organic compounds
1-Phenyl-6,7,8,9-hexahydro-1H,5H-cyclohepta[1′,2′:2,3]pyrido[6,5-c]pyrazol-4-amine: a new tacrine analogue
aSchool of Chemical Engineering and the Environment, Beijing Institute of Technology, Beijing 100081, People's Republic of China
*Correspondence e-mail: cdlijun@bit.edu.cn
The title compound, C17H18N4, contains a pyrazolopyridine system fused with a seven-membered carbocyclic ring. The pyrazole ring is coplanar with the pyridine ring, while the phenyl ring is twisted by a dihedral angle of 14.38 (14)° with respect to the pyridine ring. The seven-membered ring displays a chair conformation. The packing is stabilized by N—H⋯N hydrogen bonds and N—H⋯π(arene) interactions.
Related literature
For related literature, see: Gracon et al. (1998); Haviv et al. (2005); Kelley et al. (1988); Kim et al. (1996); Lin et al. (2007); Stachlewitz et al. (1997); Zocchi et al. (1996); Erast et al. (1987).
Experimental
Crystal data
|
Refinement
|
Data collection: CrystalClear (Rigaku, 2004); cell CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPIII (Burnett & Johnson, 1996), ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97.
Supporting information
10.1107/S1600536808013366/dn2339sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536808013366/dn2339Isup2.hkl
A solution of 0.2 g of 5-amino-4-cyanopyrazole (1.1 mmol,), 0.16 g of AlCl3 (1.2 mmol,) in 5 ml of 1,2-dichloroethane was refluxed for 4 h (monitored by TLC). The reaction mixture was cooled, dispersed into THF/water (2:1 vol.) and titrated to pH=7 by 20% sodium hydroxide. Then, the mixture was stirred for 30 min. and extracted three times with dichloromethane, the organic layers were dried and evaporated at reduced pressure to give the solid product (Fig. 3). The title compound 1 was purified by silica gel
eluting with ethyl acetate/light petroleum in 40% yield.Its single-crystal was cultured from a solution of ethanol by slow evaporation at room temperature.
The product 1, white crystal, m.p. 194–195°C, was characterized by 1H NMR, 13C NMR, ESI, IR, EA. IR (KBr) (cm-1): 3482 and 3350 (NH), 2922 (CH), 1638 and 1594 (C=N), 1501, 1358; 1H NMR (400 MHz, CDCl3, δp.p.m.): 1.62–1.90 (m, 6H, alkyl-H), 2.66–2.69 (t, 2H, alkyl-H), 3.08–3.01 (t, 2H, alkyl-H), 4.60 (s, 2H, NH2), 7.22–7.26 (t, J=7.4 Hz, 1H), 7.46–7.50 (t, J=7.5 Hz, 2H), 7.98 (s, 1H), 8.30–8.32 (d, J=7.6 Hz, 2H); 13C NMR (400 MHz, CDCl3, δp.p.m.): 25.40, 26.79, 27.56, 32.16, 39.81, 106.11, 113.24, 120.91 (2 C), 125.37, 128.89 (2 C), 130.61, 140.02, 143.69, 149.52, 165.25; ESI [M+H]+: 279.1; Anal. Calcd. for C17H18N4: C, 73.35; H, 6.52; N, 20.13. Found: C, 73.17; H, 6.52; N, 19.99.
All H atoms attached to C atoms were fixed geometrically and treated as riding with C—H = 0.93 Å (aromatic) or 0.98 Å (methine) with Uiso(H) = 1.2Ueq(C). H atoms attached to N were located in difference Fourier maps but introduced in calculated positions and treated as riding on the N atoms with N-H = 0.86 Å and Uiso(H) = 1.2Ueq(N).
