Synthesis of new pyrazolo[3,4-b]quinolines, thieno[2,3-b]quinolines and related condensed heterocyclic systems

Article abstract of DOI:10.1002/jccs.200100173

3-Amino-l H-pyrazolo[3,4-b]quinoline (2) was reacted with benzaldehyde, acetylacetone, ethyl aceto-acetate and/or phenyl isothiocyanate to give compounds 3,4,5 and 6, respectively. The interaction of 6 with some α-haloesters and/or α-haloketones produced the corresponding thiazolidinones 7a-c and thiazolines 9a-d. lH-Pyrazolo[3,4-b]quinoline-3-diazonium chloride (11) was coupled with some active methylene compounds to give the corresponding hydrazono compounds 12a, b and 13 which, in turn were cyclized into the corresponding triazinopyrazoloquinolines 14a,b and 15 by heating in acetic acid. 3-Aminothieno[2,3-b]quinoline-2-carbohydrazide (19) and 3-amino-2-(1H-benzimidazol-2-yl)thieno[2,3-b]quinoline (21) were prepared and employed as key intermediates for synthesizing the second class of the title compounds.

Full text of DOI:10.1002/jccs.200100173

JournaloftheChineseChemicalSociety, 2001, 48, 1175-1183
1175
Syn the sis of New Pyrazolo[3,4-b]quinolines, Thieno[2,3-b]quinolines and
Related CondensedHeterocyclicSystems
Etify Abdel-Ghafar Bakhite
ChemistryDepartment,FacultyofScience,AssiutUniversity,Assiut71516,Egypt
3-Amino-1H-pyrazolo[3,4-b]quinoline (2) was re acted with benzaldehyde, acetylacetone, ethyl aceto-
acetate and/or phenyl isothiocyanate to give com pounds3, 4, 5 and 6,respectively.Theinteractionof6 with
some -haloesters and/or -haloketones pro duced the cor re spond ing thiazolidinones7a-c and thiazolines
9a-d. 1 H-Pyrazolo[3,4-b]quinoline-3-diazoniumchloride(11)wascoupledwithsomeactivemethylenecom-
pounds to give the cor re spond ing hydrazono com pounds 12a,b and 13 which, in turn were cyclized into the
correspondingtriazinopyrazoloquinolines14a,b and 15 by heat ing in ace tic acid. 3-Aminothieno[2,3-
b]quinoline-2-carbohydrazide(19) and 3-amino-2-(1H-benzimidazol-2-yl)thieno[2,3-b]quinoline (21) were
preparedandemployedaskeyintermediatesforsynthesizingthesecondclassofthetitlecompounds.
Quinolines have oc cu pied a unique place in hetero-
cyclic com pounds and have re mark ably con trib uted to bi o-
logicalandmedicinalchemistry.1-5 Variousderivativesof
pyrazolepossesssignificantantibacterial,6 antifungal7 and
anti-inflammatory8 activities.Thepharmacologicalproper-
ties of some pyrazoloquinolines as antiasthmatic,9 antitumor10,11
and anti-inflammatory12 agents have been re ported. Very re-
cently,somederivativesofpyrazolo[3,4-b]quinolinewerere-
ported as antineoplastics for treat ment of pre can cer ous le-
sions.13,14 Thienoquinolines are re ported to ex hibit a broad
spectrum of bi o log i cal ef fects. Some of them are use ful as
mem ory enhancers,15 antiallergics,16 analgesicsandantipy-
retics.17 Oth ers are known to pos sess a good an ti bac te rial18
and antianaphylactic19 ac tiv ity. All these find ings prompted
ustotakeupthisprojectforsynthesizingnovelderivativesof
pyrazolo[3,4-b]quinoline and thieno[2,3-b]quinoline by in-
troducingknownbiologicallyactivemoietiesintotheirstruc-
tureshopingtogetvaluablecompounds.
2-Chloroquinoline-3-carbonitrile (1) was re acted with
hydrazine hy drate to give 3-amino-1H-pyrazolo[3,4-b]quin-
oline( 2), whichisusedasastartingcompoundforsynthesiz-
ing the tar get pyrazoloquinolines as well as their con densed
heterocyclic de riv a tives. The con den sa tion of2 with benz-
aldehyde af forded the Schiff’s base 3. On treat ment of 2 with
acetylacetone and/or ethyl acetoacetate, a cyclocondensation
reactionoccurredandthecorrespondingpyrimido[1 ,2 :1,5]-
pyrazolo[3,4-b]quinolines4 and 5 were ob tained. The re ac-
tion of 2 with phenyl isothiocyanate by heat ing in pyridine
gave the thiourea de riv a tive6 in nearly quan ti ta tive yield
(Scheme I).
Scheme I
N=CHPh
N
CH3
N
N
N
3
N
H
N
N
PhCHO
CH3
4
CN
Cl
NH2
Ace tylacetone
AcCH2CO2 Et
N2 H .H2
O
4
N
N
N
2
N
H
1
PhNCS
H
N
CH3
NHCSNHPh
N
N
N
N
N
N
H
O
5
6
tate, methyl -bromopropionate and di ethyl bromomalonate.
In view of an ear lier re port,20 the prod ucts of this re ac tion
were as signed as thiazolidinones 7a-c rather than their iso-
mers 8a-c. This type of re ac tion was as sumed to pro ceed via
thiolisation, in volv ing the -NH- group ad ja cent to the hetero-
cyclic moi ety rather than the phenyl group, fol lowed by nu-
cleophilicsubstitutionandeliminationofanalcoholmole-
cule. In the same man ner, the re ac tion of 6 with chloro ace-
tone and/or -bromoacetophenonesaffordedthecorrespond-
ing thiazoline derivatives 9a-d rather than their isomers
10a-d (Scheme II).
