v-Triazolines. Part 38. New synthesis of 4-aminoquinazolines and 6-aminopurines

Article abstract of DOI:10.1039/a703023a

2-Alkyl-4-arylaminoquinazolines 6 have been prepared by condensation of N-(2-cyanophenyl)amidines 5 with arylamines. The amidines 5 were obtained by thermal rearrangement of N-(2-cyanophenyl)-5-morpholino-v-triazolines 4. The synthesis has been applied to the preparation of 2-alkyl-6-arylaminopurines 12.

Full text of DOI:10.1039/a703023a

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v-Triazolines. Part 38.1 New synthesis of 4-aminoquinazolines and
6-aminopurines
Emanuela Erba* and Daniela Sporchia
Istituto di Chimica Organica, Facoltà di Farmacia, Università degli Studi di Milano,
Via Venezian, 21, I-20133 Milano
2-Alkyl-4-arylaminoquinazolines 6 have been prepared by condensation of N-(2-cyanophenyl)amidines 5
with arylamines. The amidines 5 were obtained by thermal rearrangement of N-(2-cyanophenyl)-5-
morpholino-v-triazolines 4. The synthesis has been applied to the preparation of 2-alkyl-6-
arylaminopurines 12.
R′
Introduction
CN
N
i
+
+
O
Previous papers from our research group have been concerned
with the synthetic use of 5-amino-4,5-dihydro-v-triazoles as
versatile precursors of N-containing heterocycles. A major
advantage of using triazolines resides in their ready availability
by 1,3-dipolar cycloaddition of enamines and azides which, in
most instances, can be performed by a very simple procedure
entailing the direct three-component reaction of an aldehyde
(or ketone), an aliphatic secondary amine and an aryl azide.
Several transformation paths are known for the 5-amino-v-
triazoline ring,2 but the most studied and synthetically useful is
the thermally induced elimination of nitrogen accompanied
by rearrangement to tertiary amidines. In the past, we found
straightforward routes to N-containing heterocycles by combin-
ing the synthesis of triazolines, their rearrangement to amidines
and appropriate transformations of the latter.1,3
HN
N
R′
CHO
N
N
N3
CN
1
2
3
O
a R′ = Me
b R′ = Et
c R′ = Bz
4
a R′ = Me
b R′ = Et
c R′ = Bz
iii
ii
NH–Ar
CN
N
iv
R′
R′
N
N
N
O
6
As a further development in this field, we now report a new
and easy synthesis of 2-alkyl-4-amino- and -4-arylaminoquin-
azolines which can be successfully applied also to the prepar-
ation of medicinally interesting 2-alkyladenines and their 6-N-
aryl derivatives.
a R′ = Et, Ar = C6H4OEt-4
5
b R′ = Et, Ar = C6H4OMe-4
c R′ = Et, Ar = C6H4Cl-4
d R′ = Et, Ar = C6H4OMe-3
e R′ = Et, Ar = C6H4CF3-3
a R′ = Me
b R′ = Et
c R′ = Bz
f
R′ = Me, Ar = Ph
g R′ = Bz, Ar = Ph
Results and discussion
Scheme 1 Reagents and conditions: i, CHCl3, RT, 4 h; ii, p-xylene,
reflux, 3 h; iii, p-xylene, reflux, 4 h; iv, ArNH2ؒHCl, 180 ЊC, 2 h or
ArNH2, EtCO2H, reflux, 2 h
Reaction of an aldehyde 1a–c with morpholine 2 and 2-
azidobenzonitrile 3 in benzene at room temperature readily
afforded the corresponding triazolines 4a–c (in the trans con-
figuration) by cycloaddition of the azide to the intermediate
enamines (see Scheme 1). Compounds 4 when heated in boiling
p-xylene gave the corresponding amidines 5a–c. Cleavage of the
N(1)᎐N(2) bond is made easier by virtue of the electron-
withdrawing effect of the electron-poor substituent on N-1;
nitrogen elimination and hydrogen migration then follow. As
expected, compounds 5 could be obtained directly when the
starting materials were allowed to react at an elevated
temperature.
aniline reactant was advantageous because some propion-
anilide was unavoidably formed as a by-product.
The structures of compounds 6a–g were established on the
1
basis of IR and H and 13C NMR data. Although tautomeric
forms of these compounds are possible, this aspect was not
studied in detail. However, the 15N NMR spectrum of 6b shows
a signal at δ 306 associated with the NH group which is typical
of a diarylamine4 suggesting the predominance of the aromatic
quinazoline form, at least in solution.