Data collection: CrystalClear (Rigaku, 2004); cell
CrystalClear (Rigaku, 2004); data reduction: CrystalClear (Rigaku, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPIII (Burnett & Johnson, 1996), ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).C17H18N4 | F(000) = 592 |
Mr = 278.35 | Dx = 1.252 Mg m−3 |
Monoclinic, P21/a | Mo Kα radiation, λ = 0.71070 Å |
Hall symbol: -P 2yab | Cell parameters from 2169 reflections |
a = 13.694 (13) Å | θ = 2.6–27.9° |
b = 6.888 (6) Å | µ = 0.08 mm−1 |
c = 16.929 (16) Å | T = 293 K |
β = 112.417 (12)° | Platelet, colorless |
V = 1476 (2) Å3 | 0.24 × 0.18 × 0.10 mm |
Z = 4 |
Rigaku Saturn diffractometer | 2593 independent reflections |
Radiation source: rotating anode | 2004 reflections with I > 2σ(I) |
Confocal monochromator | Rint = 0.045 |
Detector resolution: 7.31 pixels mm-1 | θmax = 25.0°, θmin = 1.3° |
ω scans | h = −16→16 |
Absorption correction: multi-scan (Jacobson, 1998) | k = −8→8 |
Tmin = 0.982, Tmax = 0.992 | l = −20→20 |
10708 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)] = 0.064 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.162 | H-atom parameters constrained |
S = 1.13 | w = 1/[σ2(Fo2) + (0.0737P)2 + 0.1595P] where P = (Fo2 + 2Fc2)/3 |
2593 reflections | (Δ/σ)max = 0.001 |
190 parameters | Δρmax = 0.13 e Å−3 |
0 restraints | Δρmin = −0.16 e Å−3 |
C17H18N4 | V = 1476 (2) Å3 |
Mr = 278.35 | Z = 4 |
Monoclinic, P21/a | Mo Kα radiation |
a = 13.694 (13) Å | µ = 0.08 mm−1 |
b = 6.888 (6) Å | T = 293 K |
c = 16.929 (16) Å | 0.24 × 0.18 × 0.10 mm |
β = 112.417 (12)° |
Rigaku Saturn diffractometer | 2593 independent reflections |
Absorption correction: multi-scan (Jacobson, 1998) | 2004 reflections with I > 2σ(I) |
Tmin = 0.982, Tmax = 0.992 | Rint = 0.045 |
10708 measured reflections |
R[F2 > 2σ(F2)] = 0.064 | 0 restraints |
wR(F2) = 0.162 | H-atom parameters constrained |
S = 1.13 | Δρmax = 0.13 e Å−3 |
2593 reflections | Δρmin = −0.16 e Å−3 |
190 parameters |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 | ||
N1 | 0.22712 (17) | −0.0370 (3) | 0.14030 (12) | 0.0759 (7) | |
H1A | 0.2063 | −0.1288 | 0.1645 | 0.091* | |
H1B | 0.2046 | −0.0315 | 0.0855 | 0.091* | |
N2 | 0.43578 (14) | 0.4015 (3) | 0.28441 (11) | 0.0555 (5) | |
N3 | 0.41678 (14) | 0.5193 (3) | 0.14393 (11) | 0.0561 (5) | |
N4 | 0.36441 (16) | 0.4614 (3) | 0.06027 (11) | 0.0659 (6) | |
C1 | 0.29571 (17) | 0.0997 (3) | 0.18869 (13) | 0.0520 (6) | |
C2 | 0.32949 (16) | 0.2498 (3) | 0.14847 (13) | 0.0506 (6) | |
