Single step synthesis of 2,3-dialkyl-6-nitro-quinazolin-4(3H)-imines and 3,5-dialkyl-9-nitro-imidazo[1,2-c]quinazolin-2(3H)-ones

Article abstract of DOI:10.1016/j.tet.2005.04.028

A single step synthesis of 2,3-dialkyl-6-nitro-quinazolin-4(3H)-imines and 3,5-dialkyl-9-nitro-imidazo-[1,2-c]-quinazolin-2(3H)-ones from simple carbonyl compounds, primary amines or amino acid methyl esters and 2-azido-5-nitro- benzonitrile was developed. Key intermediates were N,N′-disubstituted amidines obtained by rearrangement of 4,5-dihydrotriazoles; the new heterocyclic rings were formed by spontaneous intramolecular reaction of the amino and cyano groups which are present in the intermediates.

Full text of DOI:10.1016/j.tet.2005.04.028

Tetrahedron 61 (2005) 5778–5781
Single step synthesis of
2,3-dialkyl-6-nitro-quinazolin-4(3H)-imines and
3,5-dialkyl-9-nitro-imidazo[1,2-c]quinazolin-2(3H)-ones
*
Emanuela Erba, Donato Pocar and Pasqualina Trimarco
Istituto di Chimica Organica ‘Alessandro Marchesini’ e Centro Interuniversitario di Ricerca sulle Reazioni Pericicliche e Sintesi di Sistemi
`
Etero- e Carbociclici, Universita degli Studi di Milano, Via G. Venezian, 21, I-20133 Milano, Italy
Received 1 July 2004; revised 31 March 2005; accepted 15 April 2005
Abstract—A single step synthesis of 2,3-dialkyl-6-nitro-quinazolin-4(3H)-imines and 3,5-dialkyl-9-nitro-imidazo-[1,2-c]-quinazolin-
2(3H)-ones from simple carbonyl compounds, primary amines or amino acid methyl esters and 2-azido-5-nitro-benzonitrile was developed.
Key intermediates were N,N0-disubstituted amidines obtained by rearrangement of 4,5-dihydrotriazoles; the new heterocyclic rings were
formed by spontaneous intramolecular reaction of the amino and cyano groups which are present in the intermediates.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
group on N-1 is an highly electron-withdrawing substituent
(e.g. tosyl and aryl groups having formyl, nitro or cyano
substituents). This simple approach to the synthesis of
substituted amidines prompted us to investigate the
preparation of N,N0-disubstituted amidines bearing the
ortho-cyanoaryl group on N-1 and to study the formation
of heterocyclic products by intramolecular cyclization
processes.
Recently, we described a convenient synthesis of N,N0-
disubstituted amidines from tosyl azide, primary amines and
ketones.1 As depicted in Scheme 1, the amidines were easily
obtained through a transformation reaction of 4-amino-4,5-
dihydrotriazole intermediates A. It is well known that
compounds A readily rearrange into amidines2 when the R
Indeed, the formation of a fused azaheterocyclic ring could
be expected by virtue of the nucleophilic character of the
NH group and as a consequence of the known ability of
N-aryl amidine intermediates to give intramolecular con-
densation reactions with suitable ortho groups (Scheme 2).
2. Results and discussion
As a further development of the general synthesis of N,N0-
disubstituted amidines and in analogy with previous results,
propanal 1a, benzylamine 2a and 2-azido-5-nitro-benzo-
nitrile 3 were reacted in an inert solvent and in the presence
of molecular sieves (see Scheme 3). Surprisingly, a single
product was obtained, i.e. 3-benzyl-2-ethyl-6-nitro-quina-
zolin-4(3H)-imine 4a, derived from the direct reaction
between the secondary benzylamino group and the cyano
group. The structure of 4a was established by analytical and
Scheme 1.
Keywords: 2,3-Dialkyl-6-nitro-4(3H)-quinazolinimines; 3,5-Dialkyl-9-
nitro-imidazo[1,2-c]quinazolin-2(3)-ones; N,N0-disubstituted amidines;
Intramolecular cyclization.
1
spectroscopic data. The H NMR spectrum of 4a were in
agreement with the proposed structure and IR and 13C NMR
spectra ruled out the presence of the cyano group.
