First report on the abnormal dearylation/alkylation reaction in one-pot hantzch synthesis with 6-amino-1,3-dimethyl uracil

Article abstract of DOI:10.1081/SCC-200043171

First report on the abnormal dearylation/dealkylation reaction occurring during dehydrogenation in one-pot, three-component condensation of dihydropyrido[2,3-d]pyrimidines.

Full text of DOI:10.1081/SCC-200043171

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First Report on the Abnormal
Dearylation/Alkylation
Reaction in One‐Pot
Hantzch Synthesis with
6‐Amino‐1,3‐Dimethyl Uracil
Anu Agarwal a & Prem M. S. Chauhan a
a Medicinal and Process Chemistry Division,
Central Drug Research Institute, Lucknow, 226001,
India
Published online: 10 Jan 2011.
To cite this article: Anu Agarwal & Prem M. S. Chauhan (2004): First Report on
the Abnormal Dearylation/Alkylation Reaction in One‐Pot Hantzch Synthesis with
6‐Amino‐1,3‐Dimethyl Uracil, Synthetic Communications: An International Journal
for Rapid Communication of Synthetic Organic Chemistry, 34:24, 4447-4461
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SYNTHETIC COMMUNICATIONSw
Vol. 34, No. 24, pp. 4447–4461, 2004
First Report on the Abnormal Dearylation/
Alkylation Reaction in One-Pot Hantzch
Synthesis with 6-Amino-1,3-Dimethyl Uracil
*
Anu Agarwal and Prem M. S. Chauhan
Medicinal and Process Chemistry Division, Central Drug Research
Institute, Lucknow, India
ABSTRACT
First report on the abnormal dearylation/dealkylation reaction occurring
during dehydrogenation in one-pot, three-component condensation of
dihydropyrido[2,3-d]pyrimidines.
Key Words: Dearylation; Dihydropyrido[2,3-d]pyrimidines; Hantzch
synthesis; Uracil.
*
Correspondence: Prem M. S. Chauhan, Medicinal and Process Chemistry Division,
Central Drug Research Institute, Lucknow 226001, India; Fax: 91-0522-2223405/
2223938; E-mail: prem_chauhan_2000@yahoo.com or premsc58@hotmail.com.
4447
DOI: 10.1081/SCC-200043171
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

4448
Agarwal and Chauhan
The versatility of uracil derivatives for the synthesis of nitrogen
containing heteroaromatic species of biological importance has been well
documented in the literature.[1] Pyrazolopyridines,[2] pyrimidopyrimidines,[3]
pyridopurines,[4] pyrazolopyrimidines,[5] and xanthine derivatives[6] have all
been prepared by the functionalization of these important heterocyclic buil-
ding blocks, whose structures are interesting in their own right, as well as
biologically active pyrimidine nucleosides.[7] The diverse range of biological
activities (antitumor, anticancer, antiinflammatory, and CNS depressant
activities) have stimulated considerable interest in the synthesis of dihydro-
pyrido[2,3-d] pyrimidines via new and efficient routes. Kajino and Meguro
have reported the synthesis of dihydropyrido[2,3-d]pyrimidines using
6-amino-1,3-dimethyl uracil, but as a one-pot, three-component cycloconden-
sation reaction, this procedure suffered from very poor yields and limited
substrate tolerance.[8]
Here in this communication we have reported the one-pot, three-
component condensation of dihydropyrido[2,3-d]pyrimidines (2) in high
yields and abnormal dearylation/alkylation (3) during dehydrogenation
along with the normal dehydrogenated product (4). Bagley and Singh[9]
had synthesized dihydropyrido[2,3-d]pyrimidin4(3H)-ones in acetic acid in
72 hours but had not reported the dehydrogenation reaction.
Oxidation of dihydropyrido[2,3-d]pyrimidines had been reported by
reagents as dil. HNO3,[8] ceric ammonium nitrate(CAN),[10] and ylidene
derivatives[5,11] (formed by the condensation of active methylene compounds
with aldehyde). All the workers[5,8,10,11] had earlier reported the normal
dehydrogenated product (4), but no one had earlier reported the abnormal
dearylated or dealkylated product (3) on oxidation.
When a mixture of 6-amino-l,3-dimethyl uracil, aldehyde (aromatic or
aliphatic), and acetyl acetone is heated in acetic acid (Sch. 1), initially after
8 hours high yields of dihydropyrido[2,3-d]pyrimidines (2) are obtained
(Table 1) and oxidized product (3 and 4) is either not formed or in very neg-
ligible amounts in some cases.
As the reaction time is increased, oxidation of the dihydropyrido[2,3-d]
pyrimidine (2) takes place and the amount of dearylated/alkylated product
Scheme 1.

Abnormal Reaction in Pyrimidine Synthesis
4449
Table 1.
After
8 hr.
2
After 48 hr.
Temp.
(8C)
Entry
R
2
3
4
a.
b.
c.
d.
e.
f.
4-CH3-C6H4
4OCH3-C6H4
3,4-di-CH3-C6H3
4-CH(CH3)2-C6H4
4Cl-C6H4
110
110
110
110
110
110
110
110
110
110
110
70
90
95
82
80
94
85
86
82
92
91
90
70
78
75
40
20
18
9
30
40
42
44
38
55
22
52
20
12
18
10
30
44
20
30
25
25
44
20
32
15
28
42
36
30
22
14
25
8
3,4-diCl-C6H3
C6H5
g.
h.
i.
25
12
35
32
35
30
25
16
3,4-di-OCH3-C6H3
4CN-C6H4
j.
4NO2-C6H4
3NO2-C6H4
CH3-
k.
l.
m.
n.
CH3CH2CH2-
CH3(CH2)4-
70
70
(3) and normal dehydrogenated product (4) goes on increasing with time
(Sch. 2). As the amount of (3) and (4) increases with the time period so for
comparison the percentage of (3) and (4) formed is calculated at a particular
time period of 48 hours (Table 1).
From the table it is very clear that the percentage of the abnormal deary-
lated or alkylated product (III) is greater for electron releasing and bulkier
Scheme 2.

