Synthesis and study of novel benzothiazole derivatives with potential nonlinear optical properties

Article abstract of DOI:10.1135/cccc20071069

The synthesis of new benzothiazole push-pull systems as candidates for NLO-phores is described. Spectral (UV/VIS and solvatochromic) and theoretical studies (electronic properties based on semiempirical AM1 and PM3 methods) of the prepared compounds were carried out. The structure and physico-chemical parameters affecting the push-pull character and intramolecular charge transfer (ICT) of the studied compounds have been investigated and compounds with enhanced hyperpolarizability β have been predicted. The benzothiazolium salts were found to be much more effective NLO-phores in comparison with the corresponding neutral benzothiazoles. The 4-NPh₂ group is the most effective donor. The extension of conjugated bridge improves the studied NLO characteristics. An additional acceptor group bonded to the heterocycle causes a red shift of λ_max but does not increase hyperpolarizability.

Full text of DOI:10.1135/cccc20071069

Novel Benzothiazole Derivatives
1069
SYNTHESIS AND STUDY OF NOVEL BENZOTHIAZOLE DERIVATIVES
WITH POTENTIAL NONLINEAR OPTICAL PROPERTIES
1
2,
3
Ivica SIGMUNDOVÁ , Pavol ZAHRADNÍK * and Dušan LOOS
Department of Organic Chemistry, Faculty of Natural Sciences, Comenius University,
1
2
84104 Bratislava, Slovakia; e-mail: sigmundova@fns.uniba.sk, zahradnik@fns.uniba.sk,
loos@fns.uniba.sk
3
Received April 18, 2007
Accepted Jun e 14, 2007
Dedicated to Professor Štefan Toma on the occasion of his 70th birthday.
Th e syn th esis of n ew ben zoth iazole push -pull system s as can didates for NLO-ph ores is de-
scribed. Spectral (UV/VIS an d solvatoch rom ic) an d th eoretical studies (electron ic properties
based on sem iem pirical AM1 an d PM3 m eth ods) of th e prepared com poun ds were carried
out. Th e structure an d ph ysico-ch em ical param eters affectin g th e push -pull ch aracter an d
in tram olecular ch arge tran sfer (ICT) of th e studied com poun ds h ave been in vestigated an d
com poun ds with en h an ced h yperpolarizability β h ave been predicted. Th e ben zoth iazolium
salts were foun d to be m uch m ore effective NLO-ph ores in com parison with th e correspon d-
in g n eutral ben zoth iazoles. Th e 4-NPh 2 group is th e m ost effective don or. Th e exten sion of
con jugated bridge im proves th e studied NLO ch aracteristics. An addition al acceptor group
bon ded to th e h eterocycle causes a red sh ift of λm ax but does n ot in crease h yperpolariz-
ability.
Keyw ord s: Push -pull ben zoth iazoles; Alken es; Dien es; NLO-ph ores; In tram olecular ch arge
tran sfer; UV/VIS spectroscopy; Hyperpolarizability; Organ ic n on lin ear optic m aterials.
In th e recen t decade, a con siderable effort h as been focused on th e develop-
m en t of organ ic m olecules with en h an ced secon d order n on lin ear optical
(NLO) properties due to th eir poten tial application s in various areas such
as optical m odulation , frequen cy doublin g an d m olecular switch in g1. Or-
gan ic n on lin ear optical m aterials h ave em erged as viable altern atives to
con ven tion al in organ ic crystals in active ph oton ic com pon en ts2. Th ese or-
gan ic m aterials offer m an y possible advan tages: (i) th ey sh ow h igh er elec-
tron ic susceptibility (χ(2)) th rough h igh m olecular h yperpolarizability (β)
an d fast respon se tim e; (ii) th ey are easier to fabricate an d ch eaper to pro-
duce; (iii) th ey are com patible with th e existin g sem icon ductor tech n ology;
Collect. Czech. Chem. Commun. 2007, Vol. 72, No. 8, pp. 1069–1093
© 2007 Institute of Organic Chemistry and Biochemistry
doi:10.1135/cccc20071069

1070
Sigmundová, Zahradník, Loos:
(iv) th eir structures can be tailored in m an y ways in order to fin ely tun e
NLO properties for required application s.
Dipolar push -pull organ ic ch rom oph ores probably con stitute th e largest
class of com poun ds in vestigated for th eir NLO properties. Push -pull NLO-
ph ores basically in volve an electron don or an d an electron -acceptor groups
in teractin g th rough a π-con jugated spacer. Structure–property relation sh ips
based on th e th eoretical an d experim en tal work h ave sh own th at h igh
structure h yperpolarizabilities β gen erally arise from a com bin ation of a
stron g electron -don or an d -acceptor position ed at th e opposite en ds of a
suitable con jugation path 3. Th e n ature of th e con jugation path is of critical
im portan ce. Wh ile polyen es are superior in efficien t ch arge tran sfer from
don or to acceptor, th eir low ch em ical an d th erm al stabilities h ave sh ifted
th e in terest toward arom atic an d h eteroarom atic com poun ds because of
th eir h igh er m olecular h yperpolarizabilities, im proved optical tran spar-
en cy, an d good th erm al stability. Heteroarom atics are superior to th ose of
th e correspon din g arom atic an alogues. Ch rom oph ores con tain in g h etero-
cycles such as th ioph en e4, th iazole5, an d ben zoth iazole6 are am on g th e
m ost studied system s h avin g an optim al don or–acceptor an d con jugation
bridge com bin ation for a given ch rom oph ore.
In th is paper we presen t syn th esis, UV/VIS absorption , solvatoch rom ic
properties an d th eoretical study of a series of poten tial NLO-ph ores of th e
ben zoth iazole type 3 an d 5.
Th e studied com poun ds are dipolar push -pull ch rom oph ores con tain in g
a ben zoth iazole electron -acceptor group, alken ylen e con jugation spacer
with 1–3 double bon ds an d a don or in para position of th e substituted
ph en yl group (structure 3). Th e acceptor stren gth of ben zoth iazole h etero-
cycle can be en h an ced by m eth ylation of th e h eterocyclic n itrogen to
N-m eth yl in ben zoth iazolium salts (structure 5). An oth er m odification of
th e ben zoth iazole acceptor con sists in in troducin g an addition al acceptor
in to th e ben zoth iazole skeleton (NO2 or CN). Th e con ven tion al dim eth yl-
am in o or cyclic am in o (e.g. pyrrolidin -1-yl) groups h ave been em ployed as
Collect. Czech. Chem. Commun. 2007, Vol. 72, No. 8, pp. 1069–1093

Novel Benzothiazole Derivatives
1071
electron -don or substituen ts. Diph en ylam in o group was also ch osen because
th is m oiety brin gs h igh th erm al stability an d th e obtain ed h yperpolariz-
ability is often in creased com pared with dialkylam in o group7. Th e posi-
tion s ortho an d meta for dim eth ylam in o group were tested too.
RESULTS AND DISCUSSION
Synthesis
Th e key step in th e syn th etic approach is th e con den sation of substituted
2-m eth ylben zoth iazoles with suitable substituted aldeh ydes. Th e startin g
ben zoth iazole derivatives 1 h ave been prepared as follows:
2-Meth ylben zoth iazole-6-carbon itrile8 (1b) was prepared from 2-m eth yl-
ben zoth iazol-5-am in e by the Sandm eyer reaction. The synthesis of 2-m ethyl-
4-n itroben zoth iazole9 (1c) started from protected 2-m eth ylben zoth iazol-
5-am in e, followed by n itration , deprotection an d rem oval of am in o group.
2-Meth yl-5-n itroben zoth iazole10 (1d ) was prepared by cyclization of cor-
respon din g 2-brom oben zan ilides, 2-m eth yl-6-n itroben zoth iazole11 (1e) by
n itration of 2-m eth ylben zoth iazole. A sim ilar route to 1c was used also for
th e syn th esis of 2-m eth yl-7-n itroben zoth iazole11 (1f) startin g from 2-m eth yl-
ben zoth iazol-6-am in e.
A m odified procedure was foun d for th e syn th esis of 2-m eth yl-4,6-di-
n itroben zoth iazole. Th e previously publish ed syn th esis used an eigh t-step
reaction 12. Our startin g m aterial was m ore accessible 2-m eth yl-6-n itro-
ben zoth iazole. We studied its n itration an d ach ieved a con version of 85%
at 100 °C after 6 h with two products: 2-m eth yl-4,6-din itroben zoth iazole
an d 2-m eth yl-5,6-din itroben zoth iazole in th e 9:2 ratio (Sch em e 1). In -
creased tem perature led to un desirable oxidation products.
SCHEME 1
Arom atic aldeh ydes h ave been prepared usin g com m on protocols.
Mon oform ylation of triph en ylam in e by th e Vilsm eier reaction gave
4-(diph en ylam in o)ben zaldeh yde13 (2b). 4-Pyrrolidin -1-yl-ben zaldeh yde14
(2c) was prepared by son och em ical n ucleoph ilic arom atic substitution
of 4-fluoroben zaldeh yde. (2E,4E)-5-[4-(Dim eth ylam in o)ph en yl]pen ta-
2,4-dien al (2e) was prepared from com m ercially available 3-[4-(dim eth yl-
Collect. Czech. Chem. Commun. 2007, Vol. 72, No. 8, pp. 1069–1093

1072
Sigmundová, Zahradník, Loos:
am in o)ph en yl]propen al accordin g to th e procedure described in litera-
ture15. 3-(Dim eth ylam in o)ben zaldeh yde16 (2f) was prepared from eth yl
3-(dim eth ylam in o)ben zoate by partial reduction with th e Red-Al–
m orph olin e reagen t. 2-(Dim eth ylam in o)ben zaldeh yde17 (2g) was prepared
from 2-fluoroben zaldeh yde by n ucleoph ilic substitution with dim eth yl-
am in e.
Th e n eutral push -pull ben zoth iazoles h ave been syn th esized by th e
con den sation of 2-m eth yl- or 6-cyan o-2-m eth ylben zoth iazole with corre-
spon din g aldeh ydes (Sch em e 2). Th e structures an d yields of th e prepared
com poun ds are sum m arized in Table I.
SCHEME 2
TABLE I
Ben zoth iazoles prepared un der basic catalysis
Com poun d
R1
n
Don or
Yield, %
3a
3b
3c
3d
3e
3f
H
1
1
1
2
1
1
1
2
H
95 (ref.18, 98)
H
N(CH3)2
NPh 2
86 (ref.18, 71)
H
98
63
74
64
72
53
H
N(CH3)2
N(CH3)2
NPh 2
CN
CN
CN
CN
3g
3h
pyrrolidin -1-yl
N(CH3)2
Collect. Czech. Chem. Commun. 2007, Vol. 72, No. 8, pp. 1069–1093

Novel Benzothiazole Derivatives
1073
Basic catalysis can n ot be used for th e con den sation of n itroben zo-
th iazoles as th ey probably un dergo destructive rin g open in g. Acid m edium
h as been foun d to fulfil optim al con dition s for th is reaction (Sch em e 3 an d
Table II).
SCHEME 3
TABLE II
Ben zoth iazoles prepared un der acid catalysis
Com poun d
R1
n
Don or
Yield, %
3i
4-NO2
1
1
1
1
1
1
1
1
1
1
2
2
N(CH3)2
N(CH3)2
N(CH3)2
N(CH3)2
N(CH3)2
NPh 2
82
38
67
88
68
45
49
62
45
40
29
56
3j
5-NO2
3k
3l
6-NO2
7-NO2
3m
3n
3o
3p
3q
3r
3s
3t
4,6-(NO2)2
5-NO2
6-NO2
NPh 2
4,6-(NO2)2
6-NO2
NPh 2
pyrrolidin -1-yl
pyrrolidin -1-yl
N(CH3)2
N(CH3)2
4,6-(NO2)2
6-NO2
4,6-(NO2)2
Collect. Czech. Chem. Commun. 2007, Vol. 72, No. 8, pp. 1069–1093

1074
Sigmundová, Zahradník, Loos:
Various 2,3-dim eth ylben zoth iazolium iodides were prepared by quater-
n ization of n eutral 2-m eth ylben zoth iazoles with m eth yl iodide un der
m icrowave con dition . Sch em e 4 an d Table III presen t optim al con dition s
for th e reaction . Th e m eth ylation was un successful in th e case of
2-m eth yl-4-n itro- an d 2-m eth yl-4,6-din itroben zoth iazoles. 2,3-Dim eth yl-
ben zoth iazolium iodide (4a) was prepared accordin g to literature15
.
Meth ylation of 2-m eth ylben zoth iazole with dim eth yl sulfate yields th e
2,3-dim eth ylben zoth iazolium h ydrogen sulfate (4f). Its ph ysico-ch em ical
data were iden tical with th e reported on es19.
SCHEME 4
TABLE III
2-Meth ylben zoth iazolium iodides
Pressure
Tem perature
°C
MW power
W
Yield
%
Com poun d
R1
MPa
4b
4c
4d
4e
6-CN
115
117
118
115
60
60
60
70
1.4
1.9
1.8
1.9
81
68
86
73
5-NO2
6-NO2
7-NO2
2,3-Dim eth ylben zoth iazolium iodides con den se m ore readily with
aldeh ydes th an correspon din g n eutral 2-m eth ylben zoth iazoles due to th e
m ore acid h ydrogen s of th e 2-m eth yl group. Th e reaction un derwen t un der
m ild con dition s (pyridin e, piperidin e catalysis or with out catalysis). Th is
m eth od was used for all con jugated ben zoth iazolium derivatives (Sch em e 5,
Table IV).
Collect. Czech. Chem. Commun. 2007, Vol. 72, No. 8, pp. 1069–1093

