6692
M. Ezawa et al. / Tetrahedron Letters 56 (2015) 6689–6692
~
m = 1244,
1.82–1.90 (m, 2H), 3.12 (quin, J = 6.7 Hz, 1H), 3.77 (s, 2H), 7.21–7.33 (m, 5H)
N-Isopropyl-p-methoxybenzylamine: Yield: 61%; oil; IR (neat):
ppm; 13C NMR (100 MHz, CDCl3): d = 24.1, 33.1, 52.7, 59.1, 126.8, 128.2, 128.3,
3311 cmÀ1 1H NMR (400 MHz, CDCl3): d = 1.10 (d, J = 6.3 Hz, 6H), 2.86 (sep,
;
140.7 ppm; HRMS (ESI): calcd for C12H18N [M+H]+ 176.1434, found 176.1431.
J = 6.3 Hz, 1H), 3.73 (s, 2H), 3.79 (s, 3H), 6.86 (d, J = 8.6 Hz, 2H), 7.25 (d, J = 8.6 Hz,
2H) ppm; 13C NMR (100 MHz, CDCl3): d = 22.8, 48.0, 50.9, 55.2, 113.8, 129.3,
132.6, 158.5 ppm; HRMS (ESI): calcd for C11H18ON [M+H]+ 180.1383, found
180.1378.
À1
N-Ethylbenzylamine: (Commercial) Yield: 52%; oil; IR (neat):
= 3281 cm
;
1H
~
m
NMR (400 MHz, CDCl3): d = 1.14 (t, J = 7.2 Hz, 3H), 2.69 (q, J = 7.2 Hz, 2H), 3.79 (s,
2H), 7.22–7.33 (m, 5H) ppm; 13C NMR (100 MHz, CDCl3): d = 15.3, 43.6, 53.9,
126.9, 128.1, 128.4, 140.4 ppm.
À1
1H
~
m
N-Isopropyl-
a
-methylbenzylamine: Yield: 77%; oil; IR (neat):
= 3325 cm
;
À1
N-Isopropyl-p-chlorobenzylamine: Yield: 84%; oil; IR (neat):
m
= 3315 cm
;
1H
NMR (400 MHz, CDCl3): d = 0.99–1.03 (m, 6H), 1.34 (d, J = 6.5 Hz, 3H), 2.62 (sep,
J = 6.3 Hz, 1H), 3.89 (q, J = 6.5 Hz, 1H), 7.21–7.35 (m, 5H) ppm; 13C NMR
(100 MHz, CDCl3): d = 22.0, 24.0, 24.8, 45.5, 55.1, 126.4, 126.8, 128.4, 145.8 ppm;
HRMS (ESI): calcd for C11H18N [M+H]+ 164.1434, found 164.1434.
~
NMR (400 MHz, CDCl3): d = 1.09 (d, J = 6.3 Hz, 6H), 2.84 (sep, J = 6.3 Hz, 1H), 3.75
(s, 2H), 7.24–7.30 (m, 4H) ppm; 13C NMR (100 MHz, CDCl3): d = 22.8, 48.1, 50.7,
128.4, 129.4, 132.5, 139.1 ppm; HRMS (ESI): calcd for
184.0888, found 184.0887.
N-Isopropyl-m-chlorobenzylamine: Yield: 82%; oil; IR (neat):
C
10H15NCl [M+H]+
À1
1H
~
m
N-Isopropyl-2-phenylethylamine: Yield: 70%; oil; IR (neat):
= 3298 cm
;
À1
~
m
= 3313 cm
;
1H
NMR (400 MHz, CDCl3): d = 1.05 (d, J = 6.1 Hz, 6H), 2.78–2.90 (m, 5H), 7.19–7.23
(m, 3H), 7.28–7.32 (m, 2H) ppm; 13C NMR (100 MHz, CDCl3): d = 22.9, 36.6, 48.5,
48.8, 126.1, 128.4, 128.7, 140.1 ppm; HRMS (ESI): calcd for C11H18N [M+H]+
164.1434, found 164.1432.
NMR (400 MHz, CDCl3): d = 1.09 (d, J = 6.3 Hz, 6H), 2.84 (heptet, J = 6.3 Hz, 1H),
3.76 (s, 2H), 7.18–7.33 (m, 4H) ppm; 13C NMR (100 MHz, CDCl3): d = 22.9, 48.1,
51.0, 123.2, 126.9, 128.1, 129.6, 134.2, 143.0 ppm; HRMS (ESI): calcd for
À1
10H15NCl [M+H]+ 184.0888, found 184.0886.
