Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536805027352/bh6021sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536805027352/bh6021Isup2.hkl |
CCDC reference: 287443
The title compound was prepared by the reaction of 1,3-cyclohexanedione (0.22 g, 2 mmol), 4-methylbenzaldehyde (0.24 g, 2 mmol) and methyl-3-aminobut-2-enoate (0.23 g, 2 mmol) in the presence of triethylbenzylammonium chloride (0.2 g) in water (10 ml) at 298 K for 25 h (yield 83%). Single crystals of (I) suitable for X-ray diffraction were obtained by slow evaporation of an ethanol solution.
Atom H1, bonded to N1, was found in a Fourier map and refined with free coordinates and an isotropic displacement parameter. Other H atoms were positioned geometrically and treated as riding on their parent atoms with C—H = 0.95 Å and Uiso(H) = 1.2Ueq(C) for aromatic CH, C—H = 0.98 Å and Uiso(H) = 1.5Ueq(C) for methyl CH3, C—H = 0.99 Å and Uiso(H) = 1.2Ueq(C) for methylene CH2, and C—H = 1.00 Å and Uiso(H) = 1.2Ueq(C) for methine CH.
Data collection: CrystalClear (Rigaku, 1999); cell refinement: CrystalClear; data reduction: CrystalStructure (Rigaku/MSC, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1999); software used to prepare material for publication: SHELXTL.
C19H21NO3 | F(000) = 664 |
Mr = 311.37 | Dx = 1.300 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71070 Å |
Hall symbol: -P 2ybc | Cell parameters from 7332 reflections |
a = 7.8338 (15) Å | θ = 3.0–27.5° |
b = 15.095 (3) Å | µ = 0.09 mm−1 |
c = 13.962 (3) Å | T = 193 K |
β = 105.436 (5)° | Block, colourless |
V = 1591.5 (5) Å3 | 0.73 × 0.62 × 0.25 mm |
Z = 4 |
Rigaku Mercury diffractometer | 3637 independent reflections |
Radiation source: fine-focus sealed tube | 3378 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.021 |
Detector resolution: 7.31 pixels mm-1 | θmax = 27.5°, θmin = 3.0° |
ω scans | h = −8→10 |
Absorption correction: multi-scan (Jacobson, 1998) | k = −16→19 |
Tmin = 0.939, Tmax = 0.978 | l = −18→18 |
17357 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.046 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.124 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0636P)2 + 0.5891P] where P = (Fo2 + 2Fc2)/3 |
3637 reflections | (Δ/σ)max < 0.001 |
216 parameters | Δρmax = 0.25 e Å−3 |
0 restraints | Δρmin = −0.24 e Å−3 |
C19H21NO3 | V = 1591.5 (5) Å3 |
Mr = 311.37 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 7.8338 (15) Å | µ = 0.09 mm−1 |
b = 15.095 (3) Å | T = 193 K |
c = 13.962 (3) Å | 0.73 × 0.62 × 0.25 mm |
β = 105.436 (5)° |
Rigaku Mercury diffractometer | 3637 independent reflections |
Absorption correction: multi-scan (Jacobson, 1998) | 3378 reflections with I > 2σ(I) |
Tmin = 0.939, Tmax = 0.978 | Rint = 0.021 |
17357 measured reflections |
R[F2 > 2σ(F2)] = 0.046 | 0 restraints |
wR(F2) = 0.124 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | Δρmax = 0.25 e Å−3 |
