5-Aminouracil as a building block in heterocyclic synthesis: Part III. One-pot synthesis of novel pyrimido[5,4-b]quinoline-2,4,9-triones and pyrimido[5,4-c]isoquinolines

Article abstract of DOI:10.1515/znb-2010-1212

An efficient and direct procedure for the synthesis of pyrimido[5,4-b] quinoline-2,4,9-trione and pyrimido[5,4-c]isoquinoline derivatives has been described. The products were characterized by elemental analyses, IR, ¹H NMR, ¹³C NMR

Full text of DOI:10.1515/znb-2010-1212

5-Aminouracil as a Building Block in Heterocyclic Synthesis: Part III.
One-pot Synthesis of Novel Pyrimido[5,4-b]quinoline-2,4,9-triones and
Pyrimido[5,4-c]isoquinolines
Raafat M. Shakera, Kamal U. Sadeka, Ebtisam A. Hafezb, and Mohamed Abd Elradya
a Chemistry Department, Faculty of Science, Minia University, 61519 El-Minia, Egypt
b Chemistry Department, Faculty of Science, Cairo University, Giza-12613, Egypt
Reprint requests to Prof. Dr. Raafat M. Shaker. E-mail: rmshaker@yahoo.com
Z. Naturforsch. 2010, 65b, 1485 – 1490; received June 27, 2010
An efficient and direct procedure for the synthesis of pyrimido[5,4-b]quinoline-2,4,9-trione and
pyrimido[5,4-c]isoquinoline derivatives has been described. The products were characterized by ele-
mental analyses, IR, 1H NMR, 13C NMR and MS spectra.
Key words: 5-Aminouracil, Dimedone, One-pot Synthesis, Pyrimido[5,4-b]quinoline-2,4,9-trione,
Pyrimido[5,4-c]isoquinoline
Introduction
Polyfunctionalized heterocyclic compounds play
important roles in the drug discovery process, and anal-
ysis of drugs in late development or on the market
shows that 68 % of them are heterocycles [1]. There-
fore, it is not surprising that research on the synthesis
of polyfunctionalized heterocyclic compounds has re-
ceived significant attention. Pyrimidoquinolines have
been an object of great interest to organic, medicinal
and materials scientists over many years, as they are
present in a number of biologically active organic com-
pounds which exhibit antimalarial [2, 3], anticancer
[4], antitumor [5] antimicrobial [6], antiviral [7], anal-
gesic [8], anti-oxidant [8], and anti-inflammatory ac-
tivities [8, 9]. Furthermore, multi-component reactions
(MCRs) play an increasingly important role in organic
and medicinal chemistry for their convergence, pro-
ductivity, ease of execution, excellent yield, and broad
application in combinational chemistry [10– 18].
Recently, we reported a simple and efficient synthe-
sis of pyrimido[5,4-b]quinoline-2,4,9-triones (4) [17],
and pyrido[3,2-d:6,5-d\]dipyrimidines (6) [18] via the
reaction of 5-aminouracil (1), benzaldehyde deriva-
tives 2 and dimedone (3) or barbituric acid derivatives
5 under microwave irradiation without catalyst. These
compounds could have interesting effects on biological
targets (Scheme 1).
Scheme 1. Synthesis of pyrimido[5,4-b]quinolines 4 and
pyrido[3,2-d:6,5-d\]dipyrimidines 6.
methods for the synthesis of polyfunctionally substi-
tuted heterocyclic compounds [17– 28], we wish to
report a novel and efficient one-pot method for the
synthesis of pyrimido[5,4-b]quinoline-2,4,9-trioneand
pyrimido[5,4-c]isoquinoline derivatives with the pur-
pose of investigating in the future their possible bio-
logical activity. The mechanism of the reaction has
been proved via the synthesis of a proposed inter-
mediate.
