K.-i. Fujita et al. / Tetrahedron 65 (2009) 3624–3628
3627
3.3. N-Alkylation of carbamates with various alcohols
(Table 2)
(t, J¼8 Hz, 2H, OCH2), 1.61 (m, 2H, CH2), 1.37 (m, 2H, CH2), 0.93
(t, J¼8 Hz, 3H, CH3). 13C NMR (CDCl3)
d 156.8, 141.0, 130.4, 130.3,
130.1, 126.0, 122.6, 65.0, 44.3, 30.1, 19.0, 13.7. Anal. Calcd for
C12H16BrNO2: C, 50.37; H, 5.64; N, 4.89. Found: C, 51.06; H, 5.69; N,
4.84.
In a heavy-walled glass reactor under an atmosphere of argon
were placed [Cp*IrCl2]2 (0.025 mmol, 5.0 mol % Ir), NaOAc
(0.050 mmol, 5.0 mol %), carbamate 1 or 4 (1.0 mmol), and alcohol
(4.0 mmol). The mixture was stirred at 130 ꢀC for 17 h in the
sealed reactor. After cooled to room temperature, the products
were isolated by column chromatography (eluent: hexane/ethyl
acetate). The products 3a,16 3k,17 and 5a18 were known com-
pounds, which were identified by spectral comparison with lit-
erature data. The NMR and elemental analysis data of other
products are as follows.
3.3.8. n-Butyl N-(2-naphthylmethyl)carbamate (3i)
1H NMR (CDCl3)
d 7.82–7.70 (m, 3H, aromatic), 7.70 (s, 1H, aro-
matic), 7.48–7.38 (m, 3H, aromatic), 5.08 (br s, 1H, NH), 4.51 (d,
J¼5 Hz, 2H, NCH2), 4.11 (t, J¼8 Hz, 2H, OCH2), 1.63 (m, 2H, CH2), 1.37
(m, 2H, CH2), 0.93 (t, J¼8 Hz, 3H, CH3). 13C NMR (CDCl3)
d 156.8,
136.0, 133.3, 132.7, 128.4, 127.7, 127.6, 126.2, 126.0, 125.8, 125.7, 65.0,
45.2, 31.1, 19.0, 13.7. Anal. Calcd for C16H19NO2: C, 74.68; H, 7.44; N,
5.44. Found: C, 74.70; H, 7.51; N, 5.35.
3.3.1. n-Butyl N-(40-methylbenzyl)carbamate (3b)
1H NMR (CDCl3)
d
7.24–7.10 (m, 4H, aromatic), 5.06 (br s, 1H,
3.3.9. n-Butyl N-(2-pyridylmethyl)carbamate (3j)
NH), 4.29 (d, J¼6 Hz, 2H, NCH2), 4.07 (t, J¼7 Hz, 2H, OCH2), 2.32 (s,
1H NMR (CDCl3)
d
8.53 (d, J¼5 Hz, 1H, aromatic), 7.69–7.63 (m,
3H, Me), 1.58 (m, 2H, CH2), 1.37 (m, 2H, CH2), 0.92 (t, J¼8 Hz, 3H,
1H, aromatic), 7.29 (d, J¼8 Hz, 1H, aromatic), 7.20–7.16 (m, 1H, ar-
omatic), 5.96 (br s, 1H, NH), 4.49 (d, J¼6 Hz, 2H, NCH2), 4.09
(t, J¼6 Hz, 2H, OCH2), 1.61 (m, 2H, CH2), 1.37 (m, 2H, CH2), 0.92
CH3). 13C NMR (CDCl3)
d 156.6, 136.9, 135.5, 129.1, 127.3, 64.8, 44.7,
31.1, 21.1, 19.1, 13.8. Anal. Calcd for C13H19NO2: C, 70.56; H, 8.65; N,
6.33. Found: C, 70.81; H, 8.50; N, 6.25.
(t, J¼7 Hz, 3H, CH3). 13C NMR (CDCl3)
d 157.2, 156.9, 149.0, 136.7,
122.2,121.7, 64.8, 45.9, 31.0,19.0,13.6. Anal. Calcd for C11H16N2O2: C,
63.44; H, 7.74; N, 13.45. Found: C, 63.14; H, 7.53; N, 13.31.