N-Isopropyl-3-phenylpropylamine: Yield: 65%; oil; IR (neat):
= 3302 cm
;
1H
~
m
C
À1
~
m
N-Isopropyl-o-chlorobenzylamine: Yield: 87%; oil; IR (neat):
= 3310 cm
;
1H
NMR (400 MHz, CDCl3): d = 1.04 (d, J = 6.3 Hz, 6H), 1.81 (quin, J = 7.7 Hz, 2H),
2.61–2.68 (m, 4H), 2.77 (sep, J = 6.3 Hz, 1H), 7.16–7.20 (m, 3H), 7.26–7.31 (m,
2H) ppm; 13C NMR (100 MHz, CDCl3): d = 23.0, 32.0, 33.8, 47.1, 48.7, 125.7,
128.3, 128.4, 142.2 ppm; HRMS (ESI): calcd for C12H20N [M+H]+ 178.1590, found
178.1589.
NMR (400 MHz, CDCl3): d = 1.09 (d, J = 6.3 Hz, 6H), 2.83 (sep, J = 6.1 Hz, 1H), 3.87
(s, 2H), 7.16–7.25 (m, 2H), 7.34–7.40 (m, 2H) ppm; 13C NMR (100 MHz, CDCl3):
d = 22.9, 47.9, 49.0, 126.8, 128.2, 129.5, 130.2, 133.7, 138.0, ppm; HRMS (ESI):
calcd for C10H15NCl [M+H]+ 184.0888, found 184.0885.
~
N-Isopropyl-p-nitrobenzylamine: Yield: 88%; oil; IR (neat):
m
= 1173, 1341,
Bis(4-bromobenzyl)amine: (Commercial) Yield 64% and 47%; oil; IR (neat):
3330 cmÀ1
;
1H NMR (400 MHz, CDCl3): d = 1.12 (d, J = 6.3 Hz, 6H), 2.86 (sep,
= 3336 cm
;
1H NMR (400 MHz, CDCl3): d = 3.74 (s, 4H), 7.21 (d, J = 8.3 Hz,
À1
~
m
J = 6.3 Hz, 1H), 3.90 (s, 2H), 7.52 (d, J = 8.2 Hz 2H), 8.17 (d, J = 8.6 Hz, 2H) ppm;
13C NMR (100 MHz, CDCl3): d = 22.7, 48.3, 50.1, 123.4, 128.6, 146.8, 148.4 ppm;
HRMS (ESI): calcd for C10H15O2N2 [M+H]+ 195.1128, found 195.1125.
~
4H), 7.45 (d, J = 8.5 Hz, 4H) ppm; 13C NMR (100 MHz, CDCl3): d = 52.3, 120.8,
129.8, 131.5, 139.1 ppm.
N-Isopropyl-p-ethoxycarbonylbenzylamine: Yield: 79%; oil; IR (neat):
m
= 1714,
9. Typical experimental procedure
for oxidation
of
N,N-diisopropyl-p-
3312 cmÀ1
;
1H NMR (400 MHz, CDCl3): d = 1.10 (d, J = 6.1 Hz, 6H), 1.40 (t,
bromobenzylamine: To a solution of N,N-diisopropyl-p-bromobenzylamine
J = 7.3 Hz, 3H) 2.85 (sep, J = 6.1 Hz, 1H), 3.84 (s, 2H), 4.37 (q, J = 7.0 Hz, 2H) 7.40
(d, J = 8.4 Hz, 2H), 8.00 (d, J = 8.2 Hz, 2H) ppm; 13C NMR (100 MHz, CDCl3):
d = 14.3, 22.9, 48.2, 51.2, 60.8, 127.9, 129.0, 129.7, 146.0, 166.5 ppm; HRMS
(ESI): calcd for C13H20O2N [M+H]+ 222.1489, found 222.1484.
(0.5 mmol, 135.1 mg) in CHCl3 (5.0 mL) was added ABBX (1.5 mmol, 577.4 mg)
and K2CO3 (1.0 mmol, 138.2 mg) at room temperature, and the mixture was
stirred for 12 h. The reaction mixture was quenched by satd aq Na2SO3 (10 mL),
and extracted with Et2O (20 mL Â 3). Then, the organic layer was washed with
brine (20 mL), and dried over Na2SO4. After removal of the solvent under
reduced pressure, the residue was purified by short column chromatography on
neutral silica gel (hexane/AcOEt = 9:1) to afford p-bromobenzaldehyde in 82%
yield (76.1 mg).
À1
1H
~
N-Isopropyl-p-methylbenzylamine: Yield: 71%; oil; IR (neat):
m
= 3308 cm
;
NMR (400 MHz, CDCl3): d = 1.09 (d, J = 6.3 Hz, 6H), 2.33 (s, 3H) 2.85 (heptet,
J = 6.3 Hz, 1H), 3.75 (s, 2H), 7.13 (d, J = 7.9 Hz, 2H), 7.21 (d, J = 7.9 Hz, 2H) ppm;
13C NMR (100 MHz, CDCl3): d = 21.0, 22.8, 47.9, 51.2, 128.1, 129.1, 136.4,
137.4 ppm; HRMS (ESI): calcd for C11H18N [M+H]+ 164.1434, found 164.1428.