3637 reflections | Δρmin = −0.24 e Å−3 |
216 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 | 0.39522 (14) | 0.21452 (7) | 0.09977 (7) | 0.0346 (2) | |
O2 | 0.96668 (14) | 0.41203 (9) | 0.41562 (8) | 0.0441 (3) | |
O3 | 0.86076 (12) | 0.42985 (7) | 0.25115 (7) | 0.0309 (2) | |
N1 | 0.43779 (14) | 0.33862 (7) | 0.41278 (8) | 0.0251 (2) | |
C1 | 0.35039 (16) | 0.28794 (8) | 0.33350 (9) | 0.0220 (2) | |
C2 | 0.40187 (15) | 0.28928 (8) | 0.24778 (8) | 0.0210 (2) | |
C3 | 0.53959 (15) | 0.35590 (8) | 0.23502 (8) | 0.0221 (3) | |
H3 | 0.6117 | 0.3276 | 0.1941 | 0.027* | |
C4 | 0.66256 (16) | 0.37812 (8) | 0.33611 (9) | 0.0230 (3) | |
C5 | 0.60375 (16) | 0.37424 (8) | 0.41910 (9) | 0.0238 (3) | |
C6 | 0.33129 (16) | 0.22424 (8) | 0.17099 (9) | 0.0244 (3) | |
C7 | 0.18101 (18) | 0.16599 (9) | 0.18145 (11) | 0.0319 (3) | |
H7A | 0.2293 | 0.1081 | 0.2093 | 0.038* | |
H7B | 0.1000 | 0.1552 | 0.1148 | 0.038* | |
C8 | 0.07639 (18) | 0.20670 (9) | 0.24836 (10) | 0.0309 (3) | |
H8A | 0.0133 | 0.2603 | 0.2164 | 0.037* | |
H8B | −0.0128 | 0.1638 | 0.2585 | 0.037* | |
C9 | 0.20191 (18) | 0.23118 (9) | 0.34801 (10) | 0.0294 (3) | |
H9A | 0.1361 | 0.2636 | 0.3885 | 0.035* | |
H9B | 0.2511 | 0.1766 | 0.3843 | 0.035* | |
C10 | 0.44748 (16) | 0.43728 (8) | 0.17868 (9) | 0.0240 (3) | |
C11 | 0.3751 (3) | 0.43195 (11) | 0.07656 (11) | 0.0461 (4) | |
H11 | 0.3873 | 0.3787 | 0.0427 | 0.055* | |
C12 | 0.2854 (3) | 0.50304 (12) | 0.02328 (12) | 0.0546 (5) | |
H12 | 0.2369 | 0.4974 | −0.0464 | 0.065* | |
C13 | 0.2648 (2) | 0.58212 (10) | 0.06909 (11) | 0.0367 (3) | |
C14 | 0.33865 (18) | 0.58778 (9) | 0.17087 (10) | 0.0303 (3) | |
H14 | 0.3277 | 0.6414 | 0.2044 | 0.036* | |
C15 | 0.42844 (16) | 0.51653 (9) | 0.22486 (9) | 0.0266 (3) | |
H15 | 0.4775 | 0.5223 | 0.2945 | 0.032* | |
C16 | 0.84361 (17) | 0.40792 (9) | 0.34183 (9) | 0.0258 (3) | |
C17 | 1.03324 (17) | 0.46132 (10) | 0.24855 (11) | 0.0332 (3) | |
H17A | 1.0679 | 0.5111 | 0.2947 | 0.050* | |
H17B | 1.0292 | 0.4809 | 0.1811 | 0.050* | |
H17C | 1.1198 | 0.4133 | 0.2681 | 0.050* | |
C18 | 0.69805 (19) | 0.40596 (10) | 0.52161 (10) | 0.0333 (3) | |
H18A | 0.7600 | 0.3562 | 0.5609 | 0.050* | |
H18B | 0.6117 | 0.4306 | 0.5538 | 0.050* | |
H18C | 0.7840 | 0.4518 | 0.5169 | 0.050* | |
C19 | 0.1671 (3) | 0.65923 (12) | 0.00988 (14) | 0.0545 (5) | |
H19A | 0.1741 | 0.7107 | 0.0536 | 0.082* | |
H19B | 0.0427 | 0.6431 | −0.0184 | 0.082* | |
H19C | 0.2212 | 0.6739 | −0.0439 | 0.082* | |
H1 | 0.404 (2) | 0.3317 (12) | 0.4656 (13) | 0.036 (4)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0417 (6) | 0.0396 (6) | 0.0250 (5) | −0.0066 (4) | 0.0132 (4) | −0.0112 (4) |
O2 | 0.0264 (5) | 0.0687 (8) | 0.0327 (6) | −0.0094 (5) | −0.0001 (4) | 0.0002 (5) |
O3 | 0.0225 (4) | 0.0420 (6) | 0.0297 (5) | −0.0061 (4) | 0.0096 (4) | −0.0002 (4) |
