Reaction of pyrimidinonethione derivatives: Synthesis of N-methyl-2-hydrizinopyrimidine-4-one, thiazolo[3,4-b] N-methylpyrimidinone; 2-(1-pyrazolonyl) N-methylpyrimidine-4-one and 2-hydrazino-N-methyl pyrimidine-4-one derivatives

Article abstract of DOI:10.1002/jccs.200400082

6-Aryl-5-cyano-4-pyrimidinone-2-thion derivatives 1a-c reacted with methyl iodide (1:2) to give the corresponding 2-S,N-dimethyl pyrimidine-4-one derivatives 2a-c. Compounds 2a-c were in turn, reacted with hydrazine hydrate to give the sulfur free reaction products 3a-c. These reaction products were taken as the starting materials for the synthesis of several new heterocyclic derivatives. Reaction of 3a-c with acetic anhydride and formic acid gave pyrimido triazines 4a-c and 7a-c, respectively. Their reactions with active methylene containing reagents gave the corresponding 2-(1-pyrazonyl)-N-methyl pyrimidine derivatives 9a-c and 10a-c, respectively. Their reactions with aromatic aldehydes afforded the corresponding 2-hydrazono pyrimidine derivatives 11a-c. The structure of these reactions products were established based on both elemental analysis and spectral data studies.

Full text of DOI:10.1002/jccs.200400082

Journal of the Chinese Chemical Society, 2004, 51, 547-552
547
Reaction of Pyrimidinonethione Derivatives: Synthesis of
N-methyl-2-hydrizinopyrimidine-4-one, thiazolo[3,4-b]
N-methylpyrimidinone; 2-(1-pyrazolonyl) N-methylpyrimidine-4-one and
2-Hydrazino-N-methyl pyrimidine-4-one Derivatives
Abdullah A. Al-Karim Al-Shara’ey
Department of Chemistry, Faculty of Science, Taiz University, Taiz, Yemen
6-Aryl-5-cyano-4-pyrimidinone-2-thion derivatives 1a-c reacted with methyl iodide (1:2) to give the cor-
responding 2-S,N-dimethyl pyrimidine-4-one derivatives 2a-c. Compounds 2a-c were in turn, reacted with
hydrazine hydrate to give the sulfur free reaction products 3a-c. These reaction products were taken as the
starting materials for the synthesis of several new heterocyclic derivatives. Reaction of 3a-c with acetic anhy-
dride and formic acid gave pyrimido triazines 4a-c and 7a-c, respectively. Their reactions with active methyl-
ene containing reagents gave the corresponding 2-(1-pyrazonyl)-N-methyl pyrimidine derivatives 9a-c and
10a-c, respectively. Their reactions with aromatic aldehydes afforded the corresponding 2-hydrazono pyrimi-
dine derivatives 11a-c. The structure of these reactions products were established based on both elemental
analysis and spectral data studies.
Keywords: Pyrimidinethione; Pyrimidine; Triazine; Pyrazolopyrimidine and hydrazo pyrimidine.
INTRODUCTION
The reported biological activity of pyrimidine deriva-
6-aryl-5-cyano-N-methyl-2-hydrazino pyrimidine-4-one
3a-c (cf. Equation 1). The structure of the reaction products
3a-c was established based on the data of IR,1H-NMR spec-
tra and elemental analysis (cf. Tables 1 and 2). The IR spec-
tra of these compounds showeda band of the CN and imidic
CO as well as the band of –NH2 and –NH- in each case. The
1H-NMR spectra for compounds 3a-c revealed the signals of
aromatic (or furyl) and CH3 as well as the signals of NH, NH2
as hydrazine; moreover the mass spectrum of 3a as typical
example of the series gave m/z = 241 which corresponded to
the exact molecular formula C12H11N5O. Synthons 3a-c are
used as the starting material of synthesis of many pyrimidine
derivatives. Thus it has been found that compound 3a-c re-
acted with acetic anhydride to give the cyclized compounds
triazolo[3,4-b]pyrimidinone derivatives 4a-c. The structure
of the reaction products 4a-c were confirmed based on the
tives,1-10 especially 2-hydrazinopyrimidines as antifungal an-
tiviral and antibacterial11-14 agents as well as the leishman-
icidal activity15,16 of the annelated pyrimidine derivatives,
stimulated my interest in the synthesis of several new hetero-
cyclic derivatives of these ring systems. The 6-aryl-5-cyano-
4-pyrimidinone-2-thione derivatives 1a-c were prepared ac-
cording to literature procedures17-19 and used as good starting
material for the synthesis of the corresponding 2-hydrazino-
pyrimidine derivatives 3a-c which were used, in turn, as the
starting materials for the present study.