The amidines 5a–c underwent cyclocondensation with prim-
ary arylamines to give the corresponding 2-alkyl-4-arylamino-
quinazolines 6a–g (Scheme 1), although relatively high temper-
atures and the presence of an acid (in the form of amine salt or
free organic acid) were necessary. Preferably, the acid was used
in at least equimolar amount, which is justified by the basicity
of the products 6, obtained as salts. Two condensation tech-
niques were applied, with similar results in most cases: (i) heat-
ing of the amidine 5 with an equimolar amount of arylamine
hydrochloride without solvent in a sealed bomb or (ii) refluxing
of the arylamine and the amidine 5 in an organic acid, prefer-
ably propionic acid. In this latter case use of an excess of the
The condensation leading to compounds 6 is understandable
in terms of an acid-catalyzed addition of arylamine to the
nitrile group, followed by ring-closure and the elimination of
morpholine. The low yields of the quinazoline product
obtained for 6c and 6e even when longer reaction times were
used, is explained by the lower nucleophilicity of the substi-
tuted arylamines. In both cases, besides the expected amino-
quinazoline, 2-propyl-4-quinazolone 7 was isolated as the result
of hydrolysis. A slightly different result was obtained with 3-
phenylpropionamidine 5c when the expected 2-phenylethyl-
quinazoline 6g was accompanied by a substantial amount of 4-
amino-3-benzyl-2-morpholinoquinoline 8b, generated probably
J. Chem. Soc., Perkin Trans. 1, 1997
3021

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by competitive acid-catalyzed tautomerization of the amidine
followed by intramolecular addition of the enamine carbon to
the nitrile group (Scheme 2). This mechanism was confirmed
centrated under reduced pressure. The residue was recrystal-
lized to afford the triazolines 4a–c, the analytical and spectral
data for which are listed in Table 1.
General procedure for the preparation of 2-(2-alkylethyliden-
amino-1-morpholino)benzonitriles 5a–c
NH2
CN
R′
N
O
R′
N
O
i
i
The azide 3 (35 mmol) and the aldehyde 1a–c (52 mmol) were
dissolved in p-xylene (40 ml) and morpholine (52 mmol) were
added dropwise to the solution. The mixture was then refluxed
for 5 h until disappearance of starting material [TLC, ethyl
acetate–cyclohexane (2:3)]. The crude reaction mixture was
dried (Na2SO4) and concentrated under reduced pressure and
the residue was recrystallized. Analytical and spectral data are
listed in Table 1.
5b, c
N
H
N
8
a R′ = Et
b R′ = Bz
Scheme 2 Reagents and conditions: i, PhNEt2ؒHCl, 180 ЊC, 2 h
General procedure for the preparation of 5-(1-morpholino-
alkylamino)-1H-imidazole-4-carbonitriles 11a,b
by treating the amidines 5b,c with N,N-diethylaniline hydro-
chloride when with acidic catalysis, but in the absence of
primary amine, both compounds produced the corresponding
quinolines 8a,b as the sole reaction products.
The condensation of the amidines 5 with aliphatic amines
gave low yields of final products. However, reaction of the ami-
dine 5b with ammonium acetate afforded a 40% yield of 4-
amino-2-propylquinazoline 9. The above synthesis was suc-
cessful for the preparation of other heterocycles containing
a condensed pyrimidine ring; thus, the adenine derivatives
12a–c were obtained by the reaction of 4-methoxyaniline or
The azide 10 (8 mmol) and the aldehyde 1a,b (8 mmol) were
dissolved in toluene (10 ml) to which morpholine (8 mmol) was
then added dropwise. The reaction mixture was stirred at room
temperature for 14 h after which it was dried (Na2SO4) and
concentrated under reduced pressure. The residue was chro-
matographed with ethyl acetate. Analytical data are listed in
Table 1.
General procedure for the preparation of (2-alkylquinazolin-4-yl)-
arylamines 6a–g
Method A. The arylamine (8.1 mmol) was dissolved in prop-
ionic acid (10 ml) and amidine 5a–c (6.7 mmol) was added to
the solution. This was then refluxed for 2 h until disappearance
of starting material [TLC, ethyl acetate–cyclohexane (2:3)].
