Electronic Structure Manipulation of (Benzothiazole)zinc Complexes
2-[2-(Benzyloxy)-5-(2,3,5,6-tetrafluoropyridyl)phenyl]benzothi-
TOF): calcd. for C18H9F4N2OS [M + H]+ 377.0372; found
azole (6a): 2-[2-(Benzyloxy)-5-(4,4,5,5-tetramethyl-1,3,2-dioxabor- 377.0395.
olan-2-yl)phenyl]benzothiazole (0.400 g, 0.903 mmol), 4-bromo-
2-[2-Hydroxy-5-(2,3,4,5,6-pentafluorophenyl)phenyl]benzothiazole
(7b): Prepared as described for 7a. Yield: 84%. H NMR (CDCl3,
300 MHz): δ = 7.23 (d, J = 8.7 Hz, 1 H), 7.45 (m, 2 H), 7.55 (m, 1
H), 7.76 (s, 1 H), 7.92 (d, J = 7.9 Hz, 1 H), 8.03 (d, J = 8.1 Hz, 1
H), 12.83 (s, 1 H) ppm. HRMS (ESI-TOF): calcd. for
C19H8F5NOS [M – H]+ 392.0168; found 392.0182.
2,3,5,6-tetrafluoropyridine (0.208 g, 0.903 mmol), tetrabutylammo-
nium chloride (0.025 g, 0.09 mmol), and [PdCl2(dppf)]·CH2Cl2
(0.037 g, 0.045 mmol) were added to a two-phase mixture of tolu-
ene (20 mL) and aqueous 1 m potassium carbonate solution
(20 mL). The reaction mixture was vigorously stirred at 90 °C un-
der argon for 16 h, then the organic layer was separated, and the
aqueous phase was extracted with toluene (3ϫ20 mL). The organic
layers were combined, washed with water (2ϫ20 mL), dried with
anhydrous sodium sulfate and the solvents evaporated. Purification
was achieved by silica gel column chromatography (ethyl acetate/
1
2-(2-Hydroxy-5-phenylphenyl)benzothiazole (7c): 2-[2-(Benzyloxy)-
5-phenylphenyl]benzothiazole (0.130 g, 0.30 mmol), 10% Pd/C
(0.130 g), and ammonium formate (0.019 g, 0.30 mmol) were added
to a mixture of THF (15 mL) and methanol (15 mL), and the reac-
tion mixture was heated at reflux for 3 h. After cooling, the mixture
was filtered, and the filtrate was concentrated. Purification was
achieved by silica gel column chromatography (chloroform) to give
7c as a white powder (0.084 g, 81%). 1H NMR (CDCl3, 300 MHz):
δ = 7.15 (d, J = 8.7 Hz, 1 H), 7.41 (m, 3 H), 7.50 (m, 2 H), 7.58
(m, 3 H), 7.84 (d, J = 2.4 Hz, 1 H), 7.87 (d, J = 8.1 Hz, 1 H), 7.96
(d, J = 8.3 Hz, 1 H), 12.56 (s, 1 H) ppm. HRMS (ESI-TOF): calcd.
for C19H14NOS [M + H]+ 304.0796; found 304.0791.
1
toluene, 1:25) to give 6a as a yellowish powder (0.341 g, 81%). H
NMR (CDCl3, 300 MHz): δ = 5.42 (s, 2 H), 7.25 (d, J = 8.9 Hz, 1
H), 7.42 (m, 4 H), 7.56 (m, J = 7.6 Hz, 2 H), 7.75 (dd, J = 2.4,
7.6 Hz, 1 H), 7.89 (d, J = 7.9 Hz, 1 H), 8.08 (d, J = 8.4 Hz, 1 H),
8.80 (s, 1 H) ppm. HRMS (ESI-TOF): calcd. for C25H15F4N2OS
[M + H]+ 467.0841; found 467.0856.
2-[2-(Benzyloxy)-5-(2,3,4,5,6-pentafluorophenyl)phenyl]benzothi-
azole (6b): Prepared as described for compound 6a. Yield: 79%. 1H
NMR (CDCl3, 300 MHz): δ = 5.41 (s, 2 H), 7.23 (d, J = 8.9 Hz, 1
H), 7.42 (m, 5 H), 7.56 (dd, J = 2.3, 7.6 Hz, 2 H), 7.76 (d, J =
7.7 Hz, 1 H), 7.89 (d, J = 7.9 Hz, 1 H), 8.08 (d, J = 8.4 Hz, 1 H),
8.80 (s, 1 H) ppm. HRMS (ESI-TOF): calcd. for C26H14F5NOS [M
+ H]+ 484.0794; found 484.0767.