C3 | 0.39672 (16) | 0.3917 (3) | 0.19859 (13) | 0.0497 (5) | |
C4 | 0.40415 (17) | 0.2541 (3) | 0.32127 (13) | 0.0536 (6) | |
C5 | 0.33628 (16) | 0.1021 (3) | 0.27801 (13) | 0.0517 (6) | |
C6 | 0.31279 (19) | 0.3022 (4) | 0.06373 (14) | 0.0633 (7) | |
H6 | 0.2703 | 0.2325 | 0.0159 | 0.076* | |
C7 | 0.47904 (17) | 0.6919 (3) | 0.16101 (15) | 0.0553 (6) | |
C8 | 0.5064 (2) | 0.7724 (4) | 0.09698 (17) | 0.0709 (7) | |
H8 | 0.4837 | 0.7154 | 0.0432 | 0.085* | |
C9 | 0.5679 (2) | 0.9391 (4) | 0.1146 (2) | 0.0841 (9) | |
H9 | 0.5862 | 0.9938 | 0.0719 | 0.101* | |
C10 | 0.6020 (2) | 1.0244 (4) | 0.1935 (2) | 0.0856 (9) | |
H10 | 0.6434 | 1.1359 | 0.2045 | 0.103* | |
C11 | 0.5746 (2) | 0.9436 (4) | 0.25592 (19) | 0.0801 (8) | |
H11 | 0.5973 | 1.0013 | 0.3096 | 0.096* | |
C12 | 0.51355 (18) | 0.7772 (4) | 0.24043 (16) | 0.0650 (7) | |
H12 | 0.4959 | 0.7232 | 0.2836 | 0.078* | |
C13 | 0.4445 (2) | 0.2642 (4) | 0.41739 (14) | 0.0737 (8) | |
H13A | 0.4970 | 0.3665 | 0.4371 | 0.088* | |
H13B | 0.4791 | 0.1426 | 0.4409 | 0.088* | |
C14 | 0.3584 (2) | 0.3027 (4) | 0.45167 (17) | 0.0882 (9) | |
H14A | 0.3908 | 0.3592 | 0.5082 | 0.106* | |
H14B | 0.3100 | 0.3982 | 0.4152 | 0.106* | |
C15 | 0.2955 (2) | 0.1271 (5) | 0.45736 (17) | 0.0860 (9) | |
H15A | 0.2447 | 0.1677 | 0.4812 | 0.103* | |
H15B | 0.3433 | 0.0359 | 0.4971 | 0.103* | |
C16 | 0.2365 (2) | 0.0213 (4) | 0.37396 (15) | 0.0755 (8) | |
H16A | 0.1836 | 0.1081 | 0.3359 | 0.091* | |
H16B | 0.1997 | −0.0886 | 0.3856 | 0.091* | |
C17 | 0.3059 (2) | −0.0518 (4) | 0.32817 (15) | 0.0671 (7) | |
H17A | 0.3699 | −0.1066 | 0.3702 | 0.081* | |
H17B | 0.2689 | −0.1552 | 0.2894 | 0.081* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0947 (16) | 0.0801 (15) | 0.0543 (12) | −0.0340 (12) | 0.0301 (12) | −0.0143 (10) |
N2 | 0.0539 (11) | 0.0634 (12) | 0.0483 (11) | −0.0081 (9) | 0.0185 (9) | −0.0006 (9) |
N3 | 0.0578 (12) | 0.0610 (12) | 0.0471 (11) | −0.0037 (9) | 0.0173 (9) | 0.0050 (9) |
N4 | 0.0722 (14) | 0.0747 (14) | 0.0465 (11) | −0.0064 (11) | 0.0178 (10) | 0.0053 (10) |
C1 | 0.0523 (13) | 0.0573 (13) | 0.0484 (12) | −0.0041 (11) | 0.0214 (11) | −0.0058 (10) |
C2 | 0.0503 (13) | 0.0581 (14) | 0.0429 (12) | 0.0013 (11) | 0.0171 (10) | 0.0002 (10) |
C3 | 0.0476 (13) | 0.0577 (13) | 0.0447 (12) | −0.0002 (11) | 0.0186 (10) | 0.0035 (10) |
C4 | 0.0493 (13) | 0.0676 (15) | 0.0439 (12) | −0.0047 (11) | 0.0177 (10) | 0.0006 (10) |
C5 | 0.0530 (13) | 0.0555 (13) | 0.0485 (12) | −0.0017 (11) | 0.0217 (10) | 0.0010 (10) |
C6 | 0.0683 (16) | 0.0724 (16) | 0.0447 (13) | −0.0090 (13) | 0.0166 (11) | −0.0012 (11) |