After evaporation of most of the propionic acid, the residue
was dissolved in CH2Cl2 and the solution first washed with
aqueous NaHCO3 and then thrice extracted with 1  aqueous
HCl. The acid solution was washed with diethyl ether, basified
at pH 8 with Na2CO3 and extracted with diethyl ether. After
evaporation the crude reaction mixture was crystallized or
purified by chromatography with ethyl acetate–cyclohexane
(3:7). Analytical and spectral data are listed in Table 1.
Method B. The arylamine hydrochloride (4.6 mmol) and the
amidine 5 (5.5 mmol) mixed and sealed in a bomb (vol. 2 ml)
were heated in a bath at 180 ЊC for 2 h. The residue was taken
up with CH2Cl2 and the solution washed with aqueous
NaHCO3, dried (Na2SO4) and evaporated under reduced pres-
sure. The crude residue was purified by chromatography with
ethyl acetate–cyclohexane (3:7). Analytical and spectral data
are listed in Table 1.
O
NH2
CN
N
NH
N
N3
N
H
N
Pr
N
Pr
7
9
10
CN
NHR′′′
N
R′′
N
N
N
N
N
H
N
H
N
12
R′′
O
11
a R′′ = Et
b R′′ = Pr
a R′′ = Et, R′′′ = C6H4OMe-4
b R′′ = Pr, R′′′ = C6H3(OMe)2-3, 4
c R′′ = Pr, R′′′ = H
3,4-dimethoxyaniline with the amidines 11a,b in the presence
of ammonium acetate. The amidines 11a,b were obtained
from 4-azido-5-cyanoimidazole5 10, the aldehydes 1a,b and
morpholine.
In conclusion, the thermal rearrangement of 5-amino-v-
triazolines is the method of choice for the easy and straight-
forward preparation of functionalized amidines which are, in
turn, precursors of substituted N-heterocycles.
General procedure for the preparation of (2-alkyl-9H-purin-6-yl)-
arylamines 12a–c
The arylamine hydrochloride (3 mmol) and the amidine 11a,b
(2 mmol) mixed and sealed in a bomb (vol. 2 ml) were heated in
a bath at 180 ЊC for 2 h. The residue was taken up with CH2Cl2
(20 ml) and water (20 ml) and basified with aqueous NaHCO3.
The insoluble product was filtered off and recrystallized. Ana-
lytical and spectral data are listed in Table 1.
Experimental
Mps were determined using a Büchi 510 capillary apparatus. IR
spectra were measured using a JASCO IR Report 100 instru-
ment. NMR spectra were obtained with Bruker AC 200 and
EM-390 Varian instruments. Column chromatography was
performed on silica gel with Kieselgel 60–70, 230 ASTM. 2-
Azidobenzonitrile 36 and 5-azido-3-cyanoimidazole 105 are
known compounds.
Preparation of 3-alky-4-amino-2-morpholinoquinolines 8a,b
Diethylphenylamine hydrochloride (4.6 mmol) mixed with the
amidines 5b,c (5.5 mmol) in a sealed bomb (vol. 2 ml), were
heated in a bath at 180 ЊC for 2 h. The residue was taken up with
CH2Cl2 and the solution washed with aqueous NaHCO3, dried
(Na2SO4) and evaporated to dryness under reduced pressure.
The crude residue was purified by chromatography [ethyl
acetate–cyclohexane (2:3)]. Analytical and spectral data are
listed in Table 1.