*
Corresponding author. Tel.: C39 2 50314480; fax: C39 2 50314476;
e-mail: emanuela.erba@unimi.it
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.04.028

E. Erba et al. / Tetrahedron 61 (2005) 5778–5781
5779
basic conditions (1 M sodium hydroxide), iminoquinazoline
4a yielded 4-alkylaminoquinazoline 5a (Scheme 4).
The 1H NMR spectrum of 5a hydrochloride showed a single
signal associated with the NH2 group and the 13C NMR
C
Scheme 2.
spectrum was in agreement with the proposed structure. In
order to further validate structure 4 we reacted quinazoline-
imine 4b with a base. This second experiment gave rise to
the expected Dimroth rearrangement product 5b. The one-
pot method previously described was applied to the
synthesis of quinazoline-4(3H)imines 4a–e from carbonyl
derivatives 1a–d, primary amines 2a,b and 2-azido-5-
nitrobenzonitrile 3 (Scheme 3).
The use of amino acid esters as primary amines in the above
reaction conditions was further investigated. This procedure
should allow the amino acid function to be linked onto the
quinazoline ring. Reaction of cyclohexanone 1b and
aminoacid methyl esters 6a–c (D,L-alanine, L-phenylalanine,
L-valine methyl esters) with 2-azido-5-nitro-benzonitrile 3
afforded imidazo[1,2-c]quinazolin-2(3H)-one derivatives
7a–c in good yields and as single products. Analytical and
spectroscopic data ruled out the presence of the methyl ester
group and of exchangeable protons whereas signals related
to an aromatic group, to the cyclopentyl substituents and
those corresponding to the aminoacid backbone were
clearly identified. All 13C NMR spectra of 7a–c were
characterized by two signals (quaternary carbons) at low
frequencies (185.5–187.2 and 170.3–170.7 d) associated
with a cyclic amide group and with a cyclic N–C]N carbon
conjugated with C]O,4 respectively. These analytical data
Scheme 3. Reaction conditions; CH2Cl2, room temperature, molecular
sieves.
The 1H NMR spectrum of 4a hydrochloride in DMSO
solution showed that the resonance of the NH2C group was
split into two signals with considerable difference of
C
frequency (0.9 ppm). The rigid NH2 structure fits this
evidence, because the environment of the two protons is
very different. In order to confirm this structural hypothesis
the reactivity of 4a was examined. The base catalyzed
transposition of the alkyl group of 3-alkyl-quinazoline-
4(3H)-imines which affords 4-alkylaminoquinazolines is
well known as the Dimroth rearrangement.3 As expected, in
Scheme 5. Reaction conditions: CH2Cl2, room temperature, molecular
sieves.
Scheme 4.

5780
E. Erba et al. / Tetrahedron 61 (2005) 5778–5781
allowed assignment of the structure of 3,5-dialkyl-9-nitro-
imidazo[1,2-c]quinazolin-2(3H)-one to compounds 7a–c.
Mass spectra and elementary analysis were in agreement
with the proposed structures.
149.8 (C), 156.8 (C), 162.6 (C). ESI MzC309.2. Calcd for
C17H16N4O2 (308.33) C, 66.23; H, 5.19; N, 18.18. Found: C,
65.93; H, 5.24; N, 18.03.
3.1.2. 2-Cyclopentyl-3-ethyl-6-nitro-quinazolin-4(3H)-
imine 4b. Yield 2.5 g, 88%. Mp 164 8C (yellow crystals
from EtOH). IR 3345 (NH), 1632 (CN), 1H NMR 1.41 (3H,
t, JZ6.9 Hz, CH3), 1.68–2.10 (8H, m, 4CH2), 3.12–3.24
(1H, m, CH), 4.28 (2H, q, JZ6.9 Hz, CH2), 5.25 (1H, bs,
NH), 7.55 (1H, d, JZ9.1 Hz, H-8), 8.64 (1H, dd, JZ2.5,
9.1 Hz, H-7), 8.70 (1H, d, JZ2.5 Hz, H-5), 1H NMR of the
hydrochloride (DMSO) 1.36 (3H, t, JZ6.9 Hz, CH3), 1.70–
2.12 (8H, m, 4CH2), 3.14–3.26 (1H, m, CH), 4.44 (2H, q,
JZ6.9 Hz, CH2), 7.97 (1H, d, JZ9.1 Hz, H-8), 8.70 (1H,
dd, JZ2.2, 9.1 Hz, H-7), 10.21 and 10.98 (2H, 2bs, NH2).