4450
Agarwal and Chauhan
Scheme 3.
groups, whereas the percentage of normal dehydrogenated product (IV) is
greater for groups having electron withdrawing capacity. In the FABMS of
crude reaction mixture, the peak of ROAc is seen, indicating that R group
is eliminated in the form of Rþ, combine further with AcO2 to form ROAc.
The results are consistent with the mechanism involving elimination of a
carbonium ion during the course of oxidation (Sch. 3). They also emphasize
the important influence of steric factors.
It is clear from the results described above that in the course of oxidation
whether dearylation/alkyaltion or proton loss will occur is governed both by
the stability of the potential leaving carbonium ion and by the bulk of the
leaving group.
EXPERIMENTAL
Infrared spectra were recorded on Beckman Aculab-10, Perkin Elmer
881, and FTIR 8210 PC, Scimadzu spectrophotometers either on KBr discs
or in neat. Nuclear magnetic resonance (NMR) spectra were recorded on
either Bruker Avance DRX-300 MHz or Bruker DPX 200 FT spectrometers
using TMS as an internal reference. FAB mass spectra were recorded on
JEOL SX 102/DA 6000 mass spectrometer using Argon/Xenon (6 KV,
10 mA) as the FAB gas. Chemical analysis was carried out on a Carlo-Erba-
1108 instrument. The melting points were recorded on an electrically heated
melting point apparatus and are uncorrected.
Synthesis of 6-acetyl-5-(aryl/alkyl)-1,3,7-trimethyl-
5,8dihydro-1H-pyrido[2,3d]pyrimidine-2,4-dione (2a–2n)
6-Amino-1,3-dimethyl uracil (I) (0.3 mmol), acetyl acetone (0.35 mmol),
and aromatic or aliphatic aldehyde (0.35 mmol) were heated in acetic acid
(15 mL) for 8 hours to obtain dihydropyrido[2,3-d] pyrimidines (2). The
mixture was allowed to cool and water (50 mL) was added. The precipitated

Abnormal Reaction in Pyrimidine Synthesis
4451
solid was washed with water and dried. Recrystallization from ethanol gave
light yellow crystals of the desired compound.
6-Acetyl-1,3,7-trimethyl-5-p-tolyl-5,8dihydro-1H-pyrido[2,3-d]
pyrimidine-2,4-dione (2a)
MS 340 (Mþ1), IR (KBr) 3006, 2955, 1704, 1661, 1556, 1559, 1514,
1482 cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 7.27 (d, 2H, J ¼ 7.96 Hz),
7.09 (d, 2H, J ¼ 7.96 Hz), 6.01 (s, 1H, NH), 5.09 (s, 1H), 3.44
(s, 3H, NMe), 3.28 (s, 3H, NMe), 2.44 (s, 3H), 2.28 (s, 3H), 2.14 (s, 3H);
13C 199.4 (C55O), 161.4 (C55O), 150.6 (C55O), 141.9 (C), 141.7 (C), 137.1
(C), 130.6 (C), 128.1 (CH), 126.8 (CH), 91.5 (C), 37.4 (CH), 34.5 (C), 29.8
(N-CH3), 28.7 (N-CH3), 28.2 (CH3), 20.7 (CH3), 19.8 (CH3); Anal. Calcd.
for C19H21N3O3: C, 67.24; H, 6.24; N, 12.38; O, 14.14; Found: C, 67.52;
H, 6.34; N, 12.04; O, 14.12.
6-Acetyl-5-(4-methoxy-phenyl)-1,3,7-trimethyl-5,8dihydro-1H-pyrido-
[2,3-d]pyrimidine-2,4-dione (2b)
MS 356 (Mþ1), IR (KBr) 3025, 2953, 1705, 1682, 1619, 1502, 1388 cm21
1H NMR (CDCl3, 200 MHz) d (ppm) 7.30 (d, 2H, J ¼ 8.56 Hz), 6.81 (d, 2H,
J ¼ 8.56 Hz), 6.10 (s, 1H, NH), 5.07 (s, 1H), 3.74 (s, 3H, OMe), 3.44 (s, 3H,
NMe), 3.28 (s, 3H, NMe), 2.43 (s, 3H), 2.14 (s, 3H). 13C 199.5 (C55O), 161.5
(C55O), 158.5 (C), 150.8 (C55O), 142.0 (C), 141.8 (C), 137.1 (C), 128.8 (CH),
128.4 (C), 113.9 (CH), 91.5 (C), 55.1 (OCH3), 37.4 (CH), 29.8 (N-CH3), 28.7
(N-CH3), 28.2 (COCH3), 19.8 (CH3). Anal. Calcd. for C19H21N3O4: C, 64.21;
H, 5.96; N, 11.82; O, 18.01; Found: C, 64.05; H, 6.24; N, 11.94; O, 17.77.
6-Acetyl-5-(3,4-dimethyl-phenyl)-1,3,7-trimethyl-5,8dihydro-1H-
pyrido[2,3-d]pyrimidine-2,4-dione (2c)
MS 354 (Mþ1), IR (KBr) 3015, 2945, 1708, 1665, 1548, 1556, 1519,
1472 cm211H NMR (CDCl3, 200 MHz) d (ppm) 7.09 (d, 1 H, J ¼ 7.74 Hz),
7.04 (s, 1 H), 6.99 (d, 1 H J ¼ 7.76 Hz), 6.01 (s, 1H, NH), 5.09
(s, 1H), 3.44 (s, 3H, NMe), 3.28 (s, 3H, NMe), 2.45 (s, 3H), 2.14 (s,3H),
2.08 (s, 6H, 2CH3); 13C 199.3 (C55O), 161.4 (C55O), 134.9 (C), 150.6
(C55O), 141.8 (C), 141.5 (C), 136.9 (C), 136.2 (C), 133.8 (C), 130.2 (CH),
129.3 (CH), 125.6 (CH), 91.6 (C), 38.3 (CH), 29.7 (N-CH3), 28.6 (N-CH3),
28.2 (CH3), 20.6 (CH3), 20.3 (CH3), 19.8 (CH3); Anal. Calcd. for