C7 | 0.0480 (13) | 0.0531 (13) | 0.0633 (14) | 0.0038 (11) | 0.0195 (11) | 0.0097 (11) |
C8 | 0.0694 (16) | 0.0731 (17) | 0.0712 (16) | 0.0035 (14) | 0.0278 (14) | 0.0164 (13) |
C9 | 0.081 (2) | 0.0758 (19) | 0.103 (2) | −0.0069 (16) | 0.0428 (18) | 0.0252 (17) |
C10 | 0.081 (2) | 0.0668 (18) | 0.110 (2) | −0.0146 (15) | 0.0371 (18) | 0.0020 (17) |
C11 | 0.0773 (19) | 0.0689 (17) | 0.096 (2) | −0.0126 (14) | 0.0348 (16) | −0.0040 (15) |
C12 | 0.0638 (16) | 0.0633 (16) | 0.0712 (16) | −0.0039 (12) | 0.0294 (13) | 0.0000 (12) |
C13 | 0.0709 (17) | 0.098 (2) | 0.0462 (13) | −0.0243 (15) | 0.0163 (12) | −0.0020 (13) |
C14 | 0.111 (2) | 0.102 (2) | 0.0664 (17) | −0.0358 (18) | 0.0502 (17) | −0.0252 (15) |
C15 | 0.098 (2) | 0.106 (2) | 0.0694 (17) | −0.0220 (18) | 0.0490 (17) | −0.0144 (15) |
C16 | 0.0798 (18) | 0.0903 (19) | 0.0643 (16) | −0.0226 (15) | 0.0364 (14) | −0.0022 (14) |
C17 | 0.0829 (18) | 0.0652 (16) | 0.0568 (14) | −0.0123 (13) | 0.0305 (13) | −0.0004 (12) |
N1—C1 | 1.361 (3) | C9—C10 | 1.368 (4) |
N1—H1A | 0.8600 | C9—H9 | 0.9300 |
N1—H1B | 0.8600 | C10—C11 | 1.369 (4) |
N2—C3 | 1.345 (3) | C10—H10 | 0.9300 |
N2—C4 | 1.347 (3) | C11—C12 | 1.383 (3) |
N3—C3 | 1.377 (3) | C11—H11 | 0.9300 |
N3—N4 | 1.380 (3) | C12—H12 | 0.9300 |
N3—C7 | 1.427 (3) | C13—C14 | 1.523 (4) |
N4—C6 | 1.318 (3) | C13—H13A | 0.9700 |
C1—C5 | 1.398 (3) | C13—H13B | 0.9700 |
C1—C2 | 1.410 (3) | C14—C15 | 1.508 (4) |
C2—C3 | 1.388 (3) | C14—H14A | 0.9700 |
C2—C6 | 1.411 (3) | C14—H14B | 0.9700 |
C4—C5 | 1.406 (3) | C15—C16 | 1.519 (4) |
C4—C13 | 1.507 (3) | C15—H15A | 0.9700 |
C5—C17 | 1.512 (3) | C15—H15B | 0.9700 |
C6—H6 | 0.9300 | C16—C17 | 1.523 (3) |
C7—C12 | 1.375 (3) | C16—H16A | 0.9700 |
C7—C8 | 1.390 (3) | C16—H16B | 0.9700 |
C8—C9 | 1.388 (4) | C17—H17A | 0.9700 |
C8—H8 | 0.9300 | C17—H17B | 0.9700 |
C1—N1—H1A | 120.0 | C11—C10—H10 | 120.4 |
C1—N1—H1B | 120.0 | C10—C11—C12 | 121.0 (3) |
H1A—N1—H1B | 120.0 | C10—C11—H11 | 119.5 |
C3—N2—C4 | 113.38 (18) | C12—C11—H11 | 119.5 |
C3—N3—N4 | 110.27 (19) | C7—C12—C11 | 119.8 (2) |
C3—N3—C7 | 130.71 (19) | C7—C12—H12 | 120.1 |
N4—N3—C7 | 119.02 (18) | C11—C12—H12 | 120.1 |
C6—N4—N3 | 105.81 (18) | C4—C13—C14 | 113.6 (2) |
N1—C1—C5 | 123.9 (2) | C4—C13—H13A | 108.8 |
N1—C1—C2 | 119.7 (2) | C14—C13—H13A | 108.8 |
C5—C1—C2 | 116.4 (2) | C4—C13—H13B | 108.8 |
C3—C2—C1 | 118.98 (19) | C14—C13—H13B | 108.8 |
C3—C2—C6 | 104.73 (19) | H13A—C13—H13B | 107.7 |
C1—C2—C6 | 136.3 (2) | C15—C14—C13 | 115.4 (2) |