RESULTS AND DISCUSSION
1
data of IR, H-NMR spectra and elemental analysis (cf. Ta-
Thus it has been found that compounds 1a-c reacted
with methyl iodide (1:2) in sodium methoxide to give 2-
S,N-dimethyl-pyrimidine-4-one derivatives 2a-c. The struc-
ble 1 and 2). The IR spectra of these compounds showed
bands of CN and imidic CO in each case while the band of
NH, NH2 disappeared. The 1H-NMR spectra for compounds
4a-c revealed two –CH3 bands as well as the signals of an ar-
omatic (or furyl). The synthetic potential of 3a-c was further
directed toward the synthesis of tiazolo[3,4-b]pyrimidine de-
rivative through their reactions with formic acid. Thus it has
been found that 3a-c reacted with formic acid to give the cor-
responding triazolo[3,4-b]pyrimidine derivatives 7a-c. The
1
ture of 2a-c was established based on the data of IR, H-
NMR spectra and elemental analysis (cf. Table 1 and 2). The
IR spectra of these compounds showed a band of CN and
1
imidic CO in each case. While their H-NMR spectra re-
vealed the signal of aromatic (or furyl) and the two CH3 sig-
nals. Synthone 2a-c reacted with hydrazine hydrate to give

548 J. Chin. Chem. Soc., Vol. 51, No. 3, 2004
Al-Shara’ey
Table 1. Characterization Data of the Newly Synthesized Compounds
% of Analysis Calcd./Found
Comp. M.P. (°C) Yield (%) Cryst. Solvent. Molecular Formula
C
H
N
S
Cl
60.70
60.60
53.52
53.70
53.44
53.50
59.75
59.70
52.27
52.30
51.95
51.80
63.39
63.31
56.09
56.11
56.47
56.44
62.15
62.00
54.64
54.65
54.77
54.71
58.44
58.39
52.55
52.51
49.68
50.22
66.89
66.91
60.09
60.11
61.02
61.10
69.30
69.20
62.79
62.70
63.95
63.91
4.28
4.30
3.43
3.30
3.64
3.70
4.56
4.50
3.63
3.61
3.89
3.82
4.15
4.09
3.34
3.35
3.53
3.41
3.59
3.48
2.80
2.74
2.91
2.90
3.89
3.82
3.21
3.20
3.19
3.53
4.92
4.89
4.12
4.00
4.41
4.45
4.56
4.60
3.85
3.91
4.08
4.08
16.34
16.40
14.40
14.50
17.00
17.10
29.05
29.10
25.41
25.32
30.30
30.31
26.42
26.40
23.37
23.41
27.45
27.42
27.90
27.82
24.52
24.52
29.05
28.99
27.27
27.11
24.53
24.41
26.75
26.70
22.95
22.85
20.62
20.64
23.73
23.63
21.28
21.31
19.26
19.31
21.94
21.89
12.45
12.60
10.98
11.00
12.96
13.00
-
-
2a
272
74
78
82
65
70
84
80
78
82
80
76
82
70
65
66
76
62
65
72
82
82
Ethanol
DMF
C13H11N3SO
C13H10N3SOCl
C11H9N3SO2
C12H11N5O
-
12.18
12.20
2b
2c
> 300
-
266-8
Ethanol
Ethanol
DMF
-
-
3a
258
> 300
278
-
-
-
12.89
12.79
3b
3c
C12H10N5OCl
C10H9N5O2
-
-
-
Ethanol
Ethanol
DMF
-
-
-
-
4a
286
C14H11N5O
-
-
-
11.85
11.78
4b
4c
293
C14H10N5ClO
C12H9N5O2
-
-
-
283
Ethanol
Ethanol
DMF
-
-
-
-
7a
290
C13H9N5O
-
-
-
12.43
12.38
7b
7c
299
C13H8N5ClO
C11H7N5O2
-
-
-
288
Ethanol
DMF
-
-
-
-
9a
296
C15H12N6O2
C15H11 N6O2Cl
C13H10N6O3
C17H15N5O
-
-
10.36