4452
Agarwal and Chauhan
C20H23N3O3: C, 67.97; H, 6.56; N, 11.89; O, 13.58; Found: C, 67.72; H, 6.34;
N, 12.04; O, 13.90.
6-Acetyl-5-(4-isopropyl-phenyl)-1,3,7-trimethyl-5,8dihydro-1H-
pyrido-[2,3-d]pyrimidine-2,4-dione (2d)
MS 368 (Mþ1), IR (KBr) 3020, 2930, 1709, 1675, 1554, 1541, 1517,
1460 cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 7.38 (d, 2H, J ¼ 7.64 Hz),
7.16 (d, 2H, J ¼ 7.62 Hz), 5.98 (s, 1 H, NH), 5.11 (s,1 H), 3.44
(s, 3H, NMe), 3.28 (s, 3H, NMe), 3.18–3.23 (m, 1 H), 2.43 (s, 3H, COCH3),
2.26 (s, 3H, CH3), 1.24 (s, 6H, 2CH3); 13C 199.5 (C55O), 161.5 (C55O),
150.8 (C55O), 147.5 (C), 142.1 (C), 141.4 (C), 137.1 (C), 127.5 (CH), 126.5
(CH), 113.9 (C), 91.4 (C), 38.0 (CH), 33.7 (CH), 29.8 (N-CH3), 28.8
(N-CH3), 28.2 (CH3), 23.9 (2CH3), 19.8 (CH3); Anal. Calcd. for
C21H25N3O3: C, 68.64; H, 6.86; N, 11.44; O, 13.06; Found: C, 68.52; H,
6.54; N, 11.04; O, 13.90.
6-Acetyl-5-(4-chloro-phenyl)-1,3,7-trimethyl-5,8dihydro-1H-
pyrido[2,3-d]pyrimidine-2,4-dione (2e)
MS 360 (Mþ1), IR (KBr) 3015, 2946, 1708, 1678, 1623, 1508, 1376 cm21
1H NMR (CDCl3, 200 MHz) d (ppm) 7.33 (d, 2H, J ¼ 8.35 Hz), 7.25 (d, 2H,
J ¼ 8.36 Hz), 6.12 (s, 1H, NH), 5.09 (s, 1H), 3.45(s, 3H, NMe), 3.28 (s; 3H,
NMe), 2.43(s, 3H), 2.14 (s,3H); 13C 199.5 (C55O), 161.5 (C55O), 150.8
(C55O), 141.8 (C), 141.6 (C), 137.2 (C), 134.4 (C), 130.5 (C), 129.2 (CH),
127.6 (CH), 91.6 (C), 37.5 (CH), 29.8 (N-CH3), 28.7 (N-CH3), 28.1 (CH3),
19.8 (CH3); Anal. Calcd. for C18H18ClN3O3: C, 60.09; H, 5.04; Cl, 9.85; N,
11.68; O, 13.34; Found: C, 60.32; H, 5.24; Cl, 9.68; N, 11.84; O, 12.92.
6-Acetyl-5-(3,4-dichloro-phenyl)-1,3,7-trimethyl-5,8dihydro-1H-
pyrido[2,3-d]pyrimidine-2,4-dione (2f)
MS 394 (Mþ1) IR (KBr) 3015, 2946, 1708, 1678, 1623, 1508, 1376 cm21
1H NMR (CDCl3, 200 MHz) d (ppm) 7.38 (d, 1H, J ¼ 7.82 Hz), 7.30 (d, 1H,
J ¼ 7.84 Hz), 7.26 (s, 1 H), 5.95 (s, 1 H, NH), 5.12 (s, l H), 3.44
(s, 3H, NMe), 3.28 (s, 3H, NMe), 2.44 (s, 3H), 2.14 (s, 3H); 13C 199.5
(C55O), 161.6 (C55O), 150.7 (C55O), 141.9 (C), 141.8 (C), 137.2 (C),
135.4 (C), 132.8 (C), 130.8 (C), 127.2 (CH), 129.8 (CH), 128.7 (CH), 91.6
(C), 37.4 (CH), 29.7 (N-CH3), 28.6 (N-CH3), 28.2 (CH3), 19.8 (CH3); Anal.
Calcd. for C18H17Cl2N3O3: C, 54.84; H, 4.35; Cl, 17.98; N, 10.66; O,
12.17; Found: C, 54.62; H, 4.44; Cl, 17.85; N, 10.34; O, 12.75.

Abnormal Reaction in Pyrimidine Synthesis
4453
6-Acetyl-5-phenyl-1,3,7-trimethyl-5,8dihydro-1H-pyrido[2,3-d]
pyrimidine-2,4-dione (2g)
MS 326 (Mþ1), IR (KBr) 3005, 2953, 1708, 1676, 1619, 1514, 1388 cm21
1H NMR (CDCl3, 200 MHz) d (ppm) 7.26 (s, 1H), 7.24 (d, 2H, J ¼ 6.8 Hz),
7.16 (d, 2H, J ¼ 6.8 Hz), 6.05 (s, 1H, NH), 5.02 (s, 1H), 3.44 (s, 3H, NMe),
3.28 (s, 3H, NMe), 2.45 (s, 3H), 2.15 (s, 3H); 13C 199.6 (C55O), 161.4
(C55O), 150.7 (C55O), 142.1 (C), 141.8 (C), 137.2 (C), 135.4 (C), 127.8
(CH), 127.1 (CH), 124.6 (C), 91.6 (C), 37.5 (CH), 29.9 (NCH3), 28.7 (N-
CH3), 28.1 (COCH3), 19.8 (CH3); Anal. Calcd. for C18H19N3O3: C, 66.45;
H, 5.89; N, 12.91; O, 14.75; Found: C, 66.25; H, 6.12; N, 12.84; O, 14.79.
6-Acetyl-5-(3,4-dimethoxy-phenyl)-1,3,7-trimethyl-5,8dihydro-1H-
pyrido[2,3-d]pyrimidine-2,4-dione (2h)
MS 386 (Mþ1), IR (KBr) 3025, 2953, 1705, 1682, 1619, 1502, 1388 cm21
1H NMR (CDCl3, 200 MHz) d (ppm) 7.02 (d, 1H, J ¼ 7.8 Hz), 6.92 (d, 1H,
J ¼ 7.8 Hz), 6.84 (s, 1H), 6.10 (s, 1H, NH), 5.06 (s, 1H), 3.74 (s, 6H,
20Me), 3.44 (s, 3H, NMe), 3.28 (s, 3H, NMe), 2.43 (s, 3H), 2.15 (s, 3H);
13C 199.5 (C55O), 161.4 (C55O), 150.8 (C55O), 146.3(C), 142.5 (C), 141.8
(C), 141.6 (C), 137.2 (C), 129.4 (C), 121.8 (CH), 115.4(CH), 114.7 (CH),
91.7 (C), 54.9 (20CH3), 37.6 (CH), 29.8 (N-CH3), 28.8 (N-CH3), 28.2
(COCH3), 19.9 (CH3); Anal. Calcd. for C20H23N3O5: C, 62.33; H, 6.01; N,
10.90; O, 20.76; Found: C, 62.45; H, 6.23; N, 10.84; O, 20.48.
6-Acetyl-1,3,7-trimethyl-2,4-Dioxo-1,2,3,4,5,8hexahydro-pyrido[2,3-d]
pyrimidine-5-yl-benzonitrile (2i)
MS 351 (Mþ1), IR (KBr) 3026, 2958, 2155, 1706, 1686, 1619, 1508, 1384
cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 7.34 (d, 2H, J ¼ 8.43 Hz), 7.12
(d, 2H, J ¼ 8.44 Hz), 6.10 (s, 1H, NH), 5.10 (s,1H), 3.45 (s, 3H, NMe), 3.28
(s, 3H, NMe), 2.45 (s, 3H), 2.16 (s,3H); 13C 199.5 (C55O), 161.5 (C55O),
150.8 (C55O), 142.1 (C), 141.8 (C), 140.6 (C), 137.2 (C), 129.8
(CH), 127.9 (CH), 115.5 (C), 118.2 (CN), 91.5 (C), 37.5 (CH), 29.8
(N-CH3), 28.7 (N-CH3), 28.2 (CH3), 19.8 (CH3); Anal. Calcd. for
C19H18N4O3: C, 65.13; H, 5.18; N, 15.99; O, 13.70; Found: C, 65.42; H,
5.34; N, 16.14; O, 13.30.
6-Acetyl-)-1,3,7-trimethyl-5-(4-nitro-phenyl-5,8dihydro-1H-
pyrido[2,3-d]pyrimidine-2,4-dione (2j)
MS 371 (Mþ1), IR (KBr) 3028, 2960, 2150, 1709, 1685, 1610, 1508,
1382, 1354 cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 8.07 (d, 2H,