N1 | 0.0271 (5) | 0.0338 (6) | 0.0162 (5) | −0.0025 (4) | 0.0088 (4) | −0.0009 (4) |
C1 | 0.0220 (5) | 0.0234 (6) | 0.0204 (5) | 0.0018 (4) | 0.0052 (4) | 0.0019 (4) |
C2 | 0.0200 (5) | 0.0234 (6) | 0.0197 (5) | −0.0001 (4) | 0.0053 (4) | 0.0002 (4) |
C3 | 0.0225 (6) | 0.0271 (6) | 0.0179 (5) | −0.0031 (5) | 0.0072 (4) | −0.0024 (4) |
C4 | 0.0216 (6) | 0.0260 (6) | 0.0208 (6) | −0.0009 (5) | 0.0048 (4) | −0.0018 (4) |
C5 | 0.0242 (6) | 0.0264 (6) | 0.0198 (6) | 0.0012 (5) | 0.0041 (4) | −0.0011 (4) |
C6 | 0.0260 (6) | 0.0249 (6) | 0.0216 (6) | 0.0008 (5) | 0.0052 (5) | −0.0013 (4) |
C7 | 0.0308 (7) | 0.0294 (7) | 0.0344 (7) | −0.0070 (5) | 0.0068 (5) | −0.0066 (5) |
C8 | 0.0258 (6) | 0.0313 (7) | 0.0360 (7) | −0.0062 (5) | 0.0089 (5) | −0.0009 (5) |
C9 | 0.0302 (6) | 0.0329 (7) | 0.0276 (6) | −0.0050 (5) | 0.0120 (5) | 0.0030 (5) |
C10 | 0.0248 (6) | 0.0281 (6) | 0.0195 (6) | −0.0060 (5) | 0.0064 (5) | 0.0009 (4) |
C11 | 0.0779 (12) | 0.0317 (8) | 0.0219 (7) | 0.0030 (8) | 0.0013 (7) | −0.0022 (6) |
C12 | 0.0893 (14) | 0.0386 (9) | 0.0232 (7) | 0.0040 (9) | −0.0070 (8) | 0.0028 (6) |
C13 | 0.0424 (8) | 0.0316 (7) | 0.0323 (7) | −0.0039 (6) | 0.0034 (6) | 0.0079 (6) |
C14 | 0.0280 (6) | 0.0288 (7) | 0.0342 (7) | −0.0044 (5) | 0.0084 (5) | −0.0016 (5) |
C15 | 0.0247 (6) | 0.0323 (7) | 0.0228 (6) | −0.0041 (5) | 0.0064 (5) | −0.0028 (5) |
C16 | 0.0238 (6) | 0.0274 (6) | 0.0261 (6) | −0.0006 (5) | 0.0063 (5) | −0.0034 (5) |
C17 | 0.0244 (6) | 0.0352 (7) | 0.0428 (8) | −0.0043 (5) | 0.0141 (6) | 0.0005 (6) |
C18 | 0.0339 (7) | 0.0440 (8) | 0.0199 (6) | −0.0041 (6) | 0.0037 (5) | −0.0058 (5) |
C19 | 0.0690 (12) | 0.0375 (9) | 0.0482 (10) | 0.0043 (8) | 0.0000 (9) | 0.0112 (7) |
O1—C6 | 1.2354 (16) | C8—H8B | 0.9900 |
O2—C16 | 1.2108 (16) | C9—H9A | 0.9900 |
O3—C16 | 1.3495 (16) | C9—H9B | 0.9900 |
O3—C17 | 1.4418 (15) | C10—C15 | 1.3858 (18) |
N1—C1 | 1.3696 (16) | C10—C11 | 1.3893 (19) |
N1—C5 | 1.3878 (16) | C11—C12 | 1.386 (2) |
N1—H1 | 0.854 (18) | C11—H11 | 0.9500 |
C1—C2 | 1.3610 (16) | C12—C13 | 1.384 (2) |
C1—C9 | 1.5012 (17) | C12—H12 | 0.9500 |
C2—C6 | 1.4503 (17) | C13—C14 | 1.387 (2) |
C2—C3 | 1.5196 (16) | C13—C19 | 1.512 (2) |
C3—C4 | 1.5195 (16) | C14—C15 | 1.3920 (19) |
C3—C10 | 1.5318 (17) | C14—H14 | 0.9500 |
C3—H3 | 1.0000 | C15—H15 | 0.9500 |
C4—C5 | 1.3573 (17) | C17—H17A | 0.9800 |
C4—C16 | 1.4697 (17) | C17—H17B | 0.9800 |
C5—C18 | 1.5035 (17) | C17—H17C | 0.9800 |
C6—C7 | 1.5074 (18) | C18—H18A | 0.9800 |
C7—C8 | 1.526 (2) | C18—H18B | 0.9800 |
C7—H7A | 0.9900 | C18—H18C | 0.9800 |
C7—H7B | 0.9900 | C19—H19A | 0.9800 |
C8—C9 | 1.5201 (19) | C19—H19B | 0.9800 |
C8—H8A | 0.9900 | C19—H19C | 0.9800 |
C16—O3—C17 | 115.62 (10) | C8—C9—H9B | 109.5 |
C1—N1—C5 | 121.74 (10) | H9A—C9—H9B | 108.1 |
C1—N1—H1 | 115.3 (12) | C15—C10—C11 | 117.55 (12) |
C5—N1—H1 | 119.6 (11) | C15—C10—C3 | 123.21 (11) |
C2—C1—N1 | 120.07 (11) | C11—C10—C3 | 119.23 (12) |