General procedure for the preparation of 2-(4-alkyl-4,5-dihydro-
5-morpholino-1H-1,2,3-triazol-1-yl)benzonitriles 4a–c
The azide 3 (35 mmol) and the aldehyde 1a–c (52 mmol) were
dissolved in CHCl3 (40 ml) to which morpholine (52 mmol) was
then added dropwise. The reaction mixture was stirred at room
temperature for 4 h after which it was dried (Na2SO4) and con-
Preparation of (2-propylquinazolin-4-yl)amine 9 and (2-propyl-
9H-purin-6-yl)amine 12c
The amidine 5b or 11b (5 mmol) and NH4CO2Me (50 mmol)
mixed and sealed in a bomb (vol. 2 ml) were heated in a bath at
3022
J. Chem. Soc., Perkin Trans. 1, 1997

View Article Online
Table 1
Found (%) (requires)
Compound
(Formula)
Yield (%) Mp (T/ЊC) νmax/cmϪ1
[method] [solv.] (Nujol)
δH(J/Hz)a
C
H
N
4a
85
119
2200 (CN) 1.32 (3H, d, J 7.2, CH3), 2.21–2.39 (4H, m, CH2NCH2), 3.37–3.55
(4H, m, CH2OCH2), 4.56 (1H, dq, J 2.28 and 7.2, H-4), 5.19 (1H,
d, J 2.28, H-5), 7.17 (1H, d, J 8.00 and 1.02, H-3Ј), 7.52–7.63
(2H, m, H-2Ј and H-4Ј), 7.98 (1H, dd, J 8.00 and 1.02, H-5Ј)
61.7
6.5
25.4
(C14H17N5O)
[Pri2O]
(62.0) (6.3) (25.8)
4b
56
83
2200 (CN) 0.82 (3H, t, J 7.36, CH3), 1.27–1.58 (2H, m, CH2CH3), 2.18–2.26
62.8
6.9
24.2
(C15H19N5O)
[Pri2O]
(2H, m, CH2CH2), 3.53–3.58 (4H, m, CH2NCH2), 3.73–3.78 (4H, (63.1) (6.7) (24.6)
m, CH2OCH2), 6.77 (1H, dd, J 7.8 and 1.06, H-5Ј), 6.97 (1H, dt, J
7.8 and 1.06, H-3Ј), 7.42 (1H, dt, J 7.8 and 1.43, H-4Ј), 7.51 (1H,
dd, J 7.8 and 1.43, H-2Ј)
4c
65
85
108
2200 (CN) 1.93–2.17 (4H, m, CH2NCH2), 2.50–2.2 (1H, m, CH benzylic),
68.95 6.5
19.9
(C20H21N5O)
[Pri2O]
3.25–3.48 (5H, m, CH2OCH2 and 1H benzylic), 4.72–4.80 (1H, (69.2) (6.1) (20.2)
m, H-4), 5.26 (1H, d, J 2.52, H-5) and 7.16–7.89 (9H, m, arom.)
2200 (CN) 1.06 (3H, t, J 7.69, CH3), 2.27 (2H, q, CH2, J 7.69), 3.51–3.59
(4H, m, CH2NCH2), 3.74–3.79 (4H, m, CH2OCH2), 6.79 (1H, d,
J 7.88, H-5Ј), 6.98 (1H, t, J 7.88, H-3Ј), 7.43 (1H, dt, J 7.88 and
1.38, H-4Ј), 7.52 (1H, dd, J 7.88 and 1.38, H-2Ј)
5a
Oil
68.9
7.4
17.07
(C14H17N3O)
(69.1) (7.05) (17.3)
5b
52
83
2200 (CN) 0.82 (3H, t, J 7.36, CH3), 1.27–1.58 (2H, m, CH2CH3), 2.18–2.26
69.85 7.8
16.1
(C15H19N3O)
[Pri2O]
(2H, m, CH2CH2), 3.53–3.58 (4H, m, CH2NCH2), 3.73, 3.78 (4H, (70.1) (7.45) (16.35)
m, CH2OCH2), 6.77 (1H, dd, J 7.8 and 1.06, H-5Ј), 6.97 (1H, dt, J
7.8 and 1.06, H-3Ј), 7.42 (1H, dt, J 7.8 and 1.43, H-4Ј), 7.51 (1H,
dd, J 7.8 and 1.43, H-2Ј)
5c
52
75.6
2200 (CN) 2.52–2.78 (4H, m, CH2CH2), 3.54–3.59 (4H, m, CH2NCH2),
3.71–3.75 (4H, m, CH2OCH2), 6.59–7.55 (9H, m, arom.)