3-Amino-1H-pyrazolo[3,4-b]quinoline (2) was eas ily
diazotisedusingHClandsodiumnitriteat0°Ctoproducethe
correspondingdiazoniumchloride11 , which is ap plied in the
fol low ing steps with out iso la tion. When 11 was al lowed to
cou ple with some ac tive meth y lene com pounds such as mal-
ononitrile, ethyl cyanoacetate and/or ethyl acetoacetate, in
eth a nol in the pres ence of so dium ac e tate, at 0-5 °C, the cor-
respondinghydrazonocompounds12a, 12b and 13 were ob-
Com pound 6un der went a ring clo sure re ac tion upon
treat ment with some -haloesters namely; ethyl bromo ace-

1176 J. Chin. Chem. Soc., Vol. 48, No. 6B, 2001
Bakhite
Scheme II
Scheme III
R
CH3
NH-N
S
R
N
S
PhNHNH2
N
Ph
N
N
N
N
N -Ph
O
N
N
N
H
N
Ph
16
N
N
H
N
N
H
9a-d
10a-d
3-methyl-1-phenyl-2-pyrazolin-5-one
X
+
XCH2COR
N=NCl
NaNO2 / HCl
2
6
N
N
N
H
BrCH(R)CO2R'
11
X
X-CH2 -CN
CH3 COCH CO2 Et
2
SH
N=C-N HPh
SH
NH-C=NPh
N
N
H
N
H
N
N
N
N
H
N
N
H
N
N
N
R
N
N
C
N
X
N
N
COCH
3
C
R
H
H
O
S
EtO
O
O
12a,b
S
13
N-Ph
N
N
N-Ph
AcOH
AcOH
N
N
N
8a-c
N
H
N
N
H
H
N
N
7a-c
N
N
N
R
N
9, 10
R
N
N
X
COCH
N
N
3
a
b
H
CH3
a
b
c
CH3
C6H5
C6H4CH3(p)
NH
2
O
14a,b
12, 14
15
c
CO2C2H5
X
d
C6H4Br(p)
a
CN
b
CO Et
2
tained. Cyclization of 12a,b into 1,2,4-triazino[4 ,3 :1,5]-
pyrazolo[3,4-b]quinolines 14a,b was achieved upon reflux-
inginaceticacid. Thisreactionproceedsvia nucleophilic at-
tack of the ring ni tro gen on the cyano group. An other new
triazinopyrazolo[3,4-b]quinoline 15 was iso lated upon heat-
ing of 13 in ace tic acid where the cyclization in this case in-
volves elim i na tion of an eth a nol mol e cule. When the diazo-
nium chlo ride 11 was cou pled with 3-methyl-1-phenyl-2-
pyrazolin-5-one, the hydrazono com pound 16 was ob tained.
The lat ter com pound was also syn the sized by re act ing 13
with phenyl hydrazine (Scheme III).
imidazolylderivative20 with so dium ethoxide in boil ing eth-
a nol (Scheme IV).
Scheme IV
NH2
N H2
N2 H .H O
4
2
CO2Et
N
S
N
S
CONHNH2
19
18
ClCH2 CO2Et
CN
The re ac tion of 2-chloroquinoline-3-carbonitrile (1)
with thiourea pro duced 3-cyanoquinoline-2(1H)-thione (17)
which was then re acted with ethyl chloroacetate to give ethyl
3-aminothieno[2,3-b]quinoline-2-carboxylate (18). The re-
actionofo-aminoester 18 with hydrazine hy drate and/or with
o-phenylenediamine in the pres ence of polyphosphoric acid
produced3-aminothieno[2,3-b]quinoline-2-carbohydrazide
(19) and 3-amino-2-(1H-benzimidazol-2-yl)thieno[2,3-b]-
quinoline (21), re spec tively. The lat ter com pound 21 was
also ob tainedviare ac tion of 17 with 2-chloromethyl-1H-
benzimidazolefollowedbycyclizationoftheresultingbenz-
H2NCSNH
2
o-phenylenediamine/
1
PPA
S
N
H
17
2-chloromethyl-1H-benzimi dazole
CN
N H2
i) EtONa
ii )AcOH
H
N
H
N
SCH2
N
N
S
N
N
20
21
Compounds19 and 21were em ployed as key in ter me-
di ates for syn the siz ing the sec ond class of the tar get com-

Syn the sis of New Pyrazolo- and Thienoquinolines
J. Chin. Chem. Soc., Vol. 48, No. 6B, 2001 1177
pounds. Thus, the re ac tion of 19 with for mic acid and/or
triethyl orthoformate by heat ing at re flux tem per a ture pro-
duced the pyrimidothienoquinolines 22 and 23,respectively.
Treat ment of 23 withalcoholicpotassiumhydroxideledto
theaminopyrimidinonederivative 24. Heating of 19 in gla-
cial ace tic acid for a long time re sulted in the for ma tion of
pyrazolino[3 ,4 :4,5]thieno[2,3-b]quinoline-2-one (25).21
Thisreactionmayproceedviaacetylation fol lowed by elim i-
na tion of an acetamide mol e cule (Scheme V).
equimolar quan tity of so dium ni trite in ace tic acid pro duced
3-aminothieno[2,3-b]quinoline-2-carboazide (30). On heat-
ing of 30 in dry xylene, it un der went Curtius rearrangement
followedbyintramolecularcycloadditionreactiontofurnish
imidazo[4 ,5 :4,5]thieno[2,3-b]quinoline-2(1H,3H)-one (31)
in high yield (Scheme VI).
3-Amino-2-(1H-benzimidazol-2-yl)thieno[2,3-b]quin-
oline (21) was re acted with some re agents, namely triethyl
orthoformate,aceticanhydride, p-chlorobenzaldehyde and/or
car bon disulfide to fur nish the cor re spond ing benzimidazo-
[1 ,2 :1 ,6 ]pyrimido[4 ,5 :4,5]thieno[2,3-b]quinoline de riv-
a tives 32-35. The benzimidazotriazinothienoquinoline 36
was pre pared by treat ing21 with ni trous acid (Scheme VII).
Scheme V
N
NH
N-NHCHO
NH
N
S
N
S
Scheme VII
25
O
O
22
HCO H
AcOH
2
H
19
R
Ar
H
N
N
N
HC(OEt)3
N
N
N
N
O
N
S
N
S
KOH
N
N-NH2
N-N=CH-OEt
32, R = H
33, R = CH3
N
S
34
Ar= C6H4Cl(p)
N
S
O
HC(OEt)
3
24
ArCHO
23
or Ac
O
2
21
Thecondensationof19 with benzaldehyde af forded the
phenyl hydrazone de riv a tive 26 which, in turn, was re acted
withtriethylorthoformateand/oraceticanhydridetogivethe
pyrimidothienoquinolines 27 or 28, re spec tively. The di-
methylpyrazolylcompound 29 was ob tained upon treat ment
of 19 with acetylacetone. Di azo ti sa tion of 19 by us ing an
NaNO / HCl
2
CS
2
H
N
S
N
N
N
N
N
N
S
N
S
N
35
36
The struc tures of all newly syn the sized com pounds
wereelucidatedandconfirmedonthebasisofthierelemental
andspectroscopicanalyses(cf.Experimental).
