Synthesis of 4,6-disubstituted-2-(1H-indol-3-yl)-benzothiazoles

Article abstract of DOI:10.1135/cccc20040453

A new four-step synthesis of substituted 2-(1H-indol-3-yl)benzothiazoles is described, using N³-phenyl-1H-indole-3-carbothioamides as key intermediates. The structure of the obtained products was determined by IR, ¹H, ¹³C NMR and MS spectral methods.

Full text of DOI:10.1135/cccc20040453

Synthesis of 4,6-Disubstituted-2-(1H-indol-3-yl)benzothiazoles
453
SYNTHESIS OF 4,6-DISUBSTITUTED-2-(1H-INDOL-3-YL)-
BENZOTHIAZOLES
b
Janka ZÁLETOVÁa1, Milan DZURILLAa2, Peter KUTSCHYa3,*, Pavel PAZDERA ,
c1
c2
c3
Vladimír KOVÁČIK , Juraj ALDÖLFI and Slávka BEKEŠOVÁ
a
Institute of Chemical Sciences, Faculty of Science, P. J. Šafárik University, Moyzesova 11,
041 67 Košice, Slovak Republic; e-mail: zaletova@pobox.sk, dzurilla@kosice.upjs.sk,
kutschy@kosice.upjs.sk
Department of Organic Chemistry, Faculty of Science, Masaryk University, Kotlářská 2,
611 37 Brno, Czech Republic; e-mail: pazdera@chemi.muni.cz
Institute of Chemistry, Slovak Academy of Sciences, Dúbravska cesta 9,
842 38 Bratislava, Slovak Republic; e-mail: chemvkov@savba.sk, chemalf@savba.sk,
chembeke@savba.sk
1
2
3
b
c
1
2
3
Received August 19, 2003
Accepted Novem ber 2, 2003
A n ew four-step syn th esis of substituted 2-(1H-in dol-3-yl)ben zoth iazoles is described, usin g
N3-ph en yl-1H-in dole-3-carboth ioam ides as key in term ediates. Th e structure of th e obtain ed
products was determ in ed by IR, 1H, 13C NMR an d MS spectral m eth ods.
Keyw ord s: In doles; In dolylben zoth iazoles; Ph ytoalexin s; Heterocycles; Plan t h orm on es;
Cam alexin ; Natural products.
Pron oun ced cytotoxic activity of n um erous ben zoth iazole derivatives sug-
gests th eir poten tial use as an titum or agen ts1–4. In terestin g is also th eir in
vitro an d in vivo an tim icrobial activity, particularly again st Mycobacterium
tuberculosis5.
In th e presen t work we focused our atten tion on th e syn th esis of an alogs
of in dole ph ytoalexin cam alexin (1), n am ely ben zocam alexin (2) an d its
derivatives.
S
S
N
N
N
H
N
H
1
2
Collect. Czech. Chem. Commun. (Vol. 69) (2004)
doi:10.1135/cccc20040453

454
Záletová et al.:
Cam alexin , a cruciferous ph ytoalexin produced by Arabidopsis Thaliana6
an d Camelina sativa7 h as an tifun gal activities again st Alternaria brassicae
Cladosporium sp. an d Alternaria brassicicola6,7. Cam alexin an d oth er in dolyl
th iazoles exh ibit sign ifican t cytotoxic activity again st h um an brest can cer
cell lin e SKBr3 (ref.8). Ben zoth iazolyl derivatives in position 1 of th e in dole
rin g h ave been prepared by irradiation of in dole-1-carboth ioan ilides in
m eth an ol at am bien t tem perature9. Reaction of m eth yl 1-m eth ylin dole-
2-carboxylate with 2-am in oben zen e-1-th iol in th e presen ce of Al(Me)3 cata-
lyst afforded 2-(ben zoth iazol-2-yl)-1-m eth ylin dole10. Ben zocam alexin (2)
was previously prepared by cyclocon den sation of in dole-3-carbaldeh yde
with 2-am in oben zen e-1-th iol in a solution of aqueous HCl an d eth an ol un -
der reflux11. It was also obtain ed by cyclocon den sation of 1-(tert-butoxy-
carbon yl)-1H-in dole-3-carbaldeh yde with 2-am in oben zen e-1-th iol in a m ix-
ture of m eth an ol an d ben zen e (1:2) at am bien t tem perature an d subsequen t
rem oval of th e tert-butoxycarbon yl protectin g group with sodium m eth -
oxide in m eth an ol12.
