L. Pehlivan et al. / Tetrahedron 67 (2011) 1971e1976
1975
EIMS m/z (% relative abundance): 171 [M]þꢁ, 173 [M]þꢁ. IR nmax
2797, 2575, 1471, 751. Brown solid, 276 mg, 66%. Mp: 163 ꢀC.
:
H
H
slow
O
O
OH
N
O
N
N
9
9
9
SiH/Fe
4.1.4. 4-Bromoaniline hydrochloride (2d) [624e19e1]. 1H NMR: 7.74
(d, 2H, J¼8.8 Hz), 7.35 (2, 2H, J¼8.8 Hz). 13C NMR: 134.9, 131.6, 127.0,
124.2. EIMS m/z (% relative abundance): 171.9 [MþH]þ, 173.9
[MþH]þ. IR nmax: 2845, 2566, 1564, 1484, 1116, 1070, 1016, 815.
Beige solid, 335 mg, 80%. Mp: 190 ꢀC.
fast
NH2
9
OH
HN
SiH/Fe
N
N
H
N
H
9
9
9
9
9
9
4.1.5. 4-Chloroaniline hydrochloride (2e) [20,265e96e7]. 1H NMR:
d
132.2, 130.9, 127.0. EIMS m/z (% relative abundance): 127 [M]þꢁ, 129
[M]þꢁ (33%). IR nmax: 2808, 2602, 2571, 1488, 1092, 1010, 818. Brown
solid, 326 mg, >99%. Mp: 194 ꢀC.
Scheme 4. Formation of the didodecylamine.
¼7.57 (d, 2H, J¼8.5 Hz), 7.39 (d, 2H, J¼8.7 Hz). 13C NMR: 136.2,
The reaction was tested with an excess of TMDS in order to
observe an eventual presence of aldehyde in the reaction mixture,
which could react with the amine and form an oxime. Un-
fortunately the aldehyde was never observed.
4.1.6. 4-Cyanoaniline hydrochloride (2f) [2570e98e1]. 1H NMR:
3. Conclusion
(300 MHz,MeOD,
d
ppm):7.63(d, 2H, J¼8.5 Hz),7.10(d, 2H, J¼8.3 Hz).
13C NMR (100 MHz, MeOD,
d ppm): 137.8,135.2,124.3,111.6. EIMS m/z
We have developed a mild safe and efficient reduction pro-
cedure of the aromatic nitro function to amine. This method can
(% relative abundance): 118 [M]þꢁ. IR nmax (cmꢂ1): 2800, 2544, 2235,
1606, 1501, 833. Light brown solid, 285 mg, 92%. Mp: 168 ꢀC.
ꢀ
constitute an alternative to the Bechamp procedure, which pre-
sented several drawbacks detailed above. The good selectivity and
the easy reaction workup are an advantage since the method does
not require purification by chromatography or distillation and the
amine salts are pure (as judged by 1H NMR and 13C NMR).
4.1.7. Methyl-4-aminobenzoate hydrochloride (2g) [63,450e84e0]. 1H
NMR: 7.85 (d, 2H, J¼8.7 Hz), 6.64 (d, 2H, J¼8.8 Hz). 13C NMR: 170.2,
155.6, 133.3, 119.4, 115.2, 52.8. EIMS m/z (% relative abundance): 151
[M]þ 120 [M]þ ꢂOMe. IR nmax: 2860, 1720, 1703, 1316, 1109, 755.
ꢁ
ꢁ
White solid, 360 mg, 95%. Mp: 121 ꢀC.
4. Experimental section
4.1. General
4.1.8. 4-Aminobenzoic acid hydrochloride (2h) [22,669e27e8]. 1H
NMR: 8.10 (d, 2H, J¼8.3 Hz), 7.36 (d, 2H, J¼8.0 Hz). 13C NMR: 168.4,
137.1, 133.0, 132.2, 124.6. EIMS m/z (% relative abundance): 137
[M]þꢁ, 120 [M]þꢁꢂOH. IR nmax: 2892, 1576, 1521, 1507, 1245, 1110,
755, 741. White solid, 253 mg, 73%. Mp: 227 ꢀC.
All reagents were obtained commercially. Tetramethyldisilox-
ane, 97% (TMDS) was purchased from Acros, anhydrous THF from
Aldrich, acetylacetonate iron (Fe(acac)3), 99% from Strem Chemicals
and the nitro compounds were supplied from Acros, Sigmae
aldrich, and Alfa Aesar. All reagents and reactants were used
without further purification. All reactions were performed under
an inert atmosphere (argon) in a sealed tube except when the
reaction was performed on 3 g. In this case the reaction was per-
formed in a round bottom flask under inert atmosphere.
4.1.9. (4-Aminophenyl)-methanolhydrochloride(2i) [170,926e25e7].
1H NMR: 7.56 (d, 2H, J¼8.5 Hz), 7.40 (d, 2H, J¼8.7 Hz), 4.69 (1, 2H).