10.29
-
-
9b
9c
260-2
Acetic Acid
DMF
-
-
220-2
210
-
-
-
-
10a
10b
10c
11a
11b
11c
Acetic Acid
Acetic Acid
Acetic Acid
Acetic Acid
DMF
-
-
-
10.46
10.43
-
286-8
240-2
297-9
312
C17H14N5OCl
C15H13N5O2
C19H15N5O
-
-
-
-
-
-
-
-
-
9.77
9.66
-
C19H14N5OCl
C17H13N5O2
-
-
295-7
Acetic Acid
-
-
structure of the products 7a-c was established based on the
data given from elemental analysis, IR and 1H-NMR studies
(cf. Tables 1 and 2). The formation of triazolo[3,4-b]pyrimi-
dine derivatives 7a-c was most probably as shown in chart I
via the non isolables 6a-c. The synthetic potential of com-
pounds 3a-c was further investigated through their reaction
with ethyl cyanoacetate as active methylene containing re-
agents. Thus it has been found that 3a-c reacted with ethyl-
cyanoacetate in glacial acetic acid to afford the correspond-
ing 5-cyano-6-aryl-2-(1-pyrazolonyl) N-methyl pyrimidine-
4-one derivatives 9a-c. Compounds 9a-c were most probably
formed via elimination of ethanol to give the non isolable in-
termediates 8a-c; the latter cyclized via addition of NH to the
nitrile function and tautomerization (cf. chart 1).

Reaction of Pyrimidinonethione Derivatives
J. Chin. Chem. Soc., Vol. 51, No. 3, 2004 549
Table 2. IR, n (cm-1) and 1H-NMR d (PPM)
Comp.
IR (kBr) n (cm-1)
1H-NMR, (DMSO-d6) d (PPM)
2a
3070 (aromatic, C-H); 2985, 2972 (aliphatic, C-H); 2214
(CN); 1690 (ring CO); 1620 (C=N); and 1600(C=C).
3070 (aromatic, C-H); 2982, 2968 (aliphatic, C-H); 1690
(ring, CO); 2214 (CN); 1618 (C=N); and 1603 (C=C).
3070 (aromatic, C-H); 2975 (aliphatic, C-H); 1690 (ring,
CO); 1617 (C=N); 1600 (C=C); and 2214 (CN).
3359, 3332, 3270, 3180 (NH2 and NH); 3079 (aromatic C-
H); 2218 (CN); 1690 (ring CO); 1615 (C=N); and 1602
(C=C).
2.2 (s, 3H, N-CH3); 1.3 (s, 3H, -S-CH3); and 7.3-8.2 (m,
5H, ArH¢ s).
2.3 (s, 3H, N-CH3); 1.3 (s, 3H, -S-CH3); and 7.1-7.9 (m,
4H, ArH¢ s).
2.3 (s, 3H, N-CH3); 1.3 (s, 3H-S-CH3); and 6.4-7.2 (m,
3H, furyl).
2.2 (s, 3H, N-CH3); 6.2 (s, br, 1H, NH, hydrazino); 7.1-
8.2 (m, 5H, ArH¢ s); and 9.1 (s, br, 2H, NH2, hydrazino).
2b
2c
3a
3b
3c
3390, 3325, 3280, 3182 (NH2 and NH); 3074 (aromatic C-
H); 2217 (CN); 1690 (ring CO); 1612 (C = N); and 1600
(C=C).
3390, 3325, 3280, 3182 (NH2 and NH); 3074 (aromatic, CH);
2217 (CN); 1690 (ring, CO); 1612 (C=N); and 1600 (C=C).
2.3 (s, 3H, N-CH3); 6.4 (s, br, 1H, NH, hydrazin); 7.2-
7.9 (m, 4H, ArH¢s); and 9.3 (s, br, 2H, NH2, hydrazino).
2.2 (s, 3H, NCH3); 5.9 (s, br, 1H, NH, hydrazin); 6.4 -
7.0 (m, 3H, furyl, H¢s); and 8.6 (s, br, 2H, NH2,
hydrazino).
4a
4b
4c
7a
7b
7c
9a
3070 (aromatic, C-H); 2985, 2972 (aliphatic, C-H); 2216
(CN); 1690 (ring, CO); 1620 (C=N); and 1600 (C=C).