For th e syn th esis of 4,6-disubstituted-2-(1H-in dol-3-yl)ben zoth iazoles,
th e cyclocon den sation of in dole-3-carbaldeh yde is n ot con ven ien t, because
correspon din g derivatives of 2-am in oben zen e-1-th iol are n ot easily avail-
able. Th erefore we design ed a n ew syn th etic m eth odology, usin g com m er-
cially available m eth yl in dole-3-carboxylate (3) an d substituted an ilin es as
suitable startin g com poun ds. Th e syn th etic strategy in cluded preparation of
in dole-3-carban ilides, th eir tran sform ation to th e correspon din g th io-
an ilides an d fin al cyclization of N-arylth ioam ide m oiety to ben zoth iazole
derivatives (Sch em e 1).
Attem pts to ach ieve direct tran sform ation of m eth yl in dole-3-carboxylate
(3) to th e correspon din g am ides by its reaction with an ilin es at h igh er tem -
perature with Lewis acids or m icrowave irradiation failed. Th erefore, ester 3
was h ydrolyzed to in dole-3-carboxylic acid13 (4) with a solution of NaOH in
aqueous propan -2-ol at 85–90 °C. Am ides 6–8 were obtain ed by reaction of
acid 4 with an ilin es in th e presen ce of dicycloh exylcarbodiim ide (DCC) in
ch loroform , or by reaction of an ilin es with in dole-3-carbon yl ch loride (5).
Ch loride 5 prepared from acid 4 by treatm en t with ph osph orus trich loride
in a m ixture of toluen e an d aceton itrile (2:1) is an un stable com poun d14
.
Th erefore after its preparation th e reaction m ixture was decan ted from
ph osph orous acid separated on th e flask walls, con cen trated to a quarter of
its origin al volum e an d th e obtain ed solution was treated with an ilin es for
3 h at room tem perature. Th is approach afforded N3-(4-ch loroph en yl)-1H-
in dole-3-carboxam ide (6) in 80% yield, wh ereas am ides 7 an d 8 were ob-
tain ed in yields lower th en 50%. Am ides 7 an d 8 can be m ore advan ta-
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

Synthesis of 4,6-Disubstituted-2-(1H-indol-3-yl)benzothiazoles
455
geously prepared by direct couplin g of acid 4 with 4-m eth oxyan ilin e an d
2,4-dim eth ylan ilin e, respectively, in th e presen ce of DCC in boilin g ch loro-
form 15. Alth ough products 7 an d 8 were form ed quan titatively, th eir sepa-
ration from dicycloh exylurea was rath er difficult. It was foun d th at am ides
are well soluble in dioxan e, wh ereas dicycloh exylurea is in soluble. Th ere-
fore a m ixture of an am ide an d th e urea was stirred in dioxan e for 15 m in
at room tem perature, th e in soluble urea filtered off, an d am ide was ob-
tain ed in 80–88% yield after evaporation of dioxan e an d crystallization .
H
N
MeO
HO
O
6'
O
O
5'
4'
4
1'
2'
3a
3
5
6
NaOH, H2O
propan-2-ol
Ar-NH2, DCC
CHCl3
R2
2
R1
1
3'
N
N
N
7a
7
H
H
H
3
4
Lawesson's r.
C6H5CH3
6-8
PCl3
CH3CN, C6H5CH3
H
N
S
Ar-NH2
CH2Cl2
Cl
O
R1
R2
N
9-11
H
N
5
H
R1
R1
H
H
CH3
H
R2
Cl
CH3O
CH3
Cl
Br2
6'
5'
4'
6
7
8
9
10
11
7'
CHCl3
R2
7'a
3'a
3'
1' S
2'
N
H
CH3
CH3O
CH3
4
3a
3
5
2
1
6
N
H
7a
12-14
7
SCHEME 1
In th e n ext step, syn th etic tran sform ation of am ides 6–8 to th ioam ides
9–11 usin g P4S10 or Lawesson ’s reagen t as sulfuration reagen ts was studied.
Lawesson ’s reagen t appeared to be m ore effective an d by reflux in toluen e,
th ioam ides 9–11 were obtain ed in 78–90% yieds. In 13C NMR spectra of th e
th ioam ides, th e sign als of C=S carbon atom s appeared at 190–192 ppm ,
in stead of C=O sign als presen t in th e spectra of am ides at 163 ppm . In
th e m ass spectra of th ioam ides, th eir m olecular peaks were presen t at h igh -
er m/z values (by 16), com pared with m olecular ion s of th e correspon din g
am ides.
