Polymer-Supported Hantzsch 1,4-Dihydropyridine Ester: An Efficient Biomimetic Hydrogen Source
General Procedure for the Reduction of Ketimines 4
by Polymer 1
Preparation of Compounds 6
Compounds 6a–6c were prepared accordingly to reported
procedures. Compounds 6d was prepared as follows: a mix-
ture of methyl 2-cyano-3-phenylbut-2-enoate (1.0 mmol), N-
bromosuccinimide (1.1 mmol) and AIBN (0.05 mmol) in tet-
rachloromethane (10 mL) was heated at 658C for 24 h.
After which, the reaction mixture was concentrated, and pu-
rified by column chromatography (EtOAc:hexane=1: 30) to
To the respective imine 4 (0.5 mmol) in toluene (5.0 mL)
was added polymer 1 (0.67 g, 0.75 mmol) and trichloroacetic
acid (0.05 mmol). The reaction mixture was deaerated with
argon for 30 min and allowed to stir at room temperature
for 2 h. After which, ice-cold methanol (20 mL) was added
and the suspension that formed was filtered through filter
paper and the filter cake was washed with cold methanol
(3ꢁ10 mL). The combined filtrate and washings were con-
centrated and filtered through a small pad of silica gel and
the latter was washed with a small volume of EtOAc:hexane
(1:10) solvent mixture. The combined filtrate and washings
were concentrated to afford the respective compound 5.
N-Benzhydrylbenzenamine (5a): 1H NMR (CDCl3,
500 MHz): d=4.29 (s, 1H, PhNH), 5.57 (s, 1H, PhCHPh),
6.60–7.38 (m, 15H, ArH); 13C NMR (CDCl3, 125 MHz): d=
63.0, 113.4, 117.6, 127.3, 127.4, 128.7, 129.1, 142.9, 147.3;
HR-MS (EI, C19H17N): m/z=259.1349, calcd.: 259.1361.
N-Benzyldiphenylmethanamine (5b): 1H NMR (CDCl3,
500 MHz): d=3.94 (s, 2H, PhCH2NH), 5.06 (s, 1H,
PhCHPh), 7.38–7.50 (m, 15H, ArH); 13C NMR (CDCl3,
125 MHz): d=51.8, 66.4, 126.8, 126.9, 127.3, 128.1, 128.3,
128.4, 140.4, 143.9; HR-MS (EI, C20H19N): m/z=273.1506,
calcd.: 273.1517.
1
give 6d; yield: 70%. H NMR (CDCl3, 500 MHz): d=3.93
(s, 3H, CO2CH3), 4.88 (s, 2H, BrCH2), 7.49–7.52 (m, 5H,
ArH); 13C NMR (CDCl3, 125 MHz): d=28.1, 53.3, 106.9,
115.4, 127.7, 128.9, 131.1, 136.7, 161.6, 168.2; HR-MS (EI,
C12H10O2NBr): m/z=278.9894, calcd.: 278.9889.
General Procedure for the Reduction of (Z)-a-
Cyano-b-cyanobromethylcinnamates and Analogues
by Polymer 1
To the respective alkene 6 (0.5 mmol) in DMF (1 mL) was
added acetonitrile (5.0 mL) and polymer
1
(0.67 g,
0.75 mmol). The reaction mixture was stirred at room tem-
perature in the absence of light for 2 h. Thereafter, ice-cold
methanol (20 mL) was added and the suspension that
formed was filtered through a filter paper and the filter
cake was washed with cold methanol (3ꢁ10 mL). The com-
bined filtrate and washings were concentrated and filtered
through a small pad of silica gel and the latter was washed
with a small volume of EtOAc:hexane (1:10) solvent mix-
ture. The combined filtrated and washings were concentrat-
ed to afford the respective compound 7.
N-Cyclohexylbenzenamine (5c): 1H NMR (CDCl3,
500 MHz): d=1.23–1.21 [m, 10H, HNCHACHTNURGTNEUNG(C5H10)], 3.37–3.41
(m, 1H, PhNHCH), 6.71–7.31 (m, 5H, ArH); 13C NMR
(CDCl3, 125 MHz): d=51.8, 66.4, 126.8, 126.9, 127.3, 128.1,
128.3, 128.4, 140.4, 143.9; HR-MS (FAB, C12H17N): m/z=
175.1361, calcd.: 175.1366.
1-Phenylcyclopropane-1,1-dicarbonitrile (7a): 1H NMR
(CDCl3, 500 MHz): d=1.32–1.37 (m, 2H, PhCHCH2), 3.20–
3.26 (m, 1H, J=15.1 Hz, PhCHCH2), 7.22–7.37 (m, 5H,
ArH); 13C NMR (CDCl3, 125 MHz): d=7.2, 22.3, 35.1,
113.0, 115.3, 128.3, 129.1, 129.4, 130.5; HR-MS (EI,
C11H8N2): m/z=168.0690, calcd.: 168.0687.
