Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101010228/gd1162sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270101010228/gd1162Isup2.hkl |
CCDC reference: 173387
Ethyl propiolate (0.95 g, 9.5 mmol) was added to a suspension of 6-amino-2-methoxypyrimidin-4(3H)-one (0.50 g, 3.2 mmol) in dry dioxane (3 ml) and the reaction mixture was stirred at 393 K for 62 h. The resulting dark solution was evaporated in vacuo to dryness and the title compound was isolated and purified by flash column chromatography on silica gel using dichloromethane/acetone mixtures in an acetone gradient as eluent. Recrystallization from acetone produced colourless crystals (yield: 48%, m.p. 396–397 K). Analysis calculated for C9H12N2O3: C 55.1, H 6.2, N 14.3%; found: C 54.8, H 6.0, N 14.1%.
H atoms were treated as riding atoms with C—H distances in the range 0.95–0.99 Å and N—H distances of 0.88 Å. The position of the methyl and amino H-atom positions was confirmed on a difference map.
Data collection: KappaCCD Server Software (Nonius, 1997); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976) and PLATON (Spek, 2000); software used to prepare material for publication: SHELXL97 and WORDPERFECT macro PRPKAPPA (Ferguson, 1999).
C9H12N2O3 | F(000) = 416 |
Mr = 196.21 | Dx = 1.367 Mg m−3 |
Triclinic, P1 | Melting point: 369 K |
a = 7.4906 (2) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 10.2409 (2) Å | Cell parameters from 4295 reflections |
c = 13.1449 (3) Å | θ = 3.0–27.5° |
α = 104.9607 (9)° | µ = 0.10 mm−1 |
β = 90.7398 (9)° | T = 150 K |
γ = 101.2452 (9)° | Block, colourless |
V = 953.34 (4) Å3 | 0.40 × 0.25 × 0.15 mm |
Z = 4 |
Kappa-CCD diffractometer | 4295 independent reflections |
Radiation source: fine-focus sealed X-ray tube | 3541 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.061 |
ϕ scans, and ω scans with κ offsets | θmax = 27.5°, θmin = 3.0° |
Absorption correction: multi-scan (DENZO-SMN; Otwinowski & Minor, 1997) | h = −9→9 |
Tmin = 0.960, Tmax = 0.985 | k = −13→12 |
14744 measured reflections | l = −16→17 |
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)] = 0.051 | H-atom parameters constrained |
wR(F2) = 0.142 | w = 1/[σ2(Fo2) + (0.094P)2 + 0.1054P] where P = (Fo2 + 2Fc2)/3 |
S = 1.05 | (Δ/σ)max < 0.001 |
4295 reflections | Δρmax = 0.37 e Å−3 |
258 parameters | Δρmin = −0.42 e Å−3 |
0 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.155 (12) |
C9H12N2O3 | γ = 101.2452 (9)° |
Mr = 196.21 | V = 953.34 (4) Å3 |
Triclinic, P1 | Z = 4 |
a = 7.4906 (2) Å | Mo Kα radiation |
b = 10.2409 (2) Å | µ = 0.10 mm−1 |
c = 13.1449 (3) Å | T = 150 K |
α = 104.9607 (9)° | 0.40 × 0.25 × 0.15 mm |
