January 2012
A New Approach for the Synthesis of Some Pyrazolo[5,1-c]Triazines and
Pyrazolo[1,5-a]pyrimidines Containing Naphtofuran Moiety
121
(56%), 139 (100%), 63 (28.2%); Anal. Calcd. for C17H9N5O2
(315.29), C, 64.76; H, 2.88; N, 22.21. Found: C, 64.82; H,
3.00; N, 22.12.
Benzo[4,5]imidazo[2,1-c][1,2,4]triazin-3-yl-naphtho[2,1-b]
furan-2-yl-methanone (6e). Brown crystals from AcOH, yield
(68%), mp: 254–56ꢀC; IR (KBr): 3128 (CH, aromatic), 1662
(C¼¼O), 1633 (C¼¼N) and 1585 (C¼¼C); MS: m/z ¼ 363
(Mþ1, 35%), 328 (23%), 195 (58%), 139 (100%) and 92
(29%); Anal. Calcd. for C22H12N4O2 (364.36) C, 72.52; H,
3.32; N, 15.38. Found: C, 72.33; H, 3.25; N, 15.53%.
7-(Naphtho[1,2-b]furan-2-yl)-2-phenylpyrazolo[1,5-a]pyrim-
idine (13a), 7-(naphtho[1,2-b]furan-2-yl)-3-phenylpyrazolo
[1,5-a]pyrimidine (13b), 7-(naphtho[1,2-b]furan-2-yl)pyrazolo
[1,5-a]pyrimidine-3-carbonitrile (13c), 5-(naphtho[1,2-b]furan-
2-yl)-[1,2,4]triazolo[4,3-a]pyrimidine (13d), Naphtho[1,2-b]furan-
2-yl-benzo[4,5]imidazo[1,2-a]pyrimidine (13e). Method A. A
solution of (0.01 mol) sodium salt of 5-hydroxy-1-naphtho[2,
1-b]furan-2-ylpropenone (2) (1.3 g, 0.01 mol), the appropriate
of amino pyrazoles, aminotriazole or 2-aminobenzimidazole
(0.01 mol), and piperidine acetate (1 mL) in H2O (3 mL) was
refluxed for 15 min. Acetic acid (1.5 mL) was added to the
hot solution. The solid product was filtered off and recrystal-
lized from the proper solvent.
Method B. A mixture of the appropriate 10a–e (5 mmole),
3-dimethylamino-1-naphtho[2,1-b]furan-2-ylpropenone (7) (1.32
g, 5 mmole), ammonium acetate (0.37 g, 5 mmole) in acetic
acid (30 mL) was reflux for 4 h. The resulting solid which
formed was collected and recrystallized from acetic acid to give
products identical in all aspects mp., mixed mp. And spectra
with the corresponding obtained in method A.
9.00 (d, 1H, pyrimidine H-5); MS: m/z ¼ 286 (Mþ, 100%),
163 (25%), 129 (26%), 88 (36%) and 53 (67%); Anal. Calcd.
for C17H10N4O (286.29) C, 71.32; H, 3.52; N, 19.75. Found:
C, 70.90; H, 3.71; N, 19.92%.
4-Naphtho[2,1-b]furan-2-yl-benzo[4,5]imidazo[1,2-a]pyrimi-
dine (13e). Yellow crystals from dioxan, yield (79%), mp:
239–41ꢀC; IR (KBr): 3051 (CH, aromatic), 1634 (C¼¼N), and
1586 (C¼¼C); 1H NMR (CDCl3): d ¼ 7.52–8.58 (m, 12H,
ArH’s) and 951 (d, 1H, pyrimidine H-4); Anal. Calcd. for
C22H13N3O (335.36) C, 78;79 H, 3.91; N, 12.53. Found: C,
78.59; H, 4.20; N, 12.34%.
