Amino acids in heterocyclic synthesis: Novel synthesis of pyrano[2,3-c]pyrazoles, pyrazolo[3,4-b]pyridine, and pyrido[1,2-a]benzimidazoles

Article abstract of DOI:10.1081/SCC-200030553

The diazolones 1a-c were reacted with triethylorthoformate and hippuric acid derivatives 3 to afford the novel pyrano[2,3-c]pyrazole derivatives 4. The latter undergoes ring cleavage by reaction with acetic acid-ammonium acetate and was transformed into the corresponding pyrazolo[3,4-b]pyridine derivatives 6. The reaction of 2-cyanomethyl-benzimidazole 7 with triethylorthoformate and hippuric acid derivatives 3 to give the pyrido[1,2-a]-benzimidazoles 10 has also been discussed.

Full text of DOI:10.1081/SCC-200030553

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Amino Acids in Heterocyclic
Synthesis: Novel Synthesis
of Pyrano[2,3‐c]pyrazoles,
Pyrazolo[3,4‐b]pyridine, and
Pyrido[1,2‐a]benzimidazoles
Galal H. Elgemeie a , Ahmed H. Elghandour b &
Ahmed M. Hussein b
a Chemistry Department, Faculty of Science,
Helwan University, Helwan, Cairo, Egypt
b Chemistry Department, Faculty of Science, Cairo
University,Bani Suef Branch, Bani Suef, Egypt
Available online: 10 Jan 2011
To cite this article: Galal H. Elgemeie, Ahmed H. Elghandour & Ahmed M.
Hussein (2004): Amino Acids in Heterocyclic Synthesis: Novel Synthesis of
Pyrano[2,3‐c]pyrazoles, Pyrazolo[3,4‐b]pyridine, and Pyrido[1,2‐a]benzimidazoles,
Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 34:18, 3293-3302
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SYNTHETIC COMMUNICATIONSw
Vol. 34, No. 18, pp. 3293–3302, 2004
Amino Acids in Heterocyclic Synthesis:
Novel Synthesis of Pyrano[2,3-c]pyrazoles,
Pyrazolo[3,4-b]pyridine, and
Pyrido[1,2-a]benzimidazoles
2
Galal H. Elgemeie,1, Ahmed H. Elghandour, and
*
Ahmed M. Hussein2
1Chemistry Department, Faculty of Science
Helwan University, Helwan, Cairo, Egypt
2Chemistry Department, Faculty of Science, Cairo University,
Bani Suef Branch, Bani Suef, Egypt
ABSTRACT
The diazolones 1a–c were reacted with triethylorthoformate and
hippuric acid derivatives 3 to afford the novel pyrano[2,3-c]pyrazole
derivatives 4. The latter undergoes ring cleavage by reaction with
acetic acid-ammonium acetate and was transformed into the corre-
sponding pyrazolo[3,4-b]pyridine derivatives 6. The reaction of 2-cyano-
methyl-benzimidazole 7 with triethylorthoformate and hippuric acid
*
Correspondence: Galal H. Elgemeie, Chemistry Department, Faculty of Science,
Helwan University, Helwan, Cairo, Egypt; E-mail: elgemeie@hotmail.com.
3293
DOI: 10.1081/SCC-200030553
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