13C NMR 13.4 (CH3), 26.2 (CH2), 32.6 (CH2), 40.2 (CH2),
43.3 (CH), 119.5 (C), 120.8 (CH), 126.8 (CH), 128.9 (CH),
144.9 (C), 149.9 (C), 156.4 (C), 164.4 (C). ESI MzC287.3.
Calcd for C15H18N4O2 (286.14) C, 62.92; H, 6.34; N, 19.57.
Found: C, 62.74; H, 6.50; N, 19.32.
The formation of tricyclic derivatives 7 can be rationalized
through the cyclization of 4-iminoquinazoline intermediates
which could not be isolated in the present case. The adopted
reaction conditions were responsible for the formation of the
cyclic imide 7 by condensation of the imino group with the
ester function (Scheme 5).
It is necessary to remark that compounds 7 arising from
optically pure aminoacids lose optical activity. This is
explained by enolization of the intermediate product.
In conclusion, readily available starting materials have been
used in one-pot reactions to obtain two different hetero-
cyclic rings in good yield by suitably exploiting the
reactivity of N,N0-disubstituted amidines. This synthetic
method is versatile and allows access to several heterocyclic
rings with various substituents, depending on the structure
of the starting materials.
3.1.3. 3-Benzyl-2-cyclopentyl-6-nitro-quinazolin-4(3H)-
imine 4c. Yield 2.4 g, 70%. Mp 150 8C (yellow crystals
from EtOH). IR 3346 (NH), 1629 (C]N), H NMR 1.45
1
(8H, m, 4CH2), 3.01–3.33 (1H, m, CH), 5.54 (2H, s,
CH2Ph), 7.19–7.40 (5H, m, Ph), 7.61 (1H, d, JZ9.1 Hz,
H-8), 8.00 (1H, bs, NH), 8.38 (1H, dd, JZ2.2, 9.1 Hz, H-7),
8.74 (1H, d, JZ2.2 Hz, H-5), 1H NMR of the hydrochloride
(DMSO) 1.45–1.93 (8H, m, 4CH2), 3.25–3.42 (1H, m, CH–
C]N), 5.75 (2H, s, CH2Ph), 7.25–7.44 (5H, m, Ph), 8.02
(1H, d, JZ8.7 Hz, H-8), 8.73 (1H, dd, JZ1.8, 8.7 Hz, H-7),
9.80 (1H, d, JZ1.8 Hz, H-5), 10.3 and 11.17 (2H, 2bs,
NH2), 13C NMR 26.4 (CH2), 32.7 (CH2), 43.8 (CH), 48.3
(CH2), 119.7 (C), 121.2 (CH), 126.1 (CH), 127.2 (CH),
127.9 (CH), 129.2 (CH), 129.4 (CH), 136.5 (C), 145.3 (C),
150.0 (C), 157.0 (C), 165.3 (C). ESI MzC349.3. Calcd for
C20H20N4O2 (348.16) C, 68.95; H, 5.79; N, 16.08. Found: C,
69.00; H, 5.75; N, 16.09.
3. Experimental
Mps were determined by a Bu¨chi 510 (capillary) apparatus.
IR spectra were measured with a JASCO IR Report 100
instrument (Nujol; cmK1). NMR spectra were obtained with
Bruker Advance 300 and Varian Gemini 200 instruments. J
values are given in Hz for solutions in CDCl3 if not
indicated. Mass spectra were recorded with LCQ Advantage
Thermofinnigan equipped with electrospray ionisation
(ESI). 2-Azido-5-nitro-benzonitrile is a known compound.5
3.1. Synthesis of 3,5-dialkyl-6-nitro-quinazolin-4(3H)-
imines 4a–c: general procedure
Carbonyl compound 1a,d (10 mmol) and amine 2a,b6
(10 mmol) were dissolved in CH2Cl2 (20 mL). To the
3.1.4. 3-Benzyl-2-cyclohexyl-6-nitro-quinazolin-4(3H)-
imine 4d. Yield 2.5 g, 68%. Mp 146–147 8C (yellow
crystals from 2-propanol). IR 3350 (NH), 1630 (CN), H
˚
solution molecular sieves (4 A, 5 g) were added. After
1
30 min, 2-azido-5-nitro-benzonitrile 3 (10 mmol) was
added. The solution was stirred at room temperature for
12 h until disappearance of the starting materials (TLC:
ethyl acetate–cyclohexane 2:3). The reaction suspension
was filtered and evaporated. The crude was chromato-
graphed with ethyl acetate–cyclohexane (2:3).