3070 (aromatic, C-H); 2981, 2968 (aliphatic, C-H); 1685
(ring CO); 2214 (CN); 1618 (C=N); and 1602 (C=C).
3070 (aromatic C-H); 2975, (aliphatic C-H); 1690 (ring CO);
1618 (C=N); and 1600 (C=C); 2214 (CN).
3083 (aromatic, C-H); 2984, 2897 (aliphatic, C-H); 2218
(CN); 1693 (ring, CO); 1615 (C=N); and 1601 (C=C).
3078 (aromatic C-H); 2980, (aliphatic C-H); 2213 (CN);
1685 (ring, CO); 1612 (C=N); and 1600 (C = C).
3080 (aromatic, C-H); 2979, 2873 (aliphatic, C-H); 2215
(CN); 1687 (ring, CO); 1613 (C=N); and 1600 (C=C).
3087 (aromatic, C-H); 2216, (CN); 1685, 1690 (ring and
amidic, CO); 1612 (C=N) and 1600 (C=C).
2.3 (s, 3H, N-CH3); 1.7 (s, 3H, CH3); and 7.2-8.3 (m,
5H, ArH¢ s).
2.3 (s, 3H, N-CH3); 1.6 (s, 3H, CH3); and 7.1-7.9 (m,
4H, ArH¢ s).
2.2 (s, 3H, N-CH3); 1.6 (s, 3H, CH3); and 6.4-7.1 (m,
3H, furyl).
2.2 (s, 3H, N-CH3); and 7.0-8.4 (m, 5H, aromatic and
triazole, H-5 proton).
2.3 (s, 3H, N-CH3); and 7.0-8.3 (m, 4H, aromatic and
triazole H-5 proton).
2.2 (s, 3H, N-CH3); and 6.4-7.2 (m, 3H, furyl and
triazole, H-5).
2.2 (s, 3H, N-CH3); 3.6 (s, 1H, pyrazole H-4); 4.7 (s,
1H, N-H); 5.3 (s, br, 2H, NH2); and 6.9-7.8 (m, 5H,
ArH¢ s).
9b
9c
3094 (aromatic, C-H); 2220, (CN); 1699, 1690 (ring and
amidic, CO); 1610 (C=N) and 1600 (C=C).
3085 (aromatic, C-H); 2222, (CN); 1687, 1690 (ring and
amidic, CO); 1613 (C=N) and 1600 (C=C).
2.3 (s, 3H, N-CH3); 3.2 (s, 1H, pyrazole H4); 4.5 (s, 1H,
NH); 5.6 (s, br, 2H, NH2); and 7.1-7.9 (m, 4H, ArH¢ s).
2.2 (s, 3H, N-CH3); 3.0 (s, 1H, pyrazole H-4); 4.8 (s,
1H, N-H); 5.4 (s, br, 2H, NH2); and 6.6-6.8 (m, 3H,
furyl H¢ s).
10a
10b
10c
3078 (aromatic, C-H); 2984, 2897 (aliphatic, C-H); 2218
(CN); 1693 (ring, CO); 1615 (C=N); and 1602 (C=C).
3078 (aromatic, C-H); 2980, 2890 (aliphatic, C-H); 2213
(CN); 1685 (ring, CO); 1610 (C=N); and 1600 (C=C).
3080 (aromatic C-H); 2979, 2873 (aliphatic C-H); 2215
(CN); 1687 (ring CO); 1612 (C=N); and 1600 (C=C).
2.3 (s, 3H, N-CH3); 1.5 (s, 6H, two CH3); and 7.2-8.4
(m, 5H, aromatic and pyrazole H-4 protons).
2.2 (s, 3H, N-CH3); 1.5 (s, 6H, two CH3); and 7.1-8.5
(m, 5H, aromatic and pyrazole H-4 protons).
2.2 (s, 3H, N-CH3); 1.4 (s, 6H, two CH3); 6.2-6.8 (m,
3H, furyl H s); and 8.6 (s, br, 1H, pyrazole H-4
protons).
11a
11b
3232, 3198 (one, NH); 3070, (aromatic, C-H); 2980-2894
(aliphatic C-H); 2218 (CN); and 1690 (ring, CO).
3232, 3197 (one NH); 3084, (aromatic, C-H); 2980-2890
(aliphatic, C-H); 2222 (CN); 1612 (ring, CO); 1613 (C=N;
and 1600 (C=C).
