European Journal of Organic Chemistry
10.1002/ejoc.201800947
FULL PAPER
(
E,Z)-2-(tert-Butyl-NNO-azoxy)-3-(dimethylamino)but-2-enenitrile (6):
pyridazine oxide 10 (247 mg, 99%) as colorless crystals. An analytical
sample of pyridazine oxide 10 was obtained by recrystallization from
EtOH as colorless crystals, m.p. 214–215 °C. H NMR (500.1 MHz,
Colorless crystals (recrystallization from cyclohexane); m.p. 65–67 °C.
NMR spectra of enamine 6 show two E/Z isomers with respect to the
1
C=N bond. The (E)-6 : (Z)-6 isomer ratio was 1.8 : 1 in CDCl
3
.
[D
NH
CMe
or С-3), 143.4 (C-4), 154.5 (C-6) ppm. N NMR (36.1 MHz, [D ]acetone):
6
]acetone): δ = 1.49 (s, 9 H, CMe
3
), 2.41 (s, 3 H, Me), 6.95 (br., 2 H,
) ppm. C NMR (125.8 MHz, [D ]acetone): δ = 15.6 (Me), 25.8
), 61.4 (CMe ), 111.9 (CN), 114.5 (br., С-3 or С-5), 125.2 (br., С-5
13
2
6
1
(
3
3
Compound (E)-6: H NMR (500.1 MHz, CDCl
3
): δ = 1.37 (s, 9 H, CMe
3
),
) ppm. C NMR (125.8 MHz,
), 42.2 (NMe ), 58.9 (CMe ), 100.1 (br.,
1
4
13
2
.27 (s, 3 H, Me), 3.03 (s, 6 H, NMe
CDCl ): δ = 20.3 (Me), 25.7 (CMe
2
6
δ = –56 (N→O, ∆ν1/2 = 75 Hz), –59 (N→O, ∆ν1/2 = 90 Hz), –310 (NH
2
,
3
3
2
3
∆
ν
1/2 = 750 Hz) ppm. IR (KBr): ν = 3476 (w), 3303 (s), 2230 (w), 1615 (s),
C-2), 118.8 (CN), 156.8 (C-3) ppm.
–
1
553 (s), 1464 (s), 1413 (w), 1377 (m), 1304 (m), 1234 (w), 1205 (m) cm
1
+∙
1
14 6 2
. MS (EI, 70 eV): m/z = 250 [M ]. HRMS (ESI): m/z calcd for C10H N O
Compound (Z)-6: H NMR (500.1 MHz, CDCl
3
): δ = 1.37 (s, 9 H, CMe
3
),
+
13
[M + H] 251.1251; found 251.1250.
2
.23 (s, 3 H, Me), 3.22 (s, 6 H, NMe
CDCl ): δ = 18.3 (Me), 25.7 (CMe ), 42.9 (NMe
C-2), 117.3 (CN), 162.5 (C-3) ppm. N NMR (36.1 MHz, CDCl
2
) ppm. C NMR (125.8 MHz,
), 59.3 (CMe ), 102.0 (br.,
): δ = –51
N(O)=NtBu, ∆ν1/2 = 140 Hz] ppm. IR (KBr): ν = 2977 (m), 2936 (w), 2191
3
3
2
3
14
Solvolysis
enedinitrile (9) in CDCl
30 mg, 0.1 mmol) in CDCl
of
2,4-Bis(tert-butyl-NNO-azoxy)-3-methylpent-2-
; Isobutylene Trapping: A solution of dinitrile 9
(1 mL) was kept at 25 ºС for 24 h. Then the
3
[
3
–
1
(
3
(
s), 1589 (s), 1432 (s), 1373 (m), 1357 (s), 1293 (s), 1232 (m) cm .
+
volatile components were removed in vacuo and condensed in a cooled
trap (–196 °C). H NMR spectrum of the distillate showed characteristic
HRMS (ESI): m/z calcd for C10
18 4
H N O [M + H] 211.1553, found
1
211.1554.
2
signals of isobutylene [δ = 1.73 (s, 6 H, Me), 4.66 (s, 2 H, CH ) ppm].
1
Isobutylene was identified by comparison with authentic sample ( H
NMR).