Novel Benzothiazole Derivatives
1075
SCHEME 5
TABLE IV
Catalyst, reaction tim e an d yields of products 5b–5x
Reaction
tim e, h
Com poun d
R1
n
Don or
Catalyst
Yield, %
5b
H
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
3
4-N(CH3)2
4-N(CH3)2
4-N(CH3)2
3-N(CH3)2
2-N(CH3)2
4-N(CH3)2
3-N(CH3)2
2-N(CH3)2
4-N(CH3)2
4-NPh 2
pyridin e
5
4
82
70
88
84
72
84
65
72
68
76
76
70
77
71
75
66
64
78
98
83
80
83
77
–
5c (HSO4
5d
5e
)
H
pyridin e
5-NO2
5-NO2
5-NO2
6-NO2
6-NO2
6-(NO2)
7-NO2
H
–
6
–
8
5f
–
7
5g
5h
5i
–
8
piperidin e
–
8
8
5j
pyridin e
piperidin e
piperidin e
piperidin e
pyridin e
–
6
5k
5l
8
H
4-NPh 2
8
5m
5n
5o
5p
5q
5r
5-NO2
6-NO2
7-NO2
6-CN
H
4-NPh 2
7
4-NPh 2
10
7
4-NPh 2
4-NPh 2
piperidin e
–
4
4-pyrrolidin yl
4-pyrrolidin yl
4-N(CH3)2
4-N(CH3)2
4-N(CH3)2
4-N(CH3)2
4-N(CH3)2
4-N(CH3)2
8
6-NO2
H
–
6
5s
pyridin e
pyridin e
pyridin e
–
9
5t
5-NO2
6-NO2
7-NO2
6-CN
H
5
5u
5v
5w
5x
5
6
3
pyridin e
12
Collect. Czech. Chem. Commun. 2007, Vol. 72, No. 8, pp. 1069–1093

1076
Spectral and Theoretical Study
Sigmundová, Zahradník, Loos:
Th e in ten se low-en ergy ban d dom in ates in th e visible region of th e ab-
sorption spectra of both n eutral com poun ds an d salts. Th is ban d can be
attributed to π(NMe2)→π* (ben zoth iazole) or π*(ben zoth iazolium ) ch arge-
tran sfer excitation , respectively.
Neutral Benzothiazoles
Th e experim en tal values of absorption UV/VIS spectra ch aracteristics λm ax
an d m olar absorption coefficien t ε m easured in ch loroform as well as repre-
sen tative th eoretical electric properties of n eutral ben zoth iazoles are pre-
sen ted in Table V. Ch loroform was ch osen as solven t because of poor
solubility of th e din itro derivatives in m eth an ol. Th e n egligible value of di-
pole m om en t as well as th e low λm ax of th e un substituted ben zoth iazole de-
rivative 3a in dicate th at th is com poun d h as n o push -pull ch aracter. Th e
h igh ∆E an d m in im al β con firm th e fact.
Th e push -pull system s with effective con jugation resultin g in D→A
ch arge tran sfer are ch aracterized by a bath och rom ic sh ift of λm ax, a de-
creased value of ∆E an d in creased values of dipole m om en t µ an d, in par-
ticular, h yperpolarizability β. All th ese facts were observed wh en don or
group was in troduced in th e para position of th e ben zen e rin g.
An oth er en h an cem en t of th e push -pull ch aracter is caused by th e addi-
tion al acceptor group boun d to th e ben zoth iazole m oiety. Th e effect of th e
NO2 group is m ore distin ct th an th at of th e CN group. Th e m ost effective
ch arge tran sfer is observed wh en acceptor group is in position 6- of ben zo-
th iazole (com poun ds 3k, 3o, 3s). Th is in tram olecular ch arge tran sfer (ICT)
HOMO
LUMO
FIG. 1
Plot of calculated ch arge den sities in fron tier orbitals of ben zoth iazole derivative 3k
Collect. Czech. Chem. Commun. 2007, Vol. 72, No. 8, pp. 1069–1093

Novel Benzothiazole Derivatives
1077
represen ts “th e m ost lin ear direction ” from don or to acceptor, wh ich is also
con firm ed by a h igh value of th e m olar absorption coefficien t. Th e localiza-
tion of orbital den sity in th e don or part of HOMO orbital an d in th e accep-
tor part of th e LUMO orbital is eviden ce of th e fact (Fig. 1).
TABLE V
Lon g-wave ban d position s in th e UV/VIS absorption spectra, m olar absorption coefficien ts ε
in ch loroform , calculated values of dipole m om en ts µ, first h yperpolarizabilities β an d
HOMO-LUMO en ergy differen ces ∆E of ben zoth iazoles
λm ax
n m
ε
µ
D
β × 10–30
esu
∆E
eV
Com poun d
l m ol–1 cm –1
3a
3b
3c
3d
3e
3f
341
395
406
424
428
434
440
450
446
416
454
446
514
428
458
516
466
534
471
536
61 000
45 000
24 000
46 300
26 400
32 400
26 300
31 900
23 100
25 000
50 200
16 100
14 000
34 300
54 200
33 700
49 400
15 200
59 800
23 100
0.178
2.360
44.477
49.684
86.892
76.327
104.914
80.785
113.922
39.953
63.008
95.290
52.914
139.010
82.836
135.137
205.076
100.942
143.085
143.553
206.609
7.747
7.017
6.669
6.676
6.711
6.369
6.719
6.537
6.579
6.727
6.494
6.669
6.042
6.379
6.150
5.735
6.503
6.088
6.318
5.887
2.214
0.755
3.106
6.524
5.096
6.579
6.711
6.018
8.190
8.777
6.187
10.394
7.030
7.420
9.108
8.834
10.355
8.988
10.277
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
3s
3t
Collect. Czech. Chem. Commun. 2007, Vol. 72, No. 8, pp. 1069–1093

1078
Sigmundová, Zahradník, Loos:
A m uch m ore extensive bathochrom ic shift of long-wave band over 500 nm
can be observed in th e derivatives with two NO2 groups in position s 4 an d
6 (com poun ds 3m , 3p , 3r). Th e bath och rom ic sh ift is accom pan ied by de-
creasin g ∆E an d in creasin g h yperpolarizability β. Two double bon ds in th e
con jugated spacer produce in all cases a bath och rom ic sh ift of ca. 20 n m in
com parison with th e correspon din g com poun ds with on e double bon d (3b,
3d ; 3k, 3s; 3m , 3t; 3e, 3h pairs). ∆E an d β are also ch an ged in favour of th e
m ore effective ch arge tran sfer. In addition to th e NMe2 don or group, oth er
am in o don ors h ave been also tested. Wh ile th e pyrrolidin e don or sh ows
on ly a sm all effect, th e NPh 2 don or im proves th e ICT sign ifican tly, result-
in g in th e decreased ∆E an d in creased h yperpolarizability β.
Benzothiazolium Iodides
Table VI presents analogous physico-chem ical characteristics for the N-m ethyl-
ben zoth iazolium iodides (experim en tal spectral data) an d N-m eth ylben zo-
th iazolium cation s (calculated properties).
Quatern ization of h eterocyclic n itrogen produces a h uge bath och rom ic
sh ift of th e lon g-wave ban d of N-m eth ylben zoth iazolium salts in com pari-
son with n eutral ben zoth iazoles (ca. 120 n m ). Th is absorption is caused by
th e π→π* tran sition accom pan ied by th e im portan t ICT from th e substi-
tuted am in o don or group to th e ben zoth iazolium rin g. Th is ch arge-tran sfer
effect is m uch larger th an in th e n eutral ben zoth iazoles. Th e values of ab-
sorption m axim a exceed 500 n m in all com poun ds except for th e un substi-
tuted derivative 5a an d th e salts with th e don or group in ortho or meta
position of th e ph en yl rin g (com poun ds 5f, 5e, 5i, 5h ). Th e push -pull ch ar-
acter of th ese com poun ds is lower.
Th e values of calculated th eoretical in dices µ, β an d ∆E also express an
im portan t push -pull ch arge tran sfer. Main ly th e h yperpolarizabilities β an d
th e HOMO-LUMO ∆E values of ben zoth iazolium cation s ch an ged m uch
com pared with th e correspon din g n eutral ben zoth iazoles. An addition al
acceptor group boun d to th e ben zoth iazolium rin g (NO2 or CN) en h an ces
th e acceptor capacity of ben zoth iazolium rin g resultin g in th e bath o-
ch rom ic sh ift of th e lon g-wave ban d, en h an ced dipole m om en t an d h yper-
polarizability.
Th e len gth of th e con jugated bridge is also an im portan t factor for th e
push -pull ch aracter an d ICT. Th e com poun ds with two double bon ds in
com bin ation with NO2 or CN group sh ow th e lon g-wave absorption ban d
red-sh ifted to 600 n m . Th e h yperpolarizability β is m ore in fluen ced by th e
n um ber of double bon ds th an by th e presen ce of an addition al electron -
Collect. Czech. Chem. Commun. 2007, Vol. 72, No. 8, pp. 1069–1093

Novel Benzothiazole Derivatives
1079
acceptor group. Th e com poun d 5x with th ree double bon ds exh ibits th e
h igh est calculated static h yperpolarizability β. Th e exch an ge of th e electron -
don or NMe2 for NPh 2 group causes a sign ifican t in crease in th e β value
–
(com poun d 5l). Th e exch an ge of an ion I– for HSO4 (com poun ds 5b an d
TABLE VI
Position an d in ten sities of lon g-wave ban d in th e UV/VIS absorption spectra in m eth an ol,
calculated values of dipole m om en ts µ, h yperpolarizabilities β an d HOMO-LUMO en ergy dif-
feren ces ∆E of ben zoth iazolium cation s
λm ax
n m
ε
µ
D
β × 10–30
esu
∆E
eV
Com poun d
l m ol–1 cm –1
5a
5b
5c
5d
5e
5f
374
520
522
548
384
464
562
392
476
558
554
508
542
552
548
542
534
572
562
610
628
622
616
580
6 900
67 800
71 500
58 800
24 300
8 700
4.346
60.377
98.478
6.477
5.408
5.408
5.397
4.809
5.624
5.360
4.735
5.546
5.364
5.369
5.201
5.224
5.193
5.185
5.184
5.416
5.384
4.978
5.026
5.010
4.984
4.972
4.593
2.402
2.402
10.748
3.834
5.095
12.396
6.583
7.927
9.121
7.309
11.030
1.876
5.483
9.028
5.169
3.809
10.826
4.125
10.324
11.974
8.337
6.089
7.326
98.478
190.811
128.609
109.464
183.25
5g
5h
5i
32 700
23 800
9 100
80.301
66.379
5j
51 700
64 000
20 200
29 600
23 600
39 800
39 000
72 100
27 300
54 400
68 000
15 700
60 000
55 300
46 300
95.580
5k
5l
183.73
345.090
263.793
147.389
170.488
212.866
177.958
172.417
370.09
5m
5n
5o
5p
5q
5r
5s
5t
340.309
317.301
140.527
321.534
744.769
5u
5v
5w
5x
Collect. Czech. Chem. Commun. 2007, Vol. 72, No. 8, pp. 1069–1093

