Journal of the American Chemical Society
ARTICLE
The change in the ratio of 3 to 4 was monitored by 1H and 31P{1H}
NMR spectroscopy.
4.74 (m, 1H), 2.31 (s, 6H); 13C{1H} NMR (C6D6, 100.6 MHz, 23 °C) δ
141.82, 127.6, 127.2, 126.9, 91.3, 38.8, 5.82, 5.37.
Data for N,N-diisopropylbenzylamine (entry 7): 1H NMR (C6D5Cl,
400 MHz, 23 °C) δ 7.50ꢀ7.28 (m, 5H, overlap with solvent peaks), 3.63
(s, 2H), 3.00 (septet, J = 6.5 Hz, 2H), 1.11 (d, 12H, overlap with excess
Et2SiH2); 13C{1H} NMR (C6D5Cl, 100.6 MHz, 23 °C) δ 139.81,
128.42, 128.22, 126.33, 49.05, 47.82, 20.72.
In Situ Generation of 5 from a Mixture of 3 and 4 (Method A).
Et2SiH2 (13 μL, 0.1 mmol, 10 equiv) in toluene-d8 (0.5 mL) was added to 7
(5.9 mg, 0.01 mmol, 1 equiv) in a medium-walled NMR tube with a screw
cap. Subsequently, this mixture was allowed to stand at 23 °C for 10 min,
followed by introducing H2 via brief H2 purging through the solution. The
solution was stirred for 1 h at 23 °C to give a mixture of 3 and 4 in a ratio of
ca. 0.4:0.6. This solution containing 3 and 4 was purged with H2 for 20 min
at 23 °C, during which time excess Et2SiH2 was removed, to afford mainly
the iridium tetrahydride complex 5 (ca. 94%).
In Situ Generation of 7 from a Mixture of Monohydride 3
and Trihydride 4 (Method B). Et2SiH2 (13 μL, 0.1 mmol, 10 equiv)
in toluene-d8 (0.5 mL) was added to 7 (5.9 mg, 0.01 mmol, 1 equiv) in a
medium-walled J. Young NMR tube. Subsequently, this mixture was
allowed to stand at 23 °C for 10 min, followed by degassing by
freezeꢀpumpꢀthaw methods. H2 (1 atm) was vacuum-transferred to
the degassed J. Young NMR tube. The solution was stirred for 1 h at
23 °C to give a mixture of 3 and 4 in a ratio of ca. 0.4:0.6. This solution
containing 3 and 4 was subjected to high vacuum, resulting in a mixture
of 7 and 3 in a ratio of 0.06:0.91.
General Procedure for the Reduction of Tertiary Amides
Catalyzed by a Mixture of Monohydride 3 and Trihydride 4
with Et2SiH2 in the Presence of [Et3NH][B(C6F5)4] under H2 (1
atm). Et2SiH2 (1.5 mmol, 0.19 mL, 3.0 equiv) was added to a solution of 3
and 4 (0.005 mmol, 1.0 mol %) in C6D6 (0.3 mL) in a medium-walled J.
Young NMR tube, and the contents were well shaken. The substrate (0.5
mmol, 1.0 equiv) was then added together with [Et3NH][B(C6F5)4]
(0.005 mmol, 3.9 mg, 1.0 mol %), followed by degassing by freezeꢀ
pumpꢀthaw methods. Finally, 1 atm of H2 was vacuum-transferred to the
degassed J. Young NMR tube. The reactions were then allowed to stand at
23 °C or heated to 60 °C in an oil bath. The reaction progress was followed
by NMR spectroscopy. Conversions were determined by monitoring the
loss of tertiary amides.
Data for N,N-diphenylethylamine (entry 8): 1H NMR (C6D5Cl, 400
MHz, 23 °C) δ 7.50ꢀ7.10 (m, 10H, overlap with solvent peaks), 3.84
(q, J = 6.8 Hz, 2H), 1.31 (t, 3H, overlap with excess Et2SiH2); 13C{1H}
NMR (C6D5Cl, 100.6 MHz, 23 °C) δ 147.87, 129.28, 121.14, 120.8,
46.27, 12.50.