Potassium Salt of 2,4-Bis(tert-butyl-NNO-azoxy)-3-methylpent-2-
enedinitrile (8): A solution of salt 5 (630 mg, 1.5 mmol) in МеОН (4 mL)
was put on a column packed with Amberlyst 15 (K form), (20.0 g) and
+
Solvolysis
of
2,4-Bis(tert-butyl-NNO-azoxy)-3-methylpent-2-
absorbed material was eluted with МеОН (200 mL) until potassium salt 8
enedinitrile (9) in Organic Solvents (General Procedure): A solution
of dinitrile 9 (200 mg, 0.66 mmol) in appropriate solvent was kept at 25
ºС until the starting material disappeared (TLC control). The yields and
reaction conditions are shown in Table 1. The reaction mixture was
concentrated under reduced pressure. The residue was purified by
preparative thin-layer chromatography (petroleum ether/ethyl acetate,
disappeared in the eluate (TLC control). The eluate was concentrated
under reduced pressure, the residue was washed with CH
2 2
Cl (50 mL)
and air-dried to give potassium salt 8 (375 mg, 72%) as a yellow solid,
1
m.p. 231–233 °C (decomp.). H NMR (600.1 MHz, [D
4
]methanol): δ =
), 2.22 (s, 3 H, Me) ppm. C NMR (150.8 MHz,
]methanol): δ = 21.1 (Me), 27.2 (CMe ), 59.0 (CMe ), 101.3 (br., C-2
and C-4), 121.3 (CN), 143.1 (br., C-3) ppm. N NMR (43.4 MHz,
]methanol): δ = –46 [N(O)=NtBu, ∆ν1/2 = 260 Hz] ppm. IR (KBr): ν =
973 (m), 2924 (w), 2205 (m), 2178 (s), 1541 (s), 1438 (s), 1360 (w),
13
1.32 (s, 9 H, CMe
3
[
D
4
3
3
14
4:1) to give pyridazine oxide 10, furan 12, triazepine 13 and zwitter-ionic
1
cycle 14. The pyridazine oxide 10 obtained was identical (m.p., TLC,
NMR) to compound 10 prepared by the procedure described above.
H
[D
4
2
1
–1
305 (w), 1275 (m), 1225 (m) cm . Elemental analysis: calcd. for
K: C, 48.82; H, 6.15; N, 24.40; found C, 48.73; H, 6.19; N,
C H N O
14 21 8 2
5-Amino-4-(tert-butyl-NNO-azoxy)-3-methyl-2-furonitrile
Colorless crystals; m.p. 173–174 °C. H NMR (500.1 MHz, CDCl
(12):
): δ =
1
23.91.
3
13
1
(
.42 (s, 9 H, CMe
125.8 MHz, CDCl
С-4), 112.1 (CN), 113.4 (С-3 or C-2), 132.7 (С-2 or C-3), 155.4 (C-5)
3
), 2.38 (s, 3 H, Me), 6.21 (br., 2 H, NH
2
) ppm. C NMR
3
): δ = 11.6 (Me), 26.2 (CMe ), 58.7 (CMe
3
3
), 111.8 (br.,
2
,4-Bis(tert-butyl-NNO-azoxy)-3-methylpent-2-enedinitrile
O (35 mL) was acidified to рН ≈
with aqueous 1 N HCl at 0–5 °С and then extracted with pentane (3 ×
0 mL). The combined organic extracts were dried (Na SO ) at 0–5 °С
(9):
A
solution of salt 5 (420 mg, 1 mmol) in H
5
1
2
14
ppm. N NMR (36.1 MHz, CDCl
318 (NH , ∆ν1/2 = 650 Hz) ppm. IR (KBr): ν = 3436 (s), 3296 (s), 2971
w), 2975 (w), 2214 (s), 1655 (s), 1593 (m), 1449 (s), 1386 (w), 1346 (w),
3
): δ = –56 [N(O)=NtBu, ∆ν1/2 = 110 Hz],
–
(
2
2
4
for 15 min and concentrated under reduced pressure at 20 °С to give
dinitrile 9 (270 mg, 88%) as yellow viscous oil. Two E/Z isomers with
–1
+
14 4 2
1305 (w), 1228 (m) cm . HRMS (ESI): m/z calcd for C10H N O [M + H]
223.1190; found 223.1191.
3
respect to the C=C bond [the isomer ratio (E)-9/(Z)-9 = 4:1 (in CDCl )].