1080
Sigmundová, Zahradník, Loos:
5c) h ad n o in fluen ce on th e m easured spectral ch aracteristics. Based on
th ese con clusion s, h yperpolarizability β h as been predicted for th e cation
with un substituted N-m eth ylben zoth iazolium acceptor, con jugated h exa-
trien yl bridge an d 4-(diph en ylam in o)ph en yl don or. Th e calculated static
h yperpolarizability of th is com poun d is 950 × 10–30 esu.
Solvatochromism
UV/VIS absorption m easurem en ts of selected structurel types of n eutral
ben zoth iazoles as well as ben zoth iazolium iodides h ave been carried out in
ch loroform (dielectric perm ittivity ε = 4.8) an d m eth an ol (ε = 33). Table VII
sum m arizes th e values of lon g-wave absorption ban ds λm ax in both solven ts
an d th eir differen ces. A h ypsoch rom ic sh ift in m ore polar m eth an ol can be
observed in all studied com poun ds. Th e differen ce ∆λm ax is m uch larger in
ben zoth iazolium salts com pared with n eutral ben zoth iazoles (3n –5d ,
3l–5j). Th is differen ce in creases with th e n um ber of double bon ds in th e
TABLE VII
Solvatoch rom ic data λm ax for th e lon g-wave ICT ban d of selected n eutral an d ion ic ch rom o-
ph ores in m eth an ol an d ch loroform an d th eir differen ce ∆λm ax
λ
m ax, n m
λm ax, n m
(CHCl3)
∆λm ax, n m
Com poun d
Salt
(m eth an ol)
5b
5s
5x
3n
5d
3k
3s
3o
5g
3l
+
+
+
–
+
–
–
–
+
–
+
–
–
+
+
520
562
580
422
548
446
460
444
562
440
558
427
429
554
542
550
612
636
428
574
456
471
458
596
446
586
428
434
582
592
30
50
56
4
26
8
11
14
34
2
5j
28
1
3e
3f
5
5k
5p
28
50
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Novel Benzothiazole Derivatives
1081
con jugated bridge (5b, 5s, 5x) an d wh en NMe2 is exch an ged for NPh 2 (5k,
5p ). An alogous n egative solvatoch rom ism was observed also in a study of
sim ilar com poun ds20.
Theory and Methods
Th e restricted Hartree–Fock th eory at th e sem iem pirical level h as been ch o-
sen for th e quan tum -ch em ical calculation s. Th e optim al geom etries of th e
com poun ds un der study were obtain ed by com plete geom etry optim ization
em ployin g th e AM1 m eth od. Th is geom etry was used as in put for th e sin gle
SCF calculation by th e PM3 m eth od. Th e fin al ch aracteristics (dipole m o-
m en t µ, h yperpolarizability β as well as HOMO-LUMO gap ∆E) were ob-
tain ed in th is way. A fin ite-field m eth od for th e calculation of static first
h yperpolarizability developed by Kurtz was used. Th is procedure as well as
th e sem iem pirical m eth ods used are im plem en ted in th e AMPAC m olecular
m odelin g package21
.
Conclusion
Two series of ben zoth iazole ch rom oph ores con tain in g a con jugated alken yl
bridge, ben zoth iazole or N-m eth ylben zoth iazolium electron -acceptor an d
electron -don atin g ph en yl rin g h ave been syn th esized an d ch aracterized.
Ben zoth iazolium salts sh ow a m ore effective push -pull ch aracter th an
correspon din g n eutral ben zoth iazoles. Th e better ICT results in a h igh red
sh ift of lon g-wave ICT ban ds an d larger h yperpolarizabilities β on replacin g
ben zoth iazole with an N-m eth ylben zoth iazolium m oiety. Exten sion of th e
con jugated bridge im proves th e studied NLO ch aracteristics. An addition al
acceptor group bon ded to th e h eterocycle causes a red sh ift of λm ax but does
n ot in crease th e h yperpolarizability. 4-Diph en ylam in oph en yl h as been
foun d th e m ost effective electron -don atin g group.
EXPERIMENTAL
Meltin g poin ts were determ in ed on a Kofler apparatus an d are un corrected. 1H NMR spectra
were recorded on a Varian Gem in i spectrom eter (VNMRJ 1.1 D) at 300 MHz in CDCl3 or
DMSO-d6 with tetram eth ylsilan e as in tern al stan dard. Ch em ical sh ifts are given in ppm
(δ-scale), couplin g con stan t (J) in Hz. 13C NMR spectra were recorded at 75 MHz in CDCl3 or
DMSO-d6; determ in ed in th e APT an d 2D experim en t gHSQC, gHMBC. Th e n um berin g of
carbon atom s used in assign in g NMR data is presen ted in Fig. 2.
Elem en tal an alyses were determ in ed on a Carlo-Erba in strum en t. Th e UV/VIS spectra
(in n m ) were m easured usin g a Hewlett–Packard Diode array spectroph otom eter 8452A in
Collect. Czech. Chem. Commun. 2007, Vol. 72, No. 8, pp. 1069–1093

1082
Sigmundová, Zahradník, Loos:
m eth an ol an d ch loroform . Microwave reaction s were con ducted usin g a m icrowave syn th e-
sizer In itiator Biotage with power ran ge 0–300 W an d pressure ran ge 0–2.0 MPa in glass
m icrowave vials sealed with septum .
FIG. 2
Num berin g of carbon atom s used in assign in g NMR data
2-Meth yl-4,6-din itroben zoth iazole (1g)
A m ixture of 2-m eth yl-6-n itroben zoth iazole (3.88 g, 0.02 m ol), KNO3 (8.08 g 0.08 m ol) an d
H2SO4 (30 m l, d = 1.836) was h eated at 100 °C for 6 h . After coolin g th e m ixture was poured
in to 100 m l of ice water, th en extracted with ch loroform (2 × 50 m l), wash ed with 10% so-
lution of NaHCO3 (2 × 50 m l) an d with water (2 × 50 m l). Th e organ ic layer was dried with
an h ydrous sodium sulfate. After rem ovin g solven t, th e residue con tain in g m ain ly 4,6- an d a
m in or am oun t of 5,6-din itro isom er was crystallized twice from eth an ol. Th e yield of iso-
lated 2-m eth yl-4,6-din itroben zoth iazole (1g) was 2.49 g (52%). M.p. 186.0–187.5 °C; ref.12
gives m .p. 150 °C. 1H NMR (300 MHz, CDCl3): 9.04 d, 1 H, J(7,5) = 2.4 (H-7); 9.02 d, 1 H,
J(5,7) = 2.4 (H-5); 3.06 s, 3 H (CH3). 2-Meth yl-4,5-din itroben zoth iazole isom er was n ot iso-
lated. 1H NMR (300 MHz, CDCl3): 8.46 s, 1 H (H-7); 8.42 s, 1 H (H-4); 2.97 s, 3 H (CH3).
Reaction of 2-Meth ylben zoth iazole (1a) or 2-Meth ylben zoth iazole-6-carbon itrile (1b)
with Arom atic Aldeh ydes. Gen eral Procedure
2-Meth ylben zoth iazole (1a; 1.49 g, 10 m m ol) or 2-m eth ylben zoth iazole-6-carbon itrile (1b;
1.94 g, 10 m m ol) an d correspon din g aldeh ydes 2a–2d (10 m m ol) were added to a solution
of NaOH (1.2 g, 30 m m ol) in m eth an ol (25 m l). Th e reaction m ixture was refluxed for
6–12 h an d th e resultin g precipitate was collected an d purified by colum n ch rom atograph y
(silica gel, h exan es–eth yl acetate 4:1) or was recrystallized from m eth an ol. Yields of isolated
products 3a–3h are sum m arized in Table I.
2-((E)-Styryl)benzothiazole (3a). M.p. 110.5–112 °C (m eth an ol); ref.18 gives m .p. 111–112 °C.
2-{(E)-2-[4-(Dimethylamino)phenyl]vinyl}benzothiazole (3b ). M.p. 204–206 °C (m eth an ol);
ref.22 gives m .p. 201–202 °C (eth an ol).
2-{(E)-2-[4-(Diphenylamino)phenyl]vinyl}benzothiazole (3c). M.p. 154–156 °C. For C27H20N2S
(404.5) calculated: 80.17% C, 4.98% H, 6.92% N, 7.93% S; foun d: 80.05% C, 4.96% H,
7.98% N, 7.92% S. 1H NMR (300 MHz, CDCl3): 7.96 dd, 1 H, J(7,6) = 8.0, J(7,5) = 0.6 (H-7);
7.84 dd, 1 H, J(4,5) = 8.1, J(4,6) = 0.6 (H-4); 7.43 d, 2 H, J = 8.7 (H-2′, H-6′); 7.29 d, 1 H,
J(trans) = 15.3 (H-b); 7.48–7.42 m , 1 H (H-5); 7.37–7.31 m , 1 H (H-6); 7.32–7.24 m , 4 H
(H-Ar); 7.15–7.03 m , 6 H (H-Ar); 7.14 d, 2 H, J = 8.6 (H-3′, H-5′); 7.06 d, 1 H, J(trans) = 15.3
(H-a). 13C NMR (75 MHz, CDCl3): 167.51 (C-2); 153.91 (C-3a); 149.08 (C-4′); 147.04 (2 × C);
137.31 (C-7a); 134 20 (CH-b); 129.35 (4 × CH); 128.65 (2 × CH); 128.41 (C-2′, C-6′); 126.23
(C-5); 125.07 (4 × CH); 124.95 (C-6); 123.76 (C-7); 122.67 (C-1′); 122.23 (C-3′, C-5′); 121.42
Collect. Czech. Chem. Commun. 2007, Vol. 72, No. 8, pp. 1069–1093

Novel Benzothiazole Derivatives
1083
(C-4); 119.77 (C-a). UV/VIS (m eth an ol), λm ax (ε): 208 (52 000), 262 (12 400), 300 (21 700),
408 (36 400). UV/VIS (CHCl3), λm ax (ε): 302 (25 000), 406 (24 000).
2-{(E,E)-4-[4-(Dimethylamino)phenyl]buta-1,3-dien-1-yl}benzothiazole (3d). M.p. 191.5–193 °C;
ref.23 gives m .p. 173–175 °C. 1H NMR (300 MHz, CDCl3): 7.96–7.93 m , 1 H (H-7); 7.83–7.80 m ,
1 H (H-4); 7.46–7.27 m , 3 H (H-b, H-5, H-6); 7.39 d, 2 H, J = 9.1 (H-2′, H-6′); 7.37 d, 1 H, J =
14.4 (H-d); 6.85 d, 1 H, J = 14.4 (H-a); 6.81–6.80 m , 1 H (H-c); 6.69 d, 2 H, J = 9.0 (H-3′,
H-5′); 3.01 s, 6 H (2 × CH3). 13C NMR (75 MHz, CDCl3): 167.58 (C-2); 154.07 (C-3a); 150.75
(C-4′); 139.52 (CH-c); 134.28 (C-7a); 128.39 (2 × CH-2′, 6′); 126.14 (CH-5); 124.87 (CH-6);
124.68 (CH-b); 123.06 (CH-a); 122.73 (CH-d); 122.58 (C-7); 121.35 (CH-4); 112.18 (2 ×
CH-3′, 5′); 40.28 (N(CH3)2). UV/VIS (m eth an ol), λm ax (ε): 206 (30 600), 246 (13 500), 316
(12 500), 422 (48 600). UV/VIS (CHCl3), λm ax (ε): 316 (10 700), 424 (46 300).
2-{(E)-2-[4-(Dimethylamino)phenyl]vinyl}benzothiazole-6-carbonitrile (3e). M.p., 1H an d
13C NMR, an d UV/VIS (CHCl3) data are con sisten t with ref.24. UV/VIS (m eth an ol), λm ax (ε):
427 (17 000).
2-{(E)-2-[4-(Diphenylamino)phenyl]vinyl}benzothiazole-6-carbonitrile (3f). M.p. 202–204 °C.
For C28H19N3S (429.5) calculated: 78.29% C, 4.46% H, 9.78% N, 7.46% S; foun d: 77.93% C,
4.46% H, 9.54% N, 7.23% S. 1H NMR (300 MHz, CDCl3): 8.16 d, 1 H, J(7,5) = 1.6 (H-7);
8.00 d, 1 H, J(4,5) = 8.6 (H-4); 7.69 dd, 1 H, J(5,4) = 8.6, J(5,7) = 1.6 (H-5); 7.55 d, 1 H,
J(trans) = 16.2 (H-b); 7.44 d, 2 H, J = 8,6 (H-2′, H-6′); 7.34–7.28 m , 4 H (H-Ar); 7.25 d, 1 H,
J(trans) = 16.2 (H-a); 7.16–7.08 m , 6 H (H-Ar); 7.04 d, 2 H, J = 8.6 (H-3′, H-6′). 13C NMR
(75 MHz, CDCl3): 171.82 (C-2); 156.66 (C-3a); 150.00 (C-4′); 147.02 (2 × C); 139.91 (CH-b);
134.97 (C-7a); 129.76 (CH); 129.74 (CH); 129.08 (CH); 127.97 (C-1′); 126.25 (CH); 125.68
(CH); 124.35 (CH); 123.35 (CH); 121.93 (CH); 119.10 (CN); 118.75 (CH-a); 108.28 (CH-6).
UV/VIS (CHCl3), λm ax (ε): 434 (32 400). UV/VIS (m eth an ol), λm ax (ε): 429 (38 300).
2-[(E)-2-(4-Pyrrolidin-1-ylphenyl)vinyl]benzothiazole-6-carbonitrile (3g). M.p. 235.5–238 °C.
For C20H17N3S (331.4) calculated: 72.48% C, 5.17% H, 12.68% N; foun d: 71.92% C, 5.13% H,
12.36% N. 1H NMR (300 MHz, CDCl3): 8.12 d, 1 H, J(7,5) = 1.6 (H-7); 7.95 d, 1 H, J(4,5) =
8.2 (H-4); 7.67 dd, 1 H, J(5,4) = 8.2, J(5,7) = 1.6 (H-5); 7.54 d, 1 H, J(trans) = 15.9 (H-b);
7.48 d, 2 H, J = 8.8 (H-2′, H-6′); 7.16 d, 1 H, J(trans) = 15.9 (H-a); 6.57 d, 2 H, J = 8.8 (H-3′,
H-5′); 3.37 t, 4 H, J = 6.6 (N(CH2)2); 2.05 m , 4 H (CH2). 13C NMR (75 MHz, CDCl3): 172.79
(C-2); 156.67 (C-3a); 149.23 (C-4′); 141.11 (CH-b); 134.62 (C-7a); 129.65 (C-2′, C-6′); 129.46
(CH-7); 125.85 (CH-5); 122.66 (CH-4); 122.00 (C-1′); 119.08 (CN); 115.31 (CH-a); 111.87
(C-3′, C-5′); 107.47 (C-6); 47.59 (2 × CH2); 25.47 (2 × CH2). UV/VIS (CHCl3), λm ax (ε): 440
(26 300).
2-{(E,E)-4-[4-(Dimethylamino)phenyl]buta-1,3-dien-1-yl}benzothiazole-6-carbonitrile (3h ). M.p.
233–235 °C. For C20H17N3S (331.4) calculated: 72.48% C, 5.17% H, 12.68% N; foun d:
72.13% C, 5.12% H, 12.46% N. 1H NMR (300 MHz, CDCl3): 8.12 d, 1 H, J(7,5) = 1.5 (H-7);
7.96 d, 1 H, J(4,5) = 8.4 (H-4); 7.67 dd, 1 H, J(5,4) = 8.4, J(5,7) = 1.5 (H-5); 7.41 dd, 1 H,
J(trans) = 15.4, J = 9.5 (H-b); 7.40 d, 2 H, J = 8.8 (H-2′, H-6′); 6.92–6.77 m , 3 H (H-d, H-a,
H-c); 6.69 d, 2 H, J = 8.8 (H-3′, H-5′); 3.02 s, 6 H (2 × CH3). 13C NMR (75 MHz, CDCl3):
171.82 (C-2); 156.78 (C-3a); 151.21 (C-4′); 141.90 (CH-b); 140.73 (CH-c); 134.98 (C-7a);
129.67 (2 × CH-2′, 6′); 128.95 (CH-7); 126.11 (CH-5); 124.38 (C-1′); 123.13 (CH-a); 122.62
(CH-d); 121.63 (C-4); 119.16 (CN); 112.18 (2 × CH-3′, 5′); 107.96 (C-6); 40.40 (N(CH3)2).
UV/VIS (CHCl3), λm ax (ε): 450 (31 900).
Collect. Czech. Chem. Commun. 2007, Vol. 72, No. 8, pp. 1069–1093