Scheme VI
NH
N
O
R
2
HC(OEt)3
or Ac2
O
N-N=CHPh
N
S
CONHN=CHPh
N
S
EXPERIMENTAL
26
27, R = H
28, R = CH
3
PhCHO
All melt ing points are un cor rected and mea sured on a
NaNO2
AcOH
Fisher-Johnapparatus.IRspectrawererecordedonaShimadzu
19
Ac2CH2
470 IR-spectrophotometer us ing KBr pel lets (
in cm-1).
max
NH2
2
1H NMR spec tra were ob tained on a Varian EM-390 90 MHz
spectrometerusing TMS as internalreference (chemical
shifts in , ppm). Mass spec tra were mea sured on a Jeol
JMS-600spectrometer.Elementalanalyses(C,H,N)were
car ried out on a Perkin-Elmer 240C el e men tal analyser. Sul-
furandhalogenanalysesweredeterminedusingtheoxygen
flask method by the Microanalytical Unit at Assiut Uni ver-
sity.
NH
CO
N
N
N
S
N
S
CON3
29
30
H3C
CH3
dry xyl ene/
heat
NH2
NH
N
S
N
O
N
S
NCO
H
31

1178 J. Chin. Chem. Soc., Vol. 48, No. 6B, 2001
Bakhite
3-Amino-1H-pyrazolo[3,4-b]quinoline (2)
1680 (C=O) cm-1. 1H NMR (TFA): = 7.7-8.8 (m, 5H, ArH’s
and CH quinoline), 6.8 (s, 1H, CH py rim i dine), 3.6 (s, 3H,
CH3) ppm.
A mix ture of 2-chloroquinoline-3-carbonitrile (1)22
(1.89 g, 0.01 mol), hydrazine hy drate 99% (1 mL, 0.02 mol)
and eth a nol (40 mL) was refluxed for 3 h and then left to cool.
The pre cip i tated solid was col lected and recrystallized from
eth a nol to give 2 in the form of yel low plates; m.p. 283-286
°C; Lit.23 m.p. 178 °C; yield: 1.7 g (92%). Anal. Calcd. for
C10H8N4 (184.2): C, 65.21; H, 4.38; N, 30.42%. Found: C,
65.00; H, 4.57; N, 30.17%. IR: = 3450, 3300 (NH2), 3200
(NH). 1H NMR (DMSO-d6): = 8.4 (s, 1H, CH quinoline),
7.3-8.0 (m, 4H, ArH’s), 6.0 (s, 1H, NH), 5.5 (s, 2H, NH2)
ppm.
3-Phenyl-1-(1H-pyrazolo[3,4-b]quinolin-3-yl)thiourea (6)
A mix ture of 2 (1.84 g, 0.01 mol), phenyl iso thio cya-
nate (1.2 mL, 0.01 mol) and pyridine (30 mL) was refluxed
for 2 h. The precipitate that formed was collected and
recrystallized from pyridine into yel low crys tals of6, m.p.
290-291 °C, yield: 3.1 g (97%). Anal. Calcd. for C17H13N5S
(319.38): C, 63.93; H, 4.10; N, 21.93; S, 10.04 %. Found: C,
63.66; H, 4.01; N, 22.11; S, 10.35%. IR: = 3450, 3350
(2NH), 1240 (C=S) cm-1. 1H NMR (TFA): = 7.30-8.60 (m,
10H, ArH and CH quinoline) ppm. MS:m/z = 319 (M+, 29%).
3-Benzylideneamino-1H-pyrazolo[3,4-b]quinoline (3)
Toasuspensionof2(0.92 g, 0.005 mol), benzaldehyde
(0.5 mL, 0.005 mol) and dioxane (30 mL), and a few drops of
piperidine were added. The re sult ing mix ture was refluxed
for 3 h. The solid prod uct was col lected and recrystallized
from dioxane to give 3 as yel low crys tals; m.p. 250-253 °C;
yield 1.1 g (81%). Anal. Calcd. for C17H12N4 (272.31): C,
74.98; H, 4.44; N, 20.57%. Found: C, 75.13; H, 4.21; N,
20.26%. IR: = 3200 (NH), 1620 (C=N) cm-1 and re vealed
dis ap pear ance of the two bands char ac ter is tic for the NH2
group of com pound2.
Reaction of thiourea derivative 6 with some -haloesters
and -haloketones; formation of thiazolidinones 7a-c
and thiazolines 9a-d, respectively; general procedure
To a mix ture of6 (1.6 g, 0.005 mol), fused so dium ac e-
tate (1.64 g, 0.02 mol) and eth a nol (30 mL), the re spec tive
-haloester or -haloketone (0.005 mol) was added. The re-
sult ing mix ture was refluxed for 4 h. The solid that formed on
cool ing was fil tered off and recrystallized from the proper
solvent.
Com pound 7a was ob tained by us ing ethyl bromo-
acetate and recrystallized from pyridine as brown crys tals;
m.p. >300 °C; yield: 1.27 g (71%). Anal. Calcd. for C19H13N5OS
(359.40): C, 63.50; H, 3.65; N, 19.49; S, 8.92%. Found: C,
63.64; H, 3.52; N, 19.17; S, 9.05%. IR: = 3300 (NH), 1720
(C=O) cm-1. 1H NMR (TFA): = 8.7 (s, 1H, CH quinoline),
7.0-8.3 (m, 9H, ArH), 4.1 (s, 2H, CH2) ppm.
Com pound7b was ob tained by us ing methyl - bromo-
propionate and recrystallized from dioxane as buff crys tals;
m.p. >300 °C; yield: 1.32 g (70%). Anal. Calcd. for C20H15N5OS
(373.43): C, 64.33; H, 4.05; N, 18.75; S, 8.59%. Found: C,
64.11; H, 4.00; N, 18.93; S, 8.39%. IR: = 3300 (NH), 1710
(C=O) cm-1. 1H NMR (TFA): = 8.8 (s, 1H, CH quinoline),
7.1-8.4 (m, 9H, ArH), 3.9-4.3 (q, 1H, CH thiazolidinone), 2.1
(d, 3H, CH3) ppm.