3200 (NH) 1.03 (3H, t, J 7.53, CH3CH2), 1.44 (3H, t, J 6.96, CH3CH2O), 1.91
75.1
(75.2) (6.6) (13.2)
74.05 7.1 13.4
6.9
12.95
(C20H21N3O)
[EtOH]
176
6ab
(C19H21N3O)
60
[B]
[Pri2O]
(2H, sext, J 7.53, CH2CH2), 2.88 (2H, t, J 7.53, CH2CH2), 4.07 (74.3) (6.9) (13.6)
(2H, q, J 6.96, CH2O) 6.93–7.87 (8H, m, arom.) and 7.29 (1H, br
s, NH)
6b
65
[A]
188
3200 (NH) 1.03 (3H, t, J 7.40, CH3), 1.92 (2H, sext, J 7.40, CH2), 2.84 (2H, t,
J 7.40, CH2CH2), 3.84 (3H, s, OCH3), 6.95 (2H, d, J 9.08, H-3Ј
and H-5Ј), 7.38 (1H, br s, NH), 7.46 (1H, dt, J 8.1 and 1.35, H-6),
7.72 (2H, d, J 9.08, H-2Ј and H-6Ј), 7.77–7.87 (3H, m, H-5 and
H-7 and H-8)
73.7
6.7
14.25
(C18H19N3O)
[Pri2O]
(73.8) (6.5) (14.3)
6c
25
[A]
20
[B]
38
[A]
196
3275 (NH) 0.97 (3H, t, J 7.54, CH3), 1.86 (2H, sext, J 7.54, CH2CH3), 2.83
(2H, t, J 7.54, CH2CH2), 7.29 (2H, d, J 8.95, H-3Ј and H-5Ј),
7.38–8.54 (4H, m, arom.), 7.86 (2H, d, J 8.95, H-2Ј and H-4Ј) and
8.54 (1H, br s, NH)
3275 (NH) 1.04 (3H, t, J 7.40, CH3), 1.97 (2H, sext, J 7.40, CH2CH3), 2.93
(2H, t, J 7.40, CH2CH2), 3.87 (3H, s, OCH3), 6.68–7.89 (8H, m,
arom.), 7.48 (1H, br s, NH)
68.7
5.8
14.0
(C17H16ClN3)
[PriOH]
(68.6) (5.4) (14.1)
6d
105.5
73.6
6.7
14.2
(C18H19N3O)
[Pri2O]
(73.8) (6.5) (14.3)
6e
15
[B]
170
3250 (NH) 1.04 (3H, t, J 7.40, CH3), 1.98 (2H, sext, J 7.40, CH2CH3), 2.94
(2H, t, J 7.40, CH2CH2, 7.37–8.38 (8H, m, arom.) and 7.63 (1H,
br s, NH)
65.1
5.1
12.6
(C18H16F3N3)
[Pri2O]
(65.3) (4.9) (12.7)
6f
45
[A]
30
[A]
25
189
3200 (NH) 1.44 (3H, t, J 7.57, CH3), 2.97 (2H, q, J 7.57, CH2), 7.12–7.89
(9H, m, arom.), 7.46 (1H, br s, NH)
3200 (NH) 3.27 (4H, s, CH2CH2), 7.12–7.94 (14H, m, arom.), 7.79 (1H, br s,
NH)
77.05 6.4
(77.2) (6.1) (16.9)
81.0 6.1 12.6
(81.2) (5.9) (12.9)
69.8 7.6 16.05
(70.0) (7.4) (16.3)
16.7
(C16H15N3)
6g
[Pri2O]
141
(C22H19N3)
[EtOH]
158
8ac
3450
1.26 (3H, t, J 7.50, CH3), 2.78 (2H, q, J 7.50, CH2), 3.22 (4H, m,
(C15H19N3O)
[PriOH]
3550 (NH2) CH2NCH2), 3.90 (4H, m, CH2OCH2), 4.57 (2H, br s, NH2), 7.29–
7.84 (4H, m, arom.)
8b
28
45
168
[EtOH]
3450
3.15–3.29 (4H, m, CH2NCH2), 4.75–4.90 (4H, m, CH2OCH2),
74.9
6.8
13.0
(C20H21N3O)
3550 (NH2) 4.20 (2H, s, CH2Ph), 4.44 (2H, br s, NH2) and 7.15–7.85 (9H, m, (75.2) (6.6) (13.15)
arom.)