β = 90.7398 (9)° |
Kappa-CCD diffractometer | 4295 independent reflections |
Absorption correction: multi-scan (DENZO-SMN; Otwinowski & Minor, 1997) | 3541 reflections with I > 2σ(I) |
Tmin = 0.960, Tmax = 0.985 | Rint = 0.061 |
14744 measured reflections |
R[F2 > 2σ(F2)] = 0.051 | 0 restraints |
wR(F2) = 0.142 | H-atom parameters constrained |
S = 1.05 | Δρmax = 0.37 e Å−3 |
4295 reflections | Δρmin = −0.42 e Å−3 |
258 parameters |
Experimental. The program DENZO-SMN (Otwinowski & Minor, 1997) uses a scaling algorithm (Fox & Holmes, 1966) which effectively corrects for absorption effects. High redundancy data were used in the scaling program hence the 'multi-scan' code word was used. No transmission coefficients are available from the program (only scale factors for each frame). The scale factors in the experimental table are calculated from the 'size' command in the SHELXL97 input file. |
x | y | z | Uiso*/Ueq | ||
N11 | 0.05314 (14) | 0.09310 (11) | 0.28959 (8) | 0.0166 (3) | |
C12 | 0.01032 (17) | 0.15474 (13) | 0.21580 (10) | 0.0168 (3) | |
N12 | −0.06447 (15) | 0.07121 (11) | 0.12230 (8) | 0.0196 (3) | |
C13 | 0.03964 (18) | 0.29945 (13) | 0.23573 (10) | 0.0197 (3) | |
C14 | 0.10809 (18) | 0.37838 (13) | 0.33417 (10) | 0.0191 (3) | |
C15 | 0.15194 (17) | 0.31737 (13) | 0.41319 (10) | 0.0167 (3) | |
C151 | 0.22947 (18) | 0.40398 (13) | 0.51795 (10) | 0.0177 (3) | |
O15 | 0.24614 (14) | 0.36651 (10) | 0.59714 (7) | 0.0254 (3) | |
O151 | 0.28251 (13) | 0.53659 (9) | 0.51633 (7) | 0.0215 (2) | |
C152 | 0.35659 (18) | 0.63477 (13) | 0.61533 (10) | 0.0198 (3) | |
C153 | 0.3739 (2) | 0.77541 (14) | 0.59786 (11) | 0.0250 (3) | |
C16 | 0.12402 (17) | 0.17270 (13) | 0.38375 (9) | 0.0159 (3) | |
O16 | 0.17416 (13) | 0.11089 (9) | 0.45503 (7) | 0.0191 (2) | |
C161 | 0.18903 (19) | −0.03127 (13) | 0.41787 (10) | 0.0207 (3) | |
N21 | −0.49454 (15) | 0.10090 (11) | −0.19613 (8) | 0.0172 (3) | |
C22 | −0.54100 (18) | 0.18089 (13) | −0.25499 (10) | 0.0182 (3) | |
N22 | −0.70917 (16) | 0.14377 (12) | −0.30291 (9) | 0.0231 (3) | |
C23 | −0.41777 (19) | 0.29902 (13) | −0.26682 (10) | 0.0205 (3) | |
C24 | −0.25111 (19) | 0.33296 (13) | −0.21359 (10) | 0.0198 (3) | |
C25 | −0.19928 (18) | 0.25400 (13) | −0.14977 (10) | 0.0171 (3) | |
C251 | −0.01770 (18) | 0.29222 (12) | −0.09462 (9) | 0.0172 (3) | |
O25 | 0.04422 (13) | 0.23243 (9) | −0.03808 (7) | 0.0224 (2) | |
O251 | 0.08049 (13) | 0.40748 (9) | −0.11369 (7) | 0.0206 (2) | |
C252 | 0.26592 (18) | 0.45166 (13) | −0.06683 (10) | 0.0200 (3) | |
C253 | 0.3538 (2) | 0.57246 (15) | −0.10683 (12) | 0.0283 (3) | |
C26 | −0.33032 (18) | 0.13618 (13) | −0.14601 (9) | 0.0164 (3) | |