1084
Sigmundová, Zahradník, Loos:
Reaction of Nitro Derivatives of 2-Meth ylben zoth iazole with Arom atic Aldeh ydes.
Gen eral Procedure
A n itro derivative of 2-m eth ylben zoth iazoles 1c–1f (0.39 g, 2 m m ol) or 2-m eth yl-4,6-din itro-
ben zoth iazole (1g; 0.48 g, 2 m m ol), correspon din g aldeh ydes 2a–2d (2 m m ol) an d sulfuric
acid (0.22 g, 2.2 m m ol) was refluxed in dry dioxan e (10 m l) for 8 h . Un reacted startin g
ben zoth iazole was dissolved in dioxan e. Th e precipitated m aterial in proton ized form was
filtered off, diluted with ch loroform (30 m l) an d organ ic solution was wash ed with 10%
aqueous sodium carbon ate (3 × 20 m l) an d water (3 × 30 m l). Th e organ ic layer was dried
with an h ydrous sodium sulfate an d solven t was rem oved. Th e un reacted aldeh yde was re-
m oved from th e m ixture by distillation un der vacuum in th e Kugelroh r apparatus. Th e
crude products 3i–3t were recrystallized from m eth an ol. Th e results are given in Table II.
2-{(E)-2-[4-(Dimethylamino)phenyl]vinyl}-4-nitrobenzothiazole (3i). M.p. 184 °C. For
C
17H15N3O2S (325.4) calculated: 62.75% C, 4.65% H, 12.91% N, 9.85% S; foun d: 62.51% C,
4.61% H, 12.62% N, 9.84% S. 1H NMR (300 MHz, CDCl3): 8.15 dd, 1 H, J(5,6) = 8.1, J(5,7) =
1.2 (H-5); 8.06 dd, 1 H, J(7,6) = 8.1, J(7,5) = 1.2 (H-7); 7.54 d, 1 H, J(trans) = 15.6 (H-b);
7.50 d, 2 H, J = 9.0 (H-2′, H-6′); 7.50 t, 1 H, J = 8.1 (H-6); 7.33 d, 1 H, J(trans) = 15.6 (H-a);
6.71 d, 2 H, J = 8.7 (H-3′, H-5′); 3.05 s, 6 H (2 × CH3). 13C NMR (75 MHz, CDCl3): 172.87
(C-2); 151.86 (C-4′); 146.94 (C-3a); 141.95 (C-4); 141.59 (CH-b); 137.74 (C-7a); 129.75 (C-2′,
C-6′); 126.91 (CH-6); 123.85 (CH-7); 122.91 (C-1′); 122.87 (CH-5); 116.93 (CH-a); 112.21
(C-3′, C-5′); 40.37 (N(CH3)2). UV/VIS (CHCl3), λm ax (ε): 446 (23 100). UV/VIS (m eth an ol),
λm ax (ε): 440 (15 700).
2-{(E)-2-[4-(Dimethylamino)phenyl]vinyl}-5-nitrobenzothiazole (3j). M.p. 225–228 °C. For
C
17H15N3O2S (325.4) calculated: 62.75% C, 4.65% H, 12.91% N, 9.85% S; foun d: 62.80% C,
4.55% H, 12.82% N, 9.63% S. 1H NMR (300 MHz, CDCl3): 8.74 d, 1 H, J(4,6) = 1.8 (H-4);
8.19 dd, 1 H, J(6,7) = 9.0, J(6,4) = 1.8 (H-6); 7.92 d, 1 H, J(7,6) = 8.7 (H-7); 7.52 d, 1 H,
J(trans) = 16.2 (H-b); 7.49 d, 2 H, J = 8.7 (H-2′, H-6′); 7.19 d, 1 H, J(trans) = 16.2 (H-a);
6.72 d, 2 H, J = 8.7 (H-3′, H-5′); 3.05 s, 6 H (2 × CH3). 13C NMR (75 MHz, CDCl3): 171.57
(C-2); 154.04 (C-3a); 151.62 (C-4′); 146.86 (C-5); 140.98 (C-7a); 140.57 (C-b); 129.40 (C-2′,
C-6′); 122.61 (C-1′); 121.56 (C-6); 119.11 (C-7); 117.44 (C-4); 116.02 (C-a); 112.00 (C-3′,
C-5′); 40.17 (N(CH3)2). UV/VIS (CHCl3), λm ax (ε): 270 (13 300), 416 (16 600). UV/VIS
(m eth an ol), λm ax (ε): 204 (22 500), 232 (20 100), 314 (13 800), 416 (27 900).
2-{(E)-2-[4-(Dimethylamino)phenyl]vinyl}-6-nitrobenzothiazole (3k ). M.p. 252–253 °C. For
C
17H15N3O2S (325.4) calculated: 62.75% C, 4.65% H, 12.91% N, 9.85% S; foun d: 62.48% C,
4.65% H, 12.67% N, 9.73% S. 1H NMR (300 MHz, CDCl3): 8.74 d, 1 H, J(7,5) = 2.4 (H-7);
8.31 dd, 1 H, J(5,4) = 9.0, J(5,7) = 2.4 (H-5); 7.96 d, 1 H, J(4,5) = 9.0 (H-4); 7.56 d, 1 H,
J(trans) = 16.2 (H-b); 7.50 d, 2 H, J = 9.0 (H-2′, H-6′); 7.19 d, 1 H, J(trans) = 16.2 (H-a);
6.72 d, 2 H, J = 9.0 (H-3′, H-5′); 3.06 s, 6 H (2 × CH3). 13C NMR (75 MHz, CDCl3): 173.87
(C-2); 158.11 (C-3a); 151.75 (C-4′); 144.36 (C-6); 141.23 (CH-b); 134.47 (C-7a); 129.58
(CH-2′, 6′); 122.56 (C-1′); 122.08 (CH-4); 121.89 (CH-5); 117.84 (CH-7); 116.02 (CH-a);
111.99 (CH-3′, 5′); 40.15 (N(CH3)2). UV/VIS (CHCl3), λm ax (ε): 264 (5 000), 320 (7 700), 456
(31 200). UV/VIS (m eth an ol), λm ax (ε): 206 (9 800), 262 (5 000), 308 (5 000), 446 (9 700).
2-{(E)-2-[4-(Dimethylamino)phenyl]vinyl}-7-nitrobenzothiazole (3l). M.p. 173–175 °C. For
C
17H15N3O2S (325.4) calculated: 62.75% C, 4.65% H, 12.91% N, 9.85% S; foun d: 62.55% C,
4.57% H, 12.60% N, 9.65% S. 1H NMR (300 MHz, CDCl3): 8.14 dd, 1 H, J(6,5) = 8.1, J(6,4) =
0.9 (H-6); 8.06 dd, 1 H, J(4,5) = 8.1, J(4,6) = 0.9 (H-4); 7.54 d, 1 H, J(trans) = 15.3 (H-b);
7.50 d, 2 H, J = 8.7 (H-2′, H-6′); 7.40 t, 1 H, J = 8.1 (H-5); 7.33 d, 1 H, J(trans) = 15.3 (H-a);
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6.71 d, 2 H, J = 8.7 (H-3′, H-5′); 3.05 s, 6 H (2 × CH3). 13C NMR (75 MHz, CDCl3): 172.62
(C-2); 151.63 (C-3a); 146.70 (C-4′); 141.72 (C-7); 141.34 (CH-b); 137.51 (C-7a); 129.51
(CH-2′, 6′); 126.67 (CH-4); 123.61 (CH-5); 122.67 (C-1′); 122.62 (CH-6); 116.69 (CH-a);
111.97 (CH-3′, 5′); 40.13 (N(CH3)2). UV/VIS (CHCl3), λm ax (ε): 256 (15 4000), 320 (10 800),
446 (16 100). UV/VIS (m eth an ol), λm ax (ε): 204 (20 100), 258 (9 000), 318 (7 000), 440
(13 400).
2-{(E)-2-[4-(Dimethylamino)phenyl]vinyl}-4,6-dinitrobenzothiazole (3m ). M.p. 252.5–254.5 °C.
For C17H14N4O4S (370.4) calculated: 55.13% C, 3.81% H, 15.13% N, 8.66% S; foun d:
54.90% C, 3.94% H, 15.44% N, 8.52% S. 1H NMR (300 MHz, CDCl3): 8.99 d, 1 H, J(5,7) =
2.4 (H-5); 8.93 d, 1 H, J(7,5) = 2.4 (H-7); 7.68 d, 1 H, J(trans) = 15.9 (H-b); 7.51 d, 2 H, J =
9.0 (H-2′, H-6′); 7.30 d, 1 H, J(trans) = 15.9 (H-a); 6.70 d, 2 H, J = 9.0 (H-3′, H-5′); 3.08 s, 6 H
(2 × CH3). 13C NMR (75 MHz, CDCl3): 178.01 (C-2); 152.47 (C-3a); 150.32 (C-4′); 144.60
(CH-b); 142.62 (C-6); 138.90 (C-7a); 138.41 (C-4); 130.59 (C-2′, C-6′); 122.23 (C-1′); 121.59
(CH-7); 118.80 (CH-5); 115.67 (CH-a); 112.13 (C-3′, C-5′); 40.31 (N(CH3)2). UV/VIS (CHCl3),
λm ax (ε): 272 (16 600), 330 (14 400), 514 (14 400).
2-{(E)-2-[4-(Diphenylamino)phenyl]vinyl}-5-nitrobenzothiazole (3n ). M.p.162–164.5 °C. For
C
27H19N3O2S (449.5) calculated: 72.14% C, 4.26% H, 9.35% N, 7.13% S; foun d: 72.20% C,
4.25% H, 9.45% N, 7.04% S. 1H NMR (300 MHz, CDCl3): 8.78 d, 1 H, J(4,6) = 2.1 (H-4);
8.23 dd, 1 H, J(6,7) = 9.0, J(6,4) = 2.1 (H-6); 7.95 d, 1 H, J(7,6) = 9.0 (H-7); 7.53 d, 1 H,
J(trans) = 15.9 (H-b); 7.45 d, 2 H, J = 8.4 (H-2′, H-6′); 7.34–7.23 m , 4 H (H-Ar); 7.19–7.09 m ,
6 H (H-Ar); 7.16 d, 1 H, J(trans) = 15.9 (H-a); 7.05 d, 2 H, J = 8.7 (H-3′, H-5′). 13C NMR
(75 MHz, CDCl3): 169.85 (C-2); 152.84 (C-3a); 148.70 (C-4′); 145.86 (2 × CH); 145.78 (C-5);
139.95 (C-7a); 138.48 (C-b); 128.48 (4 × CH); 127.79 (C-2′, C-6′); 126.70 (C-1′); 125.27 (2 ×
CH); 124.40 (4 × CH); 123.07 (C-7); 120.69 (C-3′, C-5′); 118.38 (C-6); 117.48 (C-4); 116.73
(C-a). UV/VIS (CHCl3), λm ax (ε): 242 (18 600), 300 (30 600), 428 (34 300). UV/VIS (m eth a-
n ol), λm ax (ε): 208 (29 400), 296 (16 000), 422 (17 400).
2-{(E)-2-[4-(Diphenylamino)phenyl]vinyl}-6-nitro-benzothiazole (3o). M.p. 183–185 °C; ref.25
gives m .p. 184–186 °C (eth an ol).
2-{(E)-2-[4-(Diphenylamino)phenyl]vinyl}-4,6-dinitrobenzothiazole (3p ). M.p. 227–229 °C. For
C
27H18N4O4S (494.5) calculated: 65.58% C, 3.67% H, 11.33% N, 6.48% S; foun d: 65.28% C,
3.55% H, 11.21% N, 6.33% S. 1H NMR (300 MHz, CDCl3): 9.02 d, 1 H, J(5,7) = 2.1 (H-5);
8.97 d, 1 H, J(7,5) = 2.1 (H-7); 7.71 d, 1 H, J(trans) = 15.9 (H-b); 7.48 d, 2 H, J = 8.7 (H-2′,
H-6′); 7.44 d, 1 H, J(trans) = 15.9 (H-a); 7.36–7.31 m , 4 H (H-Ar); 7.18–7.12 m , 6 H (H-Ar);
7.04 d, 2 H, J = 8.7 (H-3′, H-5′). 13C NMR (75 MHz, CDCl3): 177.36 (C-2); 150.90 (C-3a);
150.32 (C-4′); 146.64 (2 × C); 143.42 (CH-b); 143.01 (C-6); 140.77 (C-4); 138.43 (C-7a);
129.84 (4 × CH); 126.98 (C-1′); 126.51 (2 × CH); 126.05 (4 × CH); 124.84 (C-2′, C-6′); 121.85
(CH-7); 121.13 (C-3′, C-5′); 118.80 (CH-5); 118.04 (CH-a). UV/VIS (CHCl3), λm ax (ε): 276
(18 800), 302 (20 000), 348 (19 400), 516 (33 700).