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

456
Záletová et al.:
Th e key step in th e syn th esis of cam alexin an alogs 12–14 is th e cycli-
zation of th ioam ides 9–11 to th e ben zoth iazole rin g. For th is purpose, we
exam in ed two reagen ts. By treatm en t of a dioxan e solution of th ioam ides
with fresh ly prepared dioxan e solution of dioxan e dibrom ide, n o reaction
took place (m on itored by TLC). Th erefore we perform ed th e cyclization un -
der th e con dition s of th e Huggersh off reaction (reaction of th ioam ides with
brom in e in ch loroform )16,17. It is assum ed th at th is reaction proceeds via
oxidative form ation of disulfide givin g correspon din g sulfen yl brom ide, in
wh ich th e sulfur atom h as electroph ilic properties. Th e electroph ilic attack
of sulfen yl brom ide on ortho-position of th e ph en yl rin g th en results in th e
form ation of th e ben zoth iazole rin g. Usin g com m ercial ch loroform , we ob-
tain ed from th ioam ides on ly th e correspon din g am ides, probably because
of th e h ydrolysis of sulfen yl brom ides with a sm all am oun t of water presen t
in th e solven t. Usin g dry ch loroform , th e cyclization of th ioam ides pro-
ceeded sm ooth ly at room tem perature an d desired ben zocam alexin deriva-
tives 12–14 were obtain ed, after ch rom atograph ic isolation an d crystalliza-
tion , in 32–64% yields.
EXPERIMENTAL
In frared absorption spectra of com poun ds (4, 6–14) were recorded on an IR 75 spectrom eter
.
(Zeiss, Jen a) in ch loroform , th e waven um bers are given in cm –1 1H NMR spectra were m ea-
sured on a Bruker Avan ce-DPX FT (300 MHz) in deuterioch loroform . 13C NMR spectra of
com poun ds 6–14 were m easured on a Bruker Avan ce-DPX FT (75 MHz) in deuterioch loro-
form . Ch em ical sh ifts (δ-scale) are reported in ppm down field from tetram eth ylsilan e.
Microan alyses were perform ed with a Perkin –Elm er, Model 2400 an alyzer. Th e m ass spectra
of com poun ds 6–14 were recorded on a Fin igan SSQ 700 spectrom eter usin g th e electron im -
pact m eth od at ion ization en ergy 70 eV. Th e reaction course was m on itored by th in layer
ch rom atograph y, usin g Silufol plates (Kavalier). Preparative colum n ch rom atograph y was
perform ed on silica gel Kieselgel Merck 60 F25 an d on Kavalier 40/100 µm silica gel. Meltin g
poin ts were m easured on a Kofler h ot stage apparatus an d are un corrected.
In dole-3-carboxylic Acid (4)
To a solution of NaOH (5.25 g, 130 m m ol) in water (125 m l), propan -2-ol (25 m l) an d m eth -
yl in dole-3-carboxylate (5 g, 28.5 m m ol) were added an d th e reaction m ixture was stirred for
1 h at 85–90 °C un til com plete dissolution of th e ester. After evaporation of propan -2-ol, th e
aqueous solution was acidified with HCl (1:1) un der ice coolin g. Th e precipitated crude
product was filtered off an d wash ed with water. Yield 61%, m .p. 208–210 °C (aceton e–
water). For C9H7NO2 (161.2) calculated: 67.08% C, 4.38% H, 8.69% N; foun d: 67.20% C,
5.00% H, 8.80% N. IR spectral data of th e product were iden tical with th ose previously pub-
lish ed13
.