Results and Discussion
Considering the above reports and in continuation
of our work in the development of new and simple and paraformaldehyde (7) in DMF and in the pres-
The reaction of 5-aminouracil (1), dimedone (3)
c
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R. M. Shaker et al. · 5-Aminouracil as a Building Block in Heterocyclic Synthesis
assume the initial formation of the 2 : 1 dimedone/
formaldehyde adduct 10, which gives the Knoeve-
nagel adduct intermediate 11. A subsequent Michael-
type addition reaction of the nucleophile C-6 in 5-
aminouracil (1) leads to the formation of interme-
diate 12, which undergoes cyclization with loss of
a water molecule and partial oxidation to render
compound 8. Neither adduct 10 nor 11 were iso-
lated in the reaction under study. To confirm the as-
sumed three-component condensation route we syn-
thesized 2,2ꢀ-methylene-bis(3-hydroxy-5,5-dimethyl-
cyclohex-2-enone) (10) [30] and brought it into reac-
Scheme 2. Synthesis of 8.
ence of triethylamine as a catalyst gave a solid prod-
uct of the composition C13H13N3O3 (m/z = 259 (30 %),
[M]+) which may be formulated as the pyrimido[5,4-
b]quinoline-2,4,9-trione 8 or its isomer 9 (Scheme 2).
tion with compound 1 under the previous conditions.
The target product formed in approximately the same
yield and was identical in all aspects to compound 8
(Scheme 3).
1
The molecular structure of 8 was indicated by its H
We also studied the alkylation of 8 with ethyl io-
dide. The reaction was carried out at r. t. in DMF
and in the presence of anhydrous potassium carbon-
ate to afford the ethylated derivative 13 (Scheme 4).
The structure of the product 13 was proved by ele-
mental analysis and spectral data. This compound is
not the O-ethylation product. Its IR spectrum contains
bands around 1662– 1708 cm−1, characteristic of car-
bonyl absorptions, and the 1H NMR spectrum revealed
that the alkylation occurs at the N-1 and N-3 atoms.
NMR spectrum which revealed three characteristic,
relatively sharp singlets at 11.56, 11.25 and 7.93 ppm.
The two former ones are assigned to the two NH
groups, 3-NH and 1-NH, respectively, and the latter
to H-10. Two singlets appear at 3.00 and 2.62 ppm
corresponding to the two CH2 groups at positions 6
and 8, respectively, in addition to the singlet for the
two methyl groups. Moreover, the 13C NMR spec-
trum of 8 showed signals at δC = 28.41 (CMe2), 33.02
(C-7), 41.88 (C-6), 50.37 (C-8), 129.01 (C-10), 133.73
(C-9a), 139.98 (C-4a), 144.62 (C-10a), 151.31 (C-6a),
162.08 (C-2), 163.31 (C-4), and 197.09 (C-9). With
these spectroscopic data the proposed linear structure
of 8 is identified. In the angular structure 9 the pyri-
dine proton signal should have appeared at a higher
field [29].
1
Thus, the H NMR spectrum of compound 13 con-
tained signals from the N1CH2 (δ = 3.81) and N3CH2
protons (δ = 3.88 ppm). Furthermore, the structure as-
signed to 13 was fully supported by its mass spec-
trum, which showed a molecular formula C17H21N3O3
(m/z = 315 (35%), [M]+). Further confirmation of
structure 13 was achieved via the synthesis of the ethy-
lated enaminoketone 15, prepared by ethylation of the
enaminoketone 14 with ethyl iodide in DMF and in the
A proposed reaction mechanism that accounts for
the multicomponent reaction is shown in Scheme 3.
Thus, the reaction may occur via a condensation, ad-
dition, cyclization, and elimination mechanism. We
Scheme 3. Proposed mechanism to pyrimido[5,4-b]quinol-
ine-2,4,9-trione 8.
Scheme 4. Ethylation of 8 and 14.
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R. M. Shaker et al. · 5-Aminouracil as a Building Block in Heterocyclic Synthesis
1487
presence of anhydrous potassium carbonate. The IR,
The formation of 18 can be described in terms of
MS, 1H NMR as well as the 13C NMR spectra agreed the initial formation of the intermediate 17. A reaction
with the proposed structure 15. Gentle heating of a of the latter with 1, which is accompanied by elimina-
dimethylformamide solution of 15 and dimethylfor- tion of the readily leaving dimethylamino group, gives
mamide dimethyl acetal (16) at 125 – 135 ◦C for 18 h rise to 18 (Scheme 5). Heating a dimethylformamide
yielded a product identical in all aspects to compound solution of compound 18 affords the pyrimido[5,4-
13 (Scheme 4).
