Chemistry - A European Journal
10.1002/chem.202001148
FULL PAPER
+
CDCl
Hz, 1H), 7.21 (dd, J = 5.4, 3.9 Hz, 1H). C NMR (101 MHz, CDCl
60.1, 154.3, 134.2, 133.3, 130.8, 128.1, 123.4, 118.6, 113.7. HRMS
3
) δ 7.98 – 7.87 (m, 3H), 7.81 – 7.74 (m, 2H), 7.52 (dd, J = 5.4, 1.3
105.3, 60.0. HRMS (ESI): m/z for C11
H
11
N
2
S ; calcd. 219.0587, found
1
3
3
) δ
219.0587.
1
+
(
7 3
ESI): m/z for C11H N SNa ; calcd. 236.0253, found 236.0251. m.p.
4
-Cyanophenyl-5-methoxythiophenyldiazene (4i). Procedure B:
1
60 °C (decomposition).
i
PrMgCl ∙ LiCl
methoxythiophene (0.10 mL, 0.82 mmol, 1.0 eq.) in dry THF (0.5 mL),
stirred for 2.5 h, ZnBr in dry THF (0.45 mL, 0.45 mmol, 0.80 eq.) stirred
(0.85 mL,
1.1 mmol,
2.0 eq.),
2-bromo-5-
4
i
-(Trifluoromethyl)phenylazothiophene
(4e).
Procedure
A:
2
PrMgCl ∙ LiCl (3.2 mL, 4.2 mmol, 2.1 eq.) 2-bromothiophene (0.30 mL,
.0 mmol, 1.5 eq.), ZnBr in dry THF (1.6 mL, 1.6 mmol, 0.80 eq.), 4-
trifluoromethyl)benzenediazonium tetrafluoroborate (528 mg, 2.03 mmol,
.00 eq.), chromatography: cyclohexane/EtOAc; 30:1, orange solid
for 70 min, 4-cyanobenzenediazonium tetrafluoroborate (136 mg,
0.564 mmol, 1.00 eq.) in dry THF/NMP, 1:1 (1 mL), stirred at –20 °C for
3
2
(
1 h and at rt for another hour, chromatography: cyclohexane/EtOAc; 5:1,
1
1
dark red solid (66 mg, 48%). H NMR (400 MHz, CDCl
3
) δ 7.82 (d, J =
1
(
(
314 mg, 61%). H NMR (400 MHz, CDCl
3
) δ 7.99 – 7.91 (m, 2H), 7.88
8.7 Hz, 2H), 7.72 (d, J = 8.8 Hz, 2H), 7.64 (d, J = 4.5 Hz, 1H), 6.40 (d, J =
1
3
dd, J = 3.8, 1.3 Hz, 1H), 7.75 (d, J = 8.3 Hz, 2H), 7.49 (dd, J = 5.4, 1.3
4.5 Hz, 1H), 4.01 (s, 3H). C NMR (101 MHz, CDCl
3
) δ 173.6, 154.7,
1
3
Hz, 1H), 7.20 (dd, J = 5.4, 3.9 Hz, 1H). C NMR (101 MHz, CDCl
3
) δ
60.0, 154.0, 133.4, 131.9 (q, J = 32.6 Hz), 129.9, 127.8, 126.3 (q, J =
146.8, 135.6, 133.2, 122.9, 119.0, 112.3, 106.6, 60.3. HRMS (ESI): m/z
+
1
3
for C12
H
9
N
3
OSNa ; calcd. 266.0358, found 266.0359. m.p. 164 °C.
1
9
.8 Hz), 125.3, 123.0. F NMR (377 MHz, CDCl
3
) δ -62.5. HRMS (ESI):
+
m/z for C12
H
9
N
2
F
3
SNa ; calcd. 250.0409, found 250.0406. m.p. 114 °C.
4
i
-Cyanophenyl-5-methylthiophenyldiazene (4j). Procedure
B:
PrMgCl ∙ LiCl (3.0 mL, 3.9 mmol, 1.9 eq.), 2-bromo-5-methylthiophene
3
-Methoxyphenylazothiophene (4f).
