6)
C11	0.0305 (7)	0.0303 (8)	0.0278 (7)	0.0053 (6)	−0.0016 (6)	−0.0026 (6)
C12	0.0472 (9)	0.0349 (9)	0.0399 (9)	−0.0046 (7)	−0.0058 (7)	−0.0024 (7)
C13	0.0518 (10)	0.0456 (10)	0.0369 (9)	−0.0033 (8)	−0.0128 (8)	−0.0083 (8)
C14	0.0479 (10)	0.0519 (11)	0.0275 (8)	0.0068 (8)	−0.0068 (7)	−0.0019 (7)
C15	0.0356 (8)	0.0439 (9)	0.0306 (8)	0.0021 (7)	0.0003 (6)	0.0029 (7)
C16	0.0248 (6)	0.0341 (8)	0.0276 (7)	0.0048 (6)	−0.0005 (5)	−0.0028 (6)
C17	0.0289 (8)	0.0520 (10)	0.0346 (8)	−0.0116 (7)	0.0008 (6)	0.0079 (7)
C18	0.0536 (11)	0.0696 (13)	0.0369 (9)	−0.0121 (10)	0.0001 (8)	−0.0082 (9)
C19	0.0369 (8)	0.0412 (9)	0.0436 (9)	0.0020 (7)	0.0055 (7)	0.0077 (7)
C20	0.0693 (13)	0.0724 (14)	0.0420 (10)	−0.0116 (11)	0.0148 (9)	0.0107 (10)

Geometric parameters (Å, º)

