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Hrobarikova et al.
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JOCArticle
1H, H-7), 7.94 (d, J=8.6 Hz, 1H, H-4), 7.59 (dd, J=8.5 Hz,
1.6 Hz, 1H, H-5), 7.51 (d, J=8.9 Hz, 2H, Har), 7.43 (d, J=
8.8 Hz, 2H, Har), 6.67 (dd, J=8.8 Hz, 0.9 Hz, 4H, Har), 3.03
(s, 6H, 2ꢀCH3), 3.00 (s, 6H, 2ꢀCH3); 13C NMR (75 MHz,
CDCl3) δ 152.2, 151.1, 150.2, 150.0, 135.4, 133.7 (2ꢀ), 132.8
(2ꢀ), 129.8, 123.7, 122.8, 121.8, 111.8 (2ꢀ), 111.6 2ꢀ), 109.7,
107.0, 99.5, 92.1, 87.1, 81.9, 40.2 (2ꢀ), 40.1 (2ꢀ). Anal. Calcd
for C27H23N3S: C 76.93, H 5.50, N 9.97. Found: C 77.14, H
5.38, N 10.10.
20% aqueous Na2CO3 (1 mL) was added slowly and the
mixture was heated to reflux for 20 h. After this time, the
reaction mixture was cooled, quenched with water (10 mL),
and extracted with ethyl acetate (3ꢀ30 mL). The combined
organic extracts were washed with water and brine and dried
over anhydrous Na2SO4. The resulting products were puri-
fied by column chromatography on silica gel (eluent EtOAc/
hexanes =1:3).
(E)-6-[4-(N,N-Dimethylamino)phenylethenyl]-2-methylbenzo-
thiazole (9a): yield 78%; Rf 0.53 (SiO2, EtOAc/hexanes =
1:2); mp 187-189 ꢁC; 1H NMR (300 MHz, CDCl3) δ 7.88 (d,
J=1.6 Hz, 1H, H-7), 7.87 (d, J=8.4 Hz, 1H, H-4), 7.58 (dd,
J=8.6, 1.6 Hz, 1H, H-5), 7.43 (d, J=8.7 Hz, 2H, Har), 7.09
(d, J = 16.3 Hz, 1H, -CHd), 6.98 (d, J = 16.3 Hz, 1H,
-CHd), 6.72 (d, J = 8.8 Hz, 2H, Har), 2.99 (s, 6H, NMe2),
2.82 (s, 3H, CH3); 13C NMR (75 MHz, CDCl3) δ 166.5,
152.3, 150.0, 136.4, 135.3, 129.3, 127.6, 124.3, 123.8, 122.2,
118.5, 112.6, 40.6, 20.2. Anal. Calcd for C18H18N2S: C 73.43,
H 6.16, N 9.51. Found: C 73.51, H 6.10, N 9.67.
(E)-6-[4-(N,N-Diphenylamino)phenylethenyl]-2-methylbenzo-
thiazole (9b): yield 90%; Rf 0.29 (SiO2, EtOAc/hexanes =
1:3); mp 161-164 ꢁC; 1H NMR (300 MHz, CDCl3) δ 7.90 (d,
J=1.6 Hz, 1H, H-7), 7.89 (d, J=8.4 Hz, 1H, H-4), 7.60 (dd,
J = 8.5, 1.6 Hz, 1H, H-5), 7.39 (d, J = 8.6 Hz, 2H, Har),
7.29-7.23 (m, 4H, Har), 7.13-7.00 (m, 10H, Har, -CHd
CH-), 2.83 (s, 3H, CH3); 13C NMR (75 MHz, CDCl3) δ
167.9, 150.6, 147.7, 147.4, 135.5, 135.4, 131.0, 129.3, 129.2,
127.4, 125.9, 125.0, 124.6, 123.3, 123.2, 121.8, 118.9, 19.7.
Anal. Calcd for C28H22N2S: C 80.35, H 5.30, N 6.69. Found:
C 80.52, H 5.21, N 6.85.