Data for N,N-diphenylbenzylamine and N,N-diphenyldiethylsilyl-
1
amine (entry 9): H NMR (C6D5Cl, 400 MHz, 23 °C, selected data)
δ 5.06 (m, 1H), 4.93 (s, 2H); 13C{1H} NMR (C6D5Cl, 100.6 MHz,
23 °C, selected data) δ 56.33, 41.57.
Data for 1-methylpiperidine (entry 10): 1H NMR (C6D5Cl, 400
MHz, 23 °C) δ 2.41 (m, 4H), 2.32 (br s, 3H), 1.71 (m, 4H), 1.52
(br s, 2H); 13C{1H} NMR (C6D5Cl, 100.6 MHz, 23 °C) δ 56.61,
46.88, 26.23, 24.15.
Data for 1-benzylpiperidine (entry 11): 1H NMR (C6D5Cl, 400
MHz, 23 °C) δ 7.50ꢀ7.31 (m, 5H, overlap with solvent peaks), 3.56
(s, 2H), 2.50 (br s, 4H), 1.71 (m, 4H), 1.58 (br s, 2H); 13C{1H} NMR
(C6D5Cl, 100.6 MHz, 23 °C) δ 139.49, 129.26, 128.19, 126.71, 63.93,
54.66, 26.33, 24.74.
Data for 1-(1-(ethyldimethylsilyl)oxy)-2,2,2-trifluoroethyl)piperidine
(entry 12): 1H NMR (C6D5Cl, 400 MHz, 23 °C) δ 4.58 (q, J = 3.5 Hz,
1H), 2.89 (t, J = 5.2 Hz, 4H), 1.70ꢀ1.52 (m, 6H), 1.18 (m, O-SiMe2Et,
overlap with excess Me2EtSiH), 0.76 (m, O-SiMe2Et, overlap with excess
Me2EtSiH); 13C{1H} NMR (C6D5Cl, 100.6 MHz, 23 °C) δ 122.84 (q, J =
285.7 Hz, overlap with solvent peaks), 86.39 (q, J = 32.1 Hz), 48.74, 26.46,
24.79, 8.49, 6.57, ꢀ2.61 (tentative).
1
Data for 1-methylpyrrolidine (entry 13): H NMR (C6D5Cl, 400
MHz, 23 °C) δ 2.40 (br s, 4H), 2.31 (s, 3H), 1.71 (m, 4H); 13C{1H}
NMR (C6D5Cl, 100.6 MHz, 23 °C) δ 56.16, 41.86, 24.18.
General Procedure for a Large-Scale Reduction of N,N-
Dibenzylbenzamide. Et2SiH2 (10.0 mmol, 1.30 mL, 3.0 equiv) was
added to a solution of 3 and 4 (0.01 mmol, 0.2 mol %) in toluene-d8
(3.0 mL) in a 25 mL flame-dried Schlenk tube containing a stir bar. The
substrate (3.32 mmol, 1.0 g, 1.0 equiv) was then added together with
Et2OHB(C6F5)4 (0.032 mmol, 24 mg, 1.0 mol %), followed by purging
H2 (1 atm) through the stirred solution for 1 min. The reaction mixture
was then heated to 60 °C overnight in an oil bath. Completion of
1
Data for 1-benzylpiperidine (entry 14): H NMR (C6D5Cl, 400
MHz, 23 °C) δ 7.40ꢀ7.22 (m, 5H, overlap with solvent peaks), 3.44
(s, 2H), 2.36 (m, 4H), 1.60ꢀ1.47 (m, 6H; 13C{1H} NMR (C6D5Cl,
100.6 MHz, 23 °C) δ 139.45, 128.87, 128.13, 127.56, 63.85, 54.57,
26.25, 24.67.
Data for N,N-dibenzyl-3-phenylpropan-1-amine (entry 15): 1H
NMR (C6D5Cl, 400 MHz, 23 °C) δ 7.45ꢀ7.06 (m, 15H, overlap with
solvent peaks), 3.55 (s, 4H), 2.58 (t, J = 7.5 Hz, 2H), 2.49 (t, J = 7.0 Hz,
2H), 1.82 (t, J = 7.0 Hz, 2H); 13C{1H} NMR (C6D5Cl, 100.6 MHz,
23 °C) δ 142.44, 139.96, 128.85, 128.40, 128.21, 128.14, 126.82, 125.75,
58.51, 52.95, 33.57, 29.27.