3.3.2. n-Butyl N-(30-methoxylbenzyl)carbamate (3c)
1H NMR (CDCl3)
d
7.24 (t, J¼8 Hz, 1H, aromatic), 6.88–6.79 (m,
3H, aromatic), 5.05 (br s,1H, NH), 4.33 (d, J¼6 Hz, 2H, NCH2), 4.09 (t,
3.4. Conversion of n-butyl N-benzylcarbamate (3a) to
benzylamine (Eq. 1)
J¼7 Hz, 2H, OCH2), 3.79 (s, 3H, OMe), 1.61 (m, 2H, CH2), 1.37 (m, 2H,
CH2), 0.92 (t, J¼7 Hz, 3H, CH3). 13C NMR (CDCl3)
d 159.8,156.8,140.2,
129.6, 119.6, 113.0, 112.8, 64.9, 55.1, 44.9, 31.0, 19.0, 13.7. Anal. Calcd
for C13H19NO3: C, 65.80; H, 8.07; N, 5.90. Found: C, 65.97; H, 7.94; N,
5.77.
In a flask, 3a (227.2 mg, 1.096 mmol), NaOH (991.2 mg,
24.8 mmol), methanol (3.0 mL), and water (3.0 mL) were placed.
The mixture was heated under reflux for 41 h. After cooled to room
temperature, the product was extracted with dichloromethane. The
yield of benzylamine was determined by GC analysis using unde-
cane as an internal standard.
3.3.3. n-Butyl N-(40-chlorobenzyl)carbamate (3d)
1H NMR (CDCl3)
d 7.30–7.19 (m, 4H, aromatic), 5.14 (br s,1H, NH),
4.30 (d, J¼6 Hz, 2H, NCH2), 4.07 (t, J¼7 Hz, 2H, OCH2), 1.61 (m, 2H,
CH2), 1.37 (m, 2H, CH2), 0.92 (t, J¼7 Hz, 3H, CH3). 13C NMR (CDCl3)
3.5. N-Alkylation of amides with various alcohols (Table 3)
d
156.6, 137.1, 133.0, 128.65, 128.55, 65.0, 44.3, 31.1, 19.1, 13.8. Anal.
Calcd for C12H16ClNO2: C, 59.63; H, 6.67; N, 5.79. Found: C, 59.58; H,
6.47; N, 5.73.
In a heavy-walled glass reactor under an atmosphere of argon
were placed [Cp*IrCl2]2 (0.025 mmol, 5.0 mol % Ir), NaOAc
(0.050 mmol, 5.0 mol %), amide 6 or 7 (1.0 mmol), and alcohol
(4.0 mmol). The mixture was stirred at 130 ꢀC for 17 h in the sealed
reactor. After cooled to room temperature, the products were iso-
lated by column chromatography (eluent: hexane/ethyl acetate).
The products 8a,19 8b,20 8d,21 8k,22 8l,9a 8m,23 9a,24 and 9b25 were
known compounds, which were identified by spectral comparison
with literature data. The NMR data of 8c26 are as follows.
3.3.4. n-Butyl N-(30-chlorobenzyl)carbamate (3e)
1H NMR (CDCl3)
d 7.27–7.16 (m, 4H, aromatic), 5.20 (br s, 1H,
NH), 4.32 (d, J¼6 Hz, 2H, NCH2), 4.08 (t, J¼7 Hz, 2H, OCH2), 1.59 (m,
2H, CH2), 1.37 (m, 2H, CH2), 0.92 (t, J¼7 Hz, 3H, CH3). 13C NMR
(CDCl3)