3294
Elgemeie, Elghandour, and Hussein
derivatives 3 to give the pyrido[1,2-a]-benzimidazoles 10 has also
been discussed.
Key Words: Pyrano[2,3-c]pyrazole; Triethylorthoformate; Hippuric
acid; Pyrido[1,2-a]-benzimidazoles; 2-Cyanomethyl-benzimidazole.
As part of a program aimed at developing new, efficient procedures for the
synthesis of azoles and fused azoles using readily available materials,[1,2] we
have previously reported that cinnamonitriles react with azolones and amino-
azoles to yield pyranoazoles and pyridoazoles in excellent yields.[3–5] In con-
junction with this work, we report here a novel synthesis of pyrano
[2,3-c]pyrazoles, pyrazolo[3,4-b]pyridines, and pyrido[1,2-a]benzimidazoles
utilizing the reactions of diazolones with hippuric acid derivatives and triethyl
orthoformate. Thus, it has been found that 3-methylpyrazolin-5-one 1a and
3-aminopyrazolin-5-one 1b react with triethyl orthoformate and hippuric
acid derivatives 3 in refluxing acetic anhydride in a one-pot reaction to
yield the novel 1-acetylpyrano[2,3-c]pyrazoles 4a–h. The structures of 4
have been established on the basis of their elemental analysis and spectral
data (mass spectrum (MS), infrared (IR), proton nuclear magnetic resonance
(1H NMR)). Thus, structure 4a is supported by its mass spectrum, which
showed a molecular formula C16H13N3O4 (Mþ 311), and 1H NMR spectrum,
which contained two signals at d ¼ 2.63 and 2.70 ppm. These signals are
assignable to two methyl groups, a pyran ring CH at d ¼ 8.44 ppm and a
singlet at d ¼ 9.64 ppm, assignable to an NH group. The formation of 4 is
assumed to take place via the intermediate 2, which cyclizes via Michael
addition of the methylene moiety in 3 to the double bond in 2, followed by
ethanol elimination and acetylation of the ring nitrogen. When 4 is refluxed
with acetic acid in the presence of ammonium acetate, its pyran ring under-
goes acid-catalyzed ring opening to afford the acyclic structure 5a–h. The
structures of 5 have been established on the basis of their elemental analysis
1
and spectral data (MS, IR, H NMR). Thus, structure 5a is supported by its
mass spectrum, which showed a molecular formula C16H16N4O4 (Mþ 328)
1
and H NMR spectrum contained two signals at d ¼ 2.34 and 3.42 ppm,
which are assignable to two methyl groups, an olefinic CH at d ¼ 7.40 ppm
and three broad singlets at d ¼ 7.89, 8.88, and 12.79 ppm, assignable to an
NH2, NH, and OH groups, respectively. Refluxing of the acyclic compounds
5 in acetic anhydride gave the corresponding pyrazolo[3,4-b]pyridines 6. The
structures of 6 have been established on the basis of their elemental analysis
1
and spectral data (MS, IR, H NMR). Thus, structure 6c is supported by its
mass spectrum, which showed a molecular formula C17H16N4O4 (Mþ 340)
1
and H NMR spectrum contained a pyridine ring CH at d ¼ 7.27 ppm and a
singlet at d ¼ 8.69 ppm, assignable to an NH group. Compounds 6 can also