2,4-Dimethylpyrimido[1 ,2 :1,5]pyrazolo[3,4-b]quinoline
(4)
To a mix ture of 2 (0.92 g, 0.005 mol), acetylacetone
(0.5 mL, 0.005 mol) and eth a nol (25 mL), a few drops of ace-
tic acid were added. The re ac tion mix ture was refluxed for 4
h,thenconcentratedandallowedtocool.Theprecipitatethat
formed was col lected and recrystallized from DMF to give 4
in the form of red crys tals; yield: 0.95 g (95%); m.p. 295-296
°C; Anal. Calcd. for C15H12N4 (248.29): C, 72.56; H, 4.87; N,
22.57%. Found: C, 72.33; H, 4.79; N, 22.32%. IR: = 1620
(C=N), 1580 (C=C) cm-1 and re vealed dis ap pear ance of the
bandscharacteristicforNH2 and NH groups of com pound2.
1H NMR (TFA): = 7.3-8.7 (m, 6H, ArH’s, CH quinoline and
CHpyrimidine);3.1(s,3H,CH3); 2.9 (s, 3H, CH3) ppm.
Com pound7c was ob tained by us ing di ethyl bromo-
malonate and recrystallized from eth a nol as yel low crys tals;
2-Methylpyrimido[1 ,2 :1,5]pyrazolo[3,4-b]quinoline-4(1H)-
one (5)
m.p. 281-283 °C, yield: 1.7 g (79%). Anal. Calcd. for C22H17N O3S
5
A mix ture of2 (1.1 g, 0.006 mol), ethyl acetoacetate
(0.75 mL, 0.006 mol) and gla cial ace tic acid (15 mL) was
refluxed for 5 h. The solid prod uct that formed af ter cool ing
was col lected and recrystallized from dioxane as wine red
crystalsof5; yield: 1.06 g (71%); m.p. >360 °C. Anal. Calcd.
(431.47): C, 61.24; H, 3.97; N, 16.23; S, 7.43%. Found: C,
61.37; H, 4.11; N, 16.00; S, 7.50%. IR: = 3300 (NH), 1730
(C=O, es ter), 1710 (C=O, thiazolidinone).
Com pound 9a was ob tained by us ing chloroacetone
and recrystallized from dioxane as yel low nee dles; m.p. >300
°C; yield: 1.35 g (75%). Anal. Calcd. for C20H15N5S (357.4):
C, 67.21; H, 4.23; N, 19.59; S, 8.97%. Found: C, 67.35; H,
for C H10N4O (250.26): C, 67.19; H, 4.03; N, 22.39%.
14
Found: C, 67.00; H, 4.22; N, 22.71%. IR: = 3160 (NH),

Syn the sis of New Pyrazolo- and Thienoquinolines
J. Chin. Chem. Soc., Vol. 48, No. 6B, 2001 1179
4.11; N, 19.30; S, 9.15%. IR: = 3250 (NH) cm-1. 1H NMR
(TFA): = 8.9 (s, 1H, CH qinoline), 8.5 (s, 1H, CH thiazo-
line), 7.3-8.3 (m, 9H, ArH’s), 2.7 (s, 3H, CH3) ppm.
Com pound9b wasobtainedbyusingphenacylbromide
and recrystallized from eth a nol-chloroform (2:1) mix ture in
the form of yel low fine nee dles; m.p. 238-240 °C; yield: 1.7 g
(81%). Anal. Calcd. for C25H17N5S (419.50): C, 71.58; H,
4.08; N, 16.69; S, 7.64%. Found: C, 71.27, H, 4.12; N, 16.88;
S, 7.50%. IR: = 3300 (NH) cm-1.
CH quinoline), 6.5 (s, 1H, NH) ppm.
Com pound12b: m.p. 228-230 °C; yield; 2.33 g (76%).
Anal. Calcd. for C15H12N6O2 (308.30): C, 58.44; H, 3.92; N,
27.26%. Found: C, 58.72; H, 3.88; N, 27.17%. IR: = 3400,
3200 (2NH), 2220 (C N), 1680 (C=O), 1620 (C=N) cm-1. 1H
NMR (DMSO-d6): = 12.8 (s, 1H, NH), 7.5-8.5 (m, 5H,
ArH’s and CH quinoline), 6.5 (s, 1H, NH), 4.2 (q, 2H, OCH2),
1.5 (t, 3H, CH3) ppm.
Com pound13: m.p. 190-191 °C; yield: 2.6 g (80%).
Anal. Calcd. for C16H15N5O3 (325.33): C, 59.07; H, 4.65; N,
21.52%. Found: C, 59.01; H, 4.66; N, 21.70%. IR: = 3400,
Com pound9c wasobtainedbyusingp-methylphenacyl
bro mide and recrystallized from eth a nol-dioxane (1:1) mix-
ture as yel low nee dles; m.p. 282-283 °C; yield: 1.85 g (86%).
Anal. Calcd. for C26H19N5S (433.53): C, 72.03; H, 4.42; N,
16.15; S, 7.40%. Found: C, 72.17; H, 4.37; N, 16.30; S,
7.25%. IR: = 3200 (NH) cm-1. MS: m/z = 433 (M+, 68%).
Com pound9dwasobtainedbyusingp-bromophenacyl
bro mide and recrystallized from dioxane in the form of yel-
low nee dles; m.p. 246-248 °C; yield: 2.1 g (84%). Anal.
Calcd. for C25H16BrN5S (498.39): C, 60.25; H, 3.23; N,
14.05; S, 6.43; Br, 16.03%. Found: C, 60.39; H, 3.28; N,
14.26; S, 6.59; Br, 15.88%. IR: = 3200 (NH) cm-1. 1H NMR
(TFA): 8.8 (s, 1H, CH quinoline), 8.6 (s, 1H, CH thiazoline),
7.1-8.5 (m, 13H, ArH’s) ppm.
1
3200 (2NH), 1700, 1680 (2CO). H NMR (CDCl3): = 12.6
(s, 1H, NH), 7.3-8.5 (m, 5H, ArH’s and CH quinoline), 6.3 (s,
1H, NH), 4.3 (q, 2H, OCH2), 2.5 (s, 3H, CH3), 1.4 (t, 3H,
CH3) ppm.
Cyclization of 12a, 12b and 13; formation of triazino-
pyrazoloquinolines 14a, 14b and 15; general procedure
Asolutionof12a, 12b or 13 (0.005 mol) in gla cial ace-
tic acid (15 mL) was refluxed for 1 h and then was left to cool.
