LETTER
Clean and Simple Chemoselective Reduction of Imines to Amines
1487
(6) (a) Perissamy, M.; Devasagayaraj, A.; Satyanarayana, N.;
H), 7.90 (d, J = 8.25 Hz, 2 H). 13C NMR (75 MHz, CDCl ):
3
Narayana, C. Synth. Commun. 1989, 19, 565. (b) Saxena, I.;
Borah, R.; Sarma, J. C. J. Chem. Soc., Perkin Trans. 1 2000,
d = 27.0, 48.2, 113.1, 118.1, 121.1, 127.5, 128.9, 129.1,
129.5, 136.3, 145.4, 147.9, 197.8. Anal. Calcd for
5
1
4
03. (c) Itsuno, S.; Sakurai, Y.; Ito, K. Chem. Commun.
988, 995. (d) Bhattacharyya, S. J. Org. Chem. 1995, 60,
928. (e) Verardo, G.; Giumanini, A. G.; Strazzolini, P.;
C H NO: C, 79.97; H, 6.71; N, 6.22. Found: C, 79.96; H,
6.73; N, 6.22. N-Phenyl-4-carboxybenzylamine (2b):
1
5
15
Yield: 99%; white solid; mp 196–198 °C. IR (KBr): 3412,
–
1
Poiana, M. Synthesis 1993, 121. (f) Varma, R. S.; Dahiya,
R. Tetrahedron 1998, 54, 6293.
3360, 3050, 2933, 2836, 1684, 1603, 1317, 1291, 760 cm .
1
H NMR (300 MHz, DMSO-d ): d = 3.64 (br s, 1 H), 4.31 (s,
6
(
7) Yoon, N. M.; Kim, E. G.; Son, H. S.; Choi, J. Synth.
Commun. 1993, 23, 1595.
2 H), 6.35 (br s, 1 H), 6.48 (t, J = 7.15 Hz, 1 H), 6.52 (d, J =
7.43 Hz, 2 H), 7.00 (t, J = 7.84 Hz, 2 H), 7.42 (d, J = 7.98
Hz, 2 H), 7.87 (d, J = 7.98 Hz, 2 H). C NMR (75 MHz,
1
3
(
8) (a) Kotsuki, H.; Yoshimura, N.; Kadota, I.; Ushio, Y.; Ochi,
M. Synthesis 1990, 401. (b) Bhattacharyya, S.; Chatterjee,
A.; Williamson, J. S. Synth. Commun. 1997, 27, 4265.
CDCl ): d = 46.9, 112.9, 116.5, 127.7, 129.5, 130.0, 130.4,
3
146.2, 149.0, 168.2. Anal. Calcd for C H NO : C, 73.99;
1
4
13
2
(
6
c) Ranu, B. C.; Majee, A.; Sarkar, A. J. Org. Chem. 1998,
3, 370.
9) (a) Bomann, M. D.; Guch, I. C.; DiMare, M. J. Org. Chem.
995, 60, 5995. (b) Pelter, A.; Rosser, R. M.; Mills, S. J.
Chem. Soc., Perkin Trans. 1 1984, 717.
H, 5.77; N, 6.16. Found: C, 73.98; H, 5.75; N, 6.18.
N-Phenyl-4-methoxycarbonylbenzylamine (2c): Yield:
98%; oil. IR (neat): 3415, 3024, 2951, 2840, 1698, 1616,
(
–
1 1
1
1521, 1123, 763, 698 cm . H NMR (300 MHz, CDCl ):
3
d = 3.87 (s, 3 H), 4.15 (br s, 1 H), 4.35 (s, 2 H), 6.56 (d, J =
7.70 Hz, 2 H), 6.69 (t, J = 7.43 Hz, 1 H), 7.13 (t, J = 7.84 Hz,
2 H), 7.38 (d, J = 7.98 Hz, 2 H), 7.96 (d, J = 8.25 Hz, 2 H).
(
(
10) Nose, A.; Kudo, T. Chem. Pharm. Bull. 1986, 34, 4817.
11) Bae, J. W.; Lee, S. H.; Cho, Y. J.; Yoon, C. M. J. Chem. Soc.,
Perkin Trans. 1 2000, 145.
1
3
C NMR (75 MHz, CDCl ): d = 48.3, 52.4, 113.1, 118.0,
3
(
12) Micćović, I. V.; Ivanoviï, M. D.; Piatak, D. M.; Bojić, V. D.
