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7.01 (d, J = 7.7 Hz, 2H, 2 ꢁ ArCH), 7.08 (d, 2H, J = 7.9 Hz, 2 ꢁ ArCH); 13C NMR
(75 MHz, CDCl3) d 13.9, 20.8, 22.5, 27.1, 29.1, 29.4, 29.5, 29.7, 31.7, 49.1, 53.4,
127.9, 128.7, 128.8, 136.1; MS-EI (m/z): 289 (M+, 1.1%), 184 (4), 135 (5), 134
(46), 120 (6), 106 (10), 105 (100), 91 (4), 77 (6), 55 (4). HRMS-EI (m/z): [M]+
Calcd for C20H35N, 289.2770; Found 289.2773.
Cyclohexyl(4-methylbenzyl)amine (1c): Orange oil; IR (CH2Cl2): 3293; 3021;
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2919; 2847; 1608; 1516; 1454; 1050; 809 cmꢀ1 1H NMR (300 MHz, CDCl3) d
;
1.30–2.03 (m, 10H, 5 ꢁ CH2), 2.45–2.50 (m, 4H, CH3, CHNH), 2.61 (s, 1H, NH),
3.86 (s, 2H, CH2NH), 7.19 (d, J = 7.5 Hz, 2H, 2 ꢁ ArCH), 7.28 (d, J = 7.6 Hz, 2H,
2xArCH); 13C NMR (75 MHz, CDCl3) d 21.3, 25.0, 26.5, 33.6, 50.8, 56.0, 128.1,
128.9, 135.6, 138.1. MS-EI (m/z): 203 (M+, 13%), 160 (38), 106 (10), 105 (100),
104 (9), 103 (13), 91 (17), 79 (17), 78 (9), 77 (24), 55 (9). HRMS-EI (m/z): [M]+
Calcd for C14H21N, 203.1674; Found 203.1680.
4-(Dimethylaminobenzyl)dodecylamine (1k): Yellow oil; IR (film): 3329, 2929,
2852, 1649, 1516, 1465, 1388, 1116, 912, 814, 732 cmꢀ1 1H NMR (300 MHz,
;
CDCl3) d 0.79 (t, J = 6.48 Hz, 3H, CH3), 1.17–1.37 (m, 20H, 10 ꢁ CH2), 2.47 (t,
J = 7.18 Hz, 2H, CH2CH2NH), 2.80 (s, 6H, 2 ꢁ CH3), 2.86 (s, 1H, NH), 3.55 (s, 2H,
ArCH2NH), 6.58 (d, J = 8.50 Hz, 2H, 2 ꢁ ArCH), 7.06 (d, J = 8.53 Hz, 2H,
2 ꢁ ArCH); 13C NMR (75 MHz, CDCl3) d 13.8, 22.4, 27.1, 29.1, 29.3, 29.4, 29.8,
31.7, 40.4, 49.0, 53.2, 112.4, 128.2, 128.8, 149.4; MS-EI (m/z): 318 (M+, 6.3%),
317 (5), 135 (11), 134 (100), 118 (6). HRMS-EI (m/z): [M]+ Calcd for C21H38N2,
318.3035; Found 318.3039.
N,N-dimethyl-4-cyclohexylaminomethylaniline (1l): Orange oil; IR (film): 3303,
2929, 2847, 1603, 1521, 1449, 1347, 1163, 937, 804, 727 cmꢀ1 1H NMR
;
(300 MHz, CDCl3) d 0.94–1.80 (m, 10H, 5 ꢁ CH2), 2.79 (s, 6H, 2 ꢁ CH3), 2.85 (s,
1H, NH), 2.92 (s, 1H, CH), 3.59 (s, 2H, CH2), 6.58 (d, J = 8.5 Hz, 2H, 2 ꢁ ArCH),
7.06 (d, J = 8.5 Hz, 2H, 2 ꢁ ArCH); 13C NMR (75 MHz, CDCl3) d 24.7, 25.9, 33.1,
40.4, 50.1, 55.6, 112.4, 128.5, 128.7, 149.4; MS-EI (m/z): 232 (M+, 14%), 231 (6),
135 (11), 134 (100), 118 (12), 91 (4). HRMS-EI (m/z): [M]+ Calcd for C15H24N2,
232.1939; Found 232.1941.
16. As suggested by one referee, we studied the reaction of p-nitrobenzaldehyde
and p-cyanobenzaldehyde with cyclohexylamine. In both cases,
a low
13. (a) Tomooka, K.; Ito, M. Main Group Metals in Organic Synthesis; Wiley-VCH:
Weinheim, 2004; (b) Rees, N. V.; Baron, R.; Kershaw, N. M.; Donohoe, T. J.;
Compton, R. G. J. Am. Chem. Soc. 2008, 130, 12256–12257.
conversion of the starting amine to complex mixture of products was
obtained, thus indicating that these reducible functional groups are not
compatible with the reaction conditions.
a
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15. Typical experimental procedure: A mixture of lithium sand (21 mg, 3.0 mmol)
and DTBB (26 mg, 0.1 mmol) in THF (2 mL) was stirred at room temperature
under nitrogen atmosphere. When the reaction mixture turned dark green (5–
20 min), indicating the formation of the lithium arenide, a solution of the
primary amine (1.0 mmol) in THF (2 mL) was slowly added by syringe,
followed by the addition of the corresponding aldehyde (1.0 mmol) in THF
(2 mL). After total conversion of the starting material (TLC, GC–MS), the
resulting suspension was diluted with ethyl ether (10 mL) and washed with
H2O (3 ꢁ 10 mL). The combined extracts were dried over anhydrous Na2SO4
and evaporated (20 mbar). The resulting residue was purified by flash column
chromatography (silica gel, hexane-ethyl acetate) to give the corresponding
secondary amine. The following known compounds included in Table 1 were
characterised by comparison of their chromatographic and spectroscopic data
(1H , 13C NMR, and MS) with those described in the literature: 1a,22 1b,4b 1e,4b
1f,4b 1g,23 1m,24 1n,22 2o,25 2p.26 Amines 1d, 1h and 1i were characterised by
comparison of their chromatographic and spectroscopic data (1H, 13C NMR, and
MS) with those of the corresponding commercially available pure samples. For
new compounds, physical and spectroscopic data follow:
17. Computational Procedure: The calculations were performed with Gaussian03.27
The initial conformational analysis of selected compounds was performed with
the semiempirical AM1 method. The geometry of the most stable conformers
thus obtained was used as starting point for the B3LYP studies of the
corresponding imines and their radical anions. The zero point energy
corrections were made at the 6-31+G⁄ level for the thermodynamic
quantities. The energies in solution were obtained with full geometry
optimization within the Tomasi’s polarized continuum model (PCM)28 as
implemented in Gaussian03. Figures were built with the GaussView program
using a spin density isosurface of 0.02.
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Dodecyl(4-methylbenzyl)amine (1j): Orange oil; IR (film): 3329, 3073, 2924,
2852, 1603, 1526, 1465, 1342, 1163, 1122, 906, 809, 722 cmꢀ1
;
1H NMR
(300 MHz, CDCl3) d 0.79 (t, J = 6.1 Hz, 3H, CH3), 1.16–1.37 (m, 20H, 10 ꢁ CH2),
2.22 (s, 3H, CH3), 2.47 (t, J = 7.1 Hz, 2H, CH2), 2.65 (s, 1H, NH), 3.60 (s, 2H, CH2),