Helvetica Chimica Acta – Vol. 96 (2013)
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1608m, 1513m, 1466m, 1364m, 1252s, 1132w, 1012w, 823m, 674m, 559m. 1H-NMR ((D6)DMSO): 2.37 (s,
Me); 3.47 (s, MeO); 7.29, 7.36 (AB, JAB ¼ 7.9, 4 arom. H); 12.83, 14.11 (2 br. s, 2 NH). 13C-NMR
((D6)DMSO): 21.2 (Me); 53.3 (MeO); 115.0 (CN); 128.5, 129.7 (4 arom. CH); 100.0, 125.1, 140.0, 141.6,
146.3, 150.2 (6 signals for 7 sp2 C); 160.2 (br.), 163.7 (2 C¼O). HR-ESI-MS: 331.08008 ([M þ Na]þ,
C16H12N4NaOþ3 ; calc. 331.08016).
Dimethyl 7-Amino-2-(4-methylphenyl)pyrazolo[1,5-a]pyrimidine-5,6-dicarboxylate (11a). Yield:
32 mg (10%; Method A). Colorless crystals. M.p. 258 – 2608 (hexane/CH2Cl2). IR (KBr): 3415s (br.,
NH), 3314s (NH2), 2951w, 1755s (C¼O), 1684s (C¼O), 1632s , 1611m, 1591s, 1570m, 1539w, 1453m,
1437m, 1326s, 1313m, 1241s, 1213m, 1092w, 1029w, 802s, 621m. 1H-NMR (CDCl3): 2.40 (s, Me); 3.89, 3.97
(2s, 2 MeO); 6.83 (s, HꢀC(3)); 7.18 (br. s, NH); 7.27, 7.85 (AB, JAB ¼ 8.0, 4 arom. H); 8.58 (br. s, NH).
13C-NMR (CDCl3): 21.4 (Me); 52.3, 52.9 (2 MeO); 95.9 (C(3)); 126.6, 129.5 (4 arom. CH); 88.7, 129.1,
139.8, 147.9, 149.4, 152.4, 158.1 (7 signals for 7 sp2 C); 165.9, 166.8 (2 C¼O). HR-ESI-MS: 363.10674
([M þ Na]þ, C17H16N4NaOþ4 ; calc. 363.10638).
Ethyl 5-Cyano-6,7-dihydro-3-(4-methylphenyl)-6-oxo-1H-pyrazolo[3,4-b]pyridine-4-carboxylate
(10b). Yield: 260 mg (81%; Method A), and 295 mg (91%; Method B). Yellowish powder. M.p. 290 –
2948 (dec., MeOH). IR (KBr): 3382 – 2803vs (br., NH), 2228m (CN), 1739s (C¼O), 1663vs (br.,
1
C¼O), 1617m, 1512s, 1467s, 1375m, 1352w, 1243vs, 1188m, 1018m, 823m, 719w, 683w, 557m. H-NMR
((D6)DMSO): 0.89 (t, J ¼ 7.2, MeCH2); 2.37 (s, MeCAr); 3.95 (q, J ¼ 7.2, MeCH2); 7.18, 7.36 (AB, JAB ¼ 8.0,
4 arom. H); 12.82, 14.13 (2 br. s, 2 NH). 13C-NMR ((D6)DMSO): 13.2 (MeCH2); 21.1 (MeCAr); 63.0
(MeCH2); 114.8 (CN); 128.4, 129.2 (4 arom. CH); 99.2, 124.9, 140.0, 141.3, 146.5, 150.4 (6 signals for 7 sp2
C); 159.9 (br.), 163.0 (2 C¼O). HR-ESI-MS: 345.09599 ([M þ Na]þ, C17H14N4NaO3þ ; calc. 345.09581).
Diethyl 7-Amino-2-(4-methylphenyl)pyrazolo[1,5-a]pyrimidine-5,6-dicarboxylate (11b). Yield:
50 mg (13%; Method A). Colorless crystals. M.p. 218 – 2208 (hexane/CH2Cl2). IR (KBr): 3382s (br.,
NH), 3287s (br., NH2), 2987w, 2975w, 1741s (C¼O), 1683s (C¼O), 1635s, 1595s, 1569m, 1540w, 1453w,
1
1393w, 1318s, 1236vs, 1213m, 1087m, 1025w, 799m. H-NMR (CDCl3): 1.35, 1.43 (2t, J ¼ 7.2, 2 MeCH2);
2.40 (s, MeCAr); 4.35, 4.43 (2q, J ¼ 7.2, 2 MeCH2); 6.83 (s, HꢀC(3)); 7.19 (br. s, NH); 7.28, 7.86 (AB, JAB
¼
8.1, 4 arom. H); 8.70 (br. s, NH). 13C-NMR (CDCl3): 14.0, 14.1 (2 MeCH2); 21.3 (MeCAr); 61.4, 62.1 (2
MeCH2); 95.6 (C(3)); 126.5, 129.5 (4 arom. CH); 87.8, 129.1, 139.7, 147.9, 149.5, 152.6, 157.9 (7 signals for
7 sp2 C); 165.7, 166.4 (2 C¼O). HR-ESI-MS: 391.13812 ([M þ Na]þ, C19H20N4NaOþ4 ; calc. 391.13768).
