organic compounds
8-Hydroxy-8-phenyl-2,3,7,8-tetrahydro-6H-1,4-dioxino[2,3-f]isoindol-6-one
aChemistry Department, Moscow State University, 119991 Moscow, Russian Federation
*Correspondence e-mail: aslanov@struct.chem.msu.ru
In the title compound, C16H13NO4, the indole system is essentially planar, whereas the dioxane ring adopts a twist conformation. The molecules are linked into chains by —O— H⋯O=C— hydrogen bonds and these chains are linked into rods by means of N—H⋯O hydrogen bonds. Exept for weak C—H⋯O interactions between the rods, no other intermolecular contacts of interest are present.
Related literature
For details of the appropriate nitrile hydrolysis, see: Moorthy & Singhal (2005).
Experimental
Crystal data
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Data collection
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Refinement
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Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell CAD-4 Software; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2000); software used to prepare material for publication: WinGX (Farrugia, 1999).
Supporting information
10.1107/S1600536808003012/rk2073sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536808003012/rk2073Isup2.hkl
A mixture of (1) (1 g, 0.0038 mol), concentrated sulfuric acid (1 ml) and trifluoroacetic acid (4 ml) was boiled under reflux. with stirring, for 5 h. The solution was then poured into ice-water (75 ml). The resulting white precipitate was filtered off, washed with water and recrystallized from acetone.
The positions of the H atoms were determined from Fourier difference maps; they were then placed in calculated positions and allowed to ride on their parent atoms [C—H = 0.93–0.97 Å, O—H = 0.82 Å and N—H = 0.86 Å]. Uiso(H) = xUeq(parent atom), where x = 1.5 for attached O and 1.2 for C and N.
Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell
CAD-4 Software (Enraf–Nonius, 1989); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2000); software used to prepare material for publication: WinGX (Farrugia, 1999).C16H13NO4 | F(000) = 592 |
Mr = 283.27 | Dx = 1.417 Mg m−3 |
Monoclinic, P21/c | Melting point = 485–486 K |
Hall symbol: -P 2ybc | Cu Kα radiation, λ = 1.54184 Å |
a = 8.6001 (17) Å | Cell parameters from 25 reflections |
b = 27.005 (5) Å | θ = 26–42° |
c = 5.7221 (5) Å | µ = 0.85 mm−1 |
β = 92.602 (10)° | T = 291 K |
V = 1327.6 (4) Å3 | Prism, colorless |
Z = 4 | 0.08 × 0.06 × 0.04 mm |
Enraf–Nonius CAD-4 diffractometer | Rint = 0.025 |
Radiation source: fine-focus sealed tube | θmax = 73.9°, θmin = 3.3° |
Graphite monochromator | h = −10→10 |
Non–profiled ω scans | k = 0→32 |
2892 measured reflections | l = 0→7 |
2653 independent reflections | 2 standard reflections every 120 min |
1784 reflections with I > 2σ(I) | intensity decay: none |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.054 | H-atom parameters constrained |
wR(F2) = 0.147 | w = 1/[σ2(Fo2) + (0.061P)2 + 0.4104P] where P = (Fo2 + 2Fc2)/3 |
S = 1.05 | (Δ/σ)max < 0.001 |
2653 reflections | Δρmax = 0.23 e Å−3 |