4454
Agarwal and Chauhan
J ¼ 8.36 Hz), 7.77 (d, 2H, J ¼ 8.36 Hz), 6.15 (s, 1H, NH), 5.18 (s,1H), 3.48
(s, 3H, NMe), 3.28 (s, 3H, NMe), 2.49 (s, 3H), 2.14 (s,3H); 13C 199.4
(C55O), 161.5 (C55O), 150.7 (C55O), 143.2 (CH), 142.1 (C), 141.8 (C),
137.6 (C), 137.2 (C), 119.8 (C), 121.5 (CH), 91.4 (C), 37.4 (CH), 29.8
(N-CH3), 28.7 (N-CH3), 28.3 (CH3), 19.9 (CH3); Anal. Calcd. for
C18H18N4O5: C, 58.37; H, 4.90; N, 15.13; O, 21.60; Found: C, 58.62; H,
4.84; N, 15.04; O, 21.70.
6-Acetyl-1,3,7-trimethyl-5-(3-nitro-phenyl)-5,8dihydro-1H-pyrido[2,3-d]
pyrimidine-2,4-dione (2k)
MS 371 (Mþ1), IR (KBr) 3026, 2958, 2155, 1706, 1686, 1619, 1550,
1508, 1384, 1350cm21 1H NMR (CDC13, 200 MHz) d (ppm) 8.09
(d, 1H, J ¼ 8.28 Hz), 8.03 (s, 1H), 7.87 (d, 1H J ¼ 8.3 0 Hz), 7.49 (t, 1H,
4.8 Hz), 6.25 (s, 1H, NH), 5.26 (s, lH), 3. 51 (s, 3H, NMe), 3.28 (s, 3H,
NMe), 2.49 (s, 3H), 2.16 (s,3H); 13C 199.4 (C55O), 161.5 (C55O), 150.8
(C55O), 146.2 (C), 142.0 (C), 141.8 (C), 137.3 (C), 134.8 (CH), 128.6
(CH), 124.2 (CH), 140.2 (C), 119.6 (C), 91.7 (C), 37.8 (CH), 29.9 (N-CH3),
28.7 (N-CH3), 28.2 (CH3), 19.8 (CH3); Anal. Calcd. for C18H18N4O5: C,
58.37; H, 4.90; N, 15.13; O, 21.60; Found: C, 58.52; H, 4.64; N, 15.04;
O, 21.80.
6-Acetyl-1,3,57-tetramethyl-5,8dihydro-1H-pyrido[2,3-d]pyrimidine-
2,4-dione (2l)
MS 264 (Mþ1), IR (KBr) 2963, 2924, 1708, 1665, 1544, 1502, 1428, 1368
cm21 1H NMR (CDC13, 200 MHz) d (ppm) 5.97 (s, 1H, NH), 4.02 (dd, 1H,
J ¼ 6.8 Hz), 3.49 (s, 3H, NMe), 3.34 (s, 3H, NMe), 2.34 (s, 3H), 2.28
(s, 3H), 1.13 (s,3H); 13C 199.7 (C55O), 161.6 (C55O), 150.9 (C55O), 141.9
(C), 141.1 (C), 139.6 (C), 95.5 (C), 30.4 (CH), 29.9 (N-CH3), 28.8
(N-CH3), 28.2 (CH3), 19.8 (CH3), 15.2 (CH3); Anal. Calcd. for
C13H17N3O3: C, 59.30; H, 6.51; N, 15.96; O, 18.23; Found: C, 59.53; H,
6.34; N, 15.74; O, 18.39.
6-Acetyl-1,3,7-trimethyl-5-propyl-5,8dihydro-1H-pyrido[2,3-d]
pyrimidine-2,4-dione (2m)
MS 292 (Mþ1), IR (KBr) 2975, 2942, 1705, 1656, 1562, 1504, 1438,
1358 cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 5.97 (s, 1H, NH), 3.96
(t, 1H, J ¼ 4.8 Hz), 3.46 (s, 3H, NMe), 3.30 (s, 3H, NMe), 2.44 (s, 3H),
2.18 (s, 3H), 1.15 (m, 4H), 1.02 (t, 3H, J ¼ 4.2); 13C 199.5 (C55O), 161.5
(C55O), 150.9 (C55O), 141.8 (C), 141.1 (C), 139.6 (C), 97.6 (C), 33.2