1-Methylethyl 5-Cyano-6,7-dihydro-3-(4-methylphenyl)-6-oxo-1H-pyrazolo[3,4-b]pyridine-4-car-
boxylate (10c). Yield: 222 mg (66%; Method A) and 260 mg (77%; Method B). Yellow powder. M.p.
254 – 2578 (dec., MeOH). IR (KBr): 3439 – 2750vs (br., NH), 2230m (CN), 1734s (C¼O), 1661vs (br.,
C¼O), 1620m, 1513m, 1466m, 1375m, 1249s, 1102m, 1006m, 847w, 823m, 683w, 557w. 1H-NMR
((D6)DMSO): 1.01 (d, J ¼ 6.6, Me2CH); 2.37 (s, MeCAr); 4.80 – 4.82 (m, Me2CH); 7.32 – 7.35 (m, 4 arom.
H); 12.81, 14.12 (2 br. s, 2 NH). 13C NMR ((D6)DMSO): 20.8 (Me2CH); 21.1 (MeCAr); 71.6 (Me2CH);
114.8 (CN); 128.5, 129.5 (4 arom. CH); 99.3, 124.8, 140.1, 141.5, 146.9, 150.4 (6 signals for 7 sp2 C); 160.0
(br.), 162.9 (2 C¼O). HR-ESI-MS: 359.11123 ([M þ Na]þ, C18H16N4NaO3þ ; calc. 359.11146).
Bis(1-methylethyl) 7-Amino-2-(4-methylphenyl)pyrazolo[1,5-a]pyrimidine-5,6-dicarboxylate (11c).
Yield: 41 mg (10%; Method A). Colorless crystals. M.p. 162 – 1648 (hexane/CH2Cl2). IR (KBr): 3420m
(br., NH), 3315m (br., NH2), 2980m, 2934w, 1738s (C¼O), 1677vs (C¼O), 1614m, 1593vs, 1571m, 1455m,
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1372m, 1334m, 1313m, 1244s, 1214m, 1166m, 1105s, 1019m, 798m. H-NMR (CDCl3): 1.36 (d, J ¼ 6.0,
Me2CH); 1.44 (d, J ¼ 6.6, Me2CH); 2.40 (s, MeCAr); 5.23 – 5.28 (m, 2 Me2CH); 6.84 (s, HꢀC(3)); 7.18 (br.
s, NH); 7.28, 7.86 (AB, JAB ¼ 7.9, 4 arom. H); 8.71 (br. s, NH). 13C-NMR (CDCl3): 21.4 (MeCAr); 21.7, 21.8
(2 Me2CH); 69.6, 70.0 (2 Me2CH); 95.5 (C(3)); 126.5, 129.5 (4 arom. CH); 88.1, 129.2, 139.6, 147.9, 149.5,
152.9, 157.8 (7 signals for 7 sp2 C); 165.3, 165.9 (2 C¼O). HR-ESI-MS: 419.16950 ([M þ Na]þ,
C21H24N4NaOþ4 ; calc. 419.16898).
Methyl 5-Cyano-6,7-dihydro-6-oxo-3-phenyl-1H-pyrazolo[3,4-b]pyridine-4-carboxylate (10d).
Yield: 157 mg (53%; Method A) and 265 mg (90%; Method B). Yellowish powder. M.p. 324 – 3308
(dec., MeOH). IR (KBr): 3367 – 2795vs (br., NH), 2226m (CN), 1746s (C¼O), 1659vs (br., C¼O),
1618m, 1545m, 1511s, 1466s, 1365m, 1247vs, 1138w, 1026s, 866m, 763m, 701m, 669m, 561m. 1H-NMR
((D6)DMSO): 3.42 (s, MeO); 7.35 – 7.45 (m, 2 arom. H); 7.50 – 7.60 (m, 3 arom. H); 12.82, 14.12 (2 br. s,
2 NH). 13C-NMR ((D6)DMSO): 53.1 (MeO); 114.8 (CN); 128.5, 129.0, 129.9 (5 arom. CH); 100.2, 142.1,