192 parameters | Δρmin = −0.24 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0051 (6) |
C16H13NO4 | V = 1327.6 (4) Å3 |
Mr = 283.27 | Z = 4 |
Monoclinic, P21/c | Cu Kα radiation |
a = 8.6001 (17) Å | µ = 0.85 mm−1 |
b = 27.005 (5) Å | T = 291 K |
c = 5.7221 (5) Å | 0.08 × 0.06 × 0.04 mm |
β = 92.602 (10)° |
Enraf–Nonius CAD-4 diffractometer | Rint = 0.025 |
2892 measured reflections | 2 standard reflections every 120 min |
2653 independent reflections | intensity decay: none |
1784 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.054 | 0 restraints |
wR(F2) = 0.147 | H-atom parameters constrained |
S = 1.05 | Δρmax = 0.23 e Å−3 |
2653 reflections | Δρmin = −0.24 e Å−3 |
192 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.3338 (2) | 0.50617 (7) | 1.1457 (3) | 0.0654 (5) | |
O2 | 0.3093 (2) | 0.70474 (6) | 0.9980 (3) | 0.0549 (5) | |
H2 | 0.2370 | 0.6906 | 1.0585 | 0.082* | |
O3 | 0.1250 (2) | 0.65694 (7) | 0.3005 (3) | 0.0568 (5) | |
O4 | 0.1351 (3) | 0.48070 (7) | 0.7532 (4) | 0.0737 (6) | |
N7 | 0.2877 (2) | 0.68919 (8) | 0.5922 (3) | 0.0498 (5) | |
H7 | 0.2972 | 0.7182 | 0.5321 | 0.060* | |
C2 | 0.2445 (4) | 0.46150 (12) | 1.1374 (6) | 0.0810 (10) | |
H2A | 0.1463 | 0.4671 | 1.2100 | 0.097* | |
H2B | 0.3003 | 0.4360 | 1.2259 | 0.097* | |
C3 | 0.2138 (5) | 0.44427 (12) | 0.8942 (7) | 0.0878 (11) | |
H3A | 0.3117 | 0.4361 | 0.8260 | 0.105* | |
H3B | 0.1510 | 0.4144 | 0.8956 | 0.105* | |
C5 | 0.1581 (3) | 0.56216 (9) | 0.6119 (4) | 0.0536 (6) | |
H5 | 0.0937 | 0.5541 | 0.4826 | 0.064* | |
C6 | 0.2011 (3) | 0.65333 (9) | 0.4881 (4) | 0.0467 (6) | |
C8 | 0.3642 (3) | 0.67510 (9) | 0.8154 (4) | 0.0455 (6) | |
C9 | 0.3521 (3) | 0.58711 (9) | 1.0021 (4) | 0.0498 (6) | |
H9 | 0.4163 | 0.5955 | 1.1313 | 0.060* | |
C10 | 0.2183 (3) | 0.60935 (9) | 0.6404 (4) | 0.0467 (6) | |
C11 | 0.3138 (3) | 0.62151 (9) | 0.8321 (4) | 0.0446 (5) | |
C12 | 0.1965 (3) | 0.52745 (10) | 0.7811 (5) | 0.0542 (6) | |
C13 | 0.2925 (3) | 0.53960 (9) | 0.9759 (4) | 0.0510 (6) | |
C14 | 0.5399 (3) | 0.68000 (9) | 0.8127 (4) | 0.0458 (6) | |
C15 | 0.6197 (3) | 0.66247 (10) | 0.6231 (4) | 0.0555 (6) | |
H15 | 0.5636 | 0.6499 | 0.4937 | 0.067* | |
C16 | 0.7790 (3) | 0.66338 (11) | 0.6228 (5) | 0.0645 (7) | |
H16 | 0.8301 | 0.6514 | 0.4946 | 0.077* | |
C17 | 0.8631 (4) | 0.68214 (12) | 0.8136 (5) | 0.0683 (8) | |
H17 | 0.9712 | 0.6829 | 0.8143 | 0.082* | |
C18 | 0.7876 (3) | 0.69959 (11) | 1.0011 (5) | 0.0678 (8) | |
H18 | 0.8449 | 0.7121 | 1.1297 | 0.081* | |
C19 | 0.6268 (3) | 0.69889 (10) | 1.0022 (4) | 0.0561 (7) | |
H19 | 0.5767 | 0.7112 | 1.1307 | 0.067* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0765 (13) | 0.0525 (11) | 0.0666 (12) | −0.0020 (9) | −0.0039 (10) | 0.0182 (9) |
O2 | 0.0654 (12) | 0.0516 (10) | 0.0488 (10) | −0.0046 (8) | 0.0138 (8) | −0.0083 (8) |
O3 | 0.0575 (11) | 0.0718 (12) | 0.0406 (9) | −0.0020 (9) | −0.0038 (8) | 0.0054 (8) |
O4 | 0.0847 (15) | 0.0480 (11) | 0.0870 (15) | −0.0136 (10) | −0.0131 (12) | 0.0040 (10) |
N7 | 0.0603 (13) | 0.0463 (11) | 0.0421 (10) | −0.0032 (9) | −0.0049 (9) | 0.0071 (9) |