1
2-tert-Butyl-6-(tert-butyl-NNO-azoxy)-5-methyl-7-oxo-2,7-dihydro-1H-
,2,3-triazepine-4-carbonitrile (13): Yellow crystals; m.p. 194–196 °C
Compound (E)-9: H NMR (600.1 MHz, CDCl
3
): δ = 1.35 (s, 9 H, CMe
3
),
13
1
1
.42 (s, 9 H, CMe
150.9 MHz, CDCl
CMe ), 61.4 (CMe
3
), 2.43 (s, 3 H, Me), 7.30 (s, 1 H, H-4) ppm. C NMR
): δ = 18.5 (Me), 25.1 (CMe ), 25.3 (CMe ), 61.0
), 68.7 (br., C-4), 110.7 (CN), 110.9 (CN), 128.0 (br.,
1
(
3 3
decomp.). H NMR (500.1 MHz, CDCl ): δ = 1.32 (s, 9 H, CMe ), 1.45 [s,
(
(
3
3
3
13
9
H, N(O)=NCMe
3
], 2.23 (s, 3 H, Me), 8.83 (br., 1 H, NH) ppm. C NMR
): δ = 16.8 (Me), 25.5 [N(O)=NCMe ], 25.8 (CMe ),
], 62.4 (CMe ), 113.7 (CN), 129.7 (C-4 or C-5 or C-6),
138.2 (C-4 or C-5 or C-6), 147.0 (C-4 or C-5 or C-6), 163.9 (C-7) ppm.
3
3
(125.8 MHz, CDCl
3
3
3
C-2), 141.3 (C-3) ppm.
6
0.7 [N(O)=NCMe
3
3
1
Compound (Z)-9: H NMR (600.1 MHz, CDCl
3
): δ = 1.38 (s, 9 H, CMe
3
),
1
4
13
N NMR (36.1 MHz, CDCl
3
): δ = –57 [N(O)=NtBu, ∆ν1/2 = 230 Hz] ppm.
1
.42 (s, 9 H, CMe
150.9 MHz, CDCl
CMe ), 61.3 (CMe
3
), 2.30 (s, 3 H, Me), 6.10 (s, 1 H, H-4) ppm. C NMR
): δ = 14.9 (Me), 25.1 (CMe ), 25.3 (CMe ), 61.2
), 73.3 (br., C-4), 110.1 (CN), 110.4 (CN), 128.4 (br.,
IR (KBr): ν = 3425 (s), 3190 (w), 3091 (m), 2971 (w), 1699 (s), 1627 (w),
(
(
3
3
3
–
1
1
495 (m), 1450 (w), 1368 (w), 1311 (m), 1212 (m) cm . HRMS (ESI):
3
3
+
14
22 6 2
m/z calcd for C14H N O [M + H] 307.1877; found 307.1876.
C-2), 141.8 (C-3) ppm. N NMR (43.4 MHz, CDCl
1/2 = 140 Hz] ppm.
3
): δ = –62 [N(O)=NtBu,
∆ν
1-(tert-Butylamino)-4-(tert-butyl-NNO-azoxy)-6-cyano-5-methyl-
pyridazin-1-ium-3-olate (14): Colorless crystals; m.p. 218–222 °C
6
2
-Amino-5-(tert-butyl-NNO-azoxy)-4-methylpyridazine-3-carbonitrile
-oxide (10): Silica gel 60 (Merck; 40–63 μm; 10.0 g) was added to a
1
(
[
decomp.). H NMR (500.1 MHz, CDCl
s, 9 H, N(O)=NCMe ], 2.34 (s, 3 H, Me), 6.56 (br., 1 H, NH) ppm.
NMR (125.8 MHz, CDCl ): δ = 13.8 (Me), 25.7 [N(O)=NCMe ], 28.1
NHCMe ), 61.2 [N(O)=NCMe ], 61.5 (NHCMe ), 110.4 (CN), 119.3 (C-4
or C-5 or C-6), 135.7 (C-4 or C-5 or C-6), 140.7 (C-4 or C-5 or C-6),
3 3
): δ = 1.34 (s, 9 H, NHCMe ), 1.49
13
3
C
solution of salt 5 (420 mg, 1 mmol) in MeOH (20 mL), and the solvent
was removed under reduced pressure. The residue was kept at 25 °C for
1
3
3
(
3
3
3
h, then it was transferred onto a Schott filter, and eluted with MeOH
(100 mL). The eluate was concentrated under reduced pressure to give
14
3
160.9 (C-3) ppm. N NMR (36.1 MHz, CDCl ): δ = –61 [N(O)=NtBu, ∆ν1/2
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