Amino Acids in Heterocyclic Synthesis
3295
be prepared when compounds 4 were heated with ammonium acetate at
1608C–1708C (bath temperature). The formation of 6 from refluxing of 4
with acetic anhydride is assumed to proceed via pyran ring opening in 4 fol-
lowed by recyclization. Similarly, 1-phenyl-3-methylpyrazolin-5-one 1c
reacts with triethyl orthoformate and hippuric acid derivatives 3 in acetic
anhydride to yield the novel 1-phenylpyrano[2,3-c]-pyrazoles 4i–l. In order
to investigate the scope of this reaction further and to prove that this type of
reaction can be extended to constitute a general approach for the synthesis
of pyrano- and pyidodiazoles, we studied the reaction of 2-cyanobenzimida-
zole 7 with triethyl orthoformate and hippuric acid derivatives under the
same conditions. Thus, it has been found that 7 reacts with triethyl orthofor-
mate and hippuric acid derivatives 3 in refluxing acetic anhydride to afford
the novel pyrido[1,2-a]benzimidazole derivatives 10. The structures of 10
have been established on the basis of their elemental analysis and spectral
1
data (MS, IR, H NMR). Thus, structure 10a is supported by its mass spec-
1
trum, which showed a molecular formula C19H12N4O2 (Mþ 328) and H
NMR spectrum contained a pyridine ring CH at d ¼ 8.34 ppm, a multiplet
at d ¼ 7.40–8.66 ppm assigned for aromatic protons, and two singlets at
d ¼ 9.60 and 13.92 ppm, assignable to NH and OH groups. The formation
of 10 is assumed to take place via the intermediates 8 then 9. The latter
cyclizes via water elimination to yield the pyrido[1,2-a]benzimidazole deriva-
tives 10.
EXPERIMENTAL
5,7-Disubstituted-3-aroylaminopyrano[2,3-c]
pyrazole-2-ones (4a–l)
General Procedure
A mixture of 3-substituted pyrazolin-5-one derivatives 1a–c (0.01 mole)
and the equivalent amounts of triethylorthoformate and hippuric acid deriva-
tives 3a–d was gently heated in acetic anhydride (30 mL) for 10–30 min. The
solvent was evaporated over a water bath and the product was collected by
filtration and recrystallized from the proper solvent.
4a: Yellow, from ethanol, m.p. 2608C, yield 85%; nmax/cm21 (KBr) 3395
(NH), 1726 (CO); 1H NMR: 2.63 (s, 3H, CH3), 3.70 (s, 3H, OCH3), 7.51–7.93
(m, 5H, C6H5), 8.44 (s, 1H, CH), 9.64 (s, 1H, NH); m/z (311); found: C, 62.0;
H, 3.8; N, 13.1%; calcd. for C16H13N3O4 (311): C, 61.73; H, 4.18; N, 13.50%.
4b: Yellow, from ethanol, m.p. 2658C, yield 82%; nmax/cm21 (KBr) 3407

3296
Elgemeie, Elghandour, and Hussein
Chart 1.
(NH), 1734 (CO); found: C, 62.4; H, 4.1; N, 13.2%; m/z (325); calcd. for
C17H15N3O4 (325): C, 62.76; H, 4.61; N, 12.92%. 4c: Yellow, from
ethanol, m.p. 2678C, yield 80%; nmax/cm21 (KBr) 3385 (NH), 1713 (CO);
m/z (341); found: C, 60.2; H, 3.9; N, 12.8%; calcd. for C17H15N3O5 (341):
C, 59.82; H, 4.39; N, 12.31%. 4d: Yellow, from ethanol, m.p. 2588C, yield

Amino Acids in Heterocyclic Synthesis
3297
Chart 2.
91%; nmax/cm21 (KBr) 3396 (NH), 1716 (CO); found: C, 56.1; H, 3.4; N,
12.2%; calcd. for C16H12N3O4Cl (345.5): C, 55.57; H, 3.47; N, 12.15%. 4e:
Brown, from ethanol, m.p. 2558C, yield 78.5%; nmax/cm21 (KBr) 3547,
1
3275 (NH, NH2), 1791, 1705 (2CO); H NMR: 2.57 (s, 3H, CH3), 6.99
(s, 2H, NH2), 7.55–8.05 (m, 5H, C6H5), 8.64 (s, 1H, CH), 12.66 (s, 1H,
NH); m/z (312); found: C, 58.1; H, 3.6; N, 18.0%; calcd. for C15H12N4O4
(312): C, 57.69; H, 3.84; N, 17.94%. 4f: Brown, from ethanol, m.p. 2628C,
yield 75%; nmax/cm21 (KBr) 3485, 3258 (NH, NH2), 1725 (CO); m/z
(326); found: C, 59.0; H, 4.4; N, 16.6%; calcd. for C16H14N4O4 (326): C,
58.89; H, 4.29; N, 17.17%. 4g: Brown, from ethanol, m.p. 2768C, yield
80%; nmax/cm21 (KBr) 3496, 3244 (NH, NH2), 1763.4 (CO); found: C,