NMR 1.52–2.59 (10H, m, 5CH2), 2.62–2.77 (1H, m, CH),
5.48 (1H, s, CH2), 7.17–7.42 (6H, m, Ph and NH), 7.58 (1H,
d, JZ8.8 Hz, H-8), 8.46 (1H, dd, JZ8.8, 1.4 Hz, H-7), 8.70
(1H, d, JZ1.4 Hz, H-5), 13C NMR 25.8 (CH2), 26.2 (CH2),
31.5 (CH2), 43.0 (CH), 47.8 (CH2), 119.6 (C), 121.1 (CH),
126.2 (CH), 127.1 (CH), 127.8 (CH), 129.0 (CH), 136.5 (C),
146.1 (C), 149.9 (C), 156.9 (C), 165.0 (C). ESI MC363.1.
Calcd for C21H22N4O2 C, 69.59; H, 6.12; N, 15.46 (362.43).
Found: C, 69.37; H, 6.24; N, 15.27.
3.1.1. 3-Benzyl-2-ethyl-6-nitro-quinazolin-4(3H)-imine
4a. Yield 2.6 g, 78%. Mp 142–144 8C (yellow crystals
from EtOH). IR 3342 (NH), 1629 (C]N), H NMR 1.33
1
(3H, t, JZ7.4 Hz, CH3), 2.75 (2H, q, JZ7.4 Hz, CH2), 5.49
(2H, s, CH2Ph), 7.22–7.41 (5H, m, Ph), 7.64 (1H, d, JZ
8.8 Hz, H-8), 8.40 (1H, dd JZ8.8, 2.2 Hz, H-7), 8.74 (1H, d,
3.1.5. 3-Benzyl-2-isobutyl-6-nitro-quinazolin-4(3H)-
imine 4e. Yield 2.9 g, 89%. Mp 156–155 8C (yellow
crystals from 2-propanol). IR 3349 (NH), 1632 (CN), H
1
1
JZ2.2 Hz, H-5), 7.40–8.90 (1H, bs, NH), H NMR of the
hydrochloride (DMSO) 1.35 (3H, t, JZ6.9 Hz, CH3), 4.43
(2H, q, JZ6.9 Hz, CH2), 5.76 (2H, s, CH2Ph), 7.25–7.44
(5H, m, Ph), 8.02 (1H, d, JZ8.7 Hz, H-8), 8.70 (1H, dd, JZ
1.8, 8.7 Hz, H-7), 9.82 (1H, d, JZ1.83 Hz, H-5), 10.30 and
11.17 (2H, 2bs, NH2), 13C NMR 11.3 (CH3), 28.4 (CH2),
47.2 (CH2), 116.7 (C), 122.8 (CH), 126.6 (CH), 127.4 (CH),
127.6 (CH), 129.3 (CH), 130.0 (CH), 136.1 (C), 145.1 (C),
NMR 1.00 (6H, d, JZ7.3 Hz, 2CH3), 2.25–2.63 (1H, m,
CH), 2.62 (2H, d, JZ7.0 Hz), 5.57 (2H, s, CH2), 7.16–7.38
(6H, m, Ph and NH), 7.65 (1H, d, JZ8.8 Hz, H-8), 8.42 (1H,
dd, JZ8.8, 2.2 Hz, H-7), 9.0 (1H, d, JZ2.2 Hz, H-5), 13C
NMR 22.7 (CH3), 27.2 (CH), 44.3 (CH2), 48.2 (CH2), 119.7
(C), 121.1 (CH), 126.1 (CH), 127.1 (CH), 127.8 (CH), 129.1
(CH), 135.9 (C), 145.2 (C), 149.5 (C), 156.5 (C), 160.7 (C).

E. Erba et al. / Tetrahedron 61 (2005) 5778–5781
5781
ESI MC337.0. Calcd for C19H20N4O2 (336.39) C, 67.84; H,
5.99; N, 16.66. Found: C, 67.68; H, 6.23; N, 16.58.