O26 | −0.28699 (13) | 0.05473 (9) | −0.08786 (7) | 0.0193 (2) | |
C261 | −0.40254 (19) | −0.08053 (13) | −0.10409 (11) | 0.0220 (3) | |
H12A | −0.0833 | −0.0190 | 0.1115 | 0.024* | |
H12B | −0.0945 | 0.1068 | 0.0719 | 0.024* | |
H13 | 0.0126 | 0.3411 | 0.1822 | 0.024* | |
H14 | 0.1264 | 0.4761 | 0.3495 | 0.023* | |
H15A | 0.4773 | 0.6200 | 0.6357 | 0.024* | |
H15B | 0.2740 | 0.6243 | 0.6722 | 0.024* | |
H15C | 0.4571 | 0.7846 | 0.5420 | 0.037* | |
H15D | 0.4223 | 0.8457 | 0.6633 | 0.037* | |
H15E | 0.2537 | 0.7880 | 0.5768 | 0.037* | |
H16A | 0.0670 | −0.0896 | 0.3980 | 0.031* | |
H16B | 0.2476 | −0.0586 | 0.4740 | 0.031* | |
H16C | 0.2626 | −0.0425 | 0.3563 | 0.031* | |
H22A | −0.7843 | 0.0698 | −0.2953 | 0.028* | |
H22B | −0.7444 | 0.1934 | −0.3420 | 0.028* | |
H23 | −0.4503 | 0.3527 | −0.3104 | 0.025* | |
H24 | −0.1672 | 0.4126 | −0.2198 | 0.024* | |
H25A | 0.3331 | 0.3757 | −0.0878 | 0.024* | |
H25B | 0.2660 | 0.4795 | 0.0111 | 0.024* | |
H25C | 0.3511 | 0.5437 | −0.1841 | 0.042* | |
H25D | 0.4806 | 0.6051 | −0.0778 | 0.042* | |
H25E | 0.2869 | 0.6472 | −0.0847 | 0.042* | |
H26A | −0.5298 | −0.0714 | −0.0963 | 0.033* | |
H26B | −0.3659 | −0.1249 | −0.0518 | 0.033* | |
H26C | −0.3903 | −0.1370 | −0.1752 | 0.033* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N11 | 0.0213 (6) | 0.0175 (6) | 0.0134 (5) | 0.0053 (4) | 0.0032 (4) | 0.0069 (4) |
C12 | 0.0177 (6) | 0.0198 (7) | 0.0148 (6) | 0.0053 (5) | 0.0035 (5) | 0.0067 (5) |
N12 | 0.0285 (6) | 0.0174 (6) | 0.0138 (5) | 0.0047 (4) | −0.0009 (4) | 0.0056 (4) |
C13 | 0.0256 (7) | 0.0208 (7) | 0.0158 (6) | 0.0062 (5) | 0.0009 (5) | 0.0094 (5) |
C14 | 0.0239 (7) | 0.0164 (6) | 0.0188 (6) | 0.0048 (5) | 0.0019 (5) | 0.0074 (5) |
C15 | 0.0193 (6) | 0.0171 (6) | 0.0150 (6) | 0.0042 (5) | 0.0019 (5) | 0.0060 (5) |
C151 | 0.0209 (6) | 0.0181 (6) | 0.0166 (6) | 0.0069 (5) | 0.0028 (5) | 0.0066 (5) |
O15 | 0.0402 (6) | 0.0217 (5) | 0.0158 (5) | 0.0066 (4) | −0.0028 (4) | 0.0076 (4) |
O151 | 0.0326 (6) | 0.0166 (5) | 0.0142 (5) | 0.0027 (4) | −0.0009 (4) | 0.0039 (4) |
C152 | 0.0241 (7) | 0.0193 (7) | 0.0145 (6) | 0.0047 (5) | −0.0012 (5) | 0.0019 (5) |
C153 | 0.0317 (8) | 0.0196 (7) | 0.0221 (7) | 0.0042 (6) | −0.0005 (6) | 0.0038 (5) |
C16 | 0.0182 (6) | 0.0197 (6) | 0.0133 (6) | 0.0063 (5) | 0.0045 (4) | 0.0083 (5) |
O16 | 0.0300 (5) | 0.0170 (5) | 0.0135 (5) | 0.0085 (4) | 0.0017 (4) | 0.0068 (3) |
C161 | 0.0310 (7) | 0.0171 (7) | 0.0180 (7) | 0.0096 (5) | 0.0033 (5) | 0.0080 (5) |
N21 | 0.0238 (6) | 0.0159 (5) | 0.0128 (5) | 0.0050 (4) | 0.0018 (4) | 0.0046 (4) |
C22 | 0.0256 (7) | 0.0176 (6) | 0.0119 (6) | 0.0071 (5) | 0.0023 (5) | 0.0029 (5) |