2-[(E)-6-Nitro-2-(4-pyrrolidin-1-ylphenyl)vinyl]benzothiazole (3q ). M.p. 268–271 °C. For
C
19H17N3O2S (351.4) calculated: 64.94% C, 4.88% H, 11.96% N, 9.12% S; foun d: 64.59% C,
4.86% H, 11.72% N, 9.14% S. 1H NMR (300 MHz, CDCl3): 8.73 d, 1 H, J(7,5) = 2.2 (H-7);
8.30 dd, 1 H, J(5,4) = 9.4, J(5,7) = 2.2 (H-5); 7.95 d, 1 H, J(4,5) = 9.4 (H-4); 7.57 d, 1 H,
J(trans) = 15.9 (H-b); 7.49 d, 2 H, J = 8.8 (H-2′, H-6′); 7.17 d, 1 H, J(trans) = 15.9 (H-a);
6.57 d, 2 H, J = 8.8 (H-3′, H-5′); 3.37 t, 4 H, J = 6.6 (N(CH2)2); 2,05 m , 4 H (2 × CH2).
13C NMR (75 MHz, CDCl3): 174.05 (C-2); 158.18 (C-3a); 149.32 (C-4′); 144.25 (C-6); 141.58
(CH-b); 134.44 (C-7a); 129.78 (CH-2′, 6′); 121.96 (C-1′); 121.94 (CH-4); 121.87 (CH-5);
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Sigmundová, Zahradník, Loos:
117.81 (CH-7); 115.32 (CH-a); 111.89 (CH-3′, 5′); 47.59 (N(CH2)2); 25.47 (2 × CH2). UV/VIS
(CHCl3), λm ax (ε): 466 (49 400).
2-[(E)-4,6-Dinitro-2-(4-pyrrolidin-1-ylphenyl)vinyl]benzothiazole (3r). M.p. 217–220 °C. For
C
19H16N4O4S (396.4) calculated: 57.57% C, 4.07% H, 14.13% N, 8.09% S; foun d: 57.90% C,
3.98% H, 14.14% N, 8.22% S. 1H NMR (300 MHz, CDCl3): 8.98 d, 1 H, J(5,7) = 2.1 (H-5);
8.89 d, 1 H, J(7,5) = 2.1 (H-7); 7.67 d, 1 H, J(trans) = 15.9 (H-b); 7.50 d, 2 H, J = 9.0 (H-2′,
H-6′); 7.28 d, 1 H, J(trans) = 15.9 (H-a); 6.56 d, 2 H, J = 9.0 (H-3′, H-5′); 3.41–3.36 m , 4 H
(2 × CH2); 2.08–2.04 m , 4 H (2 × CH2). 13C NMR (75 MHz, CDCl3): 178.99 (C-2); 151.73
(C-3a); 150.02 (C-4′); 145.46 (CH-b); 141.52 (C-6); 138.49 (C-7a); 138.50 (C-4); 130.80 (C-2′,
C-6′); 121.06 (C-1′); 122.63 (CH-7); 118.50 (CH-5); 115.23 (CH-a); 112.13 (C-3′, C-5′); 47.85
(N(CH2)2); 25.30 (2 × CH2). UV/VIS (CHCl3), λm ax (ε): 268 (9 400), 330 (6 700), 534 (15 200).
2-{(E,E)-4-[4-(Dimethylamino)phenyl]buta-1,3-dien-1-yl}-6-nitrobenzothiazole (3s). M.p.
228–230 °C. For C19H17N3O2S (351.4) calculated: 64.94% C, 4.88% H, 11.96% N, 9.12% S;
foun d: 65.12% C, 4.72% H, 12.00% N, 9.01% S. 1H NMR (300 MHz, CDCl3): 8.74 d, 1 H,
J(7,5) = 2.4 (H-7); 8.31 dd, 1 H, J(5,4) = 9.0, J(5,7) = 2.4 (H-5); 7.97 d, 1 H, J(4,5) = 9.0 (H-4);
7.46 dd, 1 H, J(trans) = 15.3, J = 9.9 (H-b); 7.43 d, 1 H, J = 12.6 (H-d); 7.41 d, 2 H, J = 8.7
(H-2′, H-6′); 6.84 d, 1 H, J = 15.3 (H-a); 6.81 dd, 1 H, J(trans) = 15.3, J = 9.9 (H-c); 6.69 d,
2 H, J = 8.7 (H-3′, H-5′); 3.03 s, 6 H (2 × CH3). 13C NMR (75 MHz, CDCl3): 172.17 (C-2);
158.07 (C-3a); 151.06 (C-4′); 144.43 (C-6); 142.19 (CH-b); 140.95 (CH-d); 134.61 (C-7a);
128.84 (2 × CH-2′, 6′); 124.12 (C-1′); 122.33, 122.27, 121.91, 121.47 (CH-4, CH-5, CH-a,
CH-b); 117.86 (CH-7); 112.06 (2 × CH-3′, 5′); 40.02 (N(CH3)2). UV/VIS (m eth an ol), λm ax (ε):
206 (7 000), 262 (4 400), 310 (3 700), 460 (3 700). UV/VIS (CHCl3), λm ax (ε): 471 (59 800).
2-{(E)-2-[4-(Dimethylamino)phenyl]buta-1,3-dien-1-yl}-4,6-dinitrobenzothiazole (3t). M.p. 210–
211.5 °C. For C19H16N4O4S (369.4) calculated: 57.57% C, 4.07% H, 14.13% N, 8.09% S;
foun d: 57.63% C, 4.06% H, 14.26% N, 8.19% S. 1H NMR (300 MHz, CDCl3): 9.00 d, 1 H,
J(5,7) = 2.1 (H-5); 8.93 d, 1 H, J(7,5) = 2.1 (H-7); 7.61 dd, 1 H, J(trans) = 14.7, J = 11.1 (H-b);
6.95 d, 2 H, J = 9.0 (H-2′, H-6′); 7.02 d, 1 H, J(trans) = 15.0 (H-d); 6.95 d, 1 H, J(trans) = 15.0
(H-a); 6.84 dd, 1 H, J(trans) = 15.0, J = 11.1 (H-c); 6.70 d, 2 H, J = 9.0 (H-3′, H-5′); 3.05 s, 6 H
(2 × CH3). 13C NMR (75 MHz, CDCl3): 174.51 (C-2); 157.06 (C-3a); 151.41 (C-4′); 145.28
(CH-b); 143.45 (CH-d); 142.15 (C-6); 138.71 (C-4); 130.50 (C-7a); 129.42 (C-2′, C-6′); 123.71
(C-1′); 121.96 (CH-c); 121.47 (CH-7); 118.80 (CH-5); 118.61 (C-3′, C-5′); 105.60 (CH-a);
40.17 (N(CH3)2). UV/VIS (CHCl3), λm ax (ε): 262 (33 800), 304 (17 800), 360 (13 600), 536
(23 100).
Syn th esis of Derivatives of 2,3-Dim eth ylben zoth iazolium Iodide 4b–4e.
Gen eral Procedure
A m ixture of 2-m eth ylben zoth iazole-6-carbon itrile (1b; 0.87 g, 5 m m ol) or a n itro derivative
of 2-m eth ylben zoth iazoles 1d –1f (0.97 g, 5 m m ol) an d iodom eth an e (2.13 g, 15 m m ol) in
m eth an ol (4 m l) was irradiated in m icrowave apparatus for 40 m in . Th e resultin g precipitate
was collected an d wash ed with cold m eth an ol. Yields an d oth er con dition s are in Table III.
6-Cyano-2,3-dimethylbenzothiazolium iodide (4b). M.p. 250–251 °C. For C10H9IN2S (316.2)
calculated: 37.99% C, 2.87% H, 8.86% N, 10.14% S; foun d: 37.69% C, 2.84% H, 8.74% N,
10.14% S. 1H NMR (300 MHz, DMSO-d6): 8.95 d, 1 H, J(7,5) = 1.2 (H-7); 8.50 d, 1 H, J(4,5) =
8.7 (H-4); 8.36 dd, 1 H, J(5,4) = 8.7, J(5,7) = 1.2 (H-5); 4.22 s, 3 H (N-CH3); 3.21 s, 3 H (CH3).
13C NMR (75 MHz, DMSO-d6): 181.63 (C-2); 144.02 (C-3a); 132.25 (CH-7); 129.69 (CH-5);
129.48 (C-7a); 118.15 (CH-4); 117.66 (CN); 110.37 (CH-6); 36.29 (N-CH3); 17.75 (CH3).
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2,3-Dimethyl-5-nitrobenzothiazolium iodide (4c). M.p. 255–257 °C. For C9H9IN2O2S (336.2)
calculated: 32.16% C, 2.70% H, 8.33% N, 9.54% S; foun d: 32.09% C, 2.69% H, 8.34% N,
9.44% S. 1H NMR (300 MHz, DMSO-d6): 9.19 d, 1 H, J(4,6) = 2.4 (H-4); 8.70 d, 1 H, J(7,6) =
9.0 (H-7); 7.71 dd, 1 H, J(6,7) = 9.0, J(6,4) = 2.4 (H-6); 4.31 s, 3 H (N-CH3); 3.23 s, 3 H (CH3).
13C NMR (75 MHz, DMSO-d6): 181.90 (C-2); 147.87 (C-3a); 141.76 (C-5); 135.00 (C-7a);
126.22 (CH-7); 122.30 (CH-6); 112.86 (CH-4); 36.88 (N-CH3); 17.79 (CH3).
2,3-Dimethyl-6-nitrobenzothiazolium iodide (4d ). M.p. 260–261 °C; ref.26 gives m .p. 240 °C
(n itrom eth an e). 1H NMR (300 MHz, DMSO-d6): 9.43 d, 1 H, J(7,5) = 2.1 (H-7); 8.68 dd, 1 H,
J(5,4) = 9.0, J(5,7) = 2.4 (H-5); 8.51 d, 1 H, J(4,5) = 9.0 (H-4); 4.25 s, 3 H (N-CH3); 3.24 s, 3 H
(CH3).
2,3-Dimethyl-7-nitrobenzothiazolium iodide (4e). M.p. 179–180 °C. For C9H9IN2O2S (336.2)
calculated: 32.16% C, 2.70% H, 8.33% N, 9.54% S; foun d: 32.07% C, 2.71% H, 8,33% N,
9.53% S. 1H NMR (300 MHz, DMSO-d6): 8.79 dd, 1 H, J(4,5) = 8.4, J(4,6) = 0.6 (H-4);
8.68 dd, 1 H, J(6,5) = 8.4, J(6,4) = 0.6 (H-6); 8.19 t, 1 H, J = 8.4 (H-5); 4.30 s, 3 H (N-CH3);
3.27 s, 3 H (CH3). 13C NMR (75 MHz, DMSO-d6): 181.03 (C-2); 143.10 (C-7); 142.17 (C-3a);
130.37 (CH-4); 124.57 (CH-5); 123.97 (C-7a); 123.88 (CH-6); 37.13 (N-CH3); 17.22 (CH3).
Syn th esis of 3-Meth yl-2-((E)-styryl)ben zoth iazol-3-ium Iodide (5a)
2-Styrylben zoth iazole (3a; 1.19 g, 5 m m ol) an d iodom eth an e (2.84 g, 1.85 m l, 20 m m ol) was
refluxed in n itrom eth an e for 12 h . Th e resultin g precipitate was collected, wash ed with
n itrom eth an e an d recrystalized from eth an ol. Yield 1.35 g (75%). M.p. 230–233 °C; ref.27
gives m .p. 223 °C. 1H NMR (300 MHz, DMSO-d6): 8.46 d, 1 H, J(7,6) = 7.5 (H-7); 8.28 d, 1 H,
J(4,5) = 7.5 (H-4); 8.24 d, 1 H, J(trans) = 15.0 (H-b); 8.09–8.06 m , 2 H (H-Ar); 8.07 d, 1 H,
J(trans) = 15.0 (H-a); 7.93–7.87 m , 1 H (H-5); 7.84–7.79 m , 1 H (H-6); 7.60–7.54 m , 3 H
(H-Ar); 4.38 s, 3 H (N-CH3). 13C NMR data are con sisten t with ref.28
.
Reaction of 2,3-Dim eth ylben zoth iazolium Iodide Derivatives
with Arom atic Ben zaldeh ydes. Gen eral Procedure
A m ixture of 2,3-dim eth ylben zoth iazolium iodide (4a; 0.58 g 2 m m ol) or 6-cyan o-2-m eth yl-
ben zoth iazolium iodide (4b; 0.63 g, 2 m m ol) or a n itro derivative of 2,3-dim eth ylben zo-
th iazolium iodides 4c–4e (0.67 g, 2 m m ol), th e correspon din g aldeh yde (2 m m ol) an d basic
catalyst (pyridin e or piperidin e 0.3 m m ol) or, altern atively, with out an y catalyst in m eth a-