Abnormal Reaction in Pyrimidine Synthesis
4455
(CH), 29.8 (N-CH3), 29.4 (CH2), 28.8 (N-CH3), 28.3 (CH3), 20.2 (CH2), 19.8
(CH3), 15.4 (CH3); Anal. Calcd. for C15H21N3O3: C, 61.84; H, 7.27; N, 14.42;
O, 16.47; Found: C, 61.52; H, 7.38; N, 14.34; O, 16.76.
6-Acetyl-1,3,7-trimethyl-5-pentyl-5,8dihydro-1H-pyrido[2,3-d]
pyrimidine-2,4-dione (2n)
MS 320 (Mþ1), IR (KBr) 2956, 2914, 1704, 1654, 1543, 1519, 1428, 1375
cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 5.99 (s, 1H, NH), 3.26 (t, 1H,
J ¼ 4.3 Hz), 3.48 (s, 3H, NMe), 3.26 (s, 3H, NMe), 2.46 (s, 3H), 2.16
(s, 3H), 1.15 (m, 8H), 1.02 (t, 3H, J ¼ 4.2); 13C 199.5 (C55O), 161.5
(C55O), 150.9 (C55O), 141.6 (C), 141.2 (C), 139.8 (C), 97.4 (C), 34.2
(CH), 29.8 (N-CH3), 28.7 (N-CH3), 28.3 (CH3), 28.2 (CH2), 24.6 (CH2),
23.1 (CH2), 20.2 (CH2), 19.8 (CH3), 14.6 (CH3); Anal. Calcd. for
C17H25N3O3: C, 63.93; H, 7.89; N, 13.16; O, 15.03; Found: C, 63.72; H,
7.54; N, 13.24; O, 15.50.
6-Acetyl-1,3,7-trimethyl-1H-pyrido[2,3-d]pyrimidine-2,4-
dione (3)
6-Amino-1,3-dimethyl uracil (I) (0.3 mmol), acetyl acetone (0.35 mmol),
and aryl/alkyl aldehyde (0.35 mmol) were heated in acetic acid (15 mL) for
48 hours. The mixture was allowed to cool and water (50 mL) was added.
The reaction mixture was extracted with chloroform and dried over sodium
sulfate to give the crude, which was purified by column chromatography (hex-
ane : ethyl acetate; 7 : 3) to give 2, 3, and 4.
MS 248 (Mþ1), IR (KBr) 2960, 2928, 1702, 1663, 1564, 1509, 1440, 1371
cm211H NMR (CDCl3, 200 MHz) d (ppm) 6.81 (s, 1H), 3.68 (s, 3H),
3.43 (s, 3H), 2.76 (s, 3H), 2.52 (s, 3H); 13C 162.77 (C55O, C55O), 162.34
;;
(C), 153.37 (C, C O), 151.82 (C), 122.14 (CH), 107.16 (C), 30.223
(CH3), 28.50 (CH3), 25.04 (CH3), 22.57 (CH3); Anal. Calcd. for C12H13N3O3:
C, 58.29; H, 5.30; N, 17.00; O, 19.41; Found: C, 58.48; H, 5.12; N, 17.24;
O, 19.17.
6-Acetyl-5-(aryl/alkyl)-1,3,7-trimethyl-1H-pyrido[2,3-d]
pyrimidine-2,4-dione (4a-1)
6-Amino-1,3-dimethyl uracil (I) (0.3 mmol), acetyl acetone (0.35 mmol),
and aryl/alkyl aldehyde (0.35 mmol) were heated in acetic acid (15 mL) for 48
hours. The mixture was allowed to cool and water (50 mL) was added. The

4456
Agarwal and Chauhan
reaction mixture was extracted with chloroform and dried over sodium
sulfate to give the crude, which was purified by column chromatography
(hexane : ethyl acetate; 7:3) to give 2, 3, and 4.
6-Acetyl-1,3,7-trimethyl-5-p-tolyl-1H-pyrido[2,3-d]pyrimidine-2,4-
dione (4a)
MS 338 (Mþ1), IR (KBr) 3012, 2952, 1708, 1678, 1548, 1553, 1518, 1485
cm21 1H NMR (CDCl13, 200 MHz) d (ppm) 7.30 (d, 2H, J ¼ 8.1 Hz), 7.18
(d, 2H, J ¼ 8.1), 3.74 (s, 3H, NMe), 3.35 (s, 3H, NMe), 2.51 (s, 3H, COCH3),
2.25 (s, 3H, CH3), 1.86 (s, 3H, CH3); 13C 204.5 (C55O), 160.2 (C55O), 159.8
(C), 151.2 (C55O), 150.6 (C), 149.8 (C), 138.5(C), 132.6 (C), 128.4 (CH),
125.7 (CH), 120.5 (C), 104.8 (C), 31.6 (NCH3), 29.9 (NCH3), 28.4 (COCH3),
23.6 (CH3), 21.3 (CH3); Anal. Calcd. for C19H19N3O3: C, 67.64; H, 5.68;
N, 12.46; O, 14.23; Found: C, 67.72; H, 5.44; N, 12.24; O, 14.60.
6-Acetyl-5-(4-methoxy-phenyl)-1,3,7-trimethyl-1H-pyrido[2,3-d]
pyrimidine-2,4-dione (4b)
MS 354 (Mþ1), IR (KBr) 3005, 2957, 1706, 1665, 1558, 1558, 1513, 1480
cm211H NMR (CDCl13, 200 MHz) d (ppm) 7.14 (d, 2H, J ¼ 8.6 Hz), 6.97
(d, 2H, J ¼ 8.6 Hz), 3.85 (s, 3H, OMe), 3.76 (s, 3H, NMe), 3.35 (s, 3H, NMe),
2.53 (s, 3H, COCH3), 1.85 (s, 3H, CH3); 13C 204.4 (C55O), 160.3 (C55O),
159.8 (C), 158.4 (C), 151.2 (C55O), 150.8 (C), 149.9 (C), 136.7 (C), 129.6
(CH), 120.7 (C), 105.2 (C), 113.4 (CH), 55.3 (OCH3), 31.7 (NCH3), 29.9
(NCH3), 28.3 (CH3), 23.5 (CH3); Anal. Calcd. for C19H19N3O4: C, 64.58;
H, 5.42; N, 11.89; O, 18.11; Found: C, 64.82; H, 5.34; N, 12.04; O, 17.80.
6-Acetyl-5-(3,4-dimethyl-phenyl)-1,3,7-trimethyl-1H-pyrido[2,3-d]
pyrimidine-2,4-dione (4c)
MS 352 (Mþ1), IR(KBr) 3018, 2972, 1709, 1642, 1542, 1511, 1475 cm21
1H NMR (CDCl3, 200 MHz) d (ppm) 7.42 (d, 1H, J ¼ 7.9 Hz), 7.35 (s, 1H),
7.15 (d, 1H, J ¼ 7.92 Hz), 3.72 (s, 3H, NMe), 3.33 (s, 3H, NMe), 2.51
(s, 3H, COCH3), 2.31 (s, 6H, 2CH3), 1.82 (s, 3H, CH3); 13C 204.6 (C55O),
161.1 (C55O), 159.6 (C), 151.4 (C55O), 150.6 (C), 149.7 (C), 138.7(C),
135.2 (C), 134.5 (C), 129.5 (CH), 126.9 (CH), 126.3 (CH), 120.5 (C), 106.8
(C), 31.5 (NCH3), 29.8 (NCH3), 28.3 (CH3), 20.7 (CH3), 20.4 (CH3),
23.5 (CH3); Anal. Calcd. for C20H21N3O3: C, 68.36; H, 6.02; N, 11.96; O,
13.66; Found: C, 68.52; H, 6.14; N, 12.04; O, 13.30.