1-(2-Methyl-6-(naphtho[2,1-b]furan-2-yl)pyridin-3-yl)etha-
none (19), ethyl 2-methyl-6-(naphtho[2,1-b]furan-2-yl)pyri-
dine-3-carboxylate (20) and 6-(2-amino-6-(naphtho[1,
2-b]furan-2-yl)pyridin-3-yl)(phenyl)methanone (22). A mix-
ture of the appropriate of acetylacetone, ethyl acetoacetate, or
benzoylacetonitrile (5 mmole), 3-dimethylamino-1-naph-
tho[2,1-b]furan-2-ylpropenone (7) (1.32 g, 5 mmole), ammo-
nium acetate (0.37 g, 5 mmole) in acetic acid (30 mL) was
reflux for 4 h. The resulting solid which formed was collected
and recrystallized from ethanol to give 19, 20, and 22.
1-(2-Methyl-6-(naphtho[2,1-b]furan-2-yl)pyridin-3-yl)ethanone
(19). Brown crystals from diluted AcOH, yield (54%), mp:
177–78ꢀC; IR (KBr): 3051 (CH, aromatic), 1682 (C¼¼O conju-
gated), 1636 (C¼¼N), and 1594 (C¼¼C); 1H NMR (CDCl3): d
¼ 2.64 (s, 3H, CH3), 2.89 (s, 3H, CH3), and 7.27–8.26 (m,
9H, ArH’s); MS: m/z ¼ 301 (Mþ, 100%), 286 (53%), 258
(16%), 240 (19%), 202 (22%), 163 (16%); Anal. Calcd. for
C20H15NO2 (301.34) C, 79.72; H, 5.02; N, 4.65. Found: C,
79.63; H, 4.91; N, 4.41%.
7-(Naphtho[2,1-b]furan-2-yl)-2-phenylpyrazolo[1,5-a]pyrimi-
dine (13a). Yellow crystals from AcOH, yield (78%), mp:
252–53ꢀC; IR (KBr): 3043 (CH, aromatic), 1613 (C¼¼N) and
1586 (C¼¼C); 1H NMR (CDCl3): d ¼ 7.09–8.52 (m, 14H,
ArH’s) and 9.11 (s, 1H, ArH); MS: m/z ¼ 361 (Mþ, 84%),
181 (10%), 163 (14%), 77 (100%) and 51 (81%); Anal. Calcd.
for C24H15N3O (361.4) C, 79.76; H, 4.18; N, 11.63. Found: C,
79.72; H, 4.22; N, 11.65%.
Ethyl 2-methyl-5-(naphtho[1,2-b]furan-2-yl)pyridine-3-car-
boxylate (20). Brown crystals from diluted AcOH, yield
(68%), mp: 141–42ꢀC; IR (KBr): 3051 (CH, aromatic), 1716
(C¼¼O), 1640 (C¼¼N) and 1580 (C¼¼C); 1H NMR (CDCl3): d
¼ 1.42 (t, 3H, ACH2CH3), 2.97 (s, 3H, pyridine CH3), 4.39
(q, 2H, ACH2CH3) and 7.27–8.34 (m, 9H, ArH’s); MS: m/z ¼
331 (Mþ, 100%), 303 (68%), 139 (20%), 88 (22%) and 63
(20%); Anal. Calcd. for C21H17NO3 (331.36) C, 76.12; H,
5.17; N, 4.23. Found: C, 76.27; H, 5.24; N, 4.18%.