2,6-Bis[4-(N,N-diphenylamino)phenylethynyl]benzothiazole
(1b): chromatography on SiO2, eluent CHCl3/hexanes=2:3;
yield 74%; Rf 0.24 (SiO2, CHCl3/hexanes = 2:3); mp 211-
213 ꢁC; 1H NMR (300 MHz, CDCl3) δ 7.99 (d, J = 1.6 Hz,
1H, H-7), 7.97 (d, J=8.4 Hz, 1H, H-4), 7.61 (dd, J=8.4 Hz,
1.6 Hz, 1H, H-5), 7.46 (d, J=8.9 Hz, 2H, Har), 7.39 (d, J=
8.8 Hz, 2H, Har), 7.34-7.28 (m, 8H, NPh2), 7.16-7.05 (m,
12H, NPh2), 7.02 (d, J=8.8 Hz, 2H, Har), 7.00 (d, J=8.8 Hz,
2H, Har); 13C NMR (75 MHz, CDCl3) δ 152.4, 149.8, 149.5,
148.1, 147.1, 146.6, 135.5, 133.3, 132.6, 130.1, 129.6, 129.4,
125.6, 125.1, 124.3, 124.0, 123.6, 123.0, 122.1, 121.5, 121.0,
115.6, 112.5, 98.1, 91.3, 88.2, 82.3. Anal. Calcd for C47H31-
N3S: C 84.28, H 4.66, N 6.27. Found: C 84.56, H 4.49, N 6.30.
2,6-Bis{4-[N,N-bis(2-acetoxyethyl)amino]phenylethynyl}-
benzothiazole (1c): chromatography on Al2O3 (B II., neutral),
eluent hexanes/EtOAc = 1:1; yield 57%; Rf 0.5 (Al2O3, hex-
1
anes/EtOAc = 1:1); mp 183-185 ꢁC; H NMR (300 MHz,
CDCl3) δ 7.97 (d, J= 1.1 Hz, 1H, H-7), 7.96 (d, J=8.5 Hz,
1H, H-4), 7.60 (dd, J=8.5, 1.6 Hz, 1H, H-5), 7.51 (d, J=8.8
Hz, 2H, Har), 7.20 (d, J=9.0 Hz, 2H, Har), 6.75 (d, J=9.0 Hz,
2H, Har), 6.73 (d, J=9.0 Hz, 2H, Har), 4.26 (t, J=8.5 Hz, 8H,
CH2-O), 3.67-3.64 (m, 8H, N-CH2), 2.06 (s, 12H, 4 ꢀ
CH3); 13C NMR (75 MHz, CDCl3) δ 170.92 (2ꢀ), 170.88
(2ꢀ), 152.3, 149.9, 148.4, 147.3, 135.4, 134.0 (2ꢀ), 133.1 (2ꢀ),
129.9, 123.8, 122.9, 121.7, 111.7 (4ꢀ), 110.7, 108.2, 98.7, 91.7,
87.4, 82.0, 61.2 (2ꢀ), 61.1 (2ꢀ), 49.52 (2ꢀ), 49.48 (2ꢀ), 20.89
(2ꢀ), 20.87 (2ꢀ). Anal. Calcd for C39H39N3O8S: C 65.99, H
5.54, N 5.92. Found: C 66.24, H 5.41, N 5.88.
General Procedure for the Preparation of Target Com-
pounds 2a and 2b (Aldol-Type Condensations). To a solution
of intermediate 9a or 9b (0.4 mmol) in DMSO (5 mL) was
added the corresponding 4-substituted benzaldehyde (10a or
10b, 0.4 mmol) and a 50% aqueous solution of KOH (1 mL)
as a base catalyst. The reaction mixture was stirred at room
temperature for 4 h. After this time, the precipitate was
collected by filtration, washed with cold methanol, and dried
to give the title compounds in 65% (2a) and 55% (2b) yields.