N22 | 0.0254 (6) | 0.0217 (6) | 0.0234 (6) | 0.0006 (5) | −0.0038 (5) | 0.0120 (5) |
C23 | 0.0288 (7) | 0.0170 (7) | 0.0181 (7) | 0.0053 (5) | −0.0005 (5) | 0.0087 (5) |
C24 | 0.0276 (7) | 0.0153 (6) | 0.0168 (6) | 0.0027 (5) | 0.0008 (5) | 0.0062 (5) |
C25 | 0.0243 (7) | 0.0157 (6) | 0.0118 (6) | 0.0048 (5) | 0.0011 (5) | 0.0040 (5) |
C251 | 0.0258 (7) | 0.0147 (6) | 0.0119 (6) | 0.0050 (5) | 0.0029 (5) | 0.0041 (5) |
O25 | 0.0300 (6) | 0.0196 (5) | 0.0193 (5) | 0.0036 (4) | −0.0044 (4) | 0.0094 (4) |
O251 | 0.0229 (5) | 0.0190 (5) | 0.0210 (5) | 0.0013 (4) | −0.0025 (4) | 0.0098 (4) |
C252 | 0.0224 (7) | 0.0210 (7) | 0.0172 (6) | 0.0039 (5) | −0.0023 (5) | 0.0064 (5) |
C253 | 0.0254 (8) | 0.0300 (8) | 0.0309 (8) | −0.0001 (6) | −0.0048 (6) | 0.0155 (6) |
C26 | 0.0252 (7) | 0.0153 (6) | 0.0108 (6) | 0.0079 (5) | 0.0034 (5) | 0.0045 (5) |
O26 | 0.0261 (5) | 0.0168 (5) | 0.0176 (5) | 0.0037 (4) | 0.0002 (4) | 0.0096 (4) |
C261 | 0.0278 (7) | 0.0163 (7) | 0.0234 (7) | 0.0018 (5) | 0.0017 (5) | 0.0097 (5) |
N11—C16 | 1.3311 (16) | N21—C26 | 1.3268 (17) |
N11—C12 | 1.3525 (15) | N21—C22 | 1.3500 (16) |
C12—N12 | 1.3449 (16) | C22—N22 | 1.3406 (17) |
C12—C13 | 1.4086 (18) | C22—C23 | 1.4159 (19) |
N12—H12A | 0.8800 | N22—H22A | 0.8800 |
N12—H12B | 0.8800 | N22—H22B | 0.8800 |
C13—C14 | 1.3681 (18) | C23—C24 | 1.3607 (18) |
C13—H13 | 0.9500 | C23—H23 | 0.9500 |
C14—C15 | 1.4084 (17) | C24—C25 | 1.4045 (17) |
C14—H14 | 0.9500 | C24—H24 | 0.9500 |
C15—C16 | 1.4034 (18) | C25—C26 | 1.4113 (18) |
C15—C151 | 1.4725 (17) | C25—C251 | 1.4660 (18) |
C151—O15 | 1.2115 (15) | C251—O25 | 1.2162 (15) |
C151—O151 | 1.3444 (16) | C251—O251 | 1.3476 (15) |
O151—C152 | 1.4494 (15) | O251—C252 | 1.4499 (15) |
C152—C153 | 1.4976 (19) | C252—C253 | 1.5058 (18) |
C152—H15A | 0.9900 | C252—H25A | 0.9900 |
C152—H15B | 0.9900 | C252—H25B | 0.9900 |
C153—H15C | 0.9800 | C253—H25C | 0.9800 |
C153—H15D | 0.9800 | C253—H25D | 0.9800 |
C153—H15E | 0.9800 | C253—H25E | 0.9800 |
C16—O16 | 1.3451 (14) | C26—O26 | 1.3468 (14) |
O16—C161 | 1.4381 (15) | O26—C261 | 1.4452 (15) |
C161—H16A | 0.9800 | C261—H26A | 0.9800 |
C161—H16B | 0.9800 | C261—H26B | 0.9800 |
C161—H16C | 0.9800 | C261—H26C | 0.9800 |
C16—N11—C12 | 118.41 (11) | C26—N21—C22 | 118.90 (11) |
N12—C12—N11 | 116.84 (11) | N22—C22—N21 | 117.36 (12) |
N12—C12—C13 | 121.18 (11) | N22—C22—C23 | 120.83 (11) |
N11—C12—C13 | 121.97 (11) | N21—C22—C23 | 121.81 (12) |
C12—N12—H12A | 120.0 | C22—N22—H22A | 120.0 |
C12—N12—H12B | 120.0 | C22—N22—H22B | 120.0 |
H12A—N12—H12B | 120.0 | H22A—N22—H22B | 120.0 |
C14—C13—C12 | 118.24 (11) | C24—C23—C22 | 117.74 (11) |