The pre cip i tate that formed was col lected and recrystallized
from dioxane to give brown crys tals of 14a, 14b or 15, re-
spectively.
Com pound 14a: m.p. >300 °C; yield: 0.9 g (70%).
Anal. Calcd. for C13H7N7 (261.24): C, 59.77; H, 2.70; N,
Diazotisation of 2; formation of 1H-pyrazolo[3,4-b]-
quinoline-3-diazonium chlo ride (11)
37.53%. Found: C, 59.58; H, 2.73; N, 37.61%. IR:
3320-3200 (NH2); 2220 (C N) cm-1. 1H NMR (DMSO-d6):
=
A so lu tion of2 (1.84 g, 0.01 mol) in conc. HCl (5 mL)
was cooled to 0-5 °C in an ice-bath and cooled so dium ni trite
so lu tion (1.5 g in 10 mL wa ter) was added to it dropwise with
stirringduring10min. Thecooledreactionmixturewasthen
stirred for an ad di tional 30 min. and ap plied in the next steps
withoutisolation.
= 7.4-8.6 (m, 5H, ArH’s and CH quinoline), 6.8 (s, 2H, NH2)
ppm.
Compound 14b: m.p. 291-293 °C; yield: 1.1 g (71%).
Anal. Calcd. for C15H12N6O2 (308.30): C, 58.44; H, 3.92; N,
27.26%. Found: C, 58.32; H, 4.11; N, 27.00%. IR: = 3300,
1
3200 (NH2), 1660 (C=O) cm-1. H NMR (DMSO-d6):
=
Coupling of diazonium salt 11 with active methylene
compounds; formation of hydrazono com pounds 12a,b
and 13; general procedure
To an ice-cooled mix ture of malononitrile, ethyl cyano-
acetate or ethyl acetoacetate (0.01 mol) and so dium ac e tate
trihydrate (6.8 g, 0.05 mol) in eth a nol (60 mL), was added
dropwise with stir ring a so lu tion of11 (0.01 mol) dur ing 15
min. Thestirringwascontinuedforafurther30min. Thepre-
cip i tated solid was col lected and recrystallized from eth a nol
to give com pounds 12a, 12bor 13,respectively.
7.3-8.5 (m, 5H, ArH’s and CH quinoline), 6.7 (s, 2H, NH2),
4.3 (q, 2H, OCH2), 1.5 (t, 3H, CH3) ppm.
Compound 15: m.p. 279-281 °C; yield: 0.95 g (68%).
Anal. Calcd. for C14H9N5O2 (279.26): C, 60.21; H, 3.25; N,
25.08%. Found: C, 60.31; H, 3.28; N, 24.90%. IR: = 3400
(NH); 1680, 1660 (2C=O). 1H NMR (TFA): = 7.5-8.7 (m,
5H, ArH’s and CH quinoline), 2.8 (s, 3H, CH3) ppm.
Coupling of diazonium salt 11 with 3-methyl-1-phenyl-
2-pyrazoline-5-one; formation of compound 16
Com pound12a: m.p. 256-257 °C; yield: 2.15 g (82%).
Anal. Calcd. for C13H7N7 (261.24): C, 59.77; H, 2.70; N,
37.53%. Found: C, 59.83; H, 2.77; N, 37.90%. IR: = 3400,
3200 (2NH); 2210, 2180 (2C N); 1630 (C=N) cm-1. 1H NMR
(DMSO-d6): = 12.9 (s, 1H, NH), 7.5-8.6 (m, 5H, ArH’s and
This cou pling was car ried out in a sim i lar pro ce dure to
that de scribed above for ac tive meth y lene com pounds. The
prod uct was recrystallized from dioxane to give 16as scar let
red crys tals; m.p. >300 °C; yield: 2.78 g (75%). Anal. Calcd.
for C20H15N7O (369.38): C, 65.03; H, 4.09; N, 26.54%.

1180 J. Chin. Chem. Soc., Vol. 48, No. 6B, 2001
Bakhite
Found: C, 65.28; H, 4.11; N, 26.71%. IR: = 3400, 3200
(2NH), 1680 (C=O) cm-1 . 1H NMR (DMSO-d6): = 13.0 (s,
1H, NH), 7.3-8.6 (m, 10H, ArH’s and CH quinoline), 6.4 (s,
1H, NH), 2.5 (s, 3H, CH3) ppm. MS: m/z = 370 (M++1, 39%),
369 (M+, 52%).
Com pound 16 was also pre pared by refluxing equi-
molar ra tios of com pound 13 (3.25 g, 0.01 mol) and phenyl
hydrazine (1.08 g, 0.01 mol) in eth a nol (30 mL) for 3 h, then
allowedtocoolwhereascarletredprecipitateformed. Itwas
col lected and recrystallized from dioxane to give a prod uct
iden ti cal to that ob tained be fore in all as pects; yield: 3.1 g
(84%).
quinoline), 7.1-8.0 (m, 8H, ArH’s), 4.0 (s, 2H, SCH2) ppm.
3-Amino-2-(1H-benzimidazol-2-yl)thieno[2,3-b]quinoline
(21)
A) A mix ture of 18 (2.7 g, 0.01 mol), o-phenyl enedi-
amine (1.08 g, 0.01 mol) and polyphosphoric acid (15 mL)
was heated at 160 °C with stir ring for 3 h. The re ac tion mix-
ture was cooled, then poured portionwise onto ice-water and
neu tral ized with aque ous am mo nia whereby a yel low solid
precipitated. It was filtered off, washed with water and
recrystallized from eth a nol to give golden yel low nee dles of
21; m.p. >300 °C; yield: 2.65 g (84%). Anal. Calcd. for
C18H12N4S (316.38): C, 68.34; H, 3.82; N, 17.71; S, 10.13%.
Found: C, 68.15; H, 3.71; N, 17.98; S, 10.30%. IR: = 3450,
3-Cyanoquinoline-2(1H)-thione (17)
Thiscompoundwaspreparedaccordingtoourprevious 3330, 3200 (NH2 and NH) cm-1. 1H NMR (DMSO-d6):
=
method.24
12.6 (s, 1H, NH), 8.6 (s, 1H, CH quinoline), 7.1-8.0 (m, 8H,
ArH’s), 6.8 (s, 2H, NH2) ppm.