(E,E)-2,6-Bis[4-(N,N-dimethylamino)phenylethenyl]benzo-
thiazole (2a): Rf 0.34 (SiO2, EtOAc/hexanes = 1:2); mp
2,6-Bis{4-[N,N-bis(2-hydroxyethyl)amino]phenylethynyl}-
benzothiazole (1d): chromatography on Al2O3 (B II., neutral),
eluent CHCl3/MeOH=9:1; yield 66%; Rf 0.3 (Al2O3, CHCl3/
MeOH=9:1); mp 300ꢁC dec; 1H NMR (300 MHz, DMSO) δ
8.30 (d, J=1.6 Hz, 1H, H-7), 7.96 (d, J=8.5 Hz, 1H, H-4),
7.62 (dd, J = 8.5, 1.6 Hz, 1H, H-5), 7.47 (d, J = 8.8 Hz, 2H,
Har), 7.35 (d, J = 8.8 Hz, 2H, Har), 6.78 (d, J = 9.1 Hz, 2H,
Har), 6.72 (d, J = 8.8 Hz, 2H, Har), 4.83-4.77 (m, 4H, OH),
3.58-3.46 (m, 16H, 4ꢀCH2-O, 4ꢀN-CH2); 13C NMR (75
MHz, DMSO) δ 151.9, 149.6, 149.3, 148,3, 135.1, 133.6 (2ꢀ),
132.7 (2ꢀ), 129.7, 124.3, 122.7, 121.0, 111.6 (4ꢀ), 111.3, 107.3,
104.4, 92.6, 86.9, 81.8, 58.0 (4ꢀ), 53.1 (4ꢀ). Anal. Calcd for
C31H31N3O4S: C 68.74, H 5.77, N 7.76. Found: C 68.93, H
5.50, N 7.90.
General Procedure for the Preparation of Compounds 9a
and 9b (Suzuki Coupling). To a solution of corresponding
acetylene (7a or 7b, 1.0 mmol) in THF (4 mL) was added
catecholborane (0.13 mL, 1.2 mmol) under an atmosphere of
nitrogen, then the solution was heated to reflux. After 1.5 h
an additional amount of catecholborane (0.1 mL, 1.0 mmol)
was added and heating was continued for a further 2 h. After
cooling to rt, a solution of 6-iodo-2-methylbenzothiazole (8)
(0.17 g, 0.625 mmol) and Pd(PPh3)4 (260 mg, 0.23 mmol) in
THF (5 mL) was added dropwise, and the reaction mixture
was stirred at room temperature for 30 min. Consequently,
1
270-274 ꢁC; H NMR (300 MHz, CDCl3) δ 7.89 (d, J =
1.4 Hz, 1H, H-7), 7.86 (d, J=8.8 Hz, 1H, H-4), 7.58 (dd, J=
8.5, 1.6 Hz, 1H, H-5), 7.48 (d, J=8.8 Hz, 2H, Har), 7.44 (d,
J=8.5 Hz, 2H, Har), 7.42 (d, J=16.2 Hz, 1H, -CHd), 7.19
(d, J = 16.2 Hz, 1H, -CHd), 7.11 (d, J = 16.2 Hz, 1H,
-CHd), 6.99 (d, J=16.2 Hz, 1H, -CHd), 6.73 (d, J=8.8
Hz, 2H, Har), 6.72 (d, J = 8.8 Hz, 2H, Har), 3.03 (s, 6H,
NMe2), 3.00 (s, 6H, NMe2); 13C NMR (75 MHz, CDCl3) δ
167.7, 153.1, 151.2, 150.2, 137.9, 135.4, 134.9, 129.2, 128.9,
127.6, 125.6, 124.5, 123.8, 123.4, 122.3, 118.3, 117.4, 112.4,
112.1, 40.5, 40.2. Anal. Calcd for C27H27N3S: C 76.20, H
6.39, N 9.87. Found: C 76.33, H 6.16, N 9.91.
(E,E)-2,6-Bis[4-(N,N-diphenylamino)phenylethenyl]benzo-
thiazole (2b): Rf 0.58 (SiO2, EtOAc/hexanes = 1:2), mp
1
188-190 ꢁC; H NMR (300 MHz, CDCl3) δ 7.92 (d, J =
1.5 Hz, 1H, H-7), 7.90 (d, J=8.6 Hz, 1H, H-4), 7.58 (dd, J=
8.6, 1.6 Hz, 1H, H-5), 7.46-7.39 (m, 5H, Har, -CHdCH-),
7.32 -7.24 (m, 4H, Har), 7.16 - 7.02 (m, 23H, Har,
-CHdCH-); 13C NMR (75 MHz, CDCl3) δ 167.4, 153.2,
149.1, 147.5, 147.4, 147.0, 137.2, 135.1, 135.0, 131.2, 129.4,
129.3, 128.70, 128.66, 128.4, 127.4, 126.2, 125.2, 124.9, 124.6,
3066 J. Org. Chem. Vol. 75, No. 9, 2010