3298
Elgemeie, Elghandour, and Hussein
Chart 3.
56.5; H, 3.8; N, 16.2%; calcd. for C16H14N4O5 (342): C, 56.14; H, 4.09; N,
16.37%. 4h: Brown, from ethanol, m.p. 2378C, yield 90%; nmax/cm21
(KBr) 3423, 3301 (NH, NH2), 1735 (CO); H NMR: 2.53 (s, 3H, OCH3);
1
7.06 (s, 2H, NH2), 7.58–8.04 (m, 4H, C6H4), 8.07 (s, 1H, CH), 12.12 (s, 1H,
NH); found: C, 516; H, 3.2; N, 16.0%; calcd. for C15H11N4O4Cl (346.5): C,
51.94; H, 3.17; N, 16.16%. 4i: Yellow, from ethanol, m.p. 1608C, yield
91%; nmax/cm21 (KBr) 3390 (NH), 1779, 1722 (2CO); 1H NMR: 2.44
(s, 3H, CH3); 7.56–8.00 (m, 10H, 2C6H5), 8.45 (s, 1H, CH), 9.77 (s, 1H,
NH); m/z (345); found: C, 59.5; H, 4.1; N, 12.4%; calcd. for C20H15N3O3

Amino Acids in Heterocyclic Synthesis
3299
(345): C, 59.56; H, 4.34; N, 12.17%. 4j: Yellow, from ethanol, m.p. 1688C,
yield 89%; nmax/cm21 (KBr) 3401 (NH), 1779 (CO); found: C, 69.8; H,
4.3; N, 11.7%; calcd. for C21H17N3O3 (359): C, 70.19; H, 4.73; N, 11.69%.
4k: Orange, from ethanol, m.p. 1658C, yield 95%; nmax/cm21 (KBr) 3416
1
(NH), 1776 (CO); H NMR: 2.34 (s, 3H, CH3), 3.89 (s, 3H, OCH3), 6.99–
7.93 (m, 9H, C6H5, C6H4); 7.47 (s, 1H, CH); 15.9 (s, 1H, NH); found: C,
66.9; H, 4.2; N, 11.8%; calcd. for C21H17N3O4 (375): C, 67.20; H, 4.53; N,
11.20%. 4l: Pale yellow, from ethanol, m.p. 1588C, yield 94%; nmax/cm21
1
(KBr) 3420 (NH), 1784, 1731 (CO); H NMR: 2.37 (s, 3H, CH3); 7.23–
7.93 (m, 9H, C6H5, C6H4); 8.51 (s, 1H, CH); 8.90 (s, 1H, NH); found: C,
63.0; H, 3.9; N, 11.2%; calcd. for C20H14N3O3Cl (379.5): C, 63.24; H,
3.68; N, 11.06%.
3-(1,3-Disubstituted-5-aminopyrazol-4-yl)-
2-aroylaminopropionic Acid (5a–l)
The performed pyrano[2,3-c]pyrazole derivatives 4a–l were refluxed in
acetic acid containing the appropriate amount of ammonium acetate for
6 hr. The reaction mixture was poured into cold water and the product was
collected by filtration and recrystallized from ethanol.
5a: Yellow, from ethanol, m.p. 1958C, yield 62%; nmax/cm21 (KBr)
1
3655–3066 (OH), 1620.4 (CO); H NMR: 2.34 (s, 3H, CH3), 3.42 (s, 3H,
OCH3), 7.40 (s, 1H, CH), 7.31–7.49 (m, 5H, C6H5), 7.89 (s, 2H, NH2),
8.88 (s, 1H, NH), 12.78 (s, 1H, OH); m/z (328); found: C, 58.3; H, 4.9; N,
17.3%; calcd. for C16H16N4O4 (328): C, 58.53; H, 4.87; N, 17.07%. 5b:
Brown, from ethanol, m.p. 2038C, yield 66%; nmax/cm21 (KBr) 3453–2835
(OH), 1680.9 (CO); m/z (342); found: C, 58.9; H, 5.6; N, 16.4%; calcd. for
C17H18N4O4 (342): C, 59.64; H, 5.26; N, 16.37%. 5c: Red, from ethanol,
m.p. 1898C, yield 52%; nmax/cm21 (KBr) 3463–2951 (OH), 1711.0 (CO);
found: C, 56.4; H, 5.4; N, 15.1%; calcd. for C17H18N4O5 (358): C, 56.98;
H, 5.02; N, 15.64%. 5d: Brown, from ethanol, m.p. 1778C, yield 65%;
nmax/cm21 (KBr) 3439–2846 (OH), 1689 (CO); found: C, 53.1; H, 4.1; N,
15.5%; calcd. for C16H15N4O4Cl (362.5): C, 52.96; H, 4.14; N, 15.45%. 5e:
Yellow, from ethanol, m.p. 2648C, yield 68%; nmax/cm21 (KBr) 3455–
1
2842 (OH), 1679.3 (CO); H NMR: 2.51 (s, 3H, CH3), 4.98 (s, 2H, NH2),
7.23–7.52 (m, 5H, C6H5), 7.41 (s, 1H, CH), 7.55 (s, 2H, NH2), 7.94 (s, 1H,
NH), 11.25 (s, 1H, OH); found: C, 54.2; H, 4.9; N, 21.0%; calcd. for
C15H15N5O4 (329): C, 54.71; H, 4.56; N, 21.27%. 5f: Yellow, from ethanol,
m.p. 2608C, yield 70%; nmax/cm21 (KBr) 3425–3001 (OH), 1710.2 (CO);
found: C, 56.1; H, 4.6; N, 20.8%; calcd. for C16H17N5O4 (343): C, 55.97;
H, 4.95; N, 20.40%. 5g: Brown, from ethanol, m.p. 2668C, yield 57%;