C2 | 0.097 (3) | 0.0529 (18) | 0.093 (2) | −0.0106 (16) | 0.0003 (19) | 0.0230 (17) |
C3 | 0.107 (3) | 0.0513 (18) | 0.104 (3) | −0.0006 (18) | −0.011 (2) | 0.0065 (18) |
C5 | 0.0578 (15) | 0.0547 (15) | 0.0480 (13) | −0.0073 (12) | −0.0020 (11) | −0.0051 (12) |
C6 | 0.0464 (13) | 0.0567 (15) | 0.0371 (11) | 0.0029 (11) | 0.0021 (10) | 0.0008 (10) |
C8 | 0.0575 (14) | 0.0446 (13) | 0.0343 (11) | −0.0017 (11) | −0.0001 (10) | −0.0005 (9) |
C9 | 0.0564 (14) | 0.0511 (14) | 0.0417 (12) | −0.0030 (11) | −0.0005 (10) | 0.0034 (11) |
C10 | 0.0512 (13) | 0.0500 (14) | 0.0388 (11) | −0.0035 (11) | 0.0017 (10) | −0.0004 (10) |
C11 | 0.0505 (13) | 0.0459 (13) | 0.0373 (12) | −0.0014 (10) | 0.0022 (10) | 0.0010 (10) |
C12 | 0.0608 (16) | 0.0454 (14) | 0.0565 (15) | −0.0078 (12) | 0.0027 (12) | −0.0041 (12) |
C13 | 0.0556 (14) | 0.0469 (14) | 0.0506 (13) | −0.0001 (11) | 0.0042 (11) | 0.0074 (11) |
C14 | 0.0567 (14) | 0.0436 (13) | 0.0370 (11) | −0.0025 (11) | 0.0011 (10) | 0.0021 (10) |
C15 | 0.0610 (16) | 0.0649 (17) | 0.0407 (12) | −0.0025 (13) | 0.0027 (11) | −0.0039 (12) |
C16 | 0.0606 (16) | 0.074 (2) | 0.0594 (17) | 0.0007 (14) | 0.0109 (13) | −0.0030 (15) |
C17 | 0.0570 (16) | 0.076 (2) | 0.0716 (19) | −0.0002 (14) | 0.0011 (14) | 0.0022 (16) |
C18 | 0.0635 (18) | 0.076 (2) | 0.0624 (17) | −0.0039 (15) | −0.0152 (14) | −0.0050 (15) |
C19 | 0.0672 (17) | 0.0599 (16) | 0.0404 (12) | 0.0001 (13) | −0.0040 (11) | −0.0032 (11) |
O1—C13 | 1.362 (3) | C8—C11 | 1.515 (3) |
O1—C2 | 1.430 (4) | C8—C14 | 1.518 (3) |
O2—C8 | 1.415 (3) | C9—C11 | 1.374 (3) |
O2—H2 | 0.8200 | C9—C13 | 1.387 (3) |
O3—C6 | 1.236 (3) | C9—H9 | 0.9300 |
O4—C12 | 1.375 (3) | C10—C11 | 1.380 (3) |
O4—C3 | 1.424 (4) | C12—C13 | 1.396 (3) |
N7—C6 | 1.344 (3) | C14—C19 | 1.386 (3) |
N7—C8 | 1.460 (3) | C14—C15 | 1.393 (3) |
N7—H7 | 0.8600 | C15—C16 | 1.370 (4) |
C2—C3 | 1.480 (5) | C15—H15 | 0.9300 |
C2—H2A | 0.9700 | C16—C17 | 1.378 (4) |
C2—H2B | 0.9700 | C16—H16 | 0.9300 |
C3—H3A | 0.9700 | C17—C18 | 1.363 (4) |
C3—H3B | 0.9700 | C17—H17 | 0.9300 |
C5—C12 | 1.376 (4) | C18—C19 | 1.384 (4) |
C5—C10 | 1.382 (3) | C18—H18 | 0.9300 |
C5—H5 | 0.9300 | C19—H19 | 0.9300 |
C6—C10 | 1.477 (3) | ||
C13—O1—C2 | 114.4 (2) | C13—C9—H9 | 120.9 |
C8—O2—H2 | 109.5 | C11—C10—C5 | 121.3 (2) |
C12—O4—C3 | 113.5 (2) | C11—C10—C6 | 108.5 (2) |
C6—N7—C8 | 114.7 (2) | C5—C10—C6 | 130.2 (2) |
C6—N7—H7 | 122.6 | C9—C11—C10 | 121.1 (2) |
C8—N7—H7 | 122.6 | C9—C11—C8 | 129.1 (2) |
O1—C2—C3 | 111.7 (3) | C10—C11—C8 | 109.8 (2) |
O1—C2—H2A | 109.3 | O4—C12—C5 | 117.7 (2) |
C3—C2—H2A | 109.3 | O4—C12—C13 | 121.2 (2) |
O1—C2—H2B | 109.3 | C5—C12—C13 | 121.0 (2) |
C3—C2—H2B | 109.3 | O1—C13—C9 | 116.9 (2) |
H2A—C2—H2B | 107.9 | O1—C13—C12 | 122.7 (2) |
O4—C3—C2 | 112.1 (3) | C9—C13—C12 | 120.4 (2) |
O4—C3—H3A | 109.2 | C19—C14—C15 | 117.8 (2) |
C2—C3—H3A | 109.2 | C19—C14—C8 | 121.7 (2) |
O4—C3—H3B | 109.2 | C15—C14—C8 | 120.3 (2) |
C2—C3—H3B | 109.2 | C16—C15—C14 | 121.5 (3) |
H3A—C3—H3B | 107.9 | C16—C15—H15 | 119.2 |
C12—C5—C10 | 117.9 (2) | C14—C15—H15 | 119.2 |
C12—C5—H5 | 121.0 | C15—C16—C17 | 119.6 (3) |
C10—C5—H5 | 121.0 | C15—C16—H16 | 120.2 |
