PAPER
Preparation of Alkyl and Aryl Alkylcarbamates from S-Methyl N-Alkylthiocarbamates
2923
CH2Cl2 to form a homogeneous solution with the reaction solvent
toluene (150 mL). This solution was washed successively with aq
5% HCl (60 mL) and H2O (60 mL), dried (Na2SO4) and evaporated
under reduced pressure. The crude oily residue, which consisted of
3d and benzyl alcohol, was purified by column chromatography
(CHCl3–MeOH, 9.5:0.5). The first eluted product was benzyl meth-
ylcarbamate [3d; 1.45 g (88% yield); 100% GC purity; colorless oil;
bp 124–125 °C/0.6 mm Hg (Lit.4 118 °C/0.5 mm Hg)]. The second
eluted product was the pure benzyl alcohol [2.05 g (95%)].
Butyl Butylcarbamate (3f)
1H NMR: d = 0.91 (t, J = 7.0 Hz, 3 H, CH3), 0.92 (t, J = 7.2 Hz, 3 H,
CH3), 0.95–1.65 (2 × m overlapping, 8 H, 2 × CH2CH2CH3), 3.16
(app q, J = 6.4 Hz, 2 H, CH2NH), 4.04 (t, J = 6.5 Hz, 2 H, CH2O),
4.67 (m, 1 H, NH). Identical to that reported.20
MS (EI, 70 eV): m/z (%) = 173(9) [M+], 131 (10), 130 (100), 118
(85), 116 (12), 100 (14), 88 (59), 75 (8), 74 (16), 62 (12), 57 (89),
56 (39), 55 (13).
Alternatively, the crude oily residue was worked up as follows: H2O
(150 mL) was added and the H2O/benzyl alcohol azeotrope was dis-
tilled under reduced pressure. The oil was dried by subsequent ad-
dition of CHCl3 (3 × 20 mL) and distillation under reduced pressure
of the CHCl3/H2O azeotropes to give 3d [1.32–1.40 g (80–85%);
100% GC purity].
Butyl 4-Methoxyphenylcarbamate (3h)
1H NMR: d = 0.95 (t, J = 7.0 Hz, 3 H, CH3), 1.29–1.44 (m, 2 H,
CH3CH2), 1.47–1.76 (m, 2 H, CH3CH2CH2), 3.25 (app q, J = 6.5
Hz, 2 H, CH2NH), 3.79 (s, 3 H, OCH3), 5.11 (m, 1 H, NH), 6.87 (d,
J = 8.8 Hz, 2 H, ArH), 7.05 (d, J = 8.8 Hz, 2 H, ArH). Similar to
that reported.11
When working on a large scale,10 excess benzyl alcohol and Et3N
could be recovered almost quantitatively by direct fractional distil-
lation of the reaction mixture.
MS (EI, 70 eV): m/z (%) = 223 (1) [M+], 125 (9), 124 (100), 109
(60), 81 (19), 56 (9).
Butyl Benzylcarbamate (3j)
Carbamates 3f (entry 13) and 3g and 3j–m (entries 15, 16, 19 and
21–25) were prepared according to the above procedure. In particu-
lar, excess butyl (entries 13 and 19) and propargyl (entry 15) alco-
hols were removed by direct distillation of the reaction mixtures
under reduced pressure. Excess octyl (entry 21) and benzyl (entries
24 and 25) alcohols were removed by distillation of the water/alco-
hol azeotropes under reduced pressure. Excess hexadecyl alcohol
(entry 22) was removed by column chromatography (CH2Cl2–
EtOAc, 9:1) and recovered pure in 95% yield.
1H NMR: d = 0.94 (t, J = 7.3 Hz, 3 H, CH3), 1.25–1.47 (m, 2 H,
CH3CH2), 1.54–2.38 (m, 2 H, CH3CH2CH2), 4.10 (t, J = 6.6 Hz,
2 H, OCH2), 4.37 (d, J = 5.9 Hz, 2 H, CH2NH), 5.07 (m, 1 H, NH),
7.24–7.40 (m, 5 H, ArH). Similar to that reported.12
MS (EI, 70 eV): m/z (%) = 207 (11) [M+], 151 (14), 150 (100), 133
(30), 132 (13), 106 (37), 105 (19), 104 (20), 91 (60), 79 (16), 78
(10), 77 (17), 65 (10), 56 (10), 51 (10).
