Synthesis of dipyrazolo[1,5ꢀa,1´,5´ꢀd]pyrazine
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 2, February, 2005
443
C(24)
C(23)
C(22)
C(25)
C(26)
C(21)
N(1)
N(10)
O(9)
N(2)
S(2B)
C(27)
C(9)
C(3A)
C(2)
O(18)
C(32)
C(29)
O(24)
C(3)
C(31)
C(36)
C(35)
C(33)
C(34)
S(1)
C(28)
C(45)
Fig. 1. Molecular structure of compound 10 in the crystal.
5ꢀMethoxycarbonylꢀ6ꢀphenylꢀ2ꢀphenyliminoꢀ6Hꢀ1,3,4ꢀthiaꢀ
diazine (7). A solution of chloropyruvate 1 (2.12 g, 0.01 mol) in
CH2Cl2 (10 mL) was added carefully dropwise to a solution of
4ꢀphenylthiosemicarbazide (1.67 g, 0.01 mol) in CH2Cl2 (30 mL)
under argon at 0 2 °C. The reaction mixture was stirred at this
temperature for 3 h, warmed to ~20 °C, and poured into water.
The organic layer was separated, and the aqueous solution was
extracted with CH2Cl2 (3×15 mL). The organic layer and the
extract were combined and dried with MgSO4. The solvent was
removed, the residue was treated with a 5% aqueous NaHCO3
solution, and the precipitate was filtered off and recrystallized
from MeOH. Compound 7 was obtained in a yield of 2.75 g
(84.6%) as paleꢀyellow crystals, m.p. 209—210 °C. Found (%):
C, 62.70; H, 4.75; N, 12.65; S, 9.97. C17H15N3O2S. Calcuꢀ
a yield of 0.8 g (61%), m.p. >360 °C. Found (%): C, 73.42;
H, 4.05; N, 16.14. C32H22N6O2. Calculated (%): C, 73.57;
H, 4.21; N, 16.09. IR, ν/cm–1: 3250 (br), 1700, 1600, 1550,
1510, 1485, 1380, 1345, 1290, 1250. 1H NMR (CD3OD), δ: 6.95
(br.t, 1 H, H(4´), NPh, J = 7.85 Hz); 7.10—7.58 (m, 9 H, NPh,
CPh); 7.90 (br.s, 1 H, NH). Crystals suitable for Xꢀray diffracꢀ
tion study were prepared by recrystallization from DMSO.
Found (%): C, 57.32; H, 5.81; N, 9.76; S, 15.05. C32H22N6O2•
•4Me2SO. Calculated (%): C, 57.56; H, 5.51; N, 10.07; S, 15.36.
Xꢀray diffraction study of compound 10 was performed on an
automated fourꢀcircle EnrafꢀNonius CADꢀ4 diffractometer. Red
plateletꢀlike crystals are triclinic, C32H22N6O2•4Me2SO, crysꢀ
tal dimensions 0.1×0.2×0.3 mm. At 20 °C, a = 6.142(6) Å, b =
13.392(8) Å, c = 14.4580(10) Å, α = 65.53(2)°, β = 85.34(4)°,
lated (%): C, 62.78; H, 4.61; N, 12.92; S, 9.86. IR, ν/cm–1
:
γ = 87.77(6)°, V = 1079(1) Å3, Z = 1, dcalc = 1.29 g cm–3, space
–
3286 (NH), 1714 (C=O), 1590 (C=N). 1H NMR (DMFꢀd7), δ:
3.80 (s, 3 H, Me); 5.63 (s, 1 H, CH); 6.70 (dd, 1 H, pꢀH (NPh),
J = 7.05 Hz, J = 7.43 Hz); 7.01—7.44 (m, 9 H, Ph, 2 oꢀH,
2 mꢀH (NPh)); 7.63 (br.s, 1 H, N(3)H).
group P1. The unit cell parameters and the intensities of
1514 reflections, of which 1443 reflections were with I ≥ 2σ,
were measured at 20 °C (λ(CuꢀKα), graphite monochromator,
ω/2θ scanning technique, θ < 73.7°). The intensities of three
check reflections showed no decrease in the course of Xꢀray data
collection. The absorption correction was applied (µ(Cu) =
23.98 cm–1). The structure was solved by direct methods using
the SIR program18 and refined first isotropically and then anisoꢀ
tropically using the SHELXLꢀ97 program package.19 Subseꢀ
quently, the position of the H atom at the N(1) atom was reꢀ
vealed from difference electron density maps. The coordinates
of other H atoms were calculated based on stereochemical criteꢀ
ria and refined using a riding model. The final R factors were
R = 0.065, Rw = 0.168 using 1443 reflections with F 2 > 4σ. All
calculations were carried out using the MolEN20 and WinGX21
program packages. The figure was drawn using the PLATON
program.22
6ꢀPhenylꢀ2ꢀphenyliminoꢀ6Hꢀ1,3,4ꢀthiadiazineꢀ5ꢀcarboxylic
acid (8). 1,3,4ꢀThiadiazine 7 (2.9 g, 0.01 mol) was refluxed in
20% hydrochloric acid (25 mL) for 2 h. The hot reaction mixꢀ
ture was filtered and the crystals that precipitated upon cooling
were filtered off and recrystallized from PriOH. Acid 8 was
isolated in a yield of 2.7 g (97%), m.p. 227—229 °C. Found (%):
C, 62.51; H, 4.25; N, 13.65; S, 10.27. C16H13N3O2S. Calcuꢀ
lated (%): C, 61.74; H, 4.18; N, 13.50; S, 10.30. IR, ν/cm–1
:
3380, 3340 (NH); 3060 (C(5)H); 1685 (C=O); 1640 (C=N).
1H NMR (CD3OD), δ: 5.68 (s, 1 H, CH); 7.01—7.45 (m,
10 H, 2 Ph).
3,8ꢀDiphenylꢀ2,7ꢀdiphenyliminoꢀ1H,6Hꢀdipyrazoꢀ
lo[1,5ꢀa,1´,5´ꢀd]pyrazine (10). A mixture of P2O5 (35 g) and
H3PO4 (10 mL) was heated with stirring at 240 °C for 1.5 h.
Then polyphosphoric acid that formed was cooled, and acid 8
(2.05 g, 0.01 mol) was dissolved in polyphosphoric acid with
stirring. The reaction mixture was kept at 100—140 °C for 1.5 h,
cooled, and diluted with water. The crystals that precipitated
were filtered off and dried in air. Compound 10 was obtained in
This study was financially supported by the Russian
Foundation for Basic Research (Project Nos 03ꢀ03ꢀ32865
and 02ꢀ03ꢀ32280) and the Charity Foundation for Supꢀ
port of Russian Science.