O3—C6—N7 | 126.1 (2) | C17—C16—H16 | 120.2 |
O3—C6—C10 | 127.7 (2) | C18—C17—C16 | 119.9 (3) |
N7—C6—C10 | 106.23 (19) | C18—C17—H17 | 120.0 |
O2—C8—N7 | 110.3 (2) | C16—C17—H17 | 120.0 |
O2—C8—C11 | 112.82 (19) | C17—C18—C19 | 120.7 (3) |
N7—C8—C11 | 100.69 (18) | C17—C18—H18 | 119.7 |
O2—C8—C14 | 108.89 (19) | C19—C18—H18 | 119.7 |
N7—C8—C14 | 112.20 (19) | C18—C19—C14 | 120.4 (3) |
C11—C8—C14 | 111.8 (2) | C18—C19—H19 | 119.8 |
C11—C9—C13 | 118.2 (2) | C14—C19—H19 | 119.8 |
C11—C9—H9 | 120.9 | ||
C13—O1—C2—C3 | 40.4 (4) | C3—O4—C12—C5 | 162.9 (3) |
C12—O4—C3—C2 | 45.2 (4) | C3—O4—C12—C13 | −18.1 (4) |
O1—C2—C3—O4 | −57.6 (4) | C10—C5—C12—O4 | 179.4 (2) |
C8—N7—C6—O3 | 179.2 (2) | C10—C5—C12—C13 | 0.3 (4) |
C8—N7—C6—C10 | −1.7 (3) | C2—O1—C13—C9 | 167.3 (3) |
C6—N7—C8—O2 | −117.5 (2) | C2—O1—C13—C12 | −13.5 (4) |
C6—N7—C8—C11 | 1.8 (3) | C11—C9—C13—O1 | 179.3 (2) |
C6—N7—C8—C14 | 120.9 (2) | C11—C9—C13—C12 | 0.1 (4) |
C12—C5—C10—C11 | −0.1 (4) | O4—C12—C13—O1 | 1.5 (4) |
C12—C5—C10—C6 | 178.4 (3) | C5—C12—C13—O1 | −179.5 (2) |
O3—C6—C10—C11 | 179.9 (2) | O4—C12—C13—C9 | −179.3 (2) |
N7—C6—C10—C11 | 0.8 (3) | C5—C12—C13—C9 | −0.4 (4) |
O3—C6—C10—C5 | 1.3 (4) | O2—C8—C14—C19 | 16.7 (3) |
N7—C6—C10—C5 | −177.8 (3) | N7—C8—C14—C19 | 139.1 (2) |
C13—C9—C11—C10 | 0.2 (4) | C11—C8—C14—C19 | −108.6 (3) |
C13—C9—C11—C8 | −178.9 (2) | O2—C8—C14—C15 | −167.4 (2) |
C5—C10—C11—C9 | −0.2 (4) | N7—C8—C14—C15 | −45.1 (3) |
C6—C10—C11—C9 | −178.9 (2) | C11—C8—C14—C15 | 67.2 (3) |
C5—C10—C11—C8 | 179.0 (2) | C19—C14—C15—C16 | 0.5 (4) |
C6—C10—C11—C8 | 0.3 (3) | C8—C14—C15—C16 | −175.6 (2) |
O2—C8—C11—C9 | −64.5 (3) | C14—C15—C16—C17 | −0.2 (4) |
N7—C8—C11—C9 | 178.0 (2) | C15—C16—C17—C18 | 0.1 (5) |
C14—C8—C11—C9 | 58.6 (3) | C16—C17—C18—C19 | −0.3 (5) |
O2—C8—C11—C10 | 116.3 (2) | C17—C18—C19—C14 | 0.5 (5) |
N7—C8—C11—C10 | −1.2 (3) | C15—C14—C19—C18 | −0.6 (4) |
C14—C8—C11—C10 | −120.5 (2) | C8—C14—C19—C18 | 175.3 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2···O3i | 0.82 | 1.95 | 2.725 (3) | 158 |
N7—H7···O2ii | 0.86 | 2.09 | 2.922 (3) | 161 |
C5—H5···O4iii | 0.93 | 2.52 | 3.404 (3) | 160 |
C19—H19···O2 | 0.93 | 2.40 | 2.734 (4) | 101 |
Symmetry codes: (i) x, y, z+1; (ii) x, −y+3/2, z−1/2; (iii) −x, −y+1, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C16H13NO4 |
Mr | 283.27 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 291 |
a, b, c (Å) | 8.6001 (17), 27.005 (5), 5.7221 (5) |
β (°) | 92.602 (10) |
V (Å3) | 1327.6 (4) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 0.85 |
Crystal size (mm) | 0.08 × 0.06 × 0.04 |
Data collection | |
Diffractometer | Enraf–Nonius CAD-4 diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2892, 2653, 1784 |
Rint | 0.025 |
(sin θ/λ)max (Å−1) | 0.623 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.054, 0.147, 1.05 |
No. of reflections | 2653 |
No. of parameters | 192 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.23, −0.24 |
Computer programs: CAD-4 Software (Enraf–Nonius, 1989), XCAD4 (Harms & Wocadlo, 1995), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 2000), WinGX (Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2···O3i | 0.82 | 1.95 | 2.725 (3) | 158.0 |