d 156.6, 140.7, 134.3, 129.7, 127.4, 127.3, 125.4, 65.0, 44.4,
31.0, 19.1, 13.8. Anal. Calcd for C12H16ClNO2: C, 59.63; H, 6.67; N,
5.79. Found: C, 59.56; H, 6.66; N, 5.80.
3.5.1. N-(30-Methoxylbenzyl)benzamide (8c)
3.3.5. n-Butyl N-(30,40-dichlorobenzyl)carbamate (3f)
1H NMR (CDCl3)
d
7.78 (d, J¼7 Hz, 2H, aromatic), 7.51–7.37
1H NMR (CDCl3)
d
7.39–7.10 (m, 3H, aromatic), 5.15 (br s,1H, NH),
(m, 3H, aromatic), 7.25 (t, J¼8 Hz, 1H, aromatic), 6.93–6.81 (m, 3H,
4.30 (d, J¼6 Hz, 2H, NCH2), 4.08 (t, J¼7 Hz, 2H, OCH2), 1.61 (m, 2H,
aromatic), 6.62 (br s, 1H, NH), 4.59 (d, J¼6 Hz, 2H, CH2), 3.78 (s, 3H,
CH2), 1.38 (m, 2H, CH2), 0.93 (t, J¼7 Hz, 3H, CH3). 13C NMR (CDCl3)
OMe).13C NMR (CDCl3)
d 167.3,159.9,139.8,134.3,131.5,129.7,128.5,
d
156.6, 139.1, 132.6, 131.3, 130.5, 129.2, 126.7, 65.1, 43.8, 31.0, 19.0,
126.9, 120.0, 113.4, 112.9, 55.2, 44.0. Anal. Calcd for C15H15NO2: C,
74.67; H, 6.27; N, 5.81. Found: C, 74.55; H, 6.32; N, 5.66.
13.7. Anal. Calcd for C12H15Cl2NO2: C, 52.19; H, 5.47; N, 5.07. Found:
C, 52.16; H, 5.37; N, 5.02.
3.6. Preparation of N-benzylidenebenzamide (10)
3.3.6. n-Butyl N-(40-bromobenzyl)carbamate (3g)
1H NMR (CDCl3)
d
7.43 (d, J¼8 Hz, 2H, aromatic), 7.16 (d, J¼8 Hz,
In a flask, benzamide (2.03 g, 16.8 mmol), PhSO2Na (5.54 g,
33.7 mmol), methanol (16 mL), and water (32 mL) were placed.
Benzaldehyde (3 mL) was then added in one portion, followed by
formic acid (1.3 mL). The mixture was stirred at 50 ꢀC for 120 h. The
precipitate was isolated by Bu¨chner funnel filtration and purified by
washing with water. Then, the white solid was transferred to
a flask, K2CO3 (1.89 g, 13.7 mmol), Na2SO4 (2.29 g, 16.1 mmol), and
toluene (30 mL) were added. The mixture was heated under reflux
for 15 h. After the mixture was filtered through a pad of Celite and
evaporation of the filtrate gave 10 (161.7 mg, 0.7730 mmol, 4.6%).
2H, aromatic), 5.02 (br s,1H, NH), 4.30 (d, J¼6 Hz, 2H, NCH2), 4.08 (t,
J¼6 Hz, 2H, OCH2), 1.62 (m, 2H, CH2), 1.37 (m, 2H, CH2), 0.92 (t,
J¼7 Hz, 3H, CH3). 13C NMR (CDCl3)
d 156.6, 137.6, 131.6, 129.0, 121.1,
65.0, 44.4, 31.1, 19.1, 13.8. Anal. Calcd for C12H16BrNO2: C, 50.37; H,
5.64; N, 4.89. Found: C, 50.56; H, 5.52; N, 4.92.
3.3.7. n-Butyl N-(30-bromobenzyl)carbamate (3h)
1H NMR (CDCl3)
d
7.43–7.37 (m, 2H, aromatic), 7.27–7.18 (m, 2H,
aromatic), 5.14 (br s, 1H, NH), 4.32 (d, J¼5 Hz, 2H, NCH2), 4.09