Abnormal Reaction in Pyrimidine Synthesis
4457
6-Acetyl-5-(4-isopropyl-phenyl)-1,3,7-trimethyl-1H-pyrido[2,3-d]
pyrimidine-2,4-dione (4d)
MS 366 (Mþ1), IR (KBr) 3004, 2956, 1708, 1662, 1558, 1536, 1513,
1484 cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 7.22 (d, 2H, J ¼ 8.3 Hz),
7.06 (d, 2H, J ¼ 8.3 Hz), 3.76 (s, 3H, NMe), 3.35 (s, 3H, NMe), 3.18–3.22
(m, 1H, CH), 3.53 (s, 3H, COCH3), 1.85 (s, 3H, CH3), 1.25 (s, 6H, 2CH3);
13C 204.5 (C55O), 160.5 (C55O), 159.7 (C), 151.1 (C55O), 150.6 (C), 149.7
(C), 146.2 (C), 138.7 (C), 127.9 (CH), 125.4 (CH), 120.9 (C), 106.2 (C),
31.8 (NCH3), 31.5 (CH), 29.9 (NCH3), 28.3 (COCH3), 23.9 (2CH3), 23.5
(CH3); Anal. Calcd. for C21H23N3O3: C, 69.02; H, 6.34; N, 11.50; O, 13.13;
Found: C, 69.26; H, 6.39; N, 11.34; O, 13.01.
6-Acetyl-5-(4-chloro-phenyl)-1,3,7-trimethyl-1H-pyrido[2,3-d]
pyrimidine-2,4-dione (4e)
MS 358 (Mþ1), IR (KBr) 3015, 2962, 1712, 1652, 1558, 1541, 1508,
1482 cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 7.54 (d, 2H, J ¼ 8.22 Hz),
7.43 (d, 2H, J ¼ 8.21 Hz), 3.74 (s, 3H, NMe), 3.32 (s, 3H, NMe), 2.55
(s, 3H, COCH3), 1.82 (s, 3H, CH3); 13C 204.4 (C55O), 160.3 (C55O), 159.6
(C), 151.2 (C55O), 150.4 (C), 149.5 (C), 139.7 (C), 132.4 (C), 130.2 (CH),
127.4 (CH), 120.9 (C), 105.5 (C), 31.7 (NCH3), 29.9 (NCH3), 28.3
(COCH3), 23.5 (CH3); Anal. Calcd. for C18H16N3O3: C, 60.42; H, 4.51; Cl,
9.91; N, 11.74; O, 13.42; Found: C, 60.52; H, 4.44; Cl, 9.72; N, 12.04; O,
13.28.
6-Acetyl-5-(3,4-dichloro-phenyl)-1,3,7-trimethyl-1H-pyrido[2,3-d]
pyrimidine-2,4-dione (4f)
MS 392 (Mþ1), IR (KBr) 3015, 2952, 1709, 1665, 1578, 1541, 1513,
1452 cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 7.62 (d, 1H, J ¼ 8.34 Hz),
7.51 (s, 1H), 7.3 8 (d, 1H, J ¼ 8.34 Hz), 3.75 (s, 3H, NMe), 3.34 (s, 3H,
NMe), 2.55 (s, 3H, COCH3), 1.85 (s, 3H, CH3); 13C 204.5 (C55O), 160.4
(C55O), 159.7 (C), 151.2 (C55O), 150.6 (C), 149.8 (C), 139.7 (C), 132.4
(C), 132.2 (C), 129.6 (CH), 128.5 (CH), 128.2 (CH), 120.6 (C), 107.7 (C),
31.5 (NCH3), 29.7 (NCH3), 28.4 (CH3), 23.6 (CH3); Anal. Calcd. for
C18H15C12N3O3: C, 55.12; H, 3.85; Cl, 18.08; N, 10.71; O, 12.24; Found:
C, 55.34; H, 3.68; Cl, 18.24; N, 10.46; O, 12.26.