A
dry Schlenk-tube under
(0.36 mL, 3.0 mmol, 1.5 eq.) in dry THF (2.0 mL), stirred at rt for 45 min,
i
nitrogen-atmosphere was charged with PrMgCl ∙ LiCl (1.3 mol/L in THF,
ZnBr
2
in
dry
THF
(1.6 mL,
1.6 mmol,
0.78 eq.),
4-
5
1
.0 mL, 6.5 mmol, 1.3 eq.) and 2-bromothiophene (0.50 mL, 5.2 mmol,
.0 eq.) was added dropwise at rt. After stirring for 45 min, the solution
cyanobenzenediazonium tetrafluoroborate (445 mg, 2.05 mmol, 1.00 eq.)
in dry THF/NMP, 4:1 (10 mL) at –50 °C. Stirred at –30 °C for 2 h,
was diluted with dry THF (4 mL), cooled to –20 °C and ZnBr
2
in dry THF
chromatography: cyclohexane/EtOAc/DCM; 7.5:1:1, dark red solid
1
(
1.0 mol/L, 2.8 mL, 2.8 mmol, 0.54 eq.) was added dropwise. After
(325 mg, 70%). H NMR (400 MHz, CDCl
3
) δ 7.88 (d, J = 8.6 Hz, 2H),
complete addition, the mixture was warmed to rt, stirred for 30 min,
diluted with dry THF (12 mL) and cooled to –60 °C afterwards. At this
temperature, 3-methoxybenzenediazonium tetrafluoroborate (1.34 g,
7.75 (d, J = 8.6 Hz, 2H), 7.70 (d, J = 3.9 Hz, 1H), 6.97 – 6.84 (m, 1H),
1
3
2.56 (d, J = 1.0 Hz, 3H). C NMR (101 MHz, CDCl
3
) δ 157.8, 154.5,
147.5, 135.2, 133.2, 126.9, 123.2, 118.8, 113.1, 17.0. HRMS (ESI): m/z
+
6
.03 mmol, 1.17 eq.) was added in small portions over a period of 30 min.
9 3
for C12H N SNa ; calcd. 250.0409, found 250.0384. m.p. 146 °C.
The deep red suspension was stirred at –60 °C for 4 h. At this
temperature, the reaction was quenched by the dropwise addition of half-
4
-(Trifluoromethyl)phenyl-5-methylthiophenyldiazene
(4k).
saturated aq. NH
diluted with Et O (25 mL) and water (10 mL). After phase separation, the
aqueous phase was extracted with Et O (3 x 20 mL) and the combined
organic phases were dried over MgSO , filtered and concentrated under
reduced pressure. The residue was purified by two consecutive flash
column chromatographies (cyclohexane/EtOAc; 1:1, then
4
Cl (10 mL) and was then slowly warmed to rt and
i
Procedure B: PrMgCl ∙ LiCl (2.8 mL, 3.6 mmol, 2.2 eq.), 2-bromo-5-
2
methylthiophene (0.36 mL, 3.0 mmol, 1.8 eq.) in dry THF (2.0 mL), a
2
stirred at rt for 1 h, ZnBr
in dry THF (1.6 mL, 1.6 mmol, 1.0 eq.), 4-
trifluoromethyl)benzene-diazonium tetrafluoroborate (442 mg, 1.68 mmol,
2
4
(
1
.00 eq.), chromatography: n-pentane/Et
2
O; 50:1), red crystalline solid
1
(
244 mg, 54%). H NMR (400 MHz, CDCl
3
) δ 7.93 – 7.86 (m, 2H), 7.77 –
cyclohexane/EtOAc; 10:1) to yield a red oil, which slowly crystallized to a
19
7
.65 (m, 3H), 6.92 – 6.86 (m, 1H), 2.56 (s, 3H). F NMR (377 MHz,
1
1
3
red solid after solvent evaporation while cooling to rt (225 mg, 20%). H
3 3
CDCl ) δ -62.5. C NMR (101 MHz, CDCl ) δ 157.9, 154.3, 146.5, 134.4,
NMR (400 MHz, CDCl
3
) δ 7.81 (dd, J = 3.9, 1.3 Hz, 1H), 7.50 (ddd, J =
1
31.4 (q, J = 32.3 Hz), 126.6, 126.4 (q, J = 3.8 Hz), 125.5, 122.9, 16.9.
7
7
.8, 1.7, 1.0 Hz, 1H), 7.45 – 7.36 (m, 3H), 7.17 (dd, J = 5.4, 3.8 Hz, 1H),
+
9 3 2
HRMS (ESI): m/z for C12H F N SNa ; calcd. 293.0331, found 293.0330.
1
3
.01 (ddd, J = 8.1, 2.5, 1.0 Hz, 1H), 3.89 (s, 3H). C NMR (101 MHz,
) δ 160.4, 160.4, 153.5, 131.9, 129.9, 128.7, 127.6, 117.9, 117.1,
m.p. 106 °C.
CDCl
3
+
1
2
05.9, 55.6. HRMS (ESI): m/z for C11
19.0589. m.p. 63 °C.