3300
Elgemeie, Elghandour, and Hussein
nmax/cm21 (KBr) 3510–3110 (OH), 1698 (CO); found: C, 53.8; H, 4.3; N,
19.2%; calcd. for C16H17N5O5 (359): C, 53.48; H, 4.73; N, 19.49%. 5h:
Yellow, from ethanol, m.p. 2468C, yield 69%; nmax/cm21 (KBr) 3488–
3102 (OH), 1694 (CO); m/z (363); found: C, 58.9; H, 5.6; N, 16.4%; calcd.
for C15H14N5O4Cl (363.5): C, 49.52; H, 3.85; N, 19.25%. 5i: Brown, from
ethanol, m.p. 1818C, yield 72%; nmax/cm21 (KBr) 3496–3103 (OH),
1
1712.7 (CO); H NMR: 2.35 (s, 3H, CH3), 7.22–7.48 (m, 10H, 2C6H5),
7.44 (s, 1H, CH), 7.89 (s, 2H, NH2), 7.93 (s, 1H, NH), 12.14 (s, 1H, OH);
m/z (362); found: C, 66.6; H, 5.1; N, 15.4%; calcd. for C20H18N4O3 (362):
C, 66.29; H, 4.97; N, 15.47%. 5j: Yellow, from ethanol, m.p. 1928C, yield
78%; nmax/cm21 (KBr) 3420–3006 (OH), 1697.7 (CO); m/z (376); found:
C, 67.3; H, 4.9; N, 15.0%; calcd. for C21H20N4O3 (376): C, 67.02; H,
5.31; N, 14.89%. 5k: Pale yellow, from ethanol, m.p. 1868C, yield 75%;
nmax/cm21 (KBr) 3413–3111 (OH), 1689.0 (CO); found: C, 64.0; H, 5.0;
N, 14.4%; calcd. for C21H20N4O4 (392): C, 64.28; H, 5.10; N, 14.28%. 5l:
Yellow, from ethanol, m.p. 1788C, yield 71%; nmax/cm21 (KBr) 3460–
2877 (OH), 1702.6 (CO); found: C, 60.2; H, 4.5; N, 16.6%; calcd. for
C20H17N4O3 Cl (396.5): C, 60.52; H, 4.28; N, 14.12%.
1,3-Disubstituted-5-aroylamino-(7H)-pyrazolo[3,4-b]
pyridin-6-ones (6a–l)
Method A
Compounds 5a–l (0.01 mole) were refluxed in acetic anhydride (30 mL)
for 1 hr. The solvent was distilled off over a water bath and the solid product
was collected by filtration and recrystallized from DMF.
Method B
The pyrano[2,3-c]pyrazole derivatives 4a–l (0.01 mole) were fused with
ammonium acetate (0.015 mole) at 1608C–1708C for 1–2 hr. The reaction
mixture was poured over water and the product was filtered off and recrystal-
lized from DMF.
6a: Red, from DMF, m.p. . 3008C, yield 91%; nmax/cm21 (KBr) 3442
(NH), 1675 (CO); m/z (310); found: C, 61.6; H, 4.8; N, 17.9%; calcd. for
C16H14N4O3 (310): C, 61.93; H, 4.52; N, 18.06%. 6b: Red, from DMF,
m.p. . 3008C, yield 82%; nmax/cm21 (KBr) 3462 (NH), 1688 (CO); found:
C, 62.8; H, 5.1; N, 16.9%; calcd. for C17H16N4O3 (324): C, 62.96; H, 4.93;
N, 17.28%. 6c: Brown, from DMF, m.p. . 3008C, yield 80%; nmax/cm21
1
(KBr) 3444 (NH), 1696 (CO); H NMR: 2.69 (s, 3H, CH3), 2.73 (s, 3H,