Ethyl 3-aminothieno[2,3-b]quinoline-2-carboxylate (18)
Thiscompoundwaspreparedbythereactingof17 with
ethylchloroacetateaccordingtoourreportedprocedure.25
B) Com pound20 (3.16 g, 0.01 mol) was dis solved in
so dium ethoxide so lu tion (0.5 g so dium in 60 mL eth a nol)
and refluxed for 20 min. The re ac tion mix ture was cooled, di-
luted with water (50 mL) and acidified with acetic acid
whereby a yel low solid pre cip i tated. It was col lected and
crystallizedfromethanoltogiveacompoundidenticaltothat
de scribed above in all as pects; yield: 2.93 (93%).
3-Aminothieno[2,3-b]quinoline-2-carbohydrazide (19)
A mix ture of the es ter 18 (5.45 g, 0.02 mol) and hy dra-
zine hy drate 99% (5 mL, 0.1 mol) was refluxed gently for 3 h.
Thereactionmixturewastrituratedwithethanol(30mL)and
allowedtocool.Theprecipitatedsolidwascollected,washed
well with eth a nol and recrystallized from dioxane to give 19
in the form of yel low nee dles; m.p. 296 °C; yield: 4.5 g
(87%). Anal. Calcd. for C12H10N4OS (258.30): C, 55.80; H,
3.90; N, 21.69; S, 12.41%. Found: C, 55.42; H, 3.91; N,
21.81; S, 12.15%. IR: = 3500, 3420, 3350 (NH2, NHNH2),
1650 (C=O) cm-1. 1H NMR (DMSO-d6): = 9.2 (s, 1H, NH),
8.5 (s, 1H, CH quinoline), 7.2-8.1 (m, 4H, ArH’s), 6.8 (s, 2H,
NH2), 4.3 (s, 2H, NH2 carbohydrazide) ppm.
3-Formylaminopyrimido[4 ,5 :4,5]thieno[2,3-b]quinoline-
4(3H)-one (22)
Asolutionof19(0.51 g, 0.002 mol) in for mic acid 85%
(25 mL) was refluxed for 5 h and then left to cool. The solid
productwascollectedandrecrystallizedfromethanoltogive
whiteneedlesof22; m.p. >300 °C; yield: 0.48 g (81%). Anal.
Calcd. for C14H8N4O2S (296.30): C, 56.75; H, 2.72; N, 18.91;
S, 10.82%. Found: C, 56.92; H, 2.73; N, 18.79; S, 10.68%.
IR:
= 3200 (NH), 1720 (C=O, formyl), 1670 (C=O,
pyrimidinone) cm-1. 1H NMR (DMSO-d6): 8.8 (s, 1H, CH
pyrimidine), 8.5 (s, 1H, CH quinoline), 8.3 (s, 1H, NH),
7.1-8.2 (m, 5H, ArH’s and CHO) ppm.
2-(1H-Benzimidazol-2-yl)methylthioquinoline-3-carbon-
itrile (20)
To a mix ture of 17 (1.86 g, 0.01 mol), 2-chloromethyl-
1 H- benzimidazole (1.67 g, 0.01 mol) and eth a nol (40 mL),
so dium ac e tate trihydrate (1.36 g, 0.01 mol) was added. The
re ac tion mix ture was refluxed for 2 h and then al lowed to
cool. The pre cip i tated prod uct was fil tered off, washed thor-
oughly with wa ter and recrystallized from eth a nol to give 20
in the form of pale yel low crys tals; m.p. 269-271 °C; yield:
2.7 g (85%). Anal. Calcd. for C18H12N4S (316.38): C, 68.34;
H, 3.82; N, 17.71; S, 10.13%. Found: C, 68.74; H, 3.95; N,
17.39; S, 9.87%. IR: = 3400-3200 (NH), 2220 (C N) cm-1.
1H NMR (CDCl3): = 12.2 (s, 1H, NH), 8.5 (s, 1H, CH
3-Ethoxymethyleneaminopyrimido[4 ,5 :4,5]thieno[2,3-b]-
quinoline-4(3H)-one (23)
Asuspensionof19 (1.29 g, 0.005 mol) in triethyl ortho-
formate (20 mL) was refluxed for 3 h and then left to cool.
The precipiate that formed was col lected and recrystallized
from eth a nol as white nee dles of23; m.p. 237-238 °C; yield:
1.36 g (84%). Anal. Calcd. for C16H12N4O2S (324.36): C,
59.25; H, 3.73; N, 17.27; S, 9.88%. Found: C, 59.33; H, 3.92;
N, 17.18; S, 10.00%. IR: = 1670 (C=O), 1620 (C=N) cm-1.
1H NMR (CDCl3): = 8.9 (s, 1H, CH py rim i dine), 8.7 (s, 1H,

Syn the sis of New Pyrazolo- and Thienoquinolines
J. Chin. Chem. Soc., Vol. 48, No. 6B, 2001 1181
CH quinoline), 7.9 (s, 1H, N=CH), 7.0-7.7 (m, 4H, ArH’s),
3.6 (q, 2H, OCH2), 1.2 (t, 3H, CH3) ppm.
Calcd. for C20H12N4OS (356.40): C, 67.40; H, 3.39; N, 15.72;
S, 8.99%. Found: C, 67.71; H, 3.32; N, 15.84; S, 9.27%. IR:
= 1670 (C=O) cm-1. 1H NMR (DMSO-d6): = 9.1 (s, 1H, CH
py rim i dine), 8.7 (s, 1H, CH quinoline), 8.5 (s, 1H, N=CH),
7.3-8.2 (m, 9H, ArH’s) ppm.
3-Aminopyrimido[4 ,5 :4,5]thieno[2,3-b]quinoline-4(3H)-
one (24)
A mix ture of 23(0.64 g, 0.002 mol) and po tas sium hy-
drox ide so lu tion 0.1 N (10 mL) was refluxed for 12 h. The
solid that sep a rated af ter cool ing was col lected and crys tal-
lized from dioxane as white nee dles of 24; m.p. 268-269 °C;
yield: 0.46 g (86%). Anal. Calcd. for C 13H8N4OS (268.29): C,
58.20; H, 3.01; N, 20.88; S, 11.95%. Found: C, 58.06; H,
2.88; N, 20.95; S, 12.09%. IR: = 3300, 3200 (NH2), 1670
(C=O) cm-1. 1H NMR (CDCl3): = 9.0 (s, 1H, CH py rim i-
dine), 8.7 (s, 1H, CH quinoline), 7.1-7.8 (m, 4H, ArH’s), 5.8
(s, 2H, NH2) ppm.