4458
Agarwal and Chauhan
6-Acetyl-1,3,7-trimethyl-5-phenyl-1H-pyrido[2,3-d]pyrimidine-2,4-
dione (4g)
MS 324 (Mþ1), IR (KBr) 3016, 2956, 1709, 1661, 1544, 1532,
1511, 1478 cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 7.48 (d, 2H,
J ¼ 8.2 Hz), 7.36 (d, 2H, J ¼ 8.6 Hz), 7.32(s, 1H), 3.72 (s, 3H, NMe), 3.31
(s, 3H, NMe), 2.54 (s, 3H, COCH3), 1.82 (s, 3H, CH3); 13C 204.6 (C55O),
160.4 (C55O), 159.9 (C), 151.3 (C55O), 150.9 (C), 149.8 (C), 140.2 (C),
127.6 (CH), 126.8 (C), 126.4 (CH), 120.8 (C), 105.6 (C), 31.7 (NCH3), 29.9
(NCH3), 28.4 (CH3), 23.6 (CH3); Anal. Calcd. for C18H17N3O3: C, 66.86;
H, 5.30; N, 13.00; O, 14.84; Found: C, 66.72; H, 5.44; N, 12.74; O, 15.10.
6-Acetyl-5-(3,4-dimethoxy-phenyl)-1,3,7-trimethyl-1h-pyrido[2,3-d]
pyrimidine-2,4-dione (4h)
MS 384 (Mþ1), IR (KBr) 3015, 2942, 1704, 1656, 1548, 1536, 1513,
1480 cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 7.18 (d, 1H, J ¼ 7.6 Hz),
7.02 (s, 1H), 6.96 (d, 1H, J ¼ 7.6 Hz), 3.85 (s, 6H, 2OMe), 3.75 (s, 3H,
NMe), 3.32 (s, 3H, NMe), 2.53 (s, 3H, COCH3), 1.85 (s, 3H, CH3); 13C
204.5 (C55O), 160.4 (C55O), 159.7 (C), 146.2 (C), 151.3 (C55O), 150.6
(C), 149.8 (C), 137.2 (C), 121.4 (CH), 114.5(CH), 120.5 (C), 105.2 (C),
114.2 (CH), 149.1(C), 55.6 (OCH3), 55.4(OMe), 31.7 (NCH3), 29.9
(NCH3), 28.4 (CH3), 23.6 (CH3); Anal. Calcd. for C20H21N3O5: C, 62.65;
H, 5.52; N, 10.96; O, 20.87; Found: C, 62.82; H, 5.64; N, 10.84; O, 20.70.
4-(6-Acetyl-1,3,7-trimethyl-2,4-dioxo-1,2,3,4-tetrahydro-pyrido[2,3-d]
pyrimidin-5yl)-benzonitrile (4i)
MS 349 (Mþ1), IR (KBr) 3008, 2948, 2150, 1708, 1675, 1546, 1553, 1514,
1484 cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 7.18 (d, 2H, J ¼ 7.9 Hz), 7.01
(d, 2H, J ¼ 7.9 Hz) 3.72 (s, 3H, NMe), 3.38 (s, 3H, NMe), 2.52 (s, 3H), 1.86
(s,3H); 13C 204.5 (C55O), 160.4 (C55O), 159.6 (C), 151.2 (C55O), 150.6 (C),
149.6 (C), 146.7 (C), 130.2 (CH), 129.3 (CH), 120.4 (C), 115.4 (CN), 111.5
(C), 105.5 (C), 31.8 (NCH3), 29.9 (NCH3), 28.4 (CH3), 23.6 (CH3); Anal.
Calcd. for C19H16N4O3: C, 65.51; H, 4.63; N, 16.08; O, 13.78; Found: C,
65.72; H, 4.34; N, 16.24; O, 13.70.
6-Acetyl-1,3,7-trimethyl-5-(4-nitro-phenyl)-1H-pyrido[2,3-d]
pyrimidine-2,4-dione (4j)
MS 369 (Mþ1), IR (KBr) 3025, 2965, 1712, 1675, 1558, 1536, 1513,
1470 cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 8.22 (d, 2H, J ¼ 8.42 Hz),

Abnormal Reaction in Pyrimidine Synthesis
4459
7.97 (d, 2H, J ¼ 8.43 Hz), 3.71 (s, 3H, NMe), 3.32 (s, 3H, NMe), 2.55 (s, 3H,
COCH3), 1.85 (s, 3H, CH3); 13C 204.5 (C55O), 160.5 (C55O), 159.7 (C),
151.2 (C55O), 151.4 (C), 150.2 (C), 148.2 (C), 143.4 (C), 129.7 (CH),
122.2 (CH), 121.5 (C), 105.5 (C), 31.6 (NCH3), 29.9 (NCH3), 28.3
(COCH3), 23.5 (CH3); Anal. Calcd. for C18H16N4O5: C, 58.69; H, 4.38; N,
15.21; O, 21.72; Found: C, 58.52; H, 4.24; N, 15.04; O, 22.20.
6-Acetyl-1,3,7-trimethyl-5-(3-nitro-phenyl)-1H-pyrido[2,3-d]
pyrimidine-2,4-dione (4k)
MS 369 (Mþ1), IR (KBr) 3005, 2948, 1709, 1660, 1588, 1548, 1512,
1480 cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 8.20 (d, 1H, J ¼ 8.52 Hz),
8.13 (s, 1H), 7.95 (t, 1H, J ¼ 4.3 Hz), 7.68 (d, 1H, J ¼ 8.54 Hz), 3.77
(s, 3H, NMe), 3.36 (s, 3H, NMe), 2.55 (s, 3H, COCH3), 1.85 (s, 3H, CH3);
13C 204.5 (C55O), 160.3 (C55O), 160.1 (C), 151.3 (C55O), 150.9 (C), 149.4
(C), 148.9 (C), 142.3 (C), 134.2 (CH), 129.4 (CH), 123.5 (CH), 122.2 (CH),
120.5 (C), 106.4 (C), 31.8 (NCH3), 29.9 (NCH3), 28.4 (CH3), 23.5 (CH3);
Anal. Calcd. for C18H16N4O5: C, 58.69; H, 4.38; N, 15.21; O, 21.72;
Found: C, 58.76; H, 4.17; N, 15.04; O, 22.03.
6-Acetyl-1,3,7-trimethyl-5-methyl-1H-pyrido[2,3-d]pyrimidine-2,4-
dione (4l)
MS 262 (Mþ1), IR (KBr) 2930, 2914, 1706, 1665, 1543, 1519, 1434,
1370 cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 3.72 (s, 3H, NMe), 3.33
(s, 3H, NMe), 2.51 (s, 3H, COCH3), 2.18 (s, 3H, CH3), 1.83 (s, 3H, CH3);
13C 204.4 (C55O), 160.8 (C55O), 159.9 (C), 151.4 (C55O), 150.6 (C), 150.2
(C), 120.8 (C), 107.8 (C), 31.7 (NCH3), 29.9 (NCH3), 28.3 (CH3), 23.5
(CH3), 18.2 (CH3); Anal. Calcd. for C13H15N3O3: C, 59.76; H, 5.79; N,
16.08; O, 18.37; Found: C, 59.44; H, 5.47; N, 16.24; O, 17.95.
6-Acetyl-1,3,7-trimethyl-5-propyl-1H-pyrido[2,3-d]pyrimidine-2,4-
dione (4m)
MS 290 (Mþ1), IR (KBr) 2948, 2932, 1708, 1654, 1564, 1510, 1452,
1360 cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 3.74 (s, 3H, NMe), 3.33
(s, 3H, NMe), 2.55 (s, 3H, COCH3), 2.52 (t, 2H, J ¼ 4.2 Hz), 1.85 (s, 3H,
CH3), 1.76 (m, 2H), 0.98 (t, 3H, J ¼ 4.6 Hz); 13C 204.6 (C55O), 160.4
(C55O), 159.4 (C), 151.3 (C55O), 150.5 (C), 148.5 (C), 123.7 (C), 108.2
(C), 31.7 (NCH3), 29.9 (NCH3), 28.3 (CH3), 24.6 (CH2), 24.1 (CH2), 23.5
(CH3), 19.6 (CH3); Anal. Calcd. for C15H19N3O3: C, 62.24; H, 6.62; N,
14.52; O, 16.59; Found: C, 62.38; H, 6.44; N, 14.24; O, 16.94.