13C NMR: 141.6, 131.2, 130.5, 124.9, 75.4. EIMS m/z (þ% relative
abundance): 123 [M]þꢁ, 122 [MþꢁꢂHꢁ]þ, 106 [MþꢁꢂOHꢁ] . IR nmax
:
1587, 1563, 1538, 1330, 1168, 1015, 798. Black solid, 250 mg, 80%.
Mp: >250 ꢀC.
1H NMR and 13C NMR spectra were recorded on a BRUKER DRX
300 or BRUKER ALS 300 (except when mentioned) in MeOD and
measurementsaregiveninpartspermillion.Chemicalshiftsaregiven
in ppm. General procedure for the reduction of nitro compounds.
In a solution of nitro compound (2 mmol) in 0.6 mL of THF were
added Fe(acac)3 (10 mmol %, 70 mg) and TMDS (1.5 equiv or three
SieH, 0.53 mL). After 24 h (unless otherwise indicated) under
heating the reaction mixture was diluted in a minimum of Et2O
with a constant stirring. HCl (2 equiv) in Et2O was then added
dropwise. A precipitate appears; the mixture was stirred for 5 min
and filtered. It was washed several times with Et2O and dried to
afford the desired product as a hydrochloride salt.
4.1.10. 4-Nitroaniline hydrochloride (2j) [15,873e51e5]. 1H NMR:
8.21 (d, 2H, J¼8.7 Hz), 7.17 (d, 2H, J¼8.8 Hz). 13C NMR: 142.8, 141.6,
127.1, 123.6. EIMS m/z (% relative abundance): 139 [MþH]þ. IR nmax
:
2808, 2558,1595,1520,1347,1323, 1133, 1110, 860, 741. Brown solid,
331 mg, 95%. Mp: 156 ꢀC.
4.1.11. 3-Nitroaniline hydrochloride (2k) [33,240e96e9]. 1H NMR:
8.19 (d, 1H, J¼8.3 Hz), 8.12 (s, 1H), 7.71 (t, 1H, J¼8.2 Hz), 7.64 (d, 1H,
¼9.0 Hz). 13C NMR: 149.4, 134.2, 132.9, 131.5, 125.3, 119.5. EIMS m/z
(% relative abundance): 139 [MþH]þ. IR nmax: 2819, 2572, 1541,
1530, 1488, 1350, 1093, 732. Brown solid, 341 mg, 98%. Mp: 166 ꢀC.
4.1.1. Aniline hydrochloride (2a) [142e04e1]. 1H NMR: 7.55 (m, 3H),
4.1.12. 1,3-Diaminobenzene hydrochloride (2l) [541e69e5]. 1H NMR:
7.54 (t, 1H, J¼8.2 Hz), 7.23 (d, 2H, J¼8.2 Hz), 7.21 (s,1H). 13C NMR: (75
MHz, D2O) 132.8, 132.2, 124.9, 119.2. EIMS m/z (% relative abun-
dance): 109 [MþH]þ. IR nmax: 2806, 2584, 1528, 1487, 1100, 671.
Brown solid, 287 mg, >99%. Mp: >250 ꢀC.
7.41 (d, 2H, J¼6.8 Hz). 13C NMR (75 MHz, MeOD,
d ppm): 132.3,132.0,
130.9, 124.8. EIMS m/z (% relative abundance): 93 [M]þꢁ. IR nmax
:
2814, 2569, 1489, 740, 685. Brown solid, 258 mg, >99%. Mp: 189 ꢀC.
4.1.2. 3-Bromoaniline hydrochloride (2b) [56,967e17e0]. 1H NMR:
7.64 (d, 1H, J¼8.3 Hz), 7.56 (s, 1H), 7.45 (t, 1H, J¼8.0 Hz), 7.35 (d,
4.1.13. 4-Methoxyaniline hydrochloride (2m) [20,265e97e8]. 1H
NMR: 7.34 (d, 2H, J¼9.0 Hz), 7.10 (d, 2H, J¼9.1 Hz), 3.86 (s, 3H). 13C
NMR: 126.1, 117.2, 57.0. EIMS m/z (% relative abundance): 124
[MþH]þ. IR nmax: 2837, 2590, 1510, 1267, 1172, 1023, 835. Blue solid,
230 mg, 72%. Mp: 182 ꢀC.
1H¼8.0 Hz). 13C NMR:
¼134.0, 133.9, 133.7, 128.0, 124.6, 124.0. EIMS
d
m/z (% relative abundance): 171 [M]þꢁ,173 [M]þꢁ. IR nmax: 2869, 2563,
1553, 1472, 1071, 783, 672. Brown solid, 380 mg, >99%. Mp: 177 ꢀC.
4.1.3. 2-Bromoaniline hydrochloride (2c) [94,718e79e3]. 1H NMR:
7.79 (d, 1H, J¼7.8 Hz), 7.47 (m, 2H,), 7.37 (d, 1H, J¼8.0 Hz). 13C NMR
4.1.14. 2-Bromo-5-methoxyaniline hydrochloride (2n) [129,968e
11e2]. 1H NMR: 7.64 (d, 2H, J¼8.9 Hz), 7.00 (s, 1H), 6.94 (d, 2H,
(100 MHz, MeOD,
d ppm): 136.0, 132.8, 131.7, 131.5, 126.8, 118.4.