N2—C3—N3 | 126.5 (2) | C15—C14—H14A | 108.4 |
N2—C3—C2 | 126.41 (19) | C13—C14—H14A | 108.4 |
N3—C3—C2 | 107.11 (19) | C15—C14—H14B | 108.4 |
N2—C4—C5 | 125.8 (2) | C13—C14—H14B | 108.4 |
N2—C4—C13 | 114.5 (2) | H14A—C14—H14B | 107.5 |
C5—C4—C13 | 119.6 (2) | C14—C15—C16 | 116.1 (2) |
C1—C5—C4 | 118.92 (19) | C14—C15—H15A | 108.3 |
C1—C5—C17 | 121.2 (2) | C16—C15—H15A | 108.3 |
C4—C5—C17 | 119.9 (2) | C14—C15—H15B | 108.3 |
N4—C6—C2 | 112.1 (2) | C16—C15—H15B | 108.3 |
N4—C6—H6 | 124.0 | H15A—C15—H15B | 107.4 |
C2—C6—H6 | 124.0 | C15—C16—C17 | 114.7 (2) |
C12—C7—C8 | 119.8 (2) | C15—C16—H16A | 108.6 |
C12—C7—N3 | 120.7 (2) | C17—C16—H16A | 108.6 |
C8—C7—N3 | 119.5 (2) | C15—C16—H16B | 108.6 |
C9—C8—C7 | 119.0 (3) | C17—C16—H16B | 108.6 |
C9—C8—H8 | 120.5 | H16A—C16—H16B | 107.6 |
C7—C8—H8 | 120.5 | C5—C17—C16 | 114.4 (2) |
C10—C9—C8 | 121.2 (3) | C5—C17—H17A | 108.7 |
C10—C9—H9 | 119.4 | C16—C17—H17A | 108.7 |
C8—C9—H9 | 119.4 | C5—C17—H17B | 108.7 |
C9—C10—C11 | 119.2 (3) | C16—C17—H17B | 108.7 |
C9—C10—H10 | 120.4 | H17A—C17—H17B | 107.6 |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1B···N4i | 0.86 | 2.28 | 3.139 (4) | 175 |
N1—H1A···Cg1ii | 0.86 | 2.84 | 3.608 (4) | 150 |
Symmetry codes: (i) −x+1/2, y−1/2, −z; (ii) x−3/2, −y−1/2, z. |
Experimental details
Crystal data | |
Chemical formula | C17H18N4 |
Mr | 278.35 |
Crystal system, space group | Monoclinic, P21/a |
Temperature (K) | 293 |
a, b, c (Å) | 13.694 (13), 6.888 (6), 16.929 (16) |
β (°) | 112.417 (12) |
V (Å3) | 1476 (2) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.08 |
Crystal size (mm) | 0.24 × 0.18 × 0.10 |
Data collection | |
Diffractometer | Rigaku Saturn diffractometer |
Absorption correction | Multi-scan (Jacobson, 1998) |
Tmin, Tmax | 0.982, 0.992 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10708, 2593, 2004 |
Rint | 0.045 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.064, 0.162, 1.13 |
No. of reflections | 2593 |
No. of parameters | 190 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.13, −0.16 |
Computer programs: CrystalClear (Rigaku, 2004), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEPIII (Burnett & Johnson, 1996), ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1B···N4i | 0.86 | 2.28 | 3.139 (4) | 175.1 |
N1—H1A···Cg1ii | 0.86 | 2.84 | 3.608 (4) | 150 |
Symmetry codes: (i) −x+1/2, y−1/2, −z; (ii) x−3/2, −y−1/2, z. |
Acknowledgements
We thank Beijing Institute of Technology for financial support and Naikai University for the X-ray diffraction analysis.