7-(Naphtho[2,1-b]furan-2-yl)-3-phenylpyrazolo[1,5-a]pyrimi-
dine (13b). Orange crystals from Dioxan, yield (66%), mp:
252–54ꢀC; IR (KBr): 3055 (CH, aromatic), 1614 (C¼¼N) and
(2-Amino-6-(naphtho[1,2-b]furan-2-yl)pyridin-3-yl)(phenyl)
methanone (22). Yellow crystals (diluted acetic acid), mp:
1
1
234–36ꢀC; H NMR (CDCl3): d ¼ 7.29–8.25 (m, 15H, ArH’s)
1585 (C¼¼C); H NMR (dimethyl sulfoxide [DMSO]-d6): d ¼
and 9.49 (s, 1H, pyridine H-6); IR (KBr), (cmꢁ1) ¼ 3483 and
3342 (NH2), 3051 (CH, aromatic), 1664 (C¼¼O amide), and
1585 (C¼¼C); MS, m/z (%) ¼ 364 (Mþ, 57%), 205 (16%), 139
(13%), and 77 (100%); Anal. Calcd. For C24H16N2O2 requires
(364.4): C, 79.11; H, 4.43; N, 7.69. Found: C, 79.33; H, 4.21;
N, 7.75%.
7.50–8.27 (m, 14H, ArH’s) and 9.17 (s, 1H, ArH); MS: m/z ¼
361 (Mþ, 84.5%), 332 (5.2%), 181 (10.2%), 163 (14.5%), 77
(100%), 51 (81.4.2%); Anal. Calcd. for C24H15N3O (361.4) C,
79.76; H, 4.18; N, 11.63. Found: C, 79.61; H, 4.11; N, 11.39%.
7-(Naphtho[2,1-b]furan-2-yl)pyrazolo[1,5-a]pyrimidine-3-car
bonitrile (13c). Orange crystals from Dioxan, yield (54%), mp:
264–66ꢀC; IR (KBr): 3049 (CH, aromatic), 2233 (CN), 1612
(C¼¼N); 1H NMR (CDCl3): d ¼ 6.95 (s, 1H, Pyrazole H-5),
7.35 (s, 1H, furan H-3), 7.58–8.05 (m, 7H, ArH’s, pyrimidine
H-5), 9.48 (d, 1H, J ¼ 8 Hz, pyrimidine H-4), 9.04 (s, 1H,
pyrazole H-5); MS: m/z ¼ 310 (Mþ, 100.5%), 155 (37.5%),
141 (56.3%), 74 (50%), 63 (62.5%); Anal. Calcd. for
C19H10N4O (310.31) C, 73.54; H, 3.25; N, 18.06. Found: C,
73.27; H, 3.34; N, 18.24%.
2-Methyl-6-(naphtho[2,1-b]furan-2-yl)pyridine-3-carbohydra-
zide (23). Equimolar amounts of ethyl 2-methyl-6-naphtho[1,2-
b]furan-2-ylpyridine-3-carboxylate (20) and hydrazine hydrate
(5 mmol for each) in ethanol (10 mL) were refluxed for 5 h.
The resulting solid, was cooled and recrystallized to give 23,
as pale yellow crystals (diluted acetic acid), mp: 258–60ꢀC; IR
(KBr), (cmꢁ1) ¼ 3289 and 3215 (NH2 amide), 1679 (C¼¼O
amide), 1637 (C¼¼N), and 1596 (C¼¼C); MS, m/z (%) ¼ 317
(Mþ, 36%), 286 (100%), 258 (14.6%), 101 (5.8%); Anal.
Calcd. For C19H15N3O2 requires (317.34): C, 71.91; H, 4.76;
N, 13.24. Found: C, 72.07; H, 4.80; N, 13.83%.
7-(Naphtho[2,l-b]furan-2-yl)-[l,2,4]triazolo[4,3-a]pyrimidine
(13d). Yellow crystals from AcOH, yield (75%), mp: 255–
57ꢀC; IR (KBr): 055 (CH, aromatic), 1614 (C¼¼N), and 1584
(C¼¼C); 1H NMR (CDCl3): d ¼ 7.56–8.27 (m, 7H, ArH’s),
8.67 ( s, 1H, triazole H-2), 8.58 (d, 1H, pyrimidine H-4) and
Azido(2-methyl-6-(naphtho[2,1-b]furan-2-yl)pyridin-3-yl)me-
thanone (24). To a stirred solution of 2-methyl-5-(naphtho[l,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet