F. Cumine et al. / Tetrahedron xxx (2018) 1e7
5
ꢀ
flask at 0 C and the mixture was stirred and allowed to warm from
0
NaH (specified amount) and reduction substrate (0.33 mmol). The
ꢀ
C to room temperature for 2 h. Then, NaH was quenched by
isopropanol (3 mL) and water. The mixture was extracted with
tube was sealed, taken outside the glovebox and the mixture was
ꢀ
stirred for 18 h at room temperature under UV light OR at 130 C
EtOAc (4 ꢁ 20 mL), the combined organic extracts were washed
without UV light, as indicated. The mixture was quenched at room
once with water, dried over Na
2
SO
4
, filtered and concentrated to
temperature with water (30 mL), extracted with Et
the combined organic extracts were washed with water
SO , filtered and concentrated. Crude
2
O (2 ꢁ 25 mL),
afford N,N-diphenyl-piperidone 25 as a brown powder (470 mg,
ꢀ
1
.76 mmol, 97%). M. Pt. 90e92 C
d
H
(400 MHz, CDCl
3
): 1.90 (2H, m,
), 3.67 (2H, t,
(3 ꢁ 25 mL), dried over Na
2
4
CH
J ¼ 6.4 Hz, CH
ArH), 7.28e7.32 (4H, m, ArH).
8.9, 118.7, 122.2, 128.8, 143.2, 168.7. IR (NEAT)
2
), 2.01 (2H, m, CH
2
), 2.60 (2H, t, J ¼ 6.4 Hz, CH
2
products were purified by column chromatography on silica eluting
with EtOAc (5%) in hexane, for isolation of azobenzene 17, azox-
ybenzene 16 and diphenylamine 28, and with EtOAc (20%) in
hexane for isolation of hydrazine 18.
2
), 7.03 (2H, tt, J ¼ 7.2, 1.2 Hz, ArH), 7.11e7.13 (4H, m,
d
C
(100 MHz, CDCl
3
): 20.6, 23.4, 32.8,
ꢂ1
4
7
n
(cm ) ¼ 642, 690,
41, 947, 1302, 1325, 1406, 1491, 1585, 1655, 2357, 2936. HRMS (CI):
þ
calcd for C17
H19ON
2
([MþH] ): 267.1492, found: 267.1493.
4.3.1. Reduction of nitrobenzene 15
4
.3.1.1. Table 1, entry 1. Nitrobenzene 15 (41 mg, 0.33 mmol) was
4.2.3. 1-(diphenylamino)piperidine (26)
treated with DMAP salt 9 (540.2 mg, 1.0 mmol) and sodium hydride
48.0 mg, 2.0 mmol) in dry DMF (5 mL) at room temperature under
UV light for 18 h to afford, following work-up and chromatography,
(
1
,2-diphenylhydrazine 18 as a white solid (25.8 mg, 0.14 mmol,
ꢀ
ꢀ
7
84%). M.Pt. 123e125 C (lit. 124e125 C)
H 3
d (400 MHz, CDCl ): 5.62
(2H, bs, NH), 6.87e6.82 (6H, m, ArH), 7.24e7.19 (4H, m, ArH).
d
C
(
100 MHz, CDCl
3
): 112.5, 120.1, 129.5, 149.0. IR (NEAT)
n
ꢂ1
LiAlH
240 mg, 0.90 mmol) and dry diethyl ether (20 mL) were added to a
00 mL 3-necked round-bottomed flask under argon. The reaction
4
(45 mg, 1.19 mmol), N,N-diphenyl-piperidone 25
(cm ) ¼ 689, 775, 927, 1072, 1454, 1483. m/z (NSI) calcd for
þ
(
1
C
H
12 13
N
2
[MþH] : 185.1073, found: 185.1073.
ꢀ
mixture was refluxed at 35 C overnight. Then LiAlH
4
was
4
.3.1.2. Table 1, entry 2. Nitrobenzene 15 (41 mg, 0.33 mmol) was
cautiously quenched by addition of isopropanol and then water.
The precipitate was filtered off and the filtrate was washed twice
with water, dried over Na SO , filtered and concentrated to afford
2 4
the crude product. Purification was made by column chrom-
treated with DMAP salt 9 (356.6 mg, 0.66 mmol) and sodium hy-
dride (31.7 mg, 1.32 mmol) in dry DMF (5 mL) at room temperature
under UV light for 18 h to afford 1,2-diphenylhydrazine 18 (17.9 mg,
0
.10 mmol, 59%), NMR spectra details as above, and azobenzene 17
atography on silica eluting with EtOAc (2%) in hexane to afford 1-
ꢀ
as an orange solid (6.9 mg, 0.04 mmol, 23%). M. Pt. 65e66 C (lit.
N,N-diphenylaminopiperidine 26
a
white solid (170 mg,
(400 MHz, CDCl ): 1.33 (2H,
), 2.69 (4H,
), 7.04-7-09 (6H, m, ArH), 7.28e7.34 (4H, m,
ꢀ
2g
6
5e66 C).
d
H
(400 MHz, CDCl
(100 MHz, CDCl
(cm ) ¼ 688, 775, 927, 1072, 1454, 1483. m/z (EI)
12 10 2
C H N [M]: 182.1.
3
): 7.55e7.46 (6H, m, ArH),
ꢀ
0
.67 mmol, 75%). M. Pt. 55e57 C
d
H
3
7.94e7.90 (4H, m, ArH).
d
C
3
): 123.0, 129.2, 131.1,
quint. J ¼ 6.0 Hz, CH
2
), 1.75 (4H, quint., J ¼ 5.6 Hz, 2 ꢁ CH
2
ꢂ1
152.8. IR (NEAT) n
t, J ¼ 5.2 Hz, 2 ꢁ CH
2
ArH).
IR (NEAT)
d
C
(100 MHz, CDCl
3
): 23.2, 26.1, 52.6, 121.7, 122.0, 128.4, 143.9.
ꢂ1
n
(cm ) ¼ 690, 748, 866, 1314, 1443, 1487, 1585, 2938.
þ
4.3.1.3. Table 1, entry 3. Nitrobenzene 15 (41 mg, 0.33 mmol) was
treated with DMAP salt 9 (267.4 mg, 0.50 mmol) and sodium hy-
dride (23.8 mg, 0.99 mmol) in dry DMF (5 mL) at room temperature
under UV light for 18 h to afford azobenzene 17 (20.4 mg,
HRMS (CI): calcd. for C17
21
H N
2
([MþH] ): 253.1699, found:
2
53.1702.
.2.4. Bipiperidine (27)5b
4
0
.11 mmol, 68%). NMR spectra details as above.
4.3.1.4. Table 1, entry 4. Nitrobenzene 15 (41 mg, 0.33 mmol) was
treated with DMAP salt 9 (178.3 mg, 0.33 mmol) and sodium hy-
dride (15.8 mg, 0.66 mmol) in dry DMF (5 mL) at room temperature
under UV light for 18 h to afford azoxybenzene 16 as a yellow oil
Piperidine (2.5 g, 29.4 mmol), NaOH (2.35 g, 58.8 mmol), H
15 mL) and AgNO (250.0 mg, 1.47 mmol). were added to a 100 mL
round-bottomed flask at 0 C. After stirring for 15 min, a solution of
2
O
(
19.6 mg, 0.10 mmol, 60%).
d
H
(400 MHz, CDCl
3
): 7.39 (1H, tt, J ¼ 6.8,
(
3
ꢀ
1.2 Hz, ArH), 7.59e7.47 (5H, m, ArH), 8.18e8.15 (2H, m, ArH),
8
.33e8.30 (2H, m, ArH).
129.0, 129.8, 131.7, 144.2, 148.5. IR (NEAT)
301, 1441, 1476. m/z (NSI) calcd for C12
d
C
(100 MHz, CDCl
3
): 122.5, 125.7, 128.9,
Na
2
S
2
O
8
(6.99 g, 29.4 mmol) in H
2
O (20 mL) was added to the
ꢂ1
ꢀ
n
(cm ) ¼ 686, 764, 1277,
mixture which was then stirred from 0 C to room temperature for
þ
1
H
11
N
2
O [MþH] : 199.0866,
4
h. The mixture was extracted with EtOAc (3 ꢁ 30 mL), the com-
found: 199.0865. A trace amount of azobenzene 17 was also
observed in the H NMR spectra of the crude product.
bined organic extracts were dried over Na SO , filtered and
2
4
1
concentrated. The crude product was purified by column chroma-
tography on silica eluting with EtOAc (10%) in hexane to afford
bipiperidine 27 as a yellow oil (1.29 g, 7.64 mmol, 52%).
400 MHz, CDCl ): 1.34 (4H, m, CH ), 1.59 (8H, m, CH ), 2.66 (8H, t,
(100 MHz, CDCl ): 24.9, 26.7, 49.3. IR (NEAT)
d
H
4.3.1.5. Table 1, entry 5. Nitrobenzene 15 (40.6 mg, 0.33 mmol) was
treated with DMAP salt 9 (540.2 mg, 1.0 mmol) and sodium hydride
(48.0 mg, 2.0 mmol) in dry DMF (5 mL) at 130 C for 18 h to afford
azobenzene 17 (3.3 mg, 0.02 mmol, 11%), 1,2-diphenylhydrazine 18
(13.7 mg, 0.07 mmol, 45%), NMR spectra details as above, and ani-
line 19 (1.2 mg, 0.01 mmol, 4%), yields were quantified by use of
(
3
2
2
ꢀ
J ¼ 5.2 Hz, CH
2
).
d
C
3
n
ꢂ1
(
cm ) ¼ 875, 1442, 2731, 2800, 2852, 2930. m/z (EI) C10
H
20
N
2
[M]:
168.1.
4.3. General reduction procedures
1,3,5-trimethoxybenzene as an internal NMR standard. Observed
1
H NMR for aniline 19:
H 3 2
d (400 MHz, CDCl ): 3.05 (2H, s, NH ),
Inside a glovebox under nitrogen atmosphere, a pressure tube
was loaded with DMAP salt 9 (specified amount), dry DMF (5 mL),
6.70e6.67 (2H, m, ArH), 6.76 (1H, t, J ¼ 7.6 Hz, ArH), 7.17e7.13 (2H,
m, ArH); data were in accordance with literature.
Please cite this article in press as: Cumine F, et al., Reduction of nitroarenes, azoarenes and hydrazine derivatives by an organic super electron
donor, Tetrahedron (2018), https://doi.org/10.1016/j.tet.2018.04.069