1
c]isoquinoline 9, the H NMR spectrum of which re-
In addition, the structure of 8 was confirmed further vealed the absence of an exocyclic NH proton and
by an alternative synthesis of its isomer 9 (Scheme 5). the presence of a singlet at δ = 8.45 ppm due to a
Thus, reacting a mixture of 5-aminouracil (1), dime- pyridine-CH proton. The structure of 9 was confirmed
done (3) and DMFDMA (16) in DMF without cat- by its elemental and spectral analyses, which showed a
alyst under reflux for 8 h afforded the pyrimidine- molecular formula C13H13N3O3 (m/z = 259 (83.3%),
2,4(1H,3H)-dione 18 (Scheme 5). The structure of [M]+). Comparison of the data of 9 with those of
compound 18 was confirmed by its elemental and 8 showed differences in melting point, IR, and 1H
spectral analyses, which showed the molecular ion NMR data which confirmed the structure of 9 for our
peak at m/z = 277.14 (98 %). Its 1H NMR spec- product.
trum showed characteristic singlets at δ = 11.09 and
Moreover, the ethylated derivative 20 was obtained
11.57 ppm for two NH groups, a doublet at δ = by reacting 9 with ethyl iodide in DMF and in the pres-
12.29 (J = 15 Hz) for an exocyclic NH group, a ence of anhydrous potassium carbonate (Scheme 5).
doublet at δ = 8.36 (J = 15 Hz) due to N-CH=, The structure of 20 was confirmed by its elemental
a singlet at δ = 7.99 due to CH-uracil, in addi- and spectral analyses, which showed the molecular ion
tion to three singlet signals for the methyl and dime- peak at m/z = 315 (15 %). Also, the 1H NMR spectrum
done protons. Furthermore, the structure of com- of 20 displayed no NH protons, but the presence of sig-
pound 18 was confirmed by an independent synthe- nals from the N1CH2 (δ = 3.86) and N3CH2 protons
sis of the same compound from an equimolar amount (δ = 4.10 ppm). Further confirmation of structure 20
of 1 and 2-dimethylaminomethylidenecyclohexane- was obtained via the synthesis of compound 19, pre-
1,3-dione (17) in DMF under reflux to afford a pared by ethylation of compound 18. The structure of
product identical in all aspects to compound 18 19 was established by its correct elemental analysis
(Scheme 5).
and compatible spectroscopic data. Subsequent heat-
ing of 19 in refluxing DMF smoothly converted it to
the final product 20 (Scheme 5). The identity of the
products of the cyclization of 19 with those obtained
by the ethylation of 9 was confirmed by comparison of
their IR and 1H NMR spectra.
Finally, cyclization and chlorination of compound
18 using phosphoryl chloride gave the dichloro deriva-
tive 21 (Scheme 5). The structure of the latter product
was confirmed on the basis of correct elemental analy-
sis and spectral data. Thus, the IR and 1H NMR spectra
of 21 revealed the absence of NH groups and signals at-
tributable to the CH-uracil and NH protons of 18. Also,
its MS gave the characteristic fragmentation pattern
due to the presence of two chlorine atoms and showed
the molecular ion peak at m/z = 296 (19.80%) in agree-
ment with its molecular formula C13H11Cl2N3O.
In conclusion, the reported three-component one-
step procedure is a simple, practical and very regiose-
lective method for the synthesis of novel pyrimido[5,4-
b]quinoline-2,4,9-trione and pyrimido[5,4-c]isoquin-
oline derivatives.
Scheme 5. Synthesis of pyrimido[5,4-c]isoquinolines 9, 20
and 21.
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R. M. Shaker et al. · 5-Aminouracil as a Building Block in Heterocyclic Synthesis
Experimental Section
General procedures
stirred for 48 – 55 h at r. t. and then poured into cold water and
extracted with chloroform (3 × 20 mL). The combined or-
ganic extracts were washed with water and dried (anhydrous
Melting points were measured with a Gallenkamp appara-
tus and are uncorrected. The reactions and purity were mon-
itored by thin layer chromatography (TLC) on aluminum
plates coated with silica gel with fluorescence indicator
(Merck, 60 F254) using CHCl3-CH3OH (10 : 1) as eluent. In-
frared spectra were recorded in potassium bromide disks on
a Jasco FT/IR-450 Plus infrared spectrophotometer. NMR
spectra were obtained on a JHA-LAA 400 WB-FT spec-
trometer (300 MHz for 1H NMR, 75 MHz for 13C NMR),
with deuterated chloroform (CDCl3) or dimethylsulfoxide
([D6]DMSO) as solvent. Chemical shifts are quoted in δ and
are referenced to TMS or the solvent signal. Mass spectra
were recorded on a Trace GC 2000/Finngan Mat SSQ 7000
and a Shimadzu GCMS-QP-1000EX mass spectrometer at
70 eV. Elemental analyses were measured with a Vario EL
III CHNOS Elemental Analyzer in the Microanalytical Cen-
ter of Cairo University. Compounds 10 [30], 14 [17] and 17
[31] were synthesized using the published procedures.