References
Burnett, M. N. & Johnson, C. K. (1996). ORTEPIII. Report ORNL-6895. Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA. Google Scholar
Erast, B., Bend, Z. & Norbert, M. (1987). German Patent DE 3 604 569. Google Scholar
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565. CrossRef IUCr Journals Google Scholar
Gracon, S. I., Knapp, M. J., Berghoff, W. G., Pierce, M., DeJong, R., Lobbestael, S. J., Symons, J., Dombey, S. L., Luscombe, F. A. & Kraemer, D. (1998). Alzheimer Dis. Assoc. Disord. 12, 93–101. Web of Science CrossRef CAS PubMed Google Scholar
Haviv, H., Wong, D. M., Greenblatt, H. M., Carlier, P. R., Han, Y. F., Pang, Y. P., Silman, I. & Sussman, J. L. (2005). J. Am. Chem. Soc. 127, 11029–11036. Web of Science CrossRef PubMed CAS Google Scholar
Jacobson, R. (1998). Private communication to the Rigaku Corporation, Tokyo, Japan. Google Scholar
Kelley, J. L., Krochmal, M. P., Linn, J. A., McLean, E. W. & Soroko, F. E. (1988). J. Med. Chem. 31, 1005-1009. CrossRef CAS PubMed Web of Science Google Scholar
Kim, Y. C., Ji, X. D. & Jacobson, K. A. (1996). J. Med. Chem. 39, 4142-4148. CrossRef CAS PubMed Web of Science Google Scholar
Lin, R., Connolly, P., Chiu, G., Yu, Y., Li, S., Emanuel, S. & Greenberger, L. (2007). 234th ACS National Meeting, Boston, August 19–23. Google Scholar
Rigaku (2004). CrystalClear. Rigaku Corporation, Tokyo, Japan. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2003). J. Appl. Cryst. 36, 7–13. Web of Science CrossRef CAS IUCr Journals Google Scholar
Stachlewitz, R. F., Arteel, G. E., Raleigh, J. A., Connor, H. D., Mason, R. P. & Thurman, R. G. J. (1997). J. Pharmacol. Exp. Ther. 282, 1591–1599. CAS PubMed Web of Science Google Scholar
Zocchi, C., Ongini, E., Conti, A., Monopoli, A., Negretti, A., Baraldi, P. G. & Dionisotti, S. (1996). J. Pharmacol. Exp. Ther. 276, 398-404. CAS PubMed Web of Science Google Scholar
This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
Tacrine (9-amino-1,2,3,4-tetrahydroacridine, THA) was the first acetylcholinesterase inhibitor approved for the palliative treatment of Alzheimer's disease (AD) (Gracon et al., 1998). But due to its undesirable side effects, especially its hepatotoxicity, the clinical usefulness is limited (Stachlewitz et al., 1997), and the research on seeking new AChE inhibitors with improved activity and reduced adverse side effects are progressing (Haviv et al., 2005). In view of the considerable biological and medicinal activities of pyrazole ring compounds, such as important adenosine antagonist (Zocchi et al., 1996), antifungals (Kim et al., 1996), plant growth regulators (Erast et al., 1987), anti-tumor agents (Lin et al., 2007), anticonvulsant agents (Kelley et al., 1988), etc. we designed and synthesized the compound 11-phenyl-1,5,6,7,8,9- hexahydrocyclohepta[b]pyrazolo[4,3-e]-pyridin-4-amine (a new Tacrine analogue) (Scheme 1).
In the title compound, the fused pyrazolopyridine moiety is roughly coplanar, with an angle of 1.4° between the pyrazole and the pyridine rings (Fig. 1), The largest deviation from the mean plane being 0.014 (2)Å at C5. Both the C3—N2 [1.345 (3) Å] and the C4—N2 [1.348 (3) Å] bond lengths of pyridine are much shorter than those observed in the pyrazole ring [C3—N3 1.378 (3) Å and N3—N4 1.380 (3) Å], indicating higher aromatic nature of the pyridine ring than the pyrazole. The amino group is sligthly twisted by 1.71 (8)° with respect to the pyrazolopyridine moiety The benzene is also twisted and make a dihedral angle of 14.38 (14)\% with the pyrazolopyridine moiety, The seven-membered ring displays a chair conformation.
There are strong intermolecular N—H···N hydrogen bonds between the amino group and one N atom of the pyrazole ring (Table 1, Fig. 2). The packing is further stabilized by N—H···π(benzene) interactions (Table 1).