n ol (5 m l) was refluxed for 6–12 h . Th e resultin g precipitate was collected, wash ed with cold
m eth an ol an d recrystalized from m eth an ol. Th e results are sum m arized in Table IV.
2-{(E)-2-[4-(Dimethylamino)pheny]vinyl}-3-methylbenzothiazol-3-ium iodide (5b). M.p. 262.5–
264 °C; ref.29 gives m .p. 249–250 °C. 1H NMR (300 MHz, DMSO-d6): 8.29 d, 1 H, J(7,6) = 8.0
(H-7); 8.09 d, 1 H, J(4,5) = 8.4 (H-4); 8.06 d, 1 H, J(trans) = 15.3 (H-b); 7.90 d, 2 H, J = 8.5
(H-2′, H-6′); 7.78 t, 1 H, J = 7.9 (H-5); 7.69 t, 1 H, J = 7.9 (H-6); 7.65 d, 1 H, J(trans) = 15.3
(H-a); 6.83 d, 2 H, J = 8.7 (H-3′, H-6′); 4.23 s, 3 H (CH3); 3.03 s, 6 H (2 × CH3). 13C NMR
(75 MHz, DMSO-d6): 171.40 (C-2); 153.59 (C-4′); 150.20 (CH-b); 142.00 (C-3a); 132.90 (C-2′,
C-6′); 128.98 (CH-5); 127.55 (CH-6); 126.85 (C-7a); 123.79 (CH-7); 121.50 (C-1′); 115.98
(CH-4); 112.03 (C-3′, C-5′); 106.24 (CH-a); 39.83 (N(CH3)2); 35.62 (N-CH3). UV/VIS data are
con sisten t with ref.30. UV/VIS (m eth an ol), λm ax (ε): 220 (30 200), 318 (7 800), 520 (67 900).
2-{(E)-2-[4-(Dimethylamino)phenyl]vinyl}-3-methylbenzothiazol-3-ium hydrogen sulfate (5c).
M.p. 295–296 °C. For C18H20N2O4S2 (392.2) calculated: 55.08% C, 5.14% H, 7.14% N,
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Sigmundová, Zahradník, Loos:
16.34% S; foun d: 54.85% C, 5.05% H, 7.25% N, 16.44% S. 1H NMR (300 MHz, DMSO-d6):
8.28 d, 1 H, J(7,6) = 8.1 (H-7); 8.09 d, 1 H, J(4,5) = 8.4 (H-4); 8.03 d, 1 H, J(trans) = 15.3
(H-b); 7.89 d, 2 H, J = 9.0 (H-2′, H-6′); 7.77 t, 1 H, J = 7.2 (H-5); 7.67 t, 1 H, J = 7.2 (H-6);
7.60 d, 1 H, J(trans) = 15.3 (H-a); 6.80 d, 2 H, J = 9.0 (H-3′, H-6′); 4.22 s, 3 H (CH3); 3.08 s,
6 H (2 × CH3). 13C NMR (75 MHz, DMSO-d6): 171.31 (C-2); 153.43 (C-4′); 150.08 (CH-b);
141.92 (C-3a); 132.81 (C-2′, C-6′); 128.85 (CH-5); 127.42 (CH-6); 126.80 (C-7a); 123.77
(CH-7); 121.44 (C-1′); 115.92 (CH-4); 111.91 (C-3′, C-5′); 106.24 (CH-a); 39.75 (N(CH3)2);
35.52 (N-CH3). UV/VIS (m eth an ol), λm ax (ε): 206 (38 300), 522 (71 500).
2-{(E)-2-[4-(Dimethylamino)phenyl]vinyl}-3-methyl-5-nitrobenzothiazol-3-ium iodide (5d ). M.p.
242–243 °C. For C18H18IN3O2S (467.3) calculated: 46.26% C, 3.88% H, 8.99% N, 6.86% S;
foun d: 46.12% C, 3.85% H, 8.79% N, 6.75% S. 1H NMR (300 MHz, DMSO-d6): 8.82 d, 1 H,
J(4,6) = 1.9 (H-4); 8.52 d, 1 H, J(7,6) = 8.8 (H-7); 8.44 dd, 1 H, J(6,7) = 8.8, J(6,4) = 1.9 (H-6);
8.12 d, 1 H, J(trans) = 15.2 (H-b); 7.96 d, 2 H, J = 8.9 (H-2′, H-6′); 7.59 d, 1 H, J(trans) = 15.2
(H-a); 6.81 d, 2 H, J = 9.0 (H-3′, H-6′); 4.26 s, 3 H (CH3); 3.12 s, 6 H (2 × CH3). 13C NMR
(75 MHz, DMSO-d6): 173.50 (C-2); 154.10 (C-4′); 152.13 (CH-b); 147.55 (C-5); 142.44 (C-3a);
133.66 (C-2′, C-6′); 133.51 (CH-7a); 125.00 (CH-7); 121.52 (C-6); 121.40 (C-1′); 112.15 (C-3′,
C-5′); 111.00 (CH-4); 105.54 (CH-a); 48.55 (N(CH3)2); 35.86 (N-CH3). UV/VIS (m eth an ol),
λm ax (ε): 548 (58 800). UV/VIS (CHCl3), λm ax (ε): 282 (6 700), 576 (42 600).
2-{(E)-2-[3-(Dimethylamino)phenyl]vinyl}-3-methyl-5-nitrobenzothiazol-3-ium iodide (5e). M.p.
224–225 °C. For C18H18IN3O2S (467.3) calculated: 46.26% C, 3.88% H, 8.99% N, 6.86% S;
foun d: 46.05% C, 3.81% H, 8.69% N, 6.84% S. 1H NMR (300 MHz, DMSO-d6): 9.10 d, 1 H,
J(4,6) = 1.8 (H-4); 8.71 d, 1 H, J(7,6) = 8.7 (H-7); 8.61 dd, 1 H, J(6,7) = 8.7, J(6,4) = 1.8 (H-6);
8.30 d, 1 H, J(trans) = 15.9 (H-b); 8.02 d, 1 H, J(trans) = 15.9 (H-a); 7.42–7.35 m , 3 H (H-Ar);
7.00–6.96 m , 1 H (H-Ar); 4.47 s, 3 H (CH3); 3.00 s, 6 H (2 × CH3). 13C NMR (75 MHz,
DMSO-d6): 175.64 (C-2); 151.96 (CH-b); 150.62 (C-3′); 147.91 (C-5); 142.41 (C-3a); 134.43,
134.21 (CH-7a, C-1′); 129.79 (CH-5′); 125.84 (CH-7); 122.52 (CH-6); 118.27, 117.10 (CH-a,
CH-6′); 113.55 (CH-2′); 113.42 (CH-4′); 112.62 (CH-4); 40.17 (N(CH3)2); 37.10 (N-CH3).
UV/VIS (m eth an ol), λm ax (ε): 206 (30 900), 218 (32 600), 256 (22 400), 272 (21 800), 384
(20 600).
2-{(E)-2-[2-(Dimethylamino)phenyl]vinyl}-3-methyl-5-nitrobenzothiazol-3-ium iodide (5f). M.p.
213–214 °C. For C18H18IN3O2S (467.3) calculated: 46.26% C, 3.88% H, 8.99% N, 6.86% S;
foun d: 46.15% C, 3.79% H, 8.72% N, 6.77% S. 1H NMR (300 MHz, DMSO-d6): 9.09 d, 1 H,
J(4,6) = 1.8 (H-4); 8.64 d, 1 H, J(7,6) = 9.0 (H-7); 8.59 dd, 1 H, J(6,7) = 9.0, J(6,4) = 1.8 (H-6);
8.38 d, 1 H, J(trans) = 16.1 (H-b); 8.09 dd, 1 H, J(6′,5′) = 7.5, J(6′,4′) = 1.5 (H-6′); 8.09 d, 1 H,
J(trans) = 15.9 (H-a); 7.55 dt, 1 H, J(4′,5′,6′) = 7.8, J(4′,6′) = 1.5 (H-4′); 7.26–7.16 m , 2 H (H-3′,
H-5′); 4.43 s, 3 H (CH3); 2.87 s, 6 H (2 × CH3). 13C NMR (75 MHz, DMSO-d6): 175.94 (C-2);
155.11 (C-2′); 147.92 (CH-b); 147.45 (C-5); 142.49 (C-3a); 133.93 (C-7a); 133.83 (CH-4′);
129.84 (C-1′); 125.98, 125.66 (CH-7, CH-6′); 122.53, 122.20 (CH-6, CH-5′); 119.09 (CH-3′);
112.53, 112.51 (CH-4, CH-a); 45.27 (N(CH3)2); 36.83 (N-CH3). UV/VIS (m eth an ol), λm ax (ε):
268 (17 000), 368 (18 400), 464 (8 700).
2-{(E)-2-[4-(Dimethylamino)phenyl]vinyl}-3-methyl-6-nitrobenzothiazol-3-ium iodide (5g). M.p.
255–258 °C. For C18H18IN3O2S (467.3) calculated: 46.26% C, 3.88% H, 8.99% N, 6.86% S;
foun d: 46.29% C, 3.85% H, 8.98% N, 6.52% S. 1H NMR (300 MHz, DMSO-d6): 9.28 d, 1 H,
J(7,5) = 1.2 (H-7); 8.56 dd, 1 H, J(5,4) = 8.8, J(5,7) = 1.2 (H-5); 8.26 d, 1 H, J(4,5) = 9.0 (H-4);
8.22 d, 1 H, J(trans) = 15.1 (H-b); 7.99 d, 2 H, J = 8.5 (H-2′, H-6′); 7.62 d, 1 H, J(trans) = 15.1
(H-a); 6.89 d, 2 H, J = 8.5 (H-3′, H-6′); 4.23 s, 3 H (CH3); 3.19 s, 6 H (2 × CH3). 13C NMR
(75 MHz, DMSO-d6): 174.32 (C-2); 154.26 (C-4′); 152.57 (CH-b); 145.98 (C-3a); 145.22
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(CH-6); 133.91 (C-2′, C-6′); 127.67 (C-7a); 124.01 (CH-5); 121.73 (C-1′); 120.19 (CH-7);
116.19 (CH-4); 112.26 (C-3′, C-5′); 105.68 (CH-a); 39.90 (N(CH3)2); 35.86 (N-CH3). UV/VIS
(m eth an ol), λm ax (ε): 562 (32 700). UV/VIS (CHCl3), λm ax (ε): 304 (2 500), 596 (18 700).
2-{(E)-2-[3-(Dimethylamino)phenyl]vinyl}-3-methyl-6-nitrobenzothiazol-3-ium iodide (5h ). M.p.
255–227 °C. For C18H18IN3O2S (467.3) calculated: 46.26% C, 3.88% H, 8.99% N, 6.86% S;
foun d: 46.01% C, 3.90% H, 8.71% N, 6.59% S. 1H NMR (300 MHz, DMSO-d6): 9.46 d, 1 H,
J(7,5) = 2.4 (H-7); 8.67 dd, 1 H, J(5,4) = 9.3, J(5,7) = 2.4 (H-5); 8.45 d, 1 H, J(4,5) = 9.3 (H-4);
8.35 d, 1 H, J(trans) = 15.9 (H-b); 8.02 d, 1 H, J(trans) = 15.9 (H-a); 7.42–7.36 m , 3 H (H-Ar);
7.00–6.97 m , 1 H (H-Ar); 4.41 s, 3 H (CH3); 3.01 s, 6 H (2 × CH3). 13C NMR (75 MHz,
DMSO-d6): 176.76 (C-2); 152.39 (CH-b); 150.70 (C-3′); 146.16 (C-6); 145.71 (C-3a); 134.48
(C-1′); 129.77 (CH-5′); 128.74 (C-7a); 124.36 (CH-5); 120.91 (CH-7); 118.06 (CH-a); 117.83
(CH-6′); 117.06 (CH-4); 113.71 (CH-2′); 113.53 (CH-4′); 40.18 (N(CH3)2); 37.06 (N-CH3).
UV/VIS (m eth an ol), λm ax (ε): 218 (14 600), 390 (23 700).
2-{(E)-2-[2-(Dimethylamino)phenyl]vinyl}-3-methyl-6-nitrobenzothiazol-3-ium iodide (5i). M.p.
208–209.8 °C. For C18H18IN3O2S (467.3) calculated: 46.26% C, 3.88% H, 8.99% N, 6.86% S;
foun d: 46.34% C, 3.85% H, 8.91% N, 6.82% S. 1H NMR (300 MHz, DMSO-d6): 9.36 d, 1 H,
J(7.5) = 2.4 (H-7); 8.66 dd, 1 H, J(5,4) = 9.2, J(5,7) = 2.4 (H-5); 8.44 d, 1 H, J(4,5) = 9.3 (H-4);
8.31 d, 1 H, J(trans) = 15.9 (H-b); 8.09 dd, 1 H, J(6′,5′) = 5.1, J(6′,4′) = 1.2 (H-6′); 8.02 d, 1 H,
J(trans) = 15.9 (H-a); 7.58–7.53 m , 1 H (H-4′); 7.26–7.15 m , 2 H (H-3′, H-5′); 4.48 s, 3 H
(CH3); 2.86 s, 6 H (2 × CH3). 13C NMR (75 MHz, DMSO-d6): 176.94 (C-2); 155.13 (CH-2′);
147.78 (C-b); 146.06 (C-6); 145.78 (C-3a); 133.86 (CH-4′); 129.94 (C-1′); 128.39 (C-7a);