2-{5-[4-(Dimethylamino)phenyl]-2-hydroxyphenyl}benzothiazole
1
(7d): Prepared as described for 7c. Yield: 82%. H NMR (CDCl3,
300 MHz): δ = 3.01 (s, 6 H), 6.84 (d, J = 8.9 Hz, 2 H), 7.15 (d, J
= 8.5 Hz, 1 H), 7.51 (m, 6 H), 7.83 (d, J = 2.2 Hz, 1 H), 7.93 (d, J
= 8.5 Hz, 1 H), 8.01 (d, J = 8.5 Hz, 1 H), 12.45 (s, 1 H) ppm.
HRMS (ESI-TOF): calcd. for C21H18N2OS [M + H]+ 347.1218;
found 347.1235.
2-[2-(Benzyloxy)-5-phenylphenyl]benzothiazole (6c): 2-[2-(Benz-
yloxy)-5-bromophenyl]benzothiazole (0.400 g, 1.01 mmol), pinacol
phenylboronate (0.206 g, 1.01 mmol), tetrabutylammonium chlo-
ride (0.028 g, 0.101 mmol), and [PdCl2(dppf)]·CH2Cl2 (0.041 g,
0.051 mmol) were added to a two-phase mixture of toluene (20 mL)
and aqueous 1 m potassium carbonate (20 mL). The reaction mix-
ture was vigorously stirred at 90 °C under argon for 24 h. The or-
ganic layer was separated, and the aqueous phase was extracted
with toluene (3 ϫ 20 mL). The organic layers were combined,
washed with water (2ϫ20 mL), and dried with anhydrous sodium
sulfate and the solvents evaporated. Purification was achieved by
silica gel column chromatography (ethyl acetate/toluene, 1:25) to
give 6c as a yellowish powder (0.310 g, 78%). 1H NMR (CDCl3,
300 MHz): δ = 5.33 (s, 2 H), 7.13 (d, J = 8.9 Hz, 1 H), 7.35 (m, 5
H), 7.45 (m, 4 H), 7.60 (m, 2 H), 7.66 (d, J = 7.1 Hz, 2 H), 7.86
(s, J = 8.1 Hz, 1 H), 8.10 (s, J = 8.1 Hz, 1 H), 8.92 (s, J = 2.4 Hz,
1 H) ppm. HRMS (ESI-TOF): calcd. for C26H19NOS [M + H]+
394.1266; found 394.1196.
Supporting Information (see footnote on the first page of this arti-
1
cle): H NMR spectra of all synthesized compounds and absorp-
tion spectra (in chloroform solution), DPV graphs, and FTIR spec-
tra of all zinc complexes.
Acknowledgments
Financial support from the Academy of Finland is greatly ac-
knowledged.
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2-{2-(Benzyloxy)-5-[4-(dimethylamino)phenyl]phenyl}benzothiazole
(6d): Prepared as described for compound 6c. Yield: 76 %. 1H
NMR (CDCl3, 300 MHz): δ = 5.33 (s, 2 H), 6.82 (d, J = 6.8 Hz, 2
H), 7.08 (d, J = 8.9 Hz, 1 H), 7.45 (m, 6 H), 7.59 (m, 4 H), 7.90
(d, J = 8.1 Hz, 1 H), 8.10 (d, J = 8.1 Hz, 1 H), 8.78 (d, J = 2.4 Hz,
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thiazole (0.320 g, 0.67 mmol) and 10% Pd/C (0.320 g) were added
to THF (25 mL), and aqueous ammonium formate (2.0 mL,
0.844 g, 13.4 mmol) was added. The reaction mixture was heated
at reflux for 3 h; then, after cooling, the mixture was filtered, and
the filtrate was concentrated. Purification was achieved by silica gel
column chromatography (ethyl acetate/toluene, 1:30) to give 7a as
a white powder (0.207 g, 82%). H NMR (CDCl3, 300 MHz): δ =
7.28 (d, J = 8.6 Hz, 1 H), 7.49 (m, 1 H), 7.58 (m, 2 H), 7.94 (m, 2
H), 8.04 (d, J = 8.3 Hz, 1 H), 13.00 (s, 1 H) ppm. HRMS (ESI-
1
Eur. J. Org. Chem. 2011, 6226–6232
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