N7—H7···O2ii | 0.86 | 2.09 | 2.922 (3) | 161.4 |
C5—H5···O4iii | 0.93 | 2.52 | 3.404 (3) | 159.5 |
C19—H19···O2 | 0.93 | 2.40 | 2.734 (4) | 101.3 |
Symmetry codes: (i) x, y, z+1; (ii) x, −y+3/2, z−1/2; (iii) −x, −y+1, −z+1. |
References
Brandenburg, K. (2000). DIAMOND. Release 2.1d. Crystal Impact GbR, Bonn, Germany. Google Scholar
Enraf–Nonius (1989). CAD-4 Software. Version 5.0. Enraf–Nonius, Delft, The Netherlands. Google Scholar
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838. CrossRef CAS IUCr Journals Google Scholar
Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany. Google Scholar
Moorthy, J. N. & Singhal, N. (2005). J. Org. Chem. 70, 1926–1929. Web of Science CrossRef PubMed CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
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To investigate mechanisms of intra- and intermolecular reactions of ortho-substituted benzenes we intended to synthesize novel ortho-acyl-substituted benzamides by hydrolysis (Moorthy & Singhal, 2005) of appropriate nitriles. In the case of hydrolysis of 7-benzoyl-2,3-dihydro-1,4-benzodioxine-6-carbonitrile (1) the compound 7-benzoyl-2,3-dihydro-1,4-benzodioxine-6-carboxamide (2) was expected to be produced (Fig. 1). Both the elemental analysis and mass spectroscopic data (M+ 283) of the compound we obtained, were in good agreement with structure (2), but 1H NMR data were not. Although 13 protons were identified in the 1H NMR spectrum, an expected signal for the NH2 group was absent. In addition, two single signals were detected in the 1H NMR spectrum, each corresponding to one proton of large difference in chemical shift (6.70 and 9.02). To determine the structure of the compound, we carried out an X-ray crystallographic analysis, which revealed that hydrolysis of (1), under the conditions specified by Moorthy & Singhal, did not produce the expected compound (2); instead the product was an isomer of compound (2), viz. 8-hydroxy-8-phenyl-2,3,7,8-tetrahydro-6H-[1,4]dioxino [2,3-f]isoindol-6-one, (3) (Fig. 1).
The dihedral angle between the planes defined by the atoms C5/C9/C10/C11/C12/C13 (plane 1) and C8/N7/C6/C10/C11 (plane 2) (Fig. 2) is 1.64 (9)°. The 6-membered dioxane ring adopts a twist conformation, with atoms C3 and C2 displaced out of plane 1 by 0.375 (4) and -0.273 (3) Å, respectively, compared with displacements of -0.012 (3) and 0.010 (3) Å for O4 and O1, respectively (Fig. 2). The torsion angle O2—C8—C14—C19 has rather a small value [16.7 (3)°]. This results from the intramolecular hydrogen bond C19—H19···O2. The packing motif, as shown in Fig.3, can be described as follows: molecules are linked by hydrogen bonds in head-to-tail fashion through oxy- and keto-groups to form infinite chains. The two adjacent chains are linked by N7—H7···O2ii hydrogen bonds, forming infinite rods running along the c axis. Neighbouring rods interact via centrosymmetric C5—H5···O4iii hydrogen bonds. Symmetry codes are listed in Table 1.