magnesium sulfate). After evaporation of some of the sol-
vent (∼ 10 mL), petroleum ether (40 mL) was added, and the
resulting precipitate was collected, dried and recrystallized
from petroleum ether-chloroform and/or n-hexane-benzene
to give 13 (yield 40 %), and/or 15 (yield 70 %), respectively.
1,3-Diethyl-7,7-dimethyl-7,8-dihydropyrimido[5,4-b]quin-
oline-2,4,9(1H,3H,6H)-trione (13)
Dark-brown powder, m. p. 209 – 212 ◦C. – IR (film):
ν = 3521, 2924, 2877, 1708, 1662.5 cm−1. – 1H NMR
(300 MHz, [D6]DMSO): δ = 0.99 (s, 6H, 2CH3), 1.12 (t,
3H, J = 6 Hz, CH3), 1.23 (t, 3H, J = 6 Hz, CH3), 2.32 (s,
2H, CH2), 2.40 (s, 2H, CH2), 3.81 (q, 2H, J = 6 Hz, CH2),
3.88 (q, 2H, J = 6 Hz, CH2), 8.41 (s, 1H, 10-H). – MS (EI,
70 eV): m/z (%) = 316 (40) [M+1]+, 315 (35) [M]+. – Anal.
for C17H21N3O3 (315.37): calcd. C 64.74, H 6.71, N 13.32;
found C 64.89, H 6.59, N 13.39.
5-(5,5-Dimethyl-3-oxocyclohex-1-enylamino)-1,3-diethyl-
pyrimidine-2,4(1H,3H)-dione (15)
7,7-Dimethyl-7,8-dihydropyrimido[5,4-b]quinoline-
2,4,9(1H,3H,6H)-trione (8)
Yellow crystals, m. p. 238 – 240 ◦C. – IR (film): ν = 3205,
3106, 2954, 2877, 1708, 1654 cm−1. – 1H NMR (300 MHz,
CDCl3): δ = 1.05 (s, 6H, 2 CH3), 1.19 (t, 3H, J = 6 Hz,
CH3), 1.28 (t, 3H, J = 6 Hz, CH3), 2.18 (s, 2H, CH2), 2.31
(s, 2H, CH2), 3.80 (q, 2H, J = 9 Hz, CH2), 4.00 (q, 2H,
J = 6 Hz, CH2), 5.41 (s, 1H, dimedone), 6.43 (s, 1H, CH
uracil), 7.24 (s, 1H, NH). – 13C NMR (75 MHz, CDCl3):
δ = 12.69, 14.23, 28.14, 32.70, 37.26, 43.77, 45.31, 50.11,
99.99, 114.35, 131.12, 148.86, 158.59, 160.09, 197.95. – MS
(EI, 70 eV): m/z (%) = 305.15 (35.58) [M]+, 290 (100) [M–
CH3]+. – Anal. for C16H23N3O3 (305.37): calcd. C 62.93,
H 7.59, N 13.76; found C 62.82, H 7.71, N 13.81.
Method A: A mixture of 5-aminouracil (1) (0.13 g,
1 mmol), dimedone (3) (0.28 g, 2 mmol) and paraformalde-
hyde 7 (0.64 g, 2 mmol) along with triethylamine (0.05 g,
0.5 mmol) in DMF (10 mL) was refluxed for 20 h (TLC con-
trol using a solvent system of chloroform-methanol (5 : 2)).
The solvent was evaporated under vacuum; the resulting
solid was then collected and crystallized from dioxane; yield:
81 %.