O1—C19	1.206 (2)	C7—C8	1.551 (2)
O2—C10	1.2072 (16)	C8—C9	1.537 (2)
O3—C7	1.1978 (19)	C9—C16	1.5040 (19)
O4—C17	1.221 (2)	C9—C10	1.521 (2)
O5—C8	1.4197 (18)	C9—H9A	0.9800
O5—H5A	0.8200	C11—C12	1.388 (2)
N1—C17	1.4065 (19)	C11—C16	1.391 (2)
N1—C7	1.4169 (19)	C12—C13	1.385 (2)
N1—C6	1.436 (2)	C12—H12A	0.9300
N2—C10	1.4059 (19)	C13—C14	1.381 (3)
N2—C19	1.414 (2)	C13—H13A	0.9300
N2—C11	1.4419 (18)	C14—C15	1.394 (2)
C1—C2	1.387 (2)	C14—H14A	0.9300
C1—C6	1.394 (2)	C15—C16	1.386 (2)
C1—C8	1.502 (2)	C15—H15A	0.9300
C2—C3	1.393 (3)	C17—C18	1.487 (3)
C2—H2A	0.9300	C18—H18A	0.9600
C3—C4	1.378 (3)	C18—H18B	0.9600
C3—H3A	0.9300	C18—H18C	0.9600
C4—C5	1.392 (3)	C19—C20	1.495 (2)
C4—H4A	0.9300	C20—H20A	0.9600
C5—C6	1.390 (2)	C20—H20B	0.9600
C5—H5B	0.9300	C20—H20C	0.9600
C8—O5—H5A	109.5	O2—C10—N2	126.31 (14)
C17—N1—C7	125.03 (14)	O2—C10—C9	125.22 (13)
C17—N1—C6	125.94 (13)	N2—C10—C9	108.47 (12)
C7—N1—C6	108.95 (12)	C12—C11—C16	121.49 (14)
C10—N2—C19	125.83 (13)	C12—C11—N2	128.70 (15)
C10—N2—C11	109.06 (12)	C16—C11—N2	109.73 (12)
C19—N2—C11	124.48 (13)	C13—C12—C11	117.34 (16)
C2—C1—C6	120.89 (14)	C13—C12—H12A	121.3
C2—C1—C8	128.63 (14)	C11—C12—H12A	121.3
C6—C1—C8	110.47 (13)	C14—C13—C12	122.18 (15)
C1—C2—C3	118.44 (17)	C14—C13—H13A	118.9
C1—C2—H2A	120.8	C12—C13—H13A	118.9
C3—C2—H2A	120.8	C13—C14—C15	119.89 (15)
C4—C3—C2	120.35 (17)	C13—C14—H14A	120.1
C4—C3—H3A	119.8	C15—C14—H14A	120.1
C2—C3—H3A	119.8	C16—C15—C14	118.87 (16)
C3—C4—C5	121.91 (17)	C16—C15—H15A	120.6
C3—C4—H4A	119.0	C14—C15—H15A	120.6
C5—C4—H4A	119.0	C15—C16—C11	120.20 (13)
C6—C5—C4	117.61 (16)	C15—C16—C9	130.23 (14)
C6—C5—H5B	121.2	C11—C16—C9	109.24 (12)
C4—C5—H5B	121.2	O4—C17—N1	118.21 (16)
C5—C6—C1	120.81 (15)	O4—C17—C18	122.28 (15)
C5—C6—N1	129.20 (15)	N1—C17—C18	119.51 (15)
C1—C6—N1	109.98 (13)	C17—C18—H18A	109.5
O3—C7—N1	126.33 (14)	C17—C18—H18B	109.5
O3—C7—C8	125.01 (14)	H18A—C18—H18B	109.5
N1—C7—C8	108.57 (13)	C17—C18—H18C	109.5
O5—C8—C1	114.85 (12)	H18A—C18—H18C	109.5
O5—C8—C9	105.08 (11)	H18B—C18—H18C	109.5
C1—C8—C9	116.05 (13)	O1—C19—N2	119.16 (15)
O5—C8—C7	110.15 (12)	O1—C19—C20	122.50 (17)
C1—C8—C7	102.01 (12)	N2—C19—C20	118.34 (15)
C9—C8—C7	108.59 (11)	C19—C20—H20A	109.5
C16—C9—C10	103.19 (12)	C19—C20—H20B	109.5
C16—C9—C8	119.13 (12)	H20A—C20—H20B	109.5
C10—C9—C8	112.74 (11)	C19—C20—H20C	109.5
C16—C9—H9A	107.0	H20A—C20—H20C	109.5
C10—C9—H9A	107.0	H20B—C20—H20C	109.5
C8—C9—H9A	107.0
C6—C1—C2—C3	0.3 (2)	C7—C8—C9—C10	−58.88 (16)
C8—C1—C2—C3	178.55 (16)	C19—N2—C10—O2	12.5 (2)
C1—C2—C3—C4	0.1 (3)	C11—N2—C10—O2	−176.31 (14)
C2—C3—C4—C5	−0.1 (3)	C19—N2—C10—C9	−167.92 (13)
C3—C4—C5—C6	−0.3 (3)	C11—N2—C10—C9	3.25 (16)
C4—C5—C6—C1	0.6 (2)	C16—C9—C10—O2	174.33 (14)
C4—C5—C6—N1	−178.31 (15)	C8—C9—C10—O2	44.5 (2)
C2—C1—C6—C5	−0.6 (2)	C16—C9—C10—N2	−5.24 (15)
C8—C1—C6—C5	−179.21 (14)	C8—C9—C10—N2	−135.07 (13)
C2—C1—C6—N1	178.49 (14)	C10—N2—C11—C12	−176.41 (16)
C8—C1—C6—N1	−0.08 (17)	C19—N2—C11—C12	−5.1 (2)
C17—N1—C6—C5	1.2 (2)	C10—N2—C11—C16	0.31 (16)
C7—N1—C6—C5	178.06 (16)	C19—N2—C11—C16	171.63 (13)
C17—N1—C6—C1	−177.84 (13)	C16—C11—C12—C13	−0.1 (2)
C7—N1—C6—C1	−0.97 (17)	N2—C11—C12—C13	176.32 (15)
C17—N1—C7—O3	1.7 (3)	C11—C12—C13—C14	1.1 (3)
C6—N1—C7—O3	−175.16 (16)	C12—C13—C14—C15	−1.3 (3)
C17—N1—C7—C8	178.49 (13)	C13—C14—C15—C16	0.3 (2)
C6—N1—C7—C8	1.59 (16)	C14—C15—C16—C11	0.7 (2)
C2—C1—C8—O5	−58.3 (2)	C14—C15—C16—C9	−171.93 (15)
C6—C1—C8—O5	120.10 (14)	C12—C11—C16—C15	−0.9 (2)
C2—C1—C8—C9	64.7 (2)	N2—C11—C16—C15	−177.85 (13)
C6—C1—C8—C9	−116.85 (14)	C12—C11—C16—C9	173.20 (14)
C2—C1—C8—C7	−177.45 (16)	N2—C11—C16—C9	−3.79 (16)
C6—C1—C8—C7	0.98 (16)	C10—C9—C16—C15	178.73 (15)
O3—C7—C8—O5	52.9 (2)	C8—C9—C16—C15	−55.4 (2)
N1—C7—C8—O5	−123.94 (13)	C10—C9—C16—C11	5.46 (15)
O3—C7—C8—C1	175.25 (16)	C8—C9—C16—C11	131.28 (14)
N1—C7—C8—C1	−1.55 (15)	C7—N1—C17—O4	−169.04 (14)
O3—C7—C8—C9	−61.7 (2)	C6—N1—C17—O4	7.3 (2)
N1—C7—C8—C9	121.49 (13)	C7—N1—C17—C18	10.7 (2)
O5—C8—C9—C16	62.16 (16)	C6—N1—C17—C18	−172.87 (14)
C1—C8—C9—C16	−65.88 (17)	C10—N2—C19—O1	−174.21 (15)
C7—C8—C9—C16	179.99 (12)	C11—N2—C19—O1	15.9 (2)
O5—C8—C9—C10	−176.72 (12)	C10—N2—C19—C20	6.5 (2)
C1—C8—C9—C10	55.25 (16)	C11—N2—C19—C20	−163.35 (16)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O5—H5A···O4^i	0.82	2.00	2.799 (2)	164
C9—H9A···O2^ii	0.98	2.59	3.564 (2)	176
C13—H13A···O2^iii	0.93	2.49	3.143 (2)	128

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