C2—C1—C9 | 123.28 (11) | C12—C11—C10 | 121.07 (15) |
N1—C1—C9 | 116.64 (10) | C12—C11—H11 | 119.5 |
C1—C2—C6 | 119.74 (11) | C10—C11—H11 | 119.5 |
C1—C2—C3 | 119.91 (10) | C13—C12—C11 | 121.65 (14) |
C6—C2—C3 | 120.28 (10) | C13—C12—H12 | 119.2 |
C4—C3—C2 | 109.36 (9) | C11—C12—H12 | 119.2 |
C4—C3—C10 | 113.30 (10) | C12—C13—C14 | 117.29 (13) |
C2—C3—C10 | 109.80 (10) | C12—C13—C19 | 121.04 (14) |
C4—C3—H3 | 108.1 | C14—C13—C19 | 121.67 (15) |
C2—C3—H3 | 108.1 | C13—C14—C15 | 121.34 (13) |
C10—C3—H3 | 108.1 | C13—C14—H14 | 119.3 |
C5—C4—C16 | 120.58 (11) | C15—C14—H14 | 119.3 |
C5—C4—C3 | 120.53 (11) | C10—C15—C14 | 121.10 (12) |
C16—C4—C3 | 118.82 (10) | C10—C15—H15 | 119.5 |
C4—C5—N1 | 119.18 (11) | C14—C15—H15 | 119.5 |
C4—C5—C18 | 127.33 (12) | O2—C16—O3 | 122.02 (12) |
N1—C5—C18 | 113.49 (11) | O2—C16—C4 | 126.88 (12) |
O1—C6—C2 | 121.26 (11) | O3—C16—C4 | 111.09 (10) |
O1—C6—C7 | 120.20 (11) | O3—C17—H17A | 109.5 |
C2—C6—C7 | 118.51 (11) | O3—C17—H17B | 109.5 |
C6—C7—C8 | 112.63 (11) | H17A—C17—H17B | 109.5 |
C6—C7—H7A | 109.1 | O3—C17—H17C | 109.5 |
C8—C7—H7A | 109.1 | H17A—C17—H17C | 109.5 |
C6—C7—H7B | 109.1 | H17B—C17—H17C | 109.5 |
C8—C7—H7B | 109.1 | C5—C18—H18A | 109.5 |
H7A—C7—H7B | 107.8 | C5—C18—H18B | 109.5 |
C9—C8—C7 | 109.64 (11) | H18A—C18—H18B | 109.5 |
C9—C8—H8A | 109.7 | C5—C18—H18C | 109.5 |
C7—C8—H8A | 109.7 | H18A—C18—H18C | 109.5 |
C9—C8—H8B | 109.7 | H18B—C18—H18C | 109.5 |
C7—C8—H8B | 109.7 | C13—C19—H19A | 109.5 |
H8A—C8—H8B | 108.2 | C13—C19—H19B | 109.5 |
C1—C9—C8 | 110.55 (10) | H19A—C19—H19B | 109.5 |
C1—C9—H9A | 109.5 | C13—C19—H19C | 109.5 |
C8—C9—H9A | 109.5 | H19A—C19—H19C | 109.5 |
C1—C9—H9B | 109.5 | H19B—C19—H19C | 109.5 |
C5—N1—C1—C2 | −16.61 (18) | C2—C6—C7—C8 | 22.84 (17) |
C5—N1—C1—C9 | 162.02 (11) | C6—C7—C8—C9 | −53.74 (15) |
N1—C1—C2—C6 | 168.83 (11) | C2—C1—C9—C8 | −22.58 (17) |
C9—C1—C2—C6 | −9.71 (18) | N1—C1—C9—C8 | 158.83 (11) |
N1—C1—C2—C3 | −8.18 (17) | C7—C8—C9—C1 | 52.88 (15) |
C9—C1—C2—C3 | 173.28 (11) | C4—C3—C10—C15 | −20.61 (16) |
C1—C2—C3—C4 | 28.90 (15) | C2—C3—C10—C15 | 101.99 (13) |
C6—C2—C3—C4 | −148.09 (11) | C4—C3—C10—C11 | 160.92 (13) |
C1—C2—C3—C10 | −95.99 (13) | C2—C3—C10—C11 | −76.49 (16) |
C6—C2—C3—C10 | 87.01 (13) | C15—C10—C11—C12 | −0.8 (3) |
C2—C3—C4—C5 | −29.11 (16) | C3—C10—C11—C12 | 177.79 (16) |
C10—C3—C4—C5 | 93.73 (14) | C10—C11—C12—C13 | 0.3 (3) |
C2—C3—C4—C16 | 153.75 (11) | C11—C12—C13—C14 | 0.4 (3) |
C10—C3—C4—C16 | −83.41 (14) | C11—C12—C13—C19 | 179.79 (19) |
C16—C4—C5—N1 | −174.45 (11) | C12—C13—C14—C15 | −0.6 (2) |
C3—C4—C5—N1 | 8.46 (18) | C19—C13—C14—C15 | −179.97 (15) |
C16—C4—C5—C18 | 6.4 (2) | C11—C10—C15—C14 | 0.6 (2) |
C3—C4—C5—C18 | −170.67 (13) | C3—C10—C15—C14 | −177.92 (11) |
C1—N1—C5—C4 | 16.47 (18) | C13—C14—C15—C10 | 0.1 (2) |
C1—N1—C5—C18 | −164.29 (12) | C17—O3—C16—O2 | −2.07 (19) |