C14—C13—H13 | 120.9 | C24—C23—H23 | 121.1 |
C12—C13—H13 | 120.9 | C22—C23—H23 | 121.1 |
C13—C14—C15 | 121.18 (12) | C23—C24—C25 | 122.07 (12) |
C13—C14—H14 | 119.4 | C23—C24—H24 | 119.0 |
C15—C14—H14 | 119.4 | C25—C24—H24 | 119.0 |
C16—C15—C14 | 115.92 (11) | C24—C25—C26 | 115.54 (12) |
C16—C15—C151 | 123.56 (11) | C24—C25—C251 | 120.75 (11) |
C14—C15—C151 | 120.47 (11) | C26—C25—C251 | 123.68 (11) |
O15—C151—O151 | 122.26 (12) | O25—C251—O251 | 121.59 (12) |
O15—C151—C15 | 127.08 (12) | O25—C251—C25 | 127.24 (12) |
O151—C151—C15 | 110.66 (10) | O251—C251—C25 | 111.17 (10) |
C151—O151—C152 | 116.72 (10) | C251—O251—C252 | 116.01 (9) |
O151—C152—C153 | 106.47 (10) | O251—C252—C253 | 106.66 (10) |
O151—C152—H15A | 110.4 | O251—C252—H25A | 110.4 |
C153—C152—H15A | 110.4 | C253—C252—H25A | 110.4 |
O151—C152—H15B | 110.4 | O251—C252—H25B | 110.4 |
C153—C152—H15B | 110.4 | C253—C252—H25B | 110.4 |
H15A—C152—H15B | 108.6 | H25A—C252—H25B | 108.6 |
C152—C153—H15C | 109.5 | C252—C253—H25C | 109.5 |
C152—C153—H15D | 109.5 | C252—C253—H25D | 109.5 |
H15C—C153—H15D | 109.5 | H25C—C253—H25D | 109.5 |
C152—C153—H15E | 109.5 | C252—C253—H25E | 109.5 |
H15C—C153—H15E | 109.5 | H25C—C253—H25E | 109.5 |
H15D—C153—H15E | 109.5 | H25D—C253—H25E | 109.5 |
N11—C16—O16 | 118.04 (11) | N21—C26—O26 | 117.83 (11) |
N11—C16—C15 | 124.21 (11) | N21—C26—C25 | 123.89 (11) |
O16—C16—C15 | 117.75 (11) | O26—C26—C25 | 118.28 (11) |
C16—O16—C161 | 117.70 (10) | C26—O26—C261 | 117.38 (10) |
O16—C161—H16A | 109.5 | O26—C261—H26A | 109.5 |
O16—C161—H16B | 109.5 | O26—C261—H26B | 109.5 |
H16A—C161—H16B | 109.5 | H26A—C261—H26B | 109.5 |
O16—C161—H16C | 109.5 | O26—C261—H26C | 109.5 |
H16A—C161—H16C | 109.5 | H26A—C261—H26C | 109.5 |
H16B—C161—H16C | 109.5 | H26B—C261—H26C | 109.5 |
D—H···A | D—H | H···A | D···A | D—H···A |
N12—H12A···O25i | 0.88 | 2.23 | 3.0543 (15) | 156 |
N12—H12B···O26 | 0.88 | 2.41 | 3.1574 (14) | 143 |
N12—H12B···O25 | 0.88 | 2.30 | 3.0250 (14) | 139 |
N22—H22A···N11ii | 0.88 | 2.37 | 3.2167 (17) | 162 |
N22—H22B···O15iii | 0.88 | 2.14 | 2.9791 (16) | 160 |
Symmetry codes: (i) −x, −y, −z; (ii) −x−1, −y, −z; (iii) x−1, y, z−1. |
Experimental details
Crystal data | |
Chemical formula | C9H12N2O3 |
Mr | 196.21 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 150 |
a, b, c (Å) | 7.4906 (2), 10.2409 (2), 13.1449 (3) |
α, β, γ (°) | 104.9607 (9), 90.7398 (9), 101.2452 (9) |
V (Å3) | 953.34 (4) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.40 × 0.25 × 0.15 |
Data collection | |
Diffractometer | Kappa-CCD diffractometer |
Absorption correction | Multi-scan (DENZO-SMN; Otwinowski & Minor, 1997) |