3-Benzylideneamino-2-methylpyrimido[4 ,5 :4,5]thieno-
[2,3-b]quinoline-4(3H)-one (28)
Asuspensionof 26 (0.34 g, 0.001 mol) in ace tic an hy-
dride (10 mL) was refluxed for 5 h, and then al lowed to cool.
The pre cip i tated solid was col lected and recrystallized from
dioxane to give 28 as pale yel low nee dles; m.p. 285-287 °C;
yield: 0.27 g (73%). Anal. Calcd. for C21H14N4OS (370.43):
C, 68.09; H, 3.81; N, 15.12; S, 8.65%. Found: C, 68.16; H,
3.88; N, 15.41; S, 8.93%. IR: = 1680 (C=O) cm-1. 1H NMR
(DMSO-d6): = 8.6 (s, 1H, CH quinoline), 8.3 (s, 1H,
N=CH), 7.3-8.1 (m, 9H, ArH’s), 2.5 (s, 3H, CH3) ppm.
3-Pyrazolino[3 ,4 :4,5]thieno[2,3-b]quinoline-3-one (25)
A so lu tion of 19 (0.77 g, 0.003 mol) in gla cial ace tic
acid (20 mL) was refluxed for 6 h. The solid that formed on
cool ing was fil tered off and recrystallized from ace tic acid to
give 25 in the form of white nee dles; m.p. 297-298 °C; yield:
0.51 g (71%). Anal. Calcd. for C12H7N3OS (241.27): C,
59.74; H, 2.92; N, 17.42; S, 13.29%. Found: C, 60.03; H,
2.87; N, 17.29; S, 13.60%. IR: = 3200 (2NH), 1710 (C=O)
cm-1. 1H NMR (DMSO-d6): = 8.7 (s, 1H, CH quinoline), 8.5
(s, 1H, NH), 7.1-8.0 (m, 5H, ArH’s and NH) ppm. MS: m/z =
241 (M+, 100%), 239 (M+-2, 46%).
3-Amino-2-(3,5-dimethyl-1H-pyrazol-1-yl)carbonylthieno-
[2,3-b]quinoline (29)
A mix ture of19 (0.51 g, 0.002 mol), acetylacetone (2
mL) and eth a nol (25 mL) was refluxed for 5 h and then left to
cool. The precipitate that formed was collected and re-
crystallized from n-propanol to give golden yel low plates of
29; m.p. 236-237 °C; yield: 0.48 g (74%). Anal. Calcd. for
C17H14N4OS (322.38): C, 63.34; H, 4.38; N, 17.38; S, 9.94%.
Found: C, 63.71; H, 4.36; N, 17.72; S, 10.11%. IR: = 3460,
3300 (NH2), 1650 (C=O) cm-1. 1H NMR (CDCl3): = 8.5 (s,
1H, CH quinoline), 7.5-8.1 (m, 4H, ArH’s), 6.5 (s, 2H, NH2),
6.0 (s, 1H, CH pyrazole), 2.5 (s, 3H, CH3), 2.7 (s, 3H, CH3)
ppm.
N1-Benzylidene-3-aminothieno[2,3-b]quinoline-2-
carbohydrazide (26)
A mix ture of carbohydrazide 19 (1.29 g, 0.005 mol),
benzaldehyde (0.5 mL, 0.005 mol) and eth a nol (40 mL) was
refluxed for 3 h. The solid prod uct that sep a rated while hot
was col lected by fil tra tion and recrystallized from dioxane to
give orange needles of 26; m.p. 280-281 °C; yield: 1.65
(95%). Anal. Calcd. for C19H14N4OS (346.41): C, 65.88; H,
4.07; N, 16.17; S, 9.26%. Found: C, 65.93; H, 4.19; N, 16.32;
S, 9.38%. IR: = 3490, 3310 (NH2), 3150 (NH), 1650 (C=O)
cm-1. 1H NMR (DMSO-d6): = 11.2 (s, 1H, NH), 8.6 (s, 1H,
CH quinoline), 8.2 (s, 1H, N=CH), 7.2-8.0 (m, 9H, ArH’s),
5.6-6.0 (br, 2H, NH2) ppm.
3-Aminothieno[2,3-b]quinoline-2-carboazide (30)
Sodium nitrite so lu tion 10% (7 mL, 0.01 mol) was
added to a so lu tion of com pound19 (2.6 g, 0.01 mol) in gla-
cial ace tic acid (15 mL) at room tem per a ture over 5 min with
stir ring. The re ac tion mix ture was al lowed to stand at room
temperature for 1 h. The precipitated solid was filtered,
washed with wa ter, dried in air and used in the next re ac tion
with out pu ri fi ca tion; m.p. 181 °C (dec.); yield: 2.0 g (74%).
Anal. Calcd. for C12H7N5OS (269.28): C, 53.52; H, 2.62; N,
26.01; S, 11.91%. Found: C, 53.69; H, 2.67; N, 25.92; S,
12.10%. IR: = 3460, 3330 (NH2), 2150 (N3), 1670 (C=O)
cm-1.
3-Benzylideneaminopyrimido[4 ,5 :4,5]thieno[2,3-b]-
quinoline-4(3H)-one (27)
To a sus pen sion of26 (0.34 g, 0.001 mol) in triethyl
orthoformate (5 mL), ace tic an hy dride (10 mL) was added.
The re ac tion mix ture was refluxed for 4 h. The white pre cip i-
tatethat formed was col lected and recrystallized from dioxane
to give 27; m.p. 297-298 °C; yield: 0.29 g (81%). Anal.
Imidazo[4 ,5 :4,5]thieno[2,3-b]quinoline-2(1H,3H)-one
(31)
Com pound30 (0.54 g, 0.002 mol) in dry xylene (25
mL) was refluxed for 2 h and then left to cool. The pre cip i-

1182 J. Chin. Chem. Soc., Vol. 48, No. 6B, 2001
Bakhite
tated solid was col lected and recrystallized from dioxane as
pale yel low crys tals, m.p. >300 °C; yield: 0.41 g (85%). Anal.
Calcd. for C12H7N3OS (241.27): C, 59.74; H, 2.92; N, 17.42;
S, 13.29%. Found: C, 59.39; H, 2.88; N, 17.53; S, 13.00%.