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

Synthesis of 4,6-Disubstituted-2-(1H-indol-3-yl)benzothiazoles
N3-(4-Ch loroph en yl)-1H-in dole-3-carboxam ide (6)
457
To a solution of 4 (200 m g, 1.24 m m ol) in a m ixture of dry toluen e (10 m l) an d dry aceton i-
trile (5 m l), PCl3 (0.12 m l, 1.38 m m ol) was added. Th e reaction m ixture was stirred for
25 m in at room tem perature un til com plete dissolution of th e acid. Th e resultin g solution
was decan ted from ph osph orous acid deposited on th e flask walls. Th e flask was wash ed
with toluen e (10 m l) an d th e com bin ed toluen e solution was evaporated to quarter of its
origin al volum e. Th e obtain ed solution was cooled to 0 °C an d 4-ch loroan ilin e (230 m g,
1.80 m m ol) was added. Th e reaction m ixture was stirred for 3 h at room tem perature, th e
solven t was evaporated an d th e residue was purified by ch rom atograph y on silica gel
(dich lorom eth an e–m eth an ol, 90:1). Yield 88%, m .p. 225–226 °C. For C15H11ClN2O (270.7)
calculated: 66.55% C, 4.10% H, 10.35% N; foun d: 66.60% C, 4.50% H, 10.50% N. IR: 3410
(in dole N–H); 3120 (N–H); 1640 (C=O). 1H NMR: 7.00–8.63 m , 9 H (arom . H); 9.45 s, 1 H
(in dole N-H); 11.20 s, 1 H (CO-NH). 13C NMR: 110.41 (q); 112.16, 120.92, 121.21, 121.30,
122.39, 126.24 (q); 126.53, 128.59, 129.03 (q); 136.39 (q); 139.00 (q) (arom . C); 163.44
(C=O). MS, m/z (%): 270 (M+, 100), 144 (70), 126 (50).
N3-(4-Meth oxyph en yl)-1H-in dole-3-carboxam ide (7)
To a solution of 4 (2 g, 12.4 m m ol) in ch loroform (65 m l), dicycloh exylcarbodiim ide
(2.81 g, 13.6 m m ol) an d 4-m eth oxyan ilin e (1.68 g, 13.6 m m ol) dissolved in ch loroform
(10 m l) were added. Th e reaction m ixture was refluxed for 3 h . After coolin g, th e crystallin e
precipitate was filtered off with suction an d triturated with dioxan e (15 m l). Th e m ixture
was stirred for 15 m in at room tem perature an d th e crystallin e precipitate (dicycloh exylurea)
was filtered off. Th e filtrate was evaporated an d th e obtain ed residue was crystallized from a
m ixture of dieth yl eth er–h exan e (1:1). Yield 80%, m .p. 200–202 °C. For C16H14N2O2 (266.2)
calculated: 72.17% C, 5.30% H, 10.52% N; foun d: 72.45% C, 5.56% H, 11.10% N. IR: 3398
(in dole N–H); 3217 (N–H); 1631 (C=O); 1236 (C–O–C). 1H NMR: 3.76 s, 3 H (OCH3);
6.90–8.25 m , 9 H (arom . H); 9.61 s, 1 H (in dole N-H); 11.96 s, 1 H (N-H). 13C NMR: 55.13
(CH3); 110.60 (q); 111.89, 113.68, 120.53, 121.11, 121.36, 122.04, 126.40 (q); 128.28, 132.87
(q); 136.17 (q); 154.87 (q) (arom . C); 162.99 (C=O). MS, m/z (%): 266 (M+, 50), 144 (65), 123
(100).
N3-(2,4-Dim eth ylph en yl)-1H-in dole-3-carboxam ide (8)
To a solution of 4 (2 g, 12.4 m m ol) in ch loroform (70 m l), dicycloh exylcarbodim ide (2.76 g,
13.4 m m ol) an d 2,4-dim eth ylan ilin e (1.64 g, 13.5 m m ol) dissolved in ch loroform (8 m l)
were added. Th e reaction m ixture was refluxed for 3 h , th e crystallin e precipitate separated
after coolin g was filtered off with suction an d triturated with dioxan e (15 m l). Th e m ixture
was stirred for 15 m in at room tem perature. Th e crystallin e precipitate (dicycloh exylurea)
was filtered off. Th e filtrate was evaporated an d th e obtain ed residue was crystallized from a
m ixture of dieth yl eth er–h exan e (1:1). Yield 80%, m .p. 170 °C. For C17H16N2O (264.3) calcu-
lated: 77.25% C, 6.10% H, 10.60% N; foun d: 78.01% C, 6.38% H, 11.00% N. IR: 3390
(in dole N–H); 3250 (N–H); 1640 (C=O). 1H NMR: 2.53 s, 3 H (CH3); 2.59 s, 3 H (CH3);
6.13–7.36 m , 8 H (arom . H); 8.36 s, 1 H (in dole N-H); 10.82 s, 1 H (N-H). 13C NMR: 18.13
(CH3); 20.70 (CH3); 111.60 (q); 112.04 (q); 120.65, 121.21, 122.16, 126.54, 128.53,
130.91 (q); 133.22, 134.36 (q); 136.35 (q); 136.85 (q) (arom . C); 163.12 (C=O). MS, m/z (%):
264 (M+, 20), 144 (34), 120 (100).