3050
3250 (NH2) (2H, t, J 7.57, CH2CH2), 7.37–8.19 (4H, m, arom.) and 7.67 (2H,
br s, NH2)
9
213
0.93 (3H, t, J, 7.57, CH3), 1.77 (2H, sext, J 7.57, CH2CH3), 2.65
70.20 7.0
(70.58) (6.95) (22.4)
22.2
(C11H13N3)
[PriOH]
11a
60
58
37
Oil
Oil
2200 (CN) 1.12 (3H, t, J 7.52, CH3), 2.48 (2H, q, J 7.52, CH2), 3.52–3.79
(8H, m, morpholine) and 7.35 (1H, s, H-2)
56.2
(56.6) (6.5) (30.0)
58.0 7.0 28.1
(58.3) (6.9) (28.3)
58.1 5.4 24.1
(58.5) (5.6) (24.4)
6.7
29.8
(C11H15N5O)
11b
2200 (CN) 0.96 (3H, t, J 7.50, CH3), 1.45–1.72 (2H, m, CH2), 2.45–2.53 (2H,
m, CH2), 3.60–3.78 (8H, m, morpholine) and 7.44 (1H, s, H-2)
3250 (NH) 1.30 (3H, t, J. 7.6, CH3), 2.76 (2H, q, J 7.6, CH2), 3.75 (3H, s,
OCH3), 6.90 (2H, d, J 8.9, H-3Ј and H-5Ј), 7.92 (2H, d, J 8.9,
H-2Ј and H-5Ј), 8.09 (1H, s, H-2), 9.58 (1H, br s, NH᎐Ar)
3250 (NH) 1.06 (3H, t, J 7.55, CH3), 1.98–2.18 (2H, m, CH2), 2.92–3.06 (2H,
(C12H17N5O)
12ad
272
[H2O]
(C14H15N5Oؒ
H2O)
12b
(C16H19N5O2)
29
35
239
[CH3CN]
51.4
6.4
22.1
m, CH2), 3.90 and 3.96 (6H, 2 s, OCH3), 6.89 (1H, d, J 8.8, H-3Ј), (51.75) (6.1) (22.3)
7.19 (1H, dd, J 8.8 and 2.2, H-2Ј), 7.73 (1H, br s, NHAr), 7.85
(1H, d, J 2.2, H-6Ј), 7.95 (1H, s, H-2)
12c
206–7
[MeOH]
3250–
0.93 (3H, t, J 7.3, CH3), 1.72–1.82 (2H, m, CH2), 2.52–2.61 (2H,
44.7
5.3
32.5
(C8H11N5ؒHCl)
3050 (NH2) t, J 7.6, CH2), 6.95 (2H, br s, NH2)
(45.0) (5.2) (32.8)
a CDCl3; DMSO for 9 and 12c. b δC(DMSO) 13.75 (q), 20.89 (t), 41.00 (q), 55.01 (q), 119.83 (d), 128.34 (d), 128.90 (d), 130.36 (d), 132.63 (d), 137.64
(s), 137.95 (s), 155.27 (s), 157.49 (s) and 165.78 (s); δN(DMSO) 306.2 (NH). c δC(CDCl3) 12.87 (q), 19.84 (t), 52.96 (t), 67.79 (t), 110.87 (s), 117.96 (s),
120.12 (d), 123.88 (d), 128.97 (d), 146.53 (s), 148.53 (s) and 162.41 (s). d δC(DMSO) 18.28 (q), 37.36 (t), 60.41 (t), 97.80 (d), 118.85 (d), 121.44 (s),
126.83 (d), 138.35 (s), 156.1 (s), 158.52 (s), 159.70 (s) and 169.41 (s).
J. Chem. Soc., Perkin Trans. 1, 1997
3023

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3 R. Angelini, E. Erba and D. Pocar, J. Chem. Soc., Perkin Trans. 1,
1996, 837; M. Battistini, E. Erba and D. Pocar, Synthesis, 1992, 1206;
M. Battistini, E. Erba and D. Pocar, J. Chem. Soc., Perkin Trans. 1,
1993, 339; E. Erba, G. Mai and D. Pocar, J. Chem. Soc., Perkin Trans.
1, 1992, 2709.
180 ЊC for 2 h. The residue was taken up with CH2Cl2, washed
with aqueous NaHCO3, dried (Na2SO4) and evaporated to
dryness. The residue was purified by chromatography 9 or
recrystallized from water (12c). Analytical and spectral data are
listed in Table 1.
4 G. J. Martin, M. L. Martin and J. P. Goucsnard, 15N-NMR
Spectroscopy, Springer-Verlag, Berlin, 1981, 126.
5 A. P. Freitas, M. F. J. R. P. Proença and B. L. Booth, J. Heterocycl.
Chem., 1995, 32, 457.
6 M. O. Foster and H. M. Judd, J. Chem. Soc., 1910, 97, 262.
Acknowledgements
This work has been supported by M.U.R.S.T.
References
1 Part 37. E. M. Beccalli, E. Erba, M. L. Gelmi and D. Pocar, J. Chem.
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2 P. Kadaba, S. Stanovnik and M. Tisler, Adv. Heterocycl. Chem., 1984,
37, 329 and references cited therein.
Paper 7/03023A
Received 2nd May 1997
Accepted 3rd June 1997
3024
J. Chem. Soc., Perkin Trans. 1, 1997