125.94 (CH-6′); 124.35 (CH-5); 122.12 (CH-5′); 120.65 (CH-7); 119.03 (CH-3′); 117.73
(CH-4); 112.62 (CH-a); 45.26 (N(CH3)2); 36.88 (N-CH3). UV/VIS (m eth an ol), λm ax (ε): 376
(20 300), 476 (9 100).
2-{(E)-2-[4-(Dimethylamino)phenyl]vinyl}-3-methyl-7-nitrobenzothiazol-3-ium iodide (5j). M.p.
218.5–220 °C. For C18H18IN3O2S (467.3) calculated: 46.26% C, 3.88% H, 8.99% N, 6.86% S;
foun d: 46.03% C, 3.79% H, 8.75% N, 6.74% S. 1H NMR (300 MHz, DMSO-d6): 8.54 d, 1 H,
J(6,5) = 8.1 (H-6); 8.47 d, 1 H, J(4,5) = 8.1 (H-4); 8.38 d, 1 H, J(trans) = 15.0 (H-b); 8.00 t,
1 H, J(5,4,6) = 8.2 (H-5); 7.96 d, 2 H, J = 9.0 (H-2′, H-6′); 7.61 d, 1 H, J(trans) = 15.0 (H-a);
6.85 d, 2 H, J = 9.0 (H-3′, H-5′); 4.24 s, 3 H (CH3); 3.14 s, 6 H (2 × CH3). 13C NMR (75 MHz,
DMSO-d6): 172.70 (C-2); 154.20 (C-4′); 152.57 (CH-b); 143.96 (C-7); 141.73 (C-3a); 133.83
(2 × CH-2′, 6′); 129.72 (C-7a); 123.07 (CH-4); 122.80 (CH-5); 121.95 (C-1′); 121.80 (CH-6);
112.21 (2 × CH-3′, 5′); 105.22 (CH-a); 40.06 (N(CH3)2); 35.95 (N-CH3). UV/VIS (m eth an ol),
λm ax (ε): 556 (51 700). UV/VIS (CHCl3), λm ax (ε): 244 (31 400), 586 (69 900).
2-{(E)-6-Cyano-2-[4-(dimethylamino)phenyl]vinyl}-3-methylbenzothiazol-3-ium iodide (5k). M.p.
246.5–249 °C. For C19H18IN3S (447.3) calculated: 51.01% C, 4.06% H, 9.39% N, 7.17% S;
foun d: 50.89% C, 4.01% H, 9.14% N, 7.20% S. 1H NMR (300 MHz, DMSO-d6): 8.79 bs, 1 H
(H-7); 8.21 bs, 2 H (H-5, H-4); 8.19 d, 1 H, J(trans) = 15.0 (H-b); 7.96 d, 2 H, J = 9.3 (H-2′,
H-6′); 7.96 d, 1 H, J(4,5) = 9.0 (H-4); 7.61 d, 1 H, J(trans) = 15.0 (H-a); 6.88 d, 2 H, J = 9.0
(H-3′, H-6′); 4.19 s, 3 H (CH3); 3.15 s, 6 H (2 × CH3). 13C NMR (75 MHz, DMSO-d6): 173.37
(C-2); 154.26 (C-4′); 152.28 (CH-b); 144.77 (C-3a); 133.76 (C-2′, C-6′); 132.12 (CH-5); 128.47
(CH-7); 127.47 (C-7a); 121.62 (C-1′); 117.94 (CN); 116.62 (CH-4); 112.20 (C-3′, C-5′); 109.00
(CH-6); 105.53 (CH-a); 39.89 (N(CH3)2); 35.76 (N-CH3). UV/VIS (m eth an ol), λm ax (ε): 554
(64 000). UV/VIS (CHCl3), λm ax (ε): 582 (49 400).
2-{(E)-2-[4-(Diphenylamino)phenyl]vinyl}-3-methylbenzothiazol-3-ium iodide (5l). M.p. 232–
234 °C. For C28H23IN2S (543.5) calculated: 61.54% C, 4.24% H, 5.13% N, 5.87% S; foun d:
61.03% C, 4.44% H, 5.14% N, 5.75% S. 1H NMR (300 MHz, DMSO-d6): 8.37 d, 1 H, J(7,6) =
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Sigmundová, Zahradník, Loos:
8.1 (H-7); 8.19 d, 1 H, J(4,5) = 8.1 (H-4); 8.13 d, 1 H, J(trans) = 15.6 (H-b); 7.62 d, 2 H, J =
8.7 (H-2′, H-6′); 7.87–7.81 m , 1 H (H-5); 7.78–7.73 m , 1 H (H-6); 7.78 d, 1 H, J(trans) = 15.6
(H-a); 7.47–7.42 m , 4 H (H-Ar); 7.27–7.19 m , 6 H (H-Ar); 6.92 d, 2 H, J = 8.7 (H-3′, H-5′);
4.29 s, 3 H (CH3). 13C NMR (75 MHz, DMSO-d6): 171.72 (C-2); 151.37 (C-4′); 148.60 (CH-b);
145.51 (2 × C); 142.01 (C-3a); 131.85 (2 × CH-2′, 6′); 130.05 (4 × CH); 129.19 (CH-5); 128.03
(CH-6); 127.36 (2 × C-1′, 7a); 126.19 (4 × CH); 125.50 (2 × CH); 124.06 (CH-7); 119.00 (2 ×
CH-3′, 5′); 116.50 (CH-4); 110.11 (CH-a); 36.05 (N-CH3). UV/VIS (m eth an ol), λm ax (ε): 356
(28 300), 508 (20 200). UV/VIS (CHCl3), λm ax (ε): 294 (23 400), 358 (23 000), 554 (46 500).
2-{(E)-2-[4-(Diphenylamino)phenyl]vinyl}-3-methyl-5-nitrobenzothiazol-3-ium iodide (5m ). M.p.
225 °C. For C28H23IN2O2S (591.5) calculated: 56.86% C, 3.75% H, 7.10% N, 5.42% S; foun d:
56.62% C, 3.84% H, 7.03% N, 5.72% S. 1H NMR (300 MHz, DMSO-d6): 9.00 d, 1 H, J(4,6) =
2.1 (H-4); 8.62 d, 1 H, J(7,6) = 9.0 (H-7); 8.30 dd, 1 H, J(6,7) = 9.0, J(6,4) = 2.1 (H-6); 8.25 d,
1 H, J(trans) = 15.6 (H-b); 7.95 d, 2 H, J = 9.0 (H-2′, H-6′); 7.48–7.43 m , 4 H (H-Ar); 7.30–7.22 m ,
6 H (H-Ar); 7.79 d, 1 H, J(trans) = 15.3 (H-a); 6.90 d, 2 H, J = 9.3 (H-3′, H-5′); 4.36 s, 3 H
(CH3). 13C NMR (75 MHz, DMSO-d6): 174.64 (C-2); 152.01 (CH-b); 147.76 (C-5); 145.23
(C-4′); 142.45 (C-3a); 133.92 (C-7a); 132.53 (2 × CH-2′, 6′); 130.10 (4 × CH); 129.52 (2 × C);
126.43 (4 × CH); 125.88 (2 × CH); 125.83 (CH-7); 125.47 (C-1′); 122.57 (CH-6); 118.53 (2 ×
CH-3′, 5′); 112.00 (CH-4); 109.91 (CH-a); 36.05 (N-CH3). UV/VIS (m eth an ol), λm ax (ε): 208
(51 500), 296 (22 200), 542 (30 000). UV/VIS (CHCl3), λm ax (ε): 244 (31 100), 286 (30 400),
580 (71 400).
2-{(E)-2-[4-(Diphenylamino)phenyl]vinyl}-3-methyl-6-nitrobenzothiazol-3-ium iodide (5n ). M.p.
240–240.5 °C. For C28H23IN2O2S (591.5) calculated: 56.86% C, 3.75% H, 7.10% N, 5.42% S;
foun d: 56.72% C, 3.65% H, 7.23% N, 5.55% S. 1H NMR (300 MHz, DMSO-d6): 9.36 d, 1 H,
J(7,5) = 2.4 (H-7); 8.61 dd, 1 H, J(5,4) = 9.0, J(5,7) = 2.4 (H-5); 8.33 d, 1 H, J(4,5) = 9.0 (H-4);
8.26 d, 1 H, J(trans) = 15.5 (H-b); 7.96 d, 2 H, J = 8.8 (H-2′, H-6′); 7.76 d, 1 H, J(trans) = 15.5
(H-a); 7.47–7.43 m , 4 H (H-Ar); 7.31–7.23 m , 6 H (H-Ar); 6.90 d, 2 H, J = 8.7 (H-3′, H-5′);
4.27 s, 3 H (CH3). 13C NMR (75 MHz, DMSO-d6): 175.59 (C-2); 152.04 (CH-b); 151.11 (C-4′);
145.73 (C-3a); 145.65 (C-6); 145.06 (2 × C); 132.58 (2 × CH-2′, 6′); 130.02 (4 × CH); 129.42
(C-7a); 128.16 (C-1′); 126.38 (4 × CH); 125.80 (2 × CH); 124.10 (CH-5); 120.46 (CH-7);
118.30 (2 × CH-3′, 5′); 117.02 (CH-4); 109.57 (CH-a); 36.35 (N-CH3). UV/VIS (m eth an ol),
λm ax (ε): 210 (57 200), 288 (18 800), 350 (19 400), 552 (23 600). UV/VIS (CHCl3), λm ax (ε):
244 (27 300), 284 (20 000), 364 (11 800), 602 (75 200).
2-{(E)-2-[4-(Diphenylamino)phenyl]vinyl}-3-methyl-7-nitrobenzothiazol-3-ium iodide (5o). M.p.
223–224 °C. For C28H23IN2O2S (591.5) calculated: 56.86% C, 3.75% H, 7.10% N, 5.42% S;
foun d: 56.89% C, 3.62% H, 7.15% N, 5.48% S. 1H NMR (300 MHz, DMSO-d6): 8.64 d, 1 H,
J(6,5) = 8.4 (H-6); 8.61 d, 1 H, J(4,5) = 8.4 (H-4); 8.50 d, 1 H, J(trans) = 15.5 (H-b); 8.08 t,
1 H, J = 8.4 (H-5); 7.96 d, 2 H, J = 9.0 (H-2′, H-6′); 7.80 d, 1 H, J(trans) = 15.6 (H-a);
7.49–7.44 m , 4 H (H-Ar); 7.31–7.23 m , 6 H (H-Ar); 6.90 d, 2 H, J = 9.0 (H-3′, H-5′); 4.33 s,
3 H (CH3). 13C NMR (75 MHz, DMSO-d6): 173.94 (C-2); 152.13 (C-4′); 151.33 (CH-b); 145.72
(2 × C); 143.87 (C-7); 141.89 (C-3a); 132.64 (2 × CH-2′, 6′); 130.11 (4 × CH), 126.48 (4 ×
CH); 126.00 (C-7a); 125.88 (2 × CH); 125.57 (CH-4); 123.69 (CH-5); 123.31 (C-1′); 122.89
(CH-6); 118.46 (2 × CH-3′, 5′); 109.23 (CH-a); 37.19 (N-CH3). UV/VIS (m eth an ol), λm ax (ε):
244 (25 900), 288 (25 600), 548 (39 800). UV/VIS (CHCl3), λm ax (ε): 594 (73 000).
2-{(E)-6-Cyano-2-[4-(diphenylamino)pheny]vinyl}-3-methylbenzothiazol-3-ium iodide (5p ). M.p.
242–243 °C. For C29H22IN3S (571.5) calculated: 60.95% C, 3.88% H, 7.35% N, 5.61% S;
foun d: 60.90% C, 3.78% H, 7.27% N, 5.46% S. 1H NMR (300 MHz, DMSO-d6): 8.89 d, 1 H,
J(7,5) = 1.2 (H-7); 8.34 d, 1 H, J(4,5) = 8.7 (H-4); 8.28 dd, 1 H, J(5,4) = 8.7, J(5,7) = 1.2 (H-5);
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8.27 d, 1 H, J(trans) = 15.3 (H-b); 7.95 d, 2 H, J = 9.0 (H-2′, H-6′); 7.76 d, 1 H, J(trans) = 15.3
(H-a); 7.48–7.43 m , 4 H (H-Ar); 7.30–7.22 m , 6 H (H-Ar); 6.90 d, 2 H, J = 9.0 (H-3′, H-5′);
4.27 s, 3 H (CH3). 13C NMR (75 MHz, DMSO-d6): 174.58 (C-2); 152.04 (C-4′); 150.94 (CH-b);
145.23 (2 × C); 144.72 (C-3a); 132.56 (2 × CH-2′, 6′); 132.29 (CH-5); 130.11 (4 × CH); 128.76
(CH-7); 128.03 (C-7a); 126.44 (4 × CH); 125.91 (C-1′); 125.85 (2 × CH); 118.52 (2 × CH-3′, 5′);
117.79 (CN); 117.42 (CH-4); 109.80 (CH-a); 109.54 (C-6); 36.25 (N-CH3). UV/VIS (m eth a-
n ol), λm ax (ε): 304 (13 400), 542 (39 000). UV/VIS (CHCl3), λm ax (ε): 286 (15 100), 350
(8 500), 592 (78 700).
3-Methyl-2-[(E)-2-(4-pyrrolidin-1-ylphenyl)vinyl]benzothiazol-3-ium iodide (5q). M.p. 255–256 °C.