4460
Agarwal and Chauhan
6-Acetyl-1,3,7-trimethyl-5-pentyl-1H-pyrido[2,3-d]pyrimidine-2,4-
dione (4n)
MS 318 (Mþ1), IR (KBr) 2960, 2928, 1702, 1663, 1564, 1509, 1440,
1371 cm21 1H NMR (CDCl3, 200 MHz) d (ppm) 3.72 (s, 3H, NMe), 3.33
(s, 3H, NMe), 2.55 (s, 3H, COCH3), 2.51 (t, 3H, J ¼ 4.5 Hz), 1.72 (m, 2H),
1.45 (m, 2H), 1.85 (s, 3H, CH3), 0.95 (t, 3H, J ¼ 4.3 Hz); 13C 204.8
(C55O), 160.5 (C55O), 159.6 (C), 151.4 (C55O), 150.8 (C), 148.7 (C),
122.5(C), 105.4 (C), 31.8 (NCH3), 29.7 (NCH3), 28.4 (CH3), 27.1 (2CH2),
24.2 (CH2), 23.2 (CH3), 20.5 (CH2), 14.9 (CH3); Anal. Calcd. for
C17H23N3O3: C, 64.33; H, 7.30; N, 13.24; O, 15.12; Found: C, 64.56; H,
7.04; N, 13.54; O, 14.86.
ACKNOWLEDGMENT
A.A. thanks the Council of Scientific and Industrial Research (India) for
the award of fellowship. We are also thankful to S.A.I.F., CDRI, Lucknow for
providing spectroscopic data. CDRI Communication No. 6490.
REFERENCES
1. (a) Lunt, E.; Newton, C.G. Pyridodiazines and their benzo derivatives.
In Comprehensive Heterocyclic Chemistry; Vol. 3; Katritzky, A.R.,
Rees, C.W., Boulton, A.J., Mckillop, A., Eds.; Pergamon Press: Oxford,
1984; 199, 232, 260–261; (b) Bradshaw, T.K.; Hutchinson, D.W. 5-
Substituted pyrimidine nucleosides and nucleotides. Chem. Soc. Rev.
1977, 6, 43.
2. Quiroga, J.; Cruz, S.; Insuasty, B.; Abonia, R. Synthesis and structural
analysis of 5-cyanodihydropyrazolo[3,4-d]pyridines. J. Het. Chem.
2001, 38, 53.
3. Thakur, A.J.; Saikia, P.; Prajapati, D.; Sandhu, J.S. Studies on
6[(Dimethylamino)methylene] amino uracils: a Facile one pot synthesis
of pyrimido[4,5-d]pyrimidines and pyrido[2,3-d]pyridines. Synlett
2001, 8, 1299.
4. Perez-Perez, M.-J.; Pretago, E.-M.; Jimeno, M.-L.; Camarasa, M.-J. A
new and efficient one pot synthesis of pyrido[2,1-f]purine-2,4-diones
starting from 6-aminouracil derivatives. Synlett 2002, 1, 155.
5. Bhuyan, P.; Boruah, R.C.; Sandhu, J.S. Studies on uracils. A facile one
pot synthesis of pyrido[2,3-d] and pyrazolo[3,4-d]pyrimidines. J. Org.
Chem. 1990, 55, 568.

Abnormal Reaction in Pyrimidine Synthesis
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6. Muller, C.E.; Geis, U.; Hipp, J.; Schobert, U.; Frobenius, W.;
Pawlowski, M.; Suzuki, F.; Sandoval-Ramirez, J. Synthesis and structure
activity relationships of 3,7-dimethyl-1-propargyl xanthine derivatives,
A2A-selective adenosine receptor antagonists. J. Med. Chem. 1997, 40,
4396.
7. Kumar, R.; Tyrrell, D.L.J. Novel 5-vinyl pyrimidine nucleosides with
potent antihepatitis B virus activity. Bioorg. Med. Chem. Lett. 2001,
11, 2917.
8. Kajino, M.; Meguro, K. The Hantzsch synthesis with 6-amino uracils:
One step synthesis of pyrido[2,3-d]pyrimidines. Heterocycles 1990, 31,
2153.
9. Bagley, M.C.; Singh, N. A new one-pot three component condensation
reaction for the synthesis of 5-deaza-5,8-dihydropterinsChemcomm
2001, 23, 2438–2439.
10. Gordecv, M.F.; Patel, D.V.; Gordon, E.M. Approaches to combinatorial
synthesis of heterocycles: a solid phase synthesis of 1,4 dihydro pyridines.
J. Org. Chem. 1996, 61, 924.
11. El-Ahl, A.A.S.; El Bialy, S.A.A.; Ismail, M.A. A one pot synthesis of
pyrido[2,3-d] and quinolino[2,3-d]pyrimidines. Heterocycles 2001, 55,
1315.
Received in India August 6, 2004