2.3 (s, 3H, N-CH3); 5.3 (s, 1H, -CH=N-); 7.1-8.2 (m,
10H, aromatic protons); and 9.7 (s, br, 1H, N-NH).
2.3 (s, 3H, N-CH3); 5.5 (s, 1H, -CH=N-); 7.2-8.1 (m,
9H, aromatic protons); and 9.9 (s, br, 1H, N-NH-).
11c
3220, 3190 (one, NH); 3070, (aromatic, C-H); 2981-2873
(aliphatic, C-H); 2218 (CN); 1685 (ring, CO); 1610 (C=N;
and 1600 (C=C).
2.3 (s, 3H, N-CH3); 5.2 (s, 1H, -CH=N-); 6.3-6.8 (m,
5H, aromatic); and 9.7 (s, br, 1H, N-NH-).

550 J. Chin. Chem. Soc., Vol. 51, No. 3, 2004
Al-Shara’ey
O
N
O
N
O
NC
CH3
CH3
NC
Ar
NC
N
NH2NH2.H2O
H
N
N
CH3I
1:2
NHNH2
SCH3
Ar
SCH3
Ar
N
a-c
3-
a-c
2-
a-c
Ar
1-
a
b
C6H5
C6H4-Cl-p
=
=
C4H3-O-
c
=
1
Equation-
The proposed mechanism finds support by appearance
of newly formed NH2, NH bands in IR spectrum and by 1H-
NMR spectra as well as elemental analysis (cf Table 1 and 2).
The compounds 3a-c reacted in further investigation with
acetylacetone to afford the corresponding 2-(1-pyrazolonyl)
pyrimidine-4-one derivatives 10a-c, respectively. These re-
action products were most likely obtained via the elimination
of water molecules followed by cyclization through enoliza-
tion and dehydration (cf. Equation 2).
hyde in glacial acetic acid to give the Schiff’s base 11a-c. The
products showed no bands of NH2 function in IR spectra.
Their mass spectra gave m/z = 327 and 362, respectively,
which corresponded to the exact molecular weights of molec-
ular formula C19H15N5O and C19H14N5OCl of the assigned
structures (cf. chart I).
EXPERIMENTAL PROCEDURE
The structure of compounds 10a-c were confirmed by
elemental analysis, IR, and 1H-NMR (cf. Tables 1 and 2). The
IR spectra showed the signal of CN and imidic CO while the
1H-NMR spectra revealed the signal for the CH3 group as
well as aromatic (furyl protons) and pyrazole H-4 protons. A
further demonstration for the activity of compounds 3a-c was
achieved through their condensation with aromatic aldehy-
edes; thus it has been found that 3a-c reacted with benzalde-
All melting points are uncorrected. The IR spectra in
kBr discs were recorded on Perkin-Elmer FT-IR type 4 and
1
Pye Unicam SP – 1100-Spectrophotometers. The H-NMR
spectra were recorded on Varian Em 390-90 MHZ, Gemini
200 and Bruker WP-80 Spectrometers using CDCL3, DMSO-
d6 and (CD3)2 CO as solvents and TMS as an internal stan-
dard. Chemical shifs are expressed as d ppm units. Mass
O
O
NC
Ar
CH3
N
CH3
NC
Ar
N
H3CCOCH2COCH3
NHN
N
NHNH2
N
O
CH3
3-
H3C
a-c
O
O
NC
Ar
CH3
N
NC
Ar
CH3
N
N
N
N
NHN
N
CH3
CH3
HO
H3C
a-c
H3C
10-
Equation-
2

Reaction of Pyrimidinonethione Derivatives
J. Chin. Chem. Soc., Vol. 51, No. 3, 2004 551
O
O
NC
NC
CH3
NCCH2CO2C2H5
CH3
PhCHO
N
N
Ph
NHNH
NHN
N
8
N
Ar
Ar
11
H
NC
a-c
O
a-c
O
O
N
O
N
NC
Ar
CH3
N
HCO2H
NC
CH3
NC
CH3
N
N
NHNH
H
N
a-c
O
NHNH2
N
Ar
NH
Ar
O
a-c
3
5
O
HN
NC
Ar
CH3
O
N
(CH3CO)2O
NC
CH3
NH
N
N
N
H
N
C
NH
Ar
N
HO
a-c
O
H2N
9
6
a-c
O
CH2(COCH3)2
O
O
NC
Ar
CH3
NC
CH3
N
N
NC
CH3
N
N
N
N
Ar
H3C
N
N
N
N
Ar
N
C
H3C
N
CH3
HC
a-c
a-c
7
a-c
4
10
Chart-
1
spectra were recorded on a Hewlett-Packard-GC-MS type
2988 series using DIP technique at 70 ev. Microanalyses
were performed at the Microanalytical Center of Cairo Uni-
versity using a Perkin-Elmer 2400 CHN elemental analyzer.