127.3, 129.2, 129.5, 130.1, 145.2, 148.0, 167.1. Anal. Calcd
for C H NO : C, 74.67; H, 6.27; N, 5.81. Found: C, 74.70;
Synthesis 1991, 1043.
1
5
15
2
(
13) (a) Chandrasekhar, S.; Reddy, C. R.; Ahmed, M. Synlett
H, 6.37; N, 5.86. N-Methyl-4-methoxycarbonylbenzyl-
amine (2d): Yield: 99%; white solid; mp 152–153 °C. IR
(KBr): 3236, 3018, 1004, 2952, 1704, 1428, 1286, 1168, 894
2000, 1655. (b) Chandrasekhar, S.; Reddy, C. R.;
Chandraiah, L. Synth. Commun. 1999, 29, 3981. (c) Lopez,
R. M.; Fu, G. C. Tetrahedron 1997, 53, 16349. (d) Chen,
B.-C.; Sundeen, J. E.; Guo, P.; Bednarz, M. S.; Zhao, R.
Tetrahedron Lett. 2001, 42, 1245. (e) Blackwell, J. M.;
Sonmor, E. R.; Scoccitti, T.; Piers, W. E. Org. Lett. 2000, 2,
–
1 1
cm . H NMR (300 MHz, CDCl ): d = 2.42 (d, J = 5.78 Hz,
3
3 H), 3.59 (dd, J = 9.77, 13.62 Hz, 1 H), 3.93 (s, 3 H), 4.30
(dd, J = 2.89, 13.89 Hz, 1 H), 4.39 (br s, 1 H), 7.39 (d, J =
1
3
8.25 Hz, 2 H), 8.05 (d, J = 8.25 Hz, 2 H). C NMR (75 MHz,
3
1
1
921. (f) Kobayashi, S.; Yasuda, M.; Hachiya, I. Chem. Lett.
996, 407. (g) Apodaca, R.; Xiao, W. Org. Lett. 2001, 3,
745.
CDCl ): d = 40.8, 60.7, 129.7, 130.5, 130.8, 166.6. Anal.
3
Calcd for C H NO : C, 67.02; H, 7.31; N, 7.82. Found: C,
1
0
13
2
67.01; H, 7.33; N, 7.83. N-tert-Butyl-4-methoxycarbonyl-
benzylamine (2e): Yield: 98%; white solid; mp 30–31 °C.
IR (KBr): 3316, 3187, 2961, 2877, 1716, 1437, 1281, 1110,
(
14) (a) Suwa, T.; Sugiyama, E.; Shibata, I.; Baba, A. Synthesis
000, 558. (b) Suwa, T.; Sugiyama, E.; Shibata, I.; Baba, A.
2
–
1 1
Synthesis 2000, 789. (c) Hiroi, R.; Miyoshi, N.; Wada, M.
Chem. Lett. 2002, 274. (d) Suwa, T.; Shibata, I.; Nishino,
K.; Baba, A. Org. Lett. 1999, 1, 1579. (e) Shibata, I.;
Moriuchi-Kawakami, T.; Tanizawa, D.; Suwa, T.;
1019, 769 cm . H NMR (300 MHz, CDCl ): d = 1.18 (s, 9
3
H), 1.43 (s, 1 H), 3.77 (s, 2 H), 3.90 (s, 3 H), 7.40 (d, J = 7.98
Hz, 2 H), 7.96 (d, J = 8.25 Hz, 2 H). C NMR (75 MHz,
1
3
CDCl ): d = 29.5, 47.3, 51.2, 52.5, 128.3, 128.7, 129.9,
3
Sugiyama, E.; Matsuda, H.; Baba, A. J. Org. Chem. 1998,
147.1, 167.3. Anal. Calcd for C H NO : C, 70.56; H, 8.65;
1
3
19
2
6
3, 383.
N, 6.33. Found: C, 70.58; H, 8.67; N, 6.33. N-Phenyl-4-
cyanobenzylamine (2f): Yield: 99%; mp 83–84 °C. IR
(KBr): 3425, 3047, 2911, 2864, 2220, 1600, 1507, 1332,
(
(
15) Pereyre, M.; Quintard, J.-P.; Rahm, A. Tin in Organic
Synthesis; Butterworths: London, 1987, 6.
16) Narasimhan, S.; Balakumar, R. Aldrichimica Acta 1998, 31,
–
1 1
1266, 818, 765, 697 cm . H NMR (300 MHz, CDCl ): d =
3
19.