H-8), 9.26 (1H, d, JZ2.5 Hz, H-10), 13C NMR 18.5 (CH3),
26.2 (CH2), 26.4 (CH2), 33.2 (CH2), 43.2 (CH), 58.9 (CH),
115.4 (C), 123.9 (CH), 129.2 (CH), 129.8 (CH), 145.7 (C),
151.18 (C), 161.4 (C), 170.3 (C), 187.2 (C). ESI MzC
313.3. Calcd for C16H16N4O3 (312.32) C, 61.53; H, 5.16; N,
17.94. Found: C, 61.32; H, 5.29; N, 17.49.
3.2. Dimroth rearrangement: general procedure
3,5-Dialkyl-6-nitro-quinazolin-4(3H)-imines 4a,b (10 mmol)
was suspended in 30 mL of 1 M NaOH solution and heated
to 80 8C for 24 h. The reaction was monitored by TLC (ethyl
acetate–cyclohexane 1:1). The reaction mixture was extract
with dichloromethane, dried with Na2SO4 and evaporated.
The crude reaction was chromatographed with ethyl
acetate–cyclohexane (1:1).
3.3.2. 3-Benzyl-5-cyclopentyl-9-nitro-imidazo[1,2-c]-
quinazolin-2(3H)-one 7b. Yield 1.8 g, 47%. Mp 202–
203 8C (yellow crystals from EtOH). IR 1622 (C]N), 1741
(C]O), 1H NMR 1.78–2.30 (8H, m, 4CH2), 3.18–3.37 (1H,
m, CH–C]N), 3.58 (2H, d, JZ4.4 Hz, CH2Ph), 4.86 (1H, t,
JZ4.4 Hz, CH–N), 6.97–7.15 (5H, m, Ph), 7.78 (1H, d, JZ
9.1 Hz, H-7), 8.53 (1H, dd, JZ9.1, 2.5 Hz, H-8), 8.99 (1H,
d, JZ2.5 Hz, H-10), 13C NMR 26.3 (CH2), 26.5 (CH2), 31.9
(CH2), 34.1 (CH2), 37.7 (CH2), 43.5 (CH), 63.6 (CH), 114.9
(C), 123.7 (CH), 128.0 (CH), 128.8 (CH), 129.1 (CH), 129.7
(CH), 132.4 (C), 145.5 (C), 150.9 (C), 161.4 (C), 170.8 (C),
186. 3 (C). ESI MzC389.4. Calcd for C22H20N4O3 (388.42)
C, 68.03; H, 5.19; N, 14.43. Found: C, 67.79; H, 5.25; N,
14.23.
3.2.1. 4-Benzylamino-2-ethyl-6-nitro-quinazoline 5a.
Yield 2.0 g, 65%. Mp 186 8C (yellow crystals from
1
EtOH). IR 2220 (NH). H NMR 1.25 (3H, t, JZ8.1 Hz,
CH3), 2.75 (2H, q, JZ8.1 Hz, CH2), 4.80 (2H, d, JZ5.4 Hz,
CH2Ph), 7.25–7.44 (5H, m, Ph), 7.75 (1H, d, JZ9.1 Hz,
H-8), 8.42 (1H, dd, JZ9.1, 1.8 Hz, H-7), 9.36 (1H, d, JZ
1.8 Hz, H-5), 9.42 (1H, t, JZ5.4 Hz, NH), 13C NMR
(DMSO) 12.0 (CH3), 32.4 (CH2), 43.7 (CH2), 112.2 (C),
120.4 (CH), 126.0 (CH), 126.8 (CH), 127.7 (CH), 128.2
(CH), 128.4 (CH), 138.8 (C), 143.2 (C), 153.4 (C), 160.0
(C), 171.0 s. ESI MzC309.2. Calcd for C17H16N4O2
(308.33) C, 66.23; H, 5.19; N, 18.18. Found: C, 65.89; H,
5.27; N, 18.00.
