TABLE 2. 1H NMR Spectra of the Synthesized Compounds
Com-
pound
Chemical shifts, δ, ppm (J, Hz)
6a
5.58 (1H, d, J = 4.5, H-4, s, after deuterium exchange); 6.13 (1Н, d,
J = 5.7, H-5, undergoes deuterium exchange); 6.45 (1Н, d, J = 7.8, H-6); 6.51 (1H, t,
J = 8.1, H-7); 6.63 (1H, t, J = 7.8, H-8); 6.99 (1Н, d, J = 7.8, H-9); 7.34 (5H, m, CC6H5);
7.47 (1H, t, J = 7.2, NC6H5 H-4); 7.53 and
8.12 (2 × 2Н, two d, J = 8.7, 1,4-C6H4); 7.61 (2H, t, J = 7.5, NC6H5 H-3,5); 7.71 (2H, d,
J = 7.8, NC6H5 H-2,6); 8.24 (1Н, s, H-10, does not undergo deuterium exchange)
6b
(1H, d, J = 3.5, H-4); 6.12 (1Н, d, J = 5.4, H-5); 6.45 (1Н, d, J = 7.5, H-6); 6.51 (1H, t,
J = 7.5, H-7); 6.62 (1H, t, J = 7.2, H-8); 6.98 (1Н, d, J = 7.8, H-9); 7.34 (5H, m, CC6H5);
7.47 (1H, t, J = 7.2, NC6H5 H-4); 7.54 (1H, t, J = 8.4, 1,3-C6H4 H-5); 7.61 (2H, t, J = 7.5,
NC6H5 H-3,5); 7.67-7.72 (3H, m, NC6H5 H-2,6 + 1,3-C6H4 H-6); 8.00 (1H, d, J = 8.7,
1,3-C6H4 H-4); 8.18 (1H, s, 1,3-C6H4 H-2); 8.25 (1Н, s, H-10)
6c
5.47 (1H, d, J = 5.1, H-4); 5.99 (1Н, d, J = 4.8, H-5); 6.45 (1Н, d, J = 7.1, H-6);
6.51 (1H, t, J = 6.9, H-7); 6.62 (1H, t, J = 7.2, H-8); 6.95 (1Н, d, J = 7.8, H-9);
7.29 (5H, m, CC6H5); 7.32-7.36 (4H, m, 1,4-С6H4); 7.46 (1H, t, J = 7.2, NC6H5 H-4);
7.60 (2H, t, J = 7.5, NC6H5 H-3,5); 7.70 (2H, d, J = 7.8, NC6H5 H-2,6); 8.17 (1Н, s, H-10)
6d
5.47 (1H, d, J = 5.1, H-4); 5.93 (1Н, d, J = 5.2, H-5); 6.44 (1Н, d, J = 7.1, H-6);
6.50 (1H, t, J = 7.2, H-7); 6.61 (1H, t, J = 7.2, H-8); 6.93 (1Н, d, J = 7.8, H-9);
7.05 and 7.36 (2 × 2Н, two m, 1,4-C6H4); 7.31 (5H, m, CC6H5); 7.46 (1H, t,
J = 7.2, NC6H5 H-4); 7.60 (2H, t, J = 7.5, NC6H5 H-3,5); 7.70 (2H, d, J = 7.8,
NC6H5 H-2,6); 8.12 (1Н, s, H-10)
6e
6f
5.51 (1H, d, J = 4.8, H-4); 5.94 (1Н, d, J = 4.5, H-5); 6.45 (1Н, d, J = 7.5, H-6);
6.49 (1H, t, J = 7.5, H-7); 6.61 (1H, t, J = 7.2, H-8); 6.97 (1Н, d, J = 7.8, H-9);
7.12-7.16 (2H, m, 3-C5H4N H-4,5); 7.31-7.32 (3H, m, CC6H5 H-3,4,5);
7.39 (2H, m, CC6H5 H-2,6); 7.45 (1H, t, J = 7.2, NC6H5 H-4); 7.60 (3H, t, J = 7.5,
NC6H5 H-3,5 + C5H4N H-6); 7.69 (2H, d, J = 7.5, NC6H5 H-2,6); 8.15 (1Н, s, H-10);
8.51 (1H, s, C5H4N H-3)
5.46 (1H, d, J = 4.8, H-4); 6.08 (1Н, d, J = 5.4, H-5); 6.47 (1Н, d, J = 7.1, H-6);
6.52 (1H, t, J = 6.9, H-7); 6.63 (1H, t, J = 7.2, H-8); 6.96 (1Н, d, J = 7.5, H-9);
7.23 and 8.43 (2 × 2Н, two d, J = 5.4, 4-C5H4N); 7.35 (5H, m, CC6H5); 7.46 (1H, t,
J = 7.2, NC6H5 H-4); 7.60 (2H, t, J = 7.2, NC6H5 H-3,5); 7.70 (2H, d, J = 8.1,
NC6H5 H-2,6); 8.19 (1Н, s, H-10)
practically unaltered integral intensity and this was due to the steric hindrance to the deuterium exchange
process, probably via steric blocking by the neighboring N-phenyl substituent. The structure of compound 6a
was finally proved from HMQC and HMBC two dimensional heteronuclear correlation spectroscopy. The
HMQC spectrum (see Fig. 1) demonstrated the linking of the hydrogen to specific carbon atoms and hence that
two non equivalent hydrogen atoms bonded to nitrogen atoms are introduced into the molecular composition.
Additional verification of the structure came from correlation of the proton interactions with carbon atoms via
single and multiple bonds (Table 3). Analysis of the results obtained confirmed the order of the interacting atoms
in the molecule as present only in structure 6a.
According to data in [5-7] pyrazolo[3,4-b][1,5]benzodiazepines act upon the central nervous system.
Their 1,4,5,10-tetrahydro derivatives not containing a 4-substituent are known and are prepared by reduction of
the corresponding 1,10-dihydro compound [8] using sodium borohydride or the corresponding
pyrazolobenzodiazepin-4-ones [9] using lithium aluminium hydride. Hence the cyclocondensation of
5-(2-aminoanilino)-1,3-diphenylpyrazole with aromatic aldehydes can be regarded as a novel and preparatively
convenient synthesis of pyrazolo[3,4-b][1,5]benzodiazepines giving access to previously unknown compounds.
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