4.20 (br s, 1 H), 4.40 (s, 2 H), 6.55 (d, J = 7.70 Hz, 2 H), 6.71
(t, J = 7.29 Hz, 1 H), 7.14 (t, J = 7.01 Hz, 2 H), 7.44 (d, J =
(
(
17) Osby, J. O.; Ganem, B. Tetrahedron Lett. 1985, 26, 6413.
18) Reding, M. T.; Buchwald, S. L. J. Org. Chem. 1995, 60,
1
3
7.98 Hz, 2 H), 7.58 (d, J = 8.25 Hz, 2 H). C NMR (75 MHz,
7
884.
CDCl ): d = 48.1, 111.1, 113.1, 118.3, 119.1, 127.9, 129.6,
3
(
(
(
19) Alcaide, B.; López-Mardomingo, C.; Pérez-Ossorio, R.;
Plumet, J. J. Chem. Soc., Perkin Trans. 2 1983, 1649.
20) Tanaka, K. Solvent-free Organic Synthesis; Wiley-VCH:
Weinheim, 2003.
21) General Procedure for Chemoselective Reduction of
Aldimines and Ketimines. A mixture of imine derivatives
132.6, 145.6, 147.6. Anal. Calcd for C H N : C, 80.74; H,
1
4
12
2
5.81; N, 13.45. Found: C, 80.76; H, 5.78; N, 13.46. N-
Methyl-4-cyanobenzylamine (2g): Yield: 98%; white
solid; mp 108–109 °C. IR (KBr): 3158, 3013, 2854, 2260,
–
1 1
1520, 1350, 1169, 853 cm . H NMR (300 MHz, CDCl ):
3
d = 2.43 (d, J = 5.50 Hz, 3 H), 3.64 (dd, J = 7.35, 13.75 Hz,
1
(10 mmol), NaBH (10 mmol) and boric acid (10 mmol)
1 H), 4.26 (dd, J = 3.58, 13.75 Hz, 1 H), 4.68 (br s, 1 H), 7.47
4
1
3
was ground with an agate mortar and pestle for 0.5–1.0 h
until TLC showed complete disappearance of the starting
material. The mixture was quenched with a sat. aq solution
(d, J = 8.25 Hz, 2 H), 7.70 (d, J = 8.25 Hz, 2 H). C NMR
(75 MHz, CDCl ): d = 41.0, 60.4, 112.9, 118.6, 130.6, 133.0,
3
139.1. Anal. Calcd for C H N : C, 73.94; H, 6.89; N, 19.16.
9
10
2
of NaHCO , followed by filtration of the resultant
Found: C, 73.99; H, 6.95; N, 19.17. N-n-Heptyl-4-
3
suspension to give product amines 2. When the product was
cyanobenzylamine (2h): Yield: 98%, white solid; mp 63–
64 °C. IR (KBr): 3193, 2955, 2926, 2856, 2228, 1457, 1160,
liquid, it was isolated from extraction with CH Cl or Et O
2
2
2
–
1 1
instead of filtration. N-Phenyl-4-acetylbenzylamine (2a):
897, 854 cm . H NMR (300 MHz, CDCl ): d = 0.86 (t, J =
3
Yield: 98%; white solid; mp 74–75 °C. IR (KBr): 3379,
6.60 Hz, 3 H), 1.13–1.27 (m, 6 H), 1.58–1.74 (m, 4 H), 2.61–
2.67 (m, 2 H), 3.77 (dd, J =8.12, 13.34 Hz, 1 H), 4.08 (br s,
1 H), 4.17 (dd, J = 4.26, 13.34 Hz, 1 H), 7.46 (d, J = 8.25 Hz,
–
1
3
024, 2994, 2838, 1663, 1602, 1507, 1273, 749, 691 cm .
1
H NMR (300 MHz, CDCl ): d = 2.58 (s, 3 H), 4.17 (br s, 1
3
1
3
H), 4.40 (s, 2 H), 6.58 (d, J = 8.80 Hz, 2 H), 6.70 (t, J = 7.29
Hz, 1 H), 7.14 (t, J = 7.56 Hz, 2 H), 7.43 (d, J = 7.98 Hz, 2
2 H), 7.69 (d, J = 8.53 Hz, 2 H). C NMR (75 MHz, CDCl3):
d = 14.5, 22.9, 26.6, 27.0, 29.2, 31.9, 54.3, 59.2, 112.9,
Synlett 2004, No. 9, 1484–1488 © Thieme Stuttgart · New York