Tmin, Tmax | 0.960, 0.985 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 14744, 4295, 3541 |
Rint | 0.061 |
(sin θ/λ)max (Å−1) | 0.650 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.051, 0.142, 1.05 |
No. of reflections | 4295 |
No. of parameters | 258 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.37, −0.42 |
Computer programs: KappaCCD Server Software (Nonius, 1997), DENZO-SMN (Otwinowski & Minor, 1997), DENZO-SMN, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEPII (Johnson, 1976) and PLATON (Spek, 2000), SHELXL97 and WORDPERFECT macro PRPKAPPA (Ferguson, 1999).
N11—C16 | 1.3311 (16) | N21—C26 | 1.3268 (17) |
N11—C12 | 1.3525 (15) | N21—C22 | 1.3500 (16) |
C12—N12 | 1.3449 (16) | C22—N22 | 1.3406 (17) |
C12—C13 | 1.4086 (18) | C22—C23 | 1.4159 (19) |
C13—C14 | 1.3681 (18) | C23—C24 | 1.3607 (18) |
C14—C15 | 1.4084 (17) | C24—C25 | 1.4045 (17) |
C15—C16 | 1.4034 (18) | C25—C26 | 1.4113 (18) |
C15—C151 | 1.4725 (17) | C25—C251 | 1.4660 (18) |
C151—O15 | 1.2115 (15) | C251—O25 | 1.2162 (15) |
C16—N11—C12 | 118.41 (11) | C26—N21—C22 | 118.90 (11) |
N12—C12—C13 | 121.18 (11) | N21—C22—C23 | 121.81 (12) |
C14—C13—C12 | 118.24 (11) | C24—C23—C22 | 117.74 (11) |
C13—C14—C15 | 121.18 (12) | C23—C24—C25 | 122.07 (12) |
C16—C15—C14 | 115.92 (11) | C24—C25—C26 | 115.54 (12) |
N11—C16—C15 | 124.21 (11) | N21—C26—C25 | 123.89 (11) |
D—H···A | D—H | H···A | D···A | D—H···A |
N12—H12A···O25i | 0.88 | 2.23 | 3.0543 (15) | 156 |
N12—H12B···O26 | 0.88 | 2.41 | 3.1574 (14) | 143 |
N12—H12B···O25 | 0.88 | 2.30 | 3.0250 (14) | 139 |
N22—H22A···N11ii | 0.88 | 2.37 | 3.2167 (17) | 162 |
N22—H22B···O15iii | 0.88 | 2.14 | 2.9791 (16) | 160 |
Symmetry codes: (i) −x, −y, −z; (ii) −x−1, −y, −z; (iii) x−1, y, z−1. |
The title compound, (I), was obtained through a hetero-Diels–Alder/retro-Diels–Alder transformation of 4-amino-2-methoxy-3-methylpyrimidin-4(3H)-one (acting as 2-azadiene) and ethyl propiolate (acting as dienophile) (see scheme below) and the presence of a 6-amino group and an ethoxycarbonyl group as substituents on a pyridine ring in relative para positions constitutes a clear π-electron `push–pull' system which explains the main structural features found in the crystal structure.
The two unique molecules in the asymmetric unit were chosen to give a dimer formed by the three-centred R21(6) (Bernstein et al., 1995) hydrogen bond between the amino H atom attached to N21 in molecule 1, and O25 and O26 in molecule 2 (Fig. 1); the sum of the angles at the H atom is 353°. The former of these two hydrogen bonds is the shorter (Table 2) and is hence the stronger. The two molecules have similar bond lengths and angles.