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458
Záletová et al.:
N3-(4-Ch loroph en yl)-1H-in dole-3-carboth ioam ide (9)
To a suspen sion of 6 (0.13 g, 0.48 m m ol) in dry toluen e (4 m l), Lawesson ’s reagen t (0.11 g,
0.27 m m ol) was added. Th e reaction m ixture was refluxed for 15 m in . After coolin g, th e
crystallin e precipitate was filtered off with suction an d crystallized from a m ixture of
dich lorom eth an e an d h exan e. Yield 86%, m .p. 202–205 °C. For C15H11ClN2S (286.8) calcu-
lated: 62.82% C, 3.87% H, 9.77% N; foun d: 63.00% C, 3.75% H, 9.81% N. IR: 1050 (C=S);
1656 (C=C); 3410 (in dole N–H); 3210 (N–H). 1H NMR: 6.55–7.44 m , 9 H (arom . H); 9.80 s,
2 H (N-H). 13C NMR: 112.29, 118.91, 121.00, 121.87, 122.52, 126.07 (q); 126.41 (q); 128.03,
128.37, 129.25 (q); 132.58 (q); 136.99 (q); 139.14 (arom . C); 191.14 (C=S). MS, m/z (%): 286
(M+, 45), 160 (75), 126 (100).
N3-(4-Meth oxyph en yl)-1H-in dole-3-carboth ioam ide (10)
To a suspen sion of 7 (1 g, 3.76 m m ol) in dry toluen e (15 m l), Lawesson ’s reagen t (0.96 g,
2.37 m m ol) was added an d th e reaction m ixture was refluxed for 15 m in . After coolin g, th e
form ed crystallin e precipitate was filtered off with suction an d crystallized from a m ixture of
dich lorom eth an e an d h exan e. Yield 78%, m .p. 193 °C. For C16H14N2OS (282.4) calculated:
68.06% C, 5.00% H, 9.92% N; foun d: 68.40% C, 5.10% H, 10.00% N. IR: 1075 (C=S); 1650
(C=C); 3210 (N–H); 3400 (N–H). 1H NMR: 3.78 s, 3 H (OCH3); 6.96–8.53 m , 9 H (arom . H);
10.96 s, 1 H (in dole N-H); 11.82 s, 1 H (N-H). 13C NMR: 55.31 (OCH3); 112.11, 113.51,
118.62 (q); 120.72, 121.86, 122.31 (q); 126.02, 126.48, 127.33 (q); 133.01, 136.83 (q); 156.93
(q) (arom . C); 190.51 (C=S). MS, m/z (%): 282 (M+, 50), 249 (40), 160 (80), 123 (100).
N3-(2,4-Dim eth ylph en yl)-1H-in dole-3-carboth ioam ide (11)
To a suspen sion of 8 (1 g, 3.78 m m ol) in dry toluen e (30 m l), Lawesson ’s reagen t (0.77 g,
1.90 m m ol) was added an d th e reaction m ixture was refluxed for 50 m in . After coolin g,
th e crystallin e precipitate was filtered off with suction an d crystallized from a m ixture of
dich lorom eth an e an d h exan e. Yield 90%, m .p. 188 °C. For C17H16N2S (280.4) calculated:
72.82% C, 5.64% H, 9.99% N; foun d: 73.00% C, 5.75% H, 10.00% N. IR: 1100 (C=S); 1650
(C=C); 3200 (N–H); 3450 (in dole N–H). 1H NMR: 2.23 s, 3 H (CH3); 2.33 s, 3 H (CH3);
7.05–8.59 m , 8 H (arom . H); 10.69 s, 1 H (in dole N-H); 11.74 s, 1 H (N-H). 13C NMR: 17.88
(CH3); 20.82 (CH3); 112.16, 117.82 (q); 120.82, 122.02, 122.36, 126.22 (q); 126.88, 127.38,
128.18 (q); 131.03, 135.10 (q); 136.27, 136.44 (q); 136.93 (q) (arom . C); 191.88 (C=S). MS,
m/z (%): 280 (M+, 90), 160 (75), 120 (100).
2-(1H-In dol-3-yl)-6-ch loro-1,3-ben zoth iazole (12)
To a suspen sion of 9 (515 m g, 1.80 m m ol) in ch loroform (18 m l), brom in e (290 m g,
1.81 m m ol) was added dropwise. Th e reaction m ixture was stirred for 1 h at room tem pera-
ture, th en n eutralized with trieth ylam in e (0.46 m l, 3.3 m m ol), poured in to water (150 m l)
an d extracted with dieth yl eth er (2 × 50 m l). Th e extract was dried with an h ydrous sodium
sulfate, evaporated an d purified by ch rom atograph y on silica gel (cycloh exan e–aceton e, 2:1).