C1—C2—C6—O1 | −168.41 (12) | C17—O3—C16—C4 | 179.13 (11) |
C3—C2—C6—O1 | 8.59 (18) | C5—C4—C16—O2 | 17.9 (2) |
C1—C2—C6—C7 | 9.54 (18) | C3—C4—C16—O2 | −164.94 (14) |
C3—C2—C6—C7 | −173.46 (11) | C5—C4—C16—O3 | −163.35 (12) |
O1—C6—C7—C8 | −159.19 (12) | C3—C4—C16—O3 | 13.79 (16) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1i | 0.854 (18) | 2.017 (18) | 2.8343 (15) | 159.9 (16) |
Symmetry code: (i) x, −y+1/2, z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C19H21NO3 |
Mr | 311.37 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 193 |
a, b, c (Å) | 7.8338 (15), 15.095 (3), 13.962 (3) |
β (°) | 105.436 (5) |
V (Å3) | 1591.5 (5) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.73 × 0.62 × 0.25 |
Data collection | |
Diffractometer | Rigaku Mercury diffractometer |
Absorption correction | Multi-scan (Jacobson, 1998) |
Tmin, Tmax | 0.939, 0.978 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 17357, 3637, 3378 |
Rint | 0.021 |
(sin θ/λ)max (Å−1) | 0.649 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.046, 0.124, 1.05 |
No. of reflections | 3637 |
No. of parameters | 216 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.25, −0.24 |
Computer programs: CrystalClear (Rigaku, 1999), CrystalClear, CrystalStructure (Rigaku/MSC, 2004), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 1999), SHELXTL.
O1—C6 | 1.2354 (16) | O3—C17 | 1.4418 (15) |
O2—C16 | 1.2108 (16) | N1—C1 | 1.3696 (16) |
O3—C16 | 1.3495 (16) | N1—C5 | 1.3878 (16) |
C16—O3—C17 | 115.62 (10) | C1—N1—C5 | 121.74 (10) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1i | 0.854 (18) | 2.017 (18) | 2.8343 (15) | 159.9 (16) |
Symmetry code: (i) x, −y+1/2, z+1/2. |
Some of the derivatives of quinoline are naturally occurring alkaloids, so they are very attractive for their various bioactivities. For example, they have calcium modulatory properties (Rose & Draeger, 1992), antibacterial activity (Thomas et al., 2005), fungicidal activity (Prem et al., 2005), etc. As part of our programme aimed at developing new and environmentally friendly methodologies for the preparation of fine chemicals (Shi et al., 2004), we have synthesized the title compound, (I), in an aqueous medium. We report here the synthesis and crystal structure of (I).
In the molecular structure of (I) (Fig. 1, Table 1), atoms C3 and N1 deviate from the mean plane of atoms C1/C2/C4/C5 in the same direction, by 0.368 (1) and 0.166 (1) Å, respectively, so the pyridine ring adopts a boat conformation. The fused cyclohexene ring can be regarded as having an envelope conformation, with atom C8 out of the plane of atoms C1/C2/C6/C7/C9 by 0.687 (1) Å. In addition, the phenyl ring is almost perpendicular to the plane of atoms C1/C2/C4/C5, with a dihedral angle between them of 83.58 (5)°.
The crystal packing of (I) is stabilized by an intermolecular hydrogen bond (Table 2, Fig. 2).