IR: = 3500, 3300 (2NH), 1680 (C=O). 1H NMR (DMSO-
d 6): = 11.0, 9.6 (2s, 2H, 2NH imidazolone), 8.7 (s, 1H, CH
quinoline), 7.2-8.1 (m, 4H, ArH’s) ppm. MS: m/z = 241.3
(M+, 100%).
(15 mL), car bon disulfide (2 mL) was added. The re ac tion
mix ture was refluxed on a steam bath for 12 h. The solid prod-
uct that sep a rated af ter cool ing was col lected and re crys tal-
lized from pyridine as or ange nee dles of 35; m.p. >300 °C;
yield: 0.68 g (95%). Anal. Calcd. for C19H10N4S2 (358.43): C,
63.67; H, 2.81; N, 15.63; S, 17.89%. Found: C, 63.80; H,
2.76; N, 15.49; S, 18.00%. IR: = 3300 (NH) cm-1. 1H NMR
(TFA): = 8.8 (s, 1H, CH quinoline); 7.3-8.0 (m, 8H, ArH’s)
ppm. MS: m/z = 358.4 (M+, 32%).
Benzimidazo[1 ,2 :1 ,6 ]pyrimido[4 ,5 :4,5]thieno[2,3-b]-
quinoline (32)
Benzimidazo[1 ,2 :1 ,6 ]-1,2,3-triazino[4 ,5 :4,5]thieno[2,3-
b]quinoline (36)
Com pound 21 (0.63 g, 0.002 mol) in triethyl ortho-
formate (15 mL) was refluxed for 3 h. The pre cip i tate that
formed while hot was col lected and recrystallized from DMF
to give 32 as pale yel low nee dles; m.p. >300 °C; yield: 0.55 g
(85%). Anal. Calcd. for C19H10N4S (326.37): C, 69.92; H,
3.09; N, 17.17; S, 9.82%. Found: C, 70.10; H, 3.02; N, 17.33;
S, 10.00%. IR: = 1600 (C=N) cm-1. 1H NMR (TFA): = 9.0
(s, 1H, CH py rim i dine), 8.6 (s, 1H, CH quinoline), 7.2-8.0
(m, 8H, ArH’s).
To a cold so lu tion of 21 (0.63 g, 0.002 mol) in conc.
H2SO4 (2mL)glacialaceticacid(10mL), sodiumnitrite(0.2
g, 0.003 mol) dis solved in 5 mL wa ter was added dropwise
with stir ring over 10 min. at 0-10 C. Thereactionmixture
was al lowed to stand at room tem per a ture for 1 h and then di-
luted with wa ter. The pre cip i tate was fil tered off, washed
with wa ter and crys tal lized from dioxane to give 36 as pale
yel low crys tals; m.p. 292 °C (dec.); yield: 0.57 g (87%).
Anal. Calcd. for C18H9N5S (327.36): C, 66.04; H, 2.77; N,
21.39; S, 9.79%. Found: C, 66.31; H, 2.71; N, 21.11; S,
9.55%. 1H NMR (TFA): = 9.0 (s, 1H, CH quinoline), 7.3-8.1
(m, 8H, ArH’s) ppm.
7-Methylbenzimidazo[1 ,2 :1 ,6 ]pyrimido[4 ,5 :4,5]thieno-
[2,3-b]quinoline (33)
Asolutionof21(0.63 g, 0.002 mol) in ace tic an hy dride
(20 mL) was refluxed for 4 h, and then al lowed to cool. The
solid prod uct was col lected and recrystallized from ace tic
acid as pale yel low crys tals of 33; m.p. >300 °C; yield: 0.63 g
(93%). Anal. Calcd. for C20H12N4S (340.40): C, 70.57; H,
3.55; N, 16.46; S, 9.42%. Found: C, 70.82; H, 3.57; N, 16.53;
S, 9.31%. IR: = 1600 (C=N) cm-1. 1H NMR (TFA): = 8.8
(s, 1H, CH quinoline), 7.1-8.0 (m, 8H, ArH’s), 2.6 (s, 3H,
CH3) ppm.
Received May 10, 2001.
Key Words
Pyrazoloquinolines; Thiazolines; Thiazolidinones;
Pyrimidopyrazoloquinolines;
Triazinoyrazoloquinolines; Thienoquinolines;
Pyrimidothienoquinolines; Imidazothienoquinolines;
Benzimidazoles.
7,8-Dihydro-7-(p-chlorophenyl)-benzimidazo[1 ,2 :1 ,6 ]-
pyrimido[4 ,5 :4,5]thieno[2,3-b]quinoline (34)
A mix ture of 21 (0.63 g, 0.002 mol), p-chlorobenz-
aldehyde (0.28 g, 0.002 mol) and gla cial ace tic acid (15 mL)
was refluxed for 3 h and then left to cool. The pre cip i tate that
formed was col lected and recrystallized from DMF to give
or ange nee dles of 34; m.p. >300 °C; yield: 0.77 g (95%).
Anal. Calcd. for C25H15ClN4S (438.93): C, 68.41; H, 3.44; N,
12.76; S, 7.30; Cl, 8.08%. Found: C, 68.17; H, 3.60; N, 13.02;
S, 7.23; Cl, 8.21%. IR: = 3400 (NH) cm-1. 1H NMR (TFA):
= 8.9 (s, 1H, CH quinoline), 7.3-8.6 (m, 12H, ArH’s), 6.2 (s,
1H, CH at C-7) ppm.
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1. Bruce-Chwatt, L. J. ChemotherapyofMalaria, II edn.;
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2. Swee ney, T. R.; Strube, R. E. Burger’sMedicinalChem-
is try, Part II; 4th Edn.; Wolff, M. F., Eds.; John-Wiley:
New York, 1979, 333.
3. Elslager, E. F. Prog. Drug Res. 1974, 18, 99.
4. Otto, H. H. Pharm. Ztg. 1980, 125, 931.
5. Hoechst, A. G. Ger man Pat. 1976, 2, 432, 635; Chem.
Abstr. 1976, 84, 150525 y.
Benzimidazo[1 ,2 :1 ,6 ]pyrimido[4 ,5 :4,5]thieno[2,3-b]-
quinoline-7(8H)-thione (35)
6. Barot, V. M. Asian J. Chem. 1996, 8, 565.
7. Raut, A. W.; Doshi, A. G. Orient.J.Chem. 1996, 12, 79.
To a so lu tion of21 (0.63 g, 0.002 mol) in dry pyridine

Syn the sis of New Pyrazolo- and Thienoquinolines
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