For C20H21IN2S (448.4) calculated: 53.58% C, 4.72% H, 6.25% N, 7.15% S; foun d: 53.45% C,
4.62% H, 6.33% N, 7.14% S. 1H NMR (300 MHz, DMSO-d6): 8.28 d, 1 H, J(7,6) = 8.1 (H-7);
8.07 d, 1 H, J(4,5) = 8.1 (H-4); 8.04 d, 1 H, J(trans) = 15.0 (H-b); 7.91 d, 2 H, J = 8.7 (H-2′,
H-6′); 7.77 t, 1 H, J = 8.1 (H-5); 7.67 t, 1 H, J = 8.1 (H-6); 7.58 d, 1 H, J(trans) = 15.0 (H-a);
6.69 d, 2 H, J = 8.7 (H-3′, H-6′); 4.21 s, 3 H (CH3); 3.41 t, J = 6.3 (2 × CH2); 2.00 t, J = 6.3
(2 × CH2). 13C NMR (75 MHz, DMSO-d6): 171.00 (C-2); 150.88 (C-4′); 150.17 (CH-b); 141.80
(C-3a); 132.94 (C-2′, C-6′); 128.66 (CH-5); 127.17 (CH-6); 126.57 (C-7a); 123.62 (CH-7);
121.13 (C-1′); 115.68 (CH-4); 112.24 (C-3′, C-5′); 105.47 (CH-a); 47.51 (N(CH2)2); 35.33
(N-CH3); 24.77 (2 × CH2). UV/VIS (m eth an ol), λm ax (ε): 206 (35 700), 220 (26 000), 286
(6 400), 318 (4 700), 534 (72 100).
3-Methyl-6-nitro-2-[(E)-2-(4-pyrrolidin-1-ylphenyl)vinyl]benzothiazol-3-ium iodide (5r). M.p.
213–214 °C. For C20H20IN3O2S (493.4) calculated: 48.69% C, 4.09% H, 8.52% N, 6.50% S;
foun d: 48.50% C, 4.06% H, 8.52% N, 6.52% S. 1H NMR (300 MHz, DMSO-d6): 9.26 d, 1 H,
J(7,5) = 2.4 (H-7); 8.55 dd, 1 H, J(5,4) = 9.0, J(5,7) = 2.4 (H-5); 8.19 d, 1 H, J(trans) = 15.0
(H-b); 8.18 d, 1 H, J(4,5) = 9.0 (H-4); 7.98 d, 2 H, J = 8.7 (H-2′, H-6′); 7.58 d, 1 H, J(trans) =
15.0 (H-a); 6.75 d, 2 H, J = 8.7 (H-3′, H-6′); 4.20 s, 3 H (CH3); 3.44–3.47 m , 4 H (2 × CH2);
2.03–1.99 m , 4 H (2 × CH2). 13C NMR (75 MHz, DMSO-d6): 173.96 (C-2); 152.73 (C-4′);
151.87 (CH-b); 146.04 (C-3a); 145.14 (CH-6); 134.22 (C-2′, C-6′); 127.59 (C-7a); 124.00
(CH-5); 121.70 (C-1′); 120.13 (CH-7); 116.01 (CH-4); 112.88 (C-3′, C-5′); 105.06 (CH-a);
47.91 (2 × CH2); 35.72 (N-CH3); 24.83 (2 × CH2). UV/VIS (m eth an ol), λm ax (ε): 572 (27 300).
2-{(E,E)-4-[4-(Dimethylamino)phenyl]buta-1,3-dien-1-yl}-3-methylbenzothiazol-3-ium iodide
(5s). M.p. an d 1H NMR data are con sisten t with ref.15 13C NMR (75 MHz, DMSO-d6): 171.24
.
(C-2); 152.86 (CH-b); 151.83 (C-4′); 148.83 (CH-d); 142.56 (C-3a); 131.18 (2 × CH-2′, 6′);
129.72 (CH-5); 128.34 (CH-6); 127.82 (C-7a); 124.61 (CH-7); 123.54 (C-1′); 122.80 (CH-c);
116.80 (CH-4); 112.82 (2 × CH-3′, 5′); 112.76 (CH-a); 40.38 (N(CH3)2); 35.88 (N-CH3).
UV/VIS (m eth an ol), λm ax (ε): 206 (33 300), 220 (33 500), 338 (10 000), 580 (54 300). UV/VIS
(CHCl3), λm ax (ε): 248 (13 500), 300 (3 700), 344 (3 800), 612 (73 100).
2-{(E,E)-4-[4-(Dimethylamino)phenyl]buta-1,3-dien-1-yl}-3-methyl-5-nitrobenzothiazol-3-ium
iodide (5t). M.p. 253 °C. For C20H20IN3O2S (493.4) calculated: 48.69% C, 4.09% H, 8.52% N,
6.50% S; foun d: 48.55% C, 4.01% H, 8.33% N, 6.41% S. 1H NMR (300 MHz, DMSO-d6):
8.92 d, 1 H, J(4,6) = 1.8 (H-4); 8.55 d, 1 H, J(7,6) = 9.0 (H-7); 8.48 dd, 1 H, J(6,7) = 9.0,
J(6,4) = 1.8 (H-6); 8.11 dd, 1 H, J(trans) = 14.4, J = 11.1 (H-b); 7.58 d, 2 H, J = 9.0 (H-2′,
H-6′); 7.57 d, 1 H, J = 14.4 (H-d); 7.31 d, 1 H, J = 14.4 (H-a); 7.24 dd, 1 H, J(trans) = 14.4, J =
11.1 (H-c); 6.81 d, 2 H, J = 9.0 (H-3′, H-5′); 4.20 s, 3 H (CH3); 3.07 s, 6 H (2 × CH3).
13C NMR (75 MHz, DMSO-d6): 172.73 (C-2); 153.36 (C-4′); 152.44 (CH-b); 150.32 (CH-d);
147.50 (C-5); 142.23 (C-3a); 133.67 (C-7a); 131.04 (2 × CH-2′, 6′); 125.09 (CH-7); 122.58,
122.12 (CH-6, CH-c); 121.51 (C-1′); 112.06 (2 × CH-3′, 5′); 111.25, 111.13 (CH-4, CH-a);
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Sigmundová, Zahradník, Loos:
39.56 (N(CH3)2); 35.68 (N-CH3). UV/VIS (m eth an ol), λm ax (ε): 610 (68 100). UV/VIS (CHCl3),
λm ax (ε): 300 (11 300), 374 (11 300), 652 (53 700).
2-{(E,E)-4-[4-(Dimethylamino)phenyl]buta-1,3-dien-1-yl}-3-methyl-6-nitrobenzothiazol-3-ium
iodide (5u ). M.p. 201–203 °C. For C20H20IN3O2S (493.4) calculated: 48.69% C, 4.09% H,
8.52% N, 6.50% S; foun d: 48.72% C, 4.12% H, 8.40% N, 6.38% S. 1H NMR (300 MHz,
DMSO-d6): 9.28 d, 1 H, J(7,5) = 2.1 (H-7); 8.56 dd, 1 H, J(5,4) = 9.0, J(5,7) = 2.1 (H-5); 8.25 d,
1 H, J(4,5) = 9.0 (H-4); 8.14 dd, 1 H, J(trans) = 14.4, J = 11.1 (H-b); 7.58 d, 2 H, J = 9.0 (H-2′,
H-6′); 7.57 d, 1 H, J = 14.4 (H-d); 7.28 d, 1 H, J = 14.4 (H-a); 7.24 dd, 1 H, J(trans) = 14.4, J =
11.1 (H-c); 6.81 d, 2 H, J = 9.0 (H-3′, H-5′); 4.13 s, 3 H (CH3); 3.07 s, 6 H (2 × CH3).
13C NMR (75 MHz, DMSO-d6): 174.01 (C-2); 153.96 (CH-b); 152.79 (C-4′); 151.03 (CH-d);
145.84 (C-6); 145.35 (C-3a); 131.40 (2 × CH-2′, 6′); 127.94 (C-7a); 124.10 (CH-5); 122.81
(C-1′); 122.35 (CH-c); 120.30 (CH-7); 116.41 (CH-4); 112.29 (2 × CH-3′, 5′); 111.38 (CH-a);
39.67 (N(CH3)2); 35.72 (N-CH3). UV/VIS (m eth an ol), λm ax (ε): 628 (15 700). UV/VIS (CHCl3),
λm ax (ε): 384 (10 700), 676 (26 000).
2-{(E,E)-4-[4-(Dimethylamino)phenyl]buta-1,3-dien-1-yl}-3-methyl-7-nitrobenzothiazol-3-ium
iodide (5v). M.p. 201–203 °C. For C20H20IN3O2S (493.4) calculated: 48.69% C, 4.09% H,
8.52% N, 6.50% S; foun d: 48.55% C, 4.09% H, 8.55% N, 6.39% S. 1H NMR (300 MHz,
DMSO-d6): 8.57 d, 1 H, J(6,5) = 8.4 (H-6); 8.53 d, 1 H, J(4,5) = 8.4 (H-4); 8.34 dd, 1 H,
J(trans) = 15.0, J = 11.1 (H-b); 8.03 t, 1 H, J = 8.4 (H-6); 7.58 d, 2 H, J = 9.3 (H-2′, H-6′);
7.57 d, 1 H, J = 15.0 (H-d); 7.24 d, 1 H, J = 14.4 (H-a); 7.24 dd, 1 H, J(trans) = 14.4, J = 11.1
(H-c); 6.82 d, 2 H, J = 9.3 (H-3′, H-5′); 4.20 s, 3 H (CH3); 3.07 s, 6 H (2 × CH3). 13C NMR
(75 MHz, DMSO-d6): 172.08 (C-2); 154.08 (CH-b); 152.73 (C-4′); 150.95 (CH-d); 143.86
(C-7); 141.80 (C-3a); 131.38 (2 × CH-2′, 6′); 130.64 (CH-4); 123.21 (C-7a); 122.76 (C-1′);
122.43 (CH-5); 122.23 (CH-6); 112.27 (2 × CH-3′, 5′); 112.66 (CH-c); 110.92 (CH-a); 39.79
(N(CH3)2); 35.90 (N-CH3). UV/VIS (m eth an ol), λm ax (ε): 206 (32 300), 218 (31 200), 290
(9 700), 374 (8 600), 622 (60 000). UV/VIS (CHCl3), λm ax (ε): 292 (12 800), 380 (10 700), 662
(46 800).
6-Cyano-2-{(E,E)-4-[4-(dimethylamino)phenyl]buta-1,3dien-1-yl}-3-methylbenzothiazol-3-ium
iodide (5w ). M.p. 243 °C. For C21H20IN3S (473.4) calculated: 53.28% C, 4.26% H, 8.88% N,
6.77% S; foun d: 53.00% C, 4.25% H, 8.56% N, 56.52% S. 1H NMR (300 MHz, DMSO-d6):
8.79 bs, 1 H (H-7); 8.25 d, 1 H, J(5,4) = 9.0 (H-5); 8.23 d, 1 H, J(4,5) = 9.0 (H-4); 8.00 dd,
1 H, J(trans) = 14.4, J = 11.1 (H-b); 7.54 d, 1 H, J = 14.1 (H-d); 7.55 d, 2 H, J = 8.7 (H-2′,
H-6′); 7.28 d, 1 H, J = 14.1 (H-a); 7.22 dd, 1 H, J(trans) = 14.1, J = 11.1 (H-c); 6.78 d, 2 H, J =
8.7 (H-3′, H-5′); 4.12 s, 3 H (CH3); 3.06 s, 6 H (2 × CH3). 13C NMR (75 MHz, DMSO-d6):
172.67 (C-2); 153.61 (CH-b); 152.65 (C-4′); 150.56 (CH-d); 144.66 (C-3a); 132.22 (CH-5);
131.26 (2 × CH-2′, 6′); 128.43 (CH-7); 127.77 (C-1′); 122.79 (C-7a); 122.36 (CH-c); 117.90
(CN); 116.84 (CH-4); 112.25 (2 × CH-3′, 5′); 111.30 (CH-a); 109.21 (C-6); 39.74 (N(CH3)2);
35.63 (N-CH3). UV/VIS (m eth an ol), λm ax (ε): 616 (55 300).
2-{(E,E,E)-6-[4-(Dimethylamino)phenyl]hexa-1,3,5-trien-1-yl}-3-methylbenzothiazol-3-ium iodide
.
(5x). M.p. an d 1H NMR data are con sisten t with ref.15 13C NMR (75 MHz, DMSO-d6): 170.50
(C-2); 151.18 (C-4′); 150.08 (CH-b); 149.10 (CH-d); 142.77 (C-3a); 141.90 (CH-f); 129.49
(2 × CH-2′, 6′); 129.12 (C-1′); 128 30 (CH-5); 127.79 (C-7a); 127.35 (CH-6); 123.96, 123.73,
123.54 (CH-7, CH-e, CH-c); 116.25 (CH-4); 113.37 (CH-a); 111.96 (2 × CH-3′, 5′); 39.74
(N(CH3)2); 35.70 (N-CH3). UV/VIS (m eth an ol), λm ax (ε): 206 (30 500), 220 (29 600), 290
(12 100), 350 (10 500), 580 (46 300). UV/VIS (CHCl3), λm ax (ε): 636 (32 300).
Support by the grant No. 1/4470/07 of the Slovak Grant Agency is gratefully acknowledged.
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