Amino Acids in Heterocyclic Synthesis
3301
OCH3), 3.88 (s, 3H, COCH3), 6.97–7.87 (m, 4H, C6H4), 7.27 (s, 1H, CH),
8.64 (s, 1H, NH), 8.69 (s, 1H, NH); found: C, 60.8; H, 5.1; N, 16.9%;
calcd. for C17H16N4O4 (340): C, 60.00; H, 4.71; N, 16.47%. 6d: Red, from
dimethyl formamide (DMF), m.p. . 3008C, yield 88%; nmax/cm21 (KBr)
1
3475 (NH), 1663 (CO); H NMR: 2.28 (s, 3H, CH3), 2.55 (s, 3H, COCH3),
7.16 (s, 1H, CH), 7.26–7.52 (m, 4H, C6H4), 7.82 (s, 1H, NH), 7.94 (s, 1H,
NH); found: C, 55.6; H, 3.2; N, 16.6%; calcd. for C16H13N4O3Cl (344.5):
C, 55.73; H, 3.77; N, 16.25%. 6e: Red, from DMF, m.p. . 3008C, yield
61%; nmax/cm21 (KBr) 3468–3325 (NH, NH2), 1708 (CO); m/z (311);
found: C, 58.0; H, 4.1; N, 22.3%; calcd. for C15H13N5O3 (311): C, 57.87;
H, 4.18; N, 22.51%. 6f: Red, from DMF, m.p. . 3008C, yield 81%; nmax
/
cm21 (KBr) 3440–3348 (NH, NH2), 1698.5 (CO); found: C, 58.7; H, 4.8;
N, 21.5%; calcd. for C16H15N5O3 (325): C, 59.07; H, 4.62; N, 21.54%. 6g:
Red, from DMF, m.p. . 3008C, yield 77%; nmax/cm21 (KBr) 3511–3342
(NH, NH2), 1698.5 (CO); found: C, 56.8; H, 4.6; N, 19.8%; calcd. for
C16H15N5O4 (341): C, 56.30; H, 4.39; N, 20.53%. 6h: Brown, from DMF,
m.p. . 3008C, yield 87%; nmax/cm21 (KBr) 3481–3299 (NH, NH2), 1679
(CO); found: C, 52.7; H, 3.6; N, 20.1%; calcd. for C15H12N5O3Cl (345.5):
C, 52.09; H, 3.47; N, 20.26%. 6i: Red, from DMF, m.p. . 3008C, yield
94%; nmax/cm21 (KBr) 3449 (NH), 1678 (CO); found: C, 70.1; H, 4.8; N,
16.1%; calcd. for C20H16N4O2 (344): C, 69.76; H, 4.65; N, 16.27%. 6j:
Red, from DMF, m.p. . 3008C, yield 90%; nmax/cm21 (KBr) 3448.5 (NH),
1
1685.0 (CO); H NMR: 2.26 (s, 3H, CH3), 2.39 (s, 3H, CH3), 7.11 (s, 1H,
CH), 7.23–7.97 (m, 9H, C6H4, C6H5), 13.05 (s, 1H, NH); m/z (358);
found: C, 69.9; H, 5.1; N, 15.3%; calcd. for C21H18N4O2 (358): C, 70.39;
H, 5.07; N, 15.64%. 6k: Red, from DMF, m.p. . 3008C, yield 88%; nmax
/
cm21 (KBr) 3451 (NH), 1677 (CO); found: C, 67.0; H, 4.8; N, 15.1%;
calcd. for C21H18N4O3 (374): C, 67.37; H, 4.81; N, 14.97%. 6l: Red, from
DMF, m.p. . 3008C, yield 96%; m/z (378); found: C, 63.8; H, 3.6; N,
14.9%; calcd. for C20H15N4O2Cl (378.5): C, 63.40; H, 3.96; N, 14.79%.
2-Hydroxy-3-aroylamino-5-cyanopyrido
[1,2-a]benzimidazoles (10a–d)
General Procedure
A mixture of 2-cyanomethylbenzimidazole 7 (0.01 mole), triethylortho-
formate (0.01 mole), and hippuric acid derivatives 3 (0.01 mole) was heated
gently in acetic anhydride (30 mL) for 10 min. The precipitated product was
collected by filtration and recrystallized from the appropriate solvent.