Yield 45%, m .p. 143–145 °C (m eth an ol–water). For C15H9ClN2S (284.8) calculated: 63.27% C,
3.19% H, 9.84% N; foun d: 63.10% C, 3.20% H, 9.91% N. IR: 1173 (N–C); 1630 (C=N); 1640
(C–S); 3020 (C–H). 1H NMR: 6.75–8.55 m , 9 H (arom . H); 9.25 s, 1 H (N-H). 13C NMR:
104.67 (q); 111.63, 121.21, 122.18, 123.02 (q); 123.75, 124.08, 124.16, 125.16, 125.46 (q);
Collect. Czech. Chem. Commun. (Vol. 69) (2004)

Synthesis of 4,6-Disubstituted-2-(1H-indol-3-yl)benzothiazoles
459
131.36 (q); 133.18, 136.58 (q); 148.20 (q); 154.44 (q) (arom . C). MS, m/z (%): 284 (M+, 50),
143 (100), 116 (60).
2-(1H-In dol-3-yl)-6-m eth oxy-1,3-ben zoth iazole (13)
To a suspen sion of 10 (282 m g, 1 m m ol) in ch loroform (10 m l), brom in e (160 m g, 1 m m ol)
was added dropwise. Th e reaction m ixture was stirred for 1.5 h at room tem perature, n eu-
tralized with trieth ylam in e (0.25 m l, 1.8 m m ol), poured in to water (120 m l) an d extracted
with dieth yl eth er (2 × 40 m l). Th e extract was dried with an h ydrous sodium sulfate, evapo-
rated an d th e obtain ed residue was purified by ch rom atograph y on silica gel (cycloh exan e–
aceton e, 2:1). Yield 32%, m .p. 168–171 °C (dieth yl eth er–h exan e). For C16H12N2OS (280.4)
calculated: 68.55% C, 4.31% H, 9.99% N; foun d: 68.70% C, 4.25% H, 10.00% N. IR: 1165
(N–C); 1239 (C–O–C); 1625 (C=N); 1640 (C–S); 3000 (C–H). 1H NMR: 3.73 s, 1 H (OCH3);
6.597.88 m , 8 H (arom . H); 11.46 s, 1 H (N-H). 13C NMR: 55.11 (OCH3); 61.00 (q); 105.44,
111.84, 113.68, 114.67, 120.53, 121.44 (q); 121.60, 122.11, 125.56, 129.55 (q); 134.96 (q);
142.88 (q); 154.86 (q); 156.62 (q) (arom . C). MS, m/z (%): 280 (M+, 50), 143 (100), 116 (65),
32 (40).
2-(1H-In dol-3-yl)-4,6-dim eth yl-1,3-ben zoth iazole (14)
To a suspen sion of 11 (110 m g, 0.39 m m ol) in ch loroform (4 m l), brom in e (61 m g,
0.38 m m ol) was added dropwise. Th e reaction m ixture was stirred for 2 h at room tem pera-
ture, n eutralized with trieth ylam in e (0.10 m l, 0.72 m m ol), poured in to water (80 m l) an d
extracted with dieth yl eth er (2 × 20 m l). Th e extract was dried with an h ydrous sodium
sulfate an d evaporated. Yield 64%, m .p. 130–133 °C (eth an ol–water). For C17H14N2S (278.4)
calculated: 73.29% C, 5.07% H, 10.00% N; foun d: 73.35% C, 5.05% H, 10.06% N. IR: 1170
(N–C); 1635 (C=N); 1645 (C–S); 3025 (C–H). 1H NMR: 2.10 s, 3 H (CH3); 2.39 s, 3 H (CH3);
6.55–7.50 m , 7 H (arom . H); 8.25 s, 1 H (N-H). 13C NMR: 17.81 (CH3); 20.93 (CH3); 107.10
(q); 111.46, 121.15, 121.63, 122.25 (q); 123.06, 124.78, 125.84, 127.71 (q); 129.22 (q);
131.61 (q); 132.78, 135.12 (q); 144.37 (q); 157.18 (q) (arom . C). MS, m/z (%): 278 (M+, 15).
We thank the Grant Agency for Science, Slovak Republic (grant No. 1/9246/02) for financial sup-
port of this work.
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