N-(Furan-2-ylmethyl)-1,1-diphenylmethanamine
(5d):
1H NMR (CDCl3, 500 MHz): d=2.06 (s, 1H, CHNHCH2),
3.82 (s, 2H, CHNHCH2), 4.92 (s, 1H, , CHNHCH2), 6.22–
7.51 (m, 13H, ArH); 13C NMR (CDCl3, 125 MHz): d=44.1,
65.9, 107.0, 110.0, 127.0, 127.3, 128.5, 141.7, 143.6, 153.8;
HRMS (EI, C18H17NO): m/z=263.1316, calcd.: 263.1310.
N-Benzhydrylbutan-1-amine (5e): 1H NMR (CDCl3,
1-Methyl-3-phenylcyclopropane-1,1-dicarbonitrile
(7b):
1H NMR (CDCl3, 500 MHz): d=1.60–1.63 (m, 3H, J=
6.1 Hz, PhCHCHCH3), 2.48–2.53 (m, 1H, PhCHCHCH3),
2.95–2.97 (m, 1H, J=6.1 Hz, PhCHCHCH3), 7.29–7.42 (m,
5H, ArH); 13C NMR (CDCl3, 125 MHz): d=13.3, 14.9, 29.7,
42.4, 113.3, 113.8, 128.2, 129.1, 129.4, 131.1; HR-MS (EI,
C12H10N2): m/z=182.0835, calcd.: 182.0844.
500 MHz):
d=0.90–0.93
(m,
3H,
J=7.6 Hz,
NHCH2CH2CH2CH3),
NHCH2CH2CH2CH3),
1.34–1.41
1.51–1.64
(m,
(m,
2H,
2H,
NHCH2CH2CH2CH3), 2.59–2.62 (m, 2H, NHCH2CH2CH2),
4.84 (s, 1H, CHNHCH2), 7.21–7.43 (m, 10H, ArH);
13C NMR (CDCl3, 125 MHz): d=14.0, 20.5, 32.3, 48.0, 67.6,
126.9, 127.3, 128.4, 144.3; HR-MS (EI, C17H21N): m/z=
239.1675, calcd.: 239.1674.
Ethyl 1-cyano-2-phenylcyclopropanecarboxylate (7c):
1H NMR (CDCl3, 500 MHz): d=1.38–1.40 (m, 3H, J=
6.9 Hz, CO2CH2CH3), 2.11–2.20 (m, 2H, PhCHCH2), 3.18–
3.22 (m, 1H, J=8.8 Hz, PhCHCH2), 4.31–4.36 (m, 2H,
CO2CH2CH3), 7.29–7.39 (m, 5H, ArH); 13C NMR (CDCl3,
125 MHz): d=14.1, 22.8, 22.9, 35.4, 63.1, 116.4, 128.3, 128.6,
128.8, 133.0, 167.4; HR-MS (EI, C13H13O2N): m/z=215.0940,
calcd.: 215.0946.
Methyl 1-cyano-2-phenylcyclopropanecarboxylate (7d):
1H NMR (CDCl3, 500 MHz): d=2.10–2.19 (m, 2H,
PhCHCH2), 3.17–3.20 (m, 1H, J=8.8 Hz, PhCHCH2), 3.87
(s, 3H, CO2CH3), 7.28–7.39 (m, 5H, ArH); 13C NMR
(CDCl3, 125 MHz): d=22.7, 22.8, 35.5, 53.7, 116.2, 128.3,
128.6, 128.8, 132.8, 167.8; HR-MS (EI, C12H11O2N): m/z=
201.0790, calcd.: 201.0784.
1
N-Isopropylaniline (5f): H NMR (CDCl3, 500 MHz): d=
1.24–1.26 (d, 6H, J=6.3 Hz, CH3CHCH3), 3.64–3.69 (m,
1H, CH3CHCH3), 6.62–7.22 (m, 5H, ArH); 13C NMR
(CDCl3, 125 MHz): d=23.0, 44.1, 113.2, 116.9, 129.2, 147.5;
HR-MS (EI, C9H13N): m/z=135.1050, calcd.: 135.1048.
1
N-(Heptan-4-yl)aniline (5g): H NMR (CDCl3, 500 MHz):
d=0.97–1.00 (m, 6H, CH3CH2CH2CHCH2CH2CH3), 1.41–
1.59 (m, 8H, CH3CH2CH2CHCH2CH2CH3), 3.41–3.44 (m,
1H, CH2CHCH2), 6.62–7.23 (m, 5H, ArH); 13C NMR
(CDCl3, 125 MHz): d=14.2, 19.1, 37.3, 52.3, 112.8, 116.4,
129.2, 148.2; HR-MS (EI, C13H21N): m/z=191.1675, calcd.:
191.1674.
Adv. Synth. Catal. 2010, 352, 1752 – 1758
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1757