H
11
N
2
OS ; calcd. 219.0857, found
5
-Cyanothiophenyl-phenyldiazene (4l). To a solution of 2-bromo-5-
cyanothiophene (599 mg, 3.19 mmol, 1.04 eq.) in dry THF (2 mL) under
i
a
3
nitrogen-atmosphere at –60 °C, PrMgCl ∙ LiCl (1.3 mol/L in THF,
i
3
-Cyanophenylazothiophene (4g). Procedure A: PrMgCl ∙ LiCl (3.2 mL,
.2 mL, 4.2 mmol, 1.4 eq.) was added dropwise. After complete addition,
4
.2 mmol, 2.1 eq.), 2-bromothiophene (0.30 mL, 3.0 mmol, 1.5 eq.),
the red solution was stirred at –60 °C for 50 min and was then added
dropwise to suspension of benzenediazonium tetrafluoroborate
590 mg, 3.07 mmol, 1.00 eq.) in dry THF (4 mL) at –80 °C. The deep red
solution was stirred at this temperature for 30 min and was allowed to
warm to rt and stirred for 1.5 h. After diluting with Et O (5 mL) and
quenching the reaction with sat. aq. NH Cl (5 mL) and water (5 mL), the
phases were separated and the aqueous phase was extracted with Et
10 mL). After drying over MgSO , filtration and evaporation of the
solvents under reduced pressure, the residue was purified by two
consecutive flash column chromatographies (SiO , cyclohexane/EtOAc;
ZnBr
2
in
dry
THF
(1.6 mL,
1.6 mmol,
0.80 eq.),
3-
a
cyanobenzenediazonium tetrafluoroborate (437 mg, 2.01 mmol, 1.00 eq),
(
chromatography: cyclohexane/EtOAc; 5:1, orange solid (258 mg, 60%).
1
3
H NMR (400 MHz, CDCl ) δ 8.14 (t, J = 1.8 Hz, 1H), 8.08 (ddd, J = 8.0,
2
2
1
5
1
.0, 1.2 Hz, 1H), 7.88 (dd, J = 3.9, 1.3 Hz, 1H), 7.70 (dt, J = 7.7, 1.4 Hz,
H), 7.60 (t, J = 7.8 Hz, 1H), 7.50 (dd, J = 5.3, 1.3 Hz, 1H), 7.20 (dd, J =
4
2
O
1
3
.4, 3.9 Hz, 1H). C NMR (101 MHz, CDCl
3
) δ 159.9, 152.2, 133.8,
(
4
33.5, 130.3, 130.2, 128.0, 127.4, 126.1, 118.3, 113.5. HRMS (ESI): m/z
+
for C11
H
7
N
3
SNa ; calcd. 236.0253, found 236.0256. m.p. 126 °C.
2
1
1
0:1) to yield the product as a red solid (2 mg, 0.3%). H NMR (400 MHz,
i
5
-Methoxythiophenylazobenzene (4h). Procedure B: PrMgCl ∙ LiCl
3
CDCl ) δ 7.93 – 7.87 (m, 1H), 7.77 (d, J = 4.1 Hz, 1H), 7.65 (d, J = 4.1 Hz,
1
3
(
2.6 mL, 3.4 mmol, 2.0 eq.) 5-bromo-2-methoxythiophene (0.31 mL,
.6 mmol, 1.5 eq.) in dry THF (1.7 mL), stirred for 30 min, ZnBr in dry
THF (1.7 mL, 1.7 mmol, 1.0 eq.), benzenediazonium tetrafluoroborate
329 mg, 1.7 mmol, 1.00 eq.) in dry THF/NMP, 1:1 (3.4 mL), stirred at –
0 °C for 3.25 h, DCM extraction, two consecutive chromatographies:
0H), 7.57 – 7.49 (m, 2H). C NMR (101 MHz, CDCl
3
) δ 164.6, 151.7,
2
2
137.3, 132.7, 129.9, 129.5, 123.7, 114.5, 111.0. HRMS (ESI): m/z for
+
C
11
H
7
N
3
SNa ; calcd. 236.0253, found 236.0250. Melting point was not
(
determined due to limited amount of substance.
2
1
cyclohexane/EtOAc; 5:1, a red oil (87 mg, 24%). H NMR (400 MHz,
CDCl ) δ 7.81 – 7.75 (m, 2H), 7.54 (d, J = 4.4 Hz, 1H), 7.49 – 7.42 (m,
H), 7.41 – 7.34 (m, 1H), 6.33 (d, J = 4.4 Hz, 1H), 3.97 (s, 3H). C NMR
101 MHz, CDCl ) δ 171.1, 152.3, 147.3, 132.5, 129.8, 129.1, 122.5,
3
1
3
2
(
3
6
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