3.3.3. 5-Cyclopentyl-3-isopropyl-9-nitro-imidazo[1,2-c]
quinazolin-2(3H)-one 7c. Yield 1.6 g, 49%. Mp 176–
177 8C (yellow crystals from EtOH). IR 1620 (C]N), 1739
1
(C]O), H NMR 0.79 (3H, d, JZ6.9 Hz, CH3), 1.43 (3H,
d, JZ6.9 Hz, CH3), 1.70–2.30 (8H, m, 4CH2), 2.56–2.65
(1H, m, CH), 3.04–3.24 (1H, m, CH–C]N), 4.52 (1H, d,
JZ3.6 Hz, CH–N), 7.83 (1H, d, JZ9.1 Hz, H-7), 8.60 (1H,
dd, JZ9.1, 2.5 Hz, H-8), 9.23 (1H, d, JZ2.5 Hz, H-10), 13C
NMR 15.5 (CH3), 17.6 (CH3), 26.6 (CH2), 26.8 (CH2), 33.6
(CH2), 34.3 (CH2), 31.6 (CH), 43.6 (CH), 67.4 (CH), 115.3
(C), 124.3 (CH), 129.4 (CH), 130.0 (CH), 146.0 (C), 151.4
(C), 161.8 (C), 170.8 (C), 185.5 (C). ESI MzC341.4. Calcd
for C18H20N4O3 (340.38) C, 63.52; H, 5.92; N, 16.64.
Found: C, 63.37; H, 6.04; N, 16.52.
3.2.2. 2-Cyclopentyl-4-ethylamino-6-nitro-quinazoline
5b. Yield 1.4 g, 52%. 188–189 (yellow crystals from
EtOH). IR 2220 (NH), H NMR 1.40 (3H, t, JZ7.4 Hz,
1
CH3), 1.67–2.19 (8H, m, 4CH2), 3.27–3.34 (1H, m, CH),
3.71–3.84 (2H, q, JZ7.4 Hz, CH2), 6.08 (1H, bs, NH), 7.84
(1H, d, JZ9.2 Hz, H-8), 8.45 (1H, dd, JZ9.2, 2.6 Hz, H-7),
8.72 (1H, d, JZ2.6 Hz, H-5), 13C NMR (DMSO) 14.6
(CH3), 26.4 (CH2), 32.8 (CH2), 36.3 (CH2), 49.1 (CH),
113.1 (C), 121.1 (CH), 126.5 (CH), 129.2 (CH), 143.8 (C),
154.2 (C), 160.8 (C), 174.4 (C). ESI MzC287.3. Calcd for
C15H18N4O2 (286.14) C, 62.92; H, 6.34; N, 19.57. Found C,
62.62; H, 6.59; N, 19.24.
Acknowledgements
3.3. Synthesis of 3,5-dialkyl-9-nitro-imidazo[1,2-c]
quinazolin-2(3H)-ones 7a–c: general procedure
`
We thank Ministero dell’Istruzione, dell’Universita e della
Ricerca (MIUR) for financial support.
Amino-acid methyl ester hydrochloride 6a–c (10 mmol)
and TEA (10 mmol) were dissolved in CH2Cl2 (20 mL).
˚
Then, cyclohexanone (10 mmol) and 7 g of 4 A molecular
References and notes
sieves were added. After 30 min 2-azido-5-nitro-benzo-
nitrile 3 (10 mmol) was added. The solution was stirred for
24 h until disappearance of the starting material (TLC ethyl
acetate–cyclohexane 1:1). After filtration and evaporation
the crude reaction product was chromatographed with ethyl
acetate–cyclohexane (2:3).
1. Cassani, F.; Celentano, G.; Erba, E.; Pocar, D. Synthesis 2004,
1041–1046.
ˇ
2. Kadaba, P. K.; Stanovnik, B.; Tisler, M. Adv. Heteroatom
Chem. 1984, 37, 217–349.
3. Brown, D. J.; Ienega, K. J. Chem. Soc., Perkin Trans. 1 1975,
2182–2185.
3.3.1. 5-Cyclopentyl-3-methyl-9-nitro-imidazo[1,2-c]-
quinazolin-2(3H)-one 7a. Yield 1.6 g, 51%. Mp 218 8C
(yellow crystals from EtOH). IR 1741 (C]O), 1622
(C]N), H NMR 1.58–2.37 (11H, m, 4CH2 and CH3),
3.08–3.28 (1H, m, CH), 4.60 (1H, q, JZ7.3 Hz, CH–N),
7.85 (1H, d, JZ9.1 Hz, H-7), 8.63 (1H, dd, JZ9.1, 2.5 Hz,
4. Papadopulos, E. P. J. Heterocycl. Chem. 1982, 18, 515–518.
5. Nishiyama, K.; Anselme, J. P. J. Org. Chem. 1977, 42,
2636–2637.
1
6. In the case of ethylamine hydrochloride, an equivalent amount
of TEA was added.