The compounds 1a,b and c were prepared according to litera-
ture procedures.17-19
proper solvent (at boiling point of the solvent) and after con-
centration and cooling it gave 2a-c, respectively (cf. Table 1
and 2).
2a as pale yellow crystals with m.p. 272 °C, yield 74%;
2b as brown crystals with m.p. >300 °C, yield 78%; 2c as pale
yellow crystals with m.p. 266-268 °C, yield 82%.
Reactions with alkyl iodide
Reactions with hydrazine hydrate
Synthesis of 2-S-N-dimethyl pyridine 4-one derivatives
2a-c (General procedure)
Synthesis of 6-aryl-5-cyano-N-methyl-2-hydrazino pyri-
dines-4-one derivatives 3a-c (General procedure)
A solution of each of 1a-c (0.01 mole) in methanolic so-
dium methoxide (0.01 mole) prepared from 0.01 atom of so-
dium metal in 30 mL methanol was treated with methyl-io-
dide (0.02 mol) and heated under reflux for 10 hours. The
solid product obtained on pouring onto cold water was fil-
tered off, washed with water and recrystallized from the
A mixture of each of 2a-c (0.02 mole) in methanol (30
mL) was treated with excess hydrazine hydrate (5 mL) and
then heated under reflux for 7 hours. The solid products ob-
tained from hot solution after cooling were filtered off and
recrystallized from the proper solvent (at boiling point of the
solvent) and after concentration and cooling it gave 3a-c, re-

552 J. Chin. Chem. Soc., Vol. 51, No. 3, 2004
Al-Shara’ey
spectively (cf. Table 1 and 2).
recrystallized from the proper solvent (at boiling point of the
solvent) and after concentration and cooling it gave 11a-c, re-
spectively (cf. Table 1 and 2).
3a as pale yellow crystals with m.p. 258 °C, yield 65%;
3b as brown crystals with m.p. >300 °C, yield 70%; 3c as yel-
low crystals with m.p. 278 °C, yield 84%.
11a as orange crystals with m.p. 297-9 °C, yield 72%;
11b as yellow crystals with m.p. 312 °C, yield 82%; 11c as
brown crystals with m.p. 295-7 °C, yield 82%.
Reactions of 3a-c with formic acid and acetic anhydride
Synthesis of triazolo[3,4-b]pyrimidine derivatives 4a-c and
7a-c
A mixture of 3a-c (0.01 mole) and each of formic acid
(20 mL) or acetic anhydride (20 mL) was heated under reflux
for 4 hours – the solid products obtained hot or after cooling
were filtered off and recrystallized from the proper solvent
(at boiling point of the solvent) and after concentration and
cooling it gave 4a-c and 7a-c, respectively (cf. Table 1 and 2).
4a as pale yellow crystals with m.p. 286 °C, yield 80%;
4b as pale brown crystals with m.p. 293 °C, yield 78%; 4c as
yellow crystals with m.p. 283 °C, yield 82%; 7a as yellow
crystals with m.p. 290 °C, yield 80%; 7b as brown crystals
with m.p. 299 °C, yield 76%; 7c as yellow crystals with m.p.
288 °C, yield 82%.
Received April 28, 2003.
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9a as pale brown crystals with m.p. 296 °C, yield 70%;
9b as yellow crystals with m.p. 260-2 °C, yield 65%; 9c as
brown crystals with m.p. 220-2 °C, yield 66%; 10a as pale
yellow crystals with m.p. 210 °C, yield 76%; 10b as yellow
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with m.p. 240-2 °C, yield 65%.
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Reactions of 3a-c with benzaldehyde
Synthesis of shifts 11a-c (General procedure)
A solution of each of 3a-c (0.01 mol) in acetic acid (30
mL) was treated with benzaldehyde (0.01 mol). The reaction
mixture was heated under reflux for 5 hours. The solid prod-
ucts obtained hot or after cooling were filtered off and