Method B: A solution of equimolar amounts of 2,2ꢀ-
methylenebis(3-hydroxy-5,5-dimethylcyclohex-2-enone)
(10) (0.29 g, 1 mmol), 1 (0.13 g, 1 mmol) and triethy-
lamine (0.05 g, 0.5 mmol) in DMF (10 mL) was refluxed
for 25 h. Product 8 was isolated as described above; yield:
An alternative synthesis of compound 13
◦
83 %. Brown powder, m. p. 288 – 290 C. – IR (film): ν =
3440, 2923, 1674 cm−1. – 1H NMR (300 MHz, [D6]DMSO):
δ = 1.03 (s, 6H, 2CH3), 2.62 (s, 2H, CH2), 3.00 (s, 2H,
CH2), 7.93 (s, 1H, 6-H), 11.25 (s, 1H, NH), 11.56 (s,
1H, NH). – 13C NMR (75 MHz, [D6]DMSO): δ = 28.41,
33.02, 41.88, 50.37, 129.01, 133.73, 139.98, 144.62, 151.31,
162.08, 163.31, 197.09. – MS (EI, 70 eV): m/z (%) = 260
(16.7) [M+1]+, 259 (30) [M]+. – Anal. for C13H13N3O3
(259.26): calcd. C 60.22, H 5.05, N 16.21; found C 60.39,
H 5.17, N 16.34.
A solution of 15 (0.61 g, 2 mmol) and 16 (0.36 g, 3 mmol)
in DMF (5 mL) was gently heated (125 – 135 ◦C) (TLC con-
trol using a solvent system of toluene-acetone (5 : 4)). After
18 h, product 13 was isolated as described above; yield 50 %.
5-((4,4-Dimethyl-2,6-dioxocyclohexylidene)methylamino)-
pyrimidine-2,4(1H,3H)-dione (18)
Method A: A solution of 1 (0.25 g, 2 mmol), 3 (0.28 g,
2 mmol) and 16 (0.24 g, 2 mmol) in DMF (10 mL) was re-
fluxed for 8 h (TLC control). The solvent was evaporated un-
der vacuum; the resulting solid was then collected and crys-
tallized from DMF; yield: 80 %.
Ethylation of 8 and 14
Ethyl iodide (2.81 g, 18 mmol) was added to a mixture
of 8 and/or 14 (3 mmol) and anhydrous potassium carbonate
Method B: A solution of equimolar amounts of 17(0.4
(0.83 g, 6 mmol) in DMF (20 mL). The reaction mixture was g, 2 mmol) and 1 (0.25 g, 2 mmol) in DMF (10 mL)
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R. M. Shaker et al. · 5-Aminouracil as a Building Block in Heterocyclic Synthesis
1489
was refluxed for 8 h. Product 18 was isolated as described 1H, uracil), 8.27 (d, 1H, J = 15 Hz), 12.45 (d, 1H, J = 9 Hz,
for method A; yield 85 %. Pale-yellow crystals, m. p. 350 – NH). – 13C NMR (75 MHz, CDCl3): δ = 12.64, 14.30, 28.46,
352 ◦C. – IR (film): ν = 3127, 3081, 2954, 2929, 1731, 1666, 31.02, 37.28, 45.47, 51.30, 51.51, 115.73, 125.35, 127.97,
1
1583 cm−1. – H NMR (300 MHz, [D6]DMSO): δ = 0.99 149.02, 158.36, 163.31, 197.40, 197.73. – MS (EI, 70 eV):
(s, 6H, 2Me), 2.30 (s, 2H, CH2), 2.37 (s, 2H, CH2), 7.99 (s, m/z (%) = 335.15 (8.01) [M+2]+, 334.15 (42.27) [M+1]+,
1H, CH uracil), 8.36 (d, 1H, J = 15 Hz, C=H), 11.09 (s, 333.15 (100) [M]+. – Anal. for C17H23N3O4 (333.38):
1H, NH uracil), 11.57 (s, 1H, NH uracil), 12.29 (d, 1H, J = calcd. C 61.25, H 6.95, N 12.60; found C 61.36, H 7.04,
15 Hz, NH exocyclic). – MS (EI, 70 eV): m/z (%) = 278.28 N 12.69.
(14) [M+1]+, 277.14 (98) [M]+. – Anal. for C13H15N3O4
(277.28): calcd. C 56.31, H 5.45, N 15.15; found C 56.22,
H 5.53, N 15.11.
1,3-Diethyl-9,9-dimethyl-9,10-dihydropyrimido[5,4-c]iso-
quinoline-2,4,7(1H,3H,8H)-trione (20)
Method A: This compound was prepared in 42 % isolated
yield by ethylation of 9 using the procedure described for the
synthesis of 13. The solid product was isolated and crystal-
lized from n-hexane/benzene.