3302
Elgemeie, Elghandour, and Hussein
10a: Yellow, from ethanol-DMF, m.p. . 3008C, yield 84%; nmax/cm21
1
(KBr) 3391 (NH), 3168 (OH), 2212 (CN); 1662 (CO); H NMR: 7.40–8.66
(m, 9H, C6H4, C6H5), 8.34 (s, 1H, CH), 9.60 (s, 1H, NH), 13.92 (s, 1H,
OH); m/z (328); found: C, 69.2; H, 3.2; N, 17.3%; calcd. for C19H12N4O2
(328): C, 69.51; H, 3.66; N, 17.07%. 10b: Yellow, from ethanol-DMF,
m.p. . 3008C, yield 88%; nmax/cm21 (KBr) 3388 (NH), 3177 (OH), 2213
1
(CN); 1681 (CO); H NMR: 2.22 (s, 3H, CH3), 7.23–7.54 (m, 8H, 2C6H4);
12.79 (s, 1H, OH); found: C, 70.4; H, 3.9; N, 16.5%; calcd. for
C20H14N4O2 (342): C, 70.17; H, 4.09; N, 16.37%. 10c: Colorless, from
ethanol, m.p. . 3008C, yield 86%; nmax/cm21 (KBr) 3390 (NH), 3210
(OH), 2216 (CN); found: C, 67.0; H, 3.7; N, 15.9%; calcd. for C20H14N4O3
(358): C, 67.04; H, 3.91; N, 15.64%. 10d: Yellow, from ethanol-DMF,
m.p. . 3008C, yield 91%; nmax/cm21 (KBr) 3391 (NH), 3196 (OH), 2221
(CN); found: C, 63.0; H, 3.1; N, 14.9%; calcd. for C19H11N4O2Cl (362.5):
C, 62.89; H, 3.03; N, 15.45%.
REFERENCES
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Received in the UK July 2, 2002