The pyridine rings, while essentially planar, show deviations from regular hexagonal geometry (Table 1). In both molecules, the C—NH2 groups lie in the plane of the pyridine ring. The N atoms have predominantly sp2-character, as is shown by the C–N bond lengths [N12–C12 1.3449 (16) Å and N22–C22 1.3406 (17) Å], which are shorter than the mean value (1.360 Å) recorded for planar amino groups bonded to aromatic systems (Allen et al., 1987). It is also noteworthy that the C151–O15 [1.2115 (15) Å] and C251–O25 bonds [1.2162 (15) Å] are long compared with the mean [1.202 Å; Schweizer & Dunitz, 1982] for other carbonyl groups in aromatic carboxylic esters.
The compensation by the 6-amino lone pair of the π-electron deficiency of the 3-carboxylate group produces an increase in the acidity of the amino H atoms as well as an enhancement of the electron density of the carbonyl O atom. The partial charges thus developed favour the formation of N—H···O═C hydrogen bonds, confirmed by an analysis of the hydrogen bonding. This indicates the great contribution of canonical form (1a) (see scheme below) and hence this can be considered as an example of resonance-assisted hydrogen bonding (Gilli et al.l., 1989).
The supramolecular structure of (I) consists of a corrugated two-dimensional sheets formed by linked hydrogen bonded antiparallel chains formed by hydrogen bonding the dimers, described above, together in a head-to-tail fashion. These sheets lie in the (010) plane. Individual sheets are not linked to neighbouring sheets. The dimers are connected by the N22—H22B···O15(-1 + x, y, -1 + z) hydrogen bond producing via the N12–H12B···O25 bond a C22(16) chain which runs parallel to [101]. The C22(14) chain via O26 is shorter but, as mentioned above, the N12–H12B···O25 bond is the stronger of the pair. Crystallographic symmetry produces an alternating pattern of antiparallel chains which are linked to neighbouring chains in two distinct ways, one by the hydrogen bond between N22–H22A···N11(-1 - x, -y, -z) which produces a ribbon with alternating centrosymmetric R44(20) and R44(16) rings (Bernstein et al., 1995), centred on the inversion centres at (-0.5,0,0) and (0,0, 1/2), respectively (Fig. 2). The second linkage is produced by the N12—H12A···O25(-x, -y, -z) hydrogen bond, the ribbon so produced being made up of alternating centrosymmetric R24(8) and R44(32) rings (Bernstein et al., 1995) centred on the centres of inversion at (0,0,0) and (1/2,0, 1/2), respectively (Fig. 3).
The following related compounds were retrieved from the Cambridge Structural Database (CSD; Allen & Kennard, 1993): SAVZEU, ethyl 2-N-(6-amino-5-cyano-3-ethoxycarbonylpyridin-2-yl)aminobenzoate, C18H18N4O4 (Deady et al., 1989); ZIVHAN, 2-amino-6-methoxy-4,5-bis(methoxycarbonyl)pyridine, C10H12N2O5 (Low et al., 1996); ZIVHER, 2-amino-4,5-bis(methoxycarbonyl)-6-(methylthio)pyridine, C10H12N2O4S (Low et al., 1996). These are the only pyridine compounds with a 2-amino group para to a 5-carboxylate group (6-amino and 3-carboxylate in the numbering of the title compound) and they all crystallize in space group P1, like compound (I). These are all push–pull systems simialr to (I) and in all cases formation of N—H···O═C hydrogen bonds is observed. These hydrogen bonds form C(8) chains in ZIVHAN and ZIVHER, which have only one molecule in the asymmetric unit. Antiparallel chains link together to form a ribbon consisting of alternating R22(14) and R24(18) rings. In SAVZEU, in which the asymmetric unit, like that of (I), contains two molecules, the chain is of C22(16) type, as in (I), and antiparallel chains are linked to form a ribbon consisting of alternating R44(36) and R24(8) rings. Thus, although ribbons are formed in all these structures, only in (I) do these ribbons combine to form a sheet structure.