1
the reaction was confirmed by H NMR spectroscopy. The volatiles
were removed under reduced pressure. The residue was dissolved in
pentane and washed three times with 10 mL of NaOH (1 M) solution.
The organic layer was concentrated in vacuo to give a crude product.
The crude product was purified by recrystallization from ethanol to yield
0.86 g of tribenzylamine as a white solid (90%).
1
Data for tribenzylamine (entry 16): H NMR (C6D5Cl, 400 MHz,
23 °C) δ 7.48ꢀ7.22 (m, 15H, overlap with solvent peaks), 3.55 (s, 6H);
13C{1H} NMR (C6D5Cl, 100.6 MHz, 23 °C) δ 139.67, 128.89, 128.21,
126.88, 58.04.
NMR Spectroscopic Data of Amine Products in Table 1.4l
Data for N,N-dimethylisobutylamine (entry 1): 1H NMR (C6D5Cl, 400
MHz, 23 °C) δ 2.30 (s, 6H), 2.11 (d, J = 7.6 Hz, 2H), 1.85 (septet, J = 6.8
Hz, 1H), 1.07 (d, J = 6.4 Hz, 6H); 13C{1H} NMR (C6D5Cl, 100.6 MHz,
23 °C) δ 68.41, 45.68, 26.46, 20.73.
Data for hemiaminal ether (7%) (entry 16): 1H NMR (C6D5Cl, 400
MHz, 23 °C, selected data) δ 5.72 (s, 1H), 4.79 (m, 1H), 3.96ꢀ3.74 (m,
4H); 13C{1H} NMR (C6D5Cl, 100.6 MHz, 23 °C, selected data) δ
86.08, 52.21.
Data for N,N,2-trimethylprop-1-en-1-amine as a side product in entry
1 (Table 2): 1H NMR (C6D6, 400 MHz, 23 °C): δ 5.38 (s, 1H), 2.39 (s,
6H), 1.79 (s, 3H), 1.66 (s, 3H); 13C{1H} NMR (C6D6, 100.6 MHz,
23 °C) δ 137.3, 121.0, 45.0, 21.9, 16.9.
Data for N,N-dibenzyl-1-(naphthalene-1-yl)methanamine (entry
1
17): H NMR (C6D5Cl, 400 MHz, 23 °C) δ 8.19ꢀ7.24 (m, 17H,
overlap with solvent peaks), 3.97 (s, 2H), 3.58 (s, 4H); 13C{1H} NMR
(C6D5Cl, 100.6 MHz, 23 °C, selected data) δ 58.67, 56.95.
Data for N,N-dibenzyl-1-cyclopropylmethanamine (entry 18):
1H NMR (C6D5Cl, 400 MHz, 23 °C) δ 7.48ꢀ7.24 (m, 10H, overlap
with solvent peaks), 3.82 (s, 4H), 2.51 (d, J = 6.4 Hz, 2H), 1.08 (br s,
1H), 0.61 (d, J = 7.2 Hz, 2H), 0.19 (br s, 2H); 13C{1H} NMR (C6D5Cl,
100.6 MHz, 23 °C) δ 140.43, 128.95, 128.01, 126.86, 58.50, 58.46,
8.72, 4.15.
1
Data for N,N-dimethylbenzylamine (entry 4): H NMR (C6D5Cl,
400 MHz, 23 °C) δ 7.49ꢀ7.35 (m, 5H, overlap with solvent peaks), 3.53
(s, 2H), 2.35 (s, 6H); 13C{1H} NMR (C6D5Cl, 100.6 MHz, 23 °C) δ
139.70, 128.82, 128.12, 126.85, 64.43, 45.22.
Data for 1-((dimethylsilyl)oxy)-N,N-dimethyl-1-phenylmethan-
amine as a product of first hydrosilylation: 1H NMR (C6D6, 400 MHz,
23 °C) δ 7.57ꢀ7.28 (m, 5H, overlap with solvent peaks), 5.51 (s, 1H),
652
dx.doi.org/10.1021/ja209567m |J. Am. Chem. Soc. 2012, 134, 640–653