9,9-Dimethyl-9,10-dihydropyrimido[5,4-c]isoquinoline-
2,4,7(1H,3H,8H)-trione (9)
A solution of compound 18 (0.28 g, 1 mmol) in DMF
(20 mL) was refluxed for 70 h (TLC control). The sol-
vent was evaporated under vacuum; the resulting solid was
crystallized from dioxane, yield 45 %. Brown powder, m. p.
288 – 290 ◦C. – IR (film): ν = 3430, 3340, 3175, 2957,
Method B: This compound was prepared in 50 % isolated
yield by heating 19 in refluxing DMF for 60 h. The prod-
uct 20 was isolated as described above. Dark-brown powder,
m. p. 182 – 185 ◦C. – IR (film): ν = 2931, 2877, 1708, 1651,
1577 cm−1. – 1H NMR (300 MHz, CDCl3): δ = 1.08 (s, 6H,
2Me), 1.26 (t, 3H, J = 6 Hz, CHMe), 1.35 (t, 3H, J = 6 Hz,
CHMe) 2.65 (s, 2H, CH2), 2.85 (s, 2H, CH2), 3.86 (q, 2H,
J = 9 Hz, CH2), 4.10 (q, 2H, J = 6 Hz, CH2), 8.27 (s, 1H,
CH). – MS (EI, 70 eV): m/z (%) = 315 (15) [M]+, 314 (10)
[M–1]+. – Anal. for C17H21N3O3 (315.37): calcd. C 64.74,
H , 6.71, N 13.32; found C 64.79, H , 6.82, N 13.38.
1
1687 cm−1. – H NMR (300 MHz, [D6]DMSO): δ = 1.12
(s, 6H, 2CH3), 2.32 (s, 2H, CH2), 2.40 (s, 2H, CH2), 8.45 (s,
1H, 6-H), 11.30 (s, 1H, NH), 11.60 (s, 1H, NH). – MS (EI,
70 eV): m/z (%) = 259 (83.3) [M]+. – Anal. for C13H13N3O3
(259.26): calcd. C 60.22, H 5.05, N 16.21; found C 60.28
H 5.21, N 16.29.
5-((4,4-Dimethyl-2,6-dioxocyclohexylidene)methylamino)-
1,3-diethylpyrimidine-2,4(1H,3H)-dione (19)
2,4-Dichloro-9,9-dimethyl-9,10-dihydropyrimido[5,4-c]iso-
quinoline-7(8H)-one (21)
Compound 18 (0.56 g, 2 mmol) was refluxed in phospho-
rus oxychloride (5 mL) for 12 h. The mixture was cooled and
poured onto ice-water to give a precipitate which was filtered
off, dried and recrystallized from petroleum ether/methylene
chloride to afford 21. Yield 50 %. Brown powder, m. p. 222 –
Ethyl iodide (1.87 g, 12 mmol) was added to a mixture
of 18 (0.56 g, 2 mmol) and anhydrous potassium carbonate
(0.83 g, 6 mmol) in DMF (20 mL). The reaction mixture was
stirred for 36 h at r. t., concentrated to 3 mL and then poured
into cold water. After stirring for 15 min, the precipitate was
collected by filtration, washed with water, dried and crys-
tallized from petroleum ether/chloroform; yield 55 %. Yel-
low crystals, m. p. 232 – 234 ◦C. – IR (film): ν = 3440, 2927,
2873, 1651, 1581 cm−1. – 1H NMR (300 MHz, CDCl3): δ =
1.04 (s, 6H, 2 CH3), 1.22 (t, 3H, J = 6 Hz, CH3), 1.35 (t, 3H,
J = 6 Hz, CH3), 2.36 (s, 2H, CH2), 2.42 (s, 2H, CH2), 3.88
(q, 2H, J = 9 Hz, CH2), 4.03 (q, 2H, J = 6 Hz, CH2), 7.43 (s,
◦
224 C. – IR (film): ν = 2958, 2831, 1697, 1512 cm−1. –
1H NMR (300 MHz, [D6]DMSO): δ = 1.07 (s, 6H, 2Me),
2.72 (s, 2H, CH2), 2.86 (s, 2H, CH2), 8.32 (s, 1H, CH). –
MS (EI, 70 eV): m/z (%) = 297 (21.05) [M+1]+, 296 (19.75)
[M]+, 295.00 (13.25) [M–1]+. – Anal. for C13H11Cl2N3O
(296.15): calcd. C 52.72, H 3.74, N 14.19; found C 52.81,
H 3.81, N 14.25.
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