Octyl Benzylcarbamate (3k)
Butyl Butylcarbamate (3f)
The title compound is mentioned in the literature,13 but physical and
spectral data were not reported.
Table 1, Entry 14: A mixture of the crude S-methyl N-butylthiocar-
bamate (1; R = Bu; 1.47 g, 10 mmol), 1-butanol (2; R¢ = Bu; 5 mL),
and Et3N (2.22 g, 22 mmol) was heated at reflux with an oil bath
maintained at 120–123 °C, under stirring. After 4 h, GC and GC-
MS analyses of the solution showed the disappearance of the start-
ing thiocarbamate and the presence of butyl butylcarbamate (3f) as
the only product. Excess butanol and Et3N were removed by distil-
lation under reduced pressure to give the title compound 3f [1.70 g
(98%); 99.9% GC purity].
1H NMR: d = 0.89 (t, J = 5.7 Hz, 3 H, CH3), 1.15–1.45 [m, 10 H,
CH3(CH2)5CH2], 1.59 (m, 2 H, CH2CH2O), 4.09 (t, J = 6.4 Hz, 2 H,
CH2CH2O), 4.37 (d, J = 5.5 Hz, CH2NH), 5.03 (m, NH), 7.31 (m,
5 H, ArH).
13C NMR: d = 15.53 (CH3), 24.08, 27.30, 30.48, 30.65, 33.22 (CH2),
46.47 (CH2NH), 66.68 (CH2O), 128.87, 130.07 (CH), 140.08 (C),
158.25 (C=O).
MS (EI, 70 eV): m/z (%) = 263 (8) [M+], 151 (23), 150 (100), 134
(16), 132 (7), 106 (25), 105 (13), 104 (10), 91 (35), 79 (8), 77 (8),
69 (7), 56 (8), 55 (10).
When working on a large scale,10 excess butanol and Et3N could be
recovered almost quantitatively by direct fractional distillation of
the reaction mixture.
Anal. Calcd for C16H25NO2: C, 72.96; H, 9.57; N, 5.32. Found: C,
73.05; H, 9.63; N, 5.38.
Methyl butylcarbamate (3e) was prepared according to the above
procedure (entry 12).
Yields, GC purity and physical data (mp and bp) of all the carbam-
ates 3a–o are reported in Table 1. Spectral data (1H NMR and MS)
of carbamates 3b–d, 3g, 3i and 3n were identical to those previously
prepared.4
Hexadecyl Benzylcarbamate (3l)
1H NMR: d = 3.07 (t, J = 6.3 Hz, 3 H, CH3), 1.17–1.37 [m, 28 H,
CH3(CH2)14CH2], 1.55–1.68 (m, 2 H, CH2CH2O), 4.10 (t, J = 6.4
Hz, 2 H, CH2CH2O), 4.38 (d, J = 5.6 Hz, CH2NH), 4.95 (m, NH),
7.27–7.38 (m, 5 H, ArH).
4-Bromophenyl Methylcarbamate (3a)
MS (EI, 70 eV): m/z (%) = 375 (1) [M+], 150 (55), 133 (76), 132
(29), 105 (32), 104 (38), 97 (23), 91 (65), 83 (29), 77 (28), 69 (26),
57 (26), 55 (31).
13C NMR: d = 15.54 (CH3), 24.12, 27.30, 30.47, 30.73, 30.79,
31.01, 31.11, 33.45 (CH2), 66.69 (CH2O), 46.50 (CH2NH), 128.87,
130.07 (CH), 140.06 (C), 158.21 (C=O).
Only 13C NMR data are reported in the literature.18
1H NMR: d = 2.89 (d, J = 4.6 Hz, 3 H, CH3), 5.11 (m, 1 H, NH),
6.96 (d, J = 8.8 Hz, 2 H, ArH), 7.46 (d, J = 8.8 Hz, 2 H, ArH).
MS (EI, 70 eV): m/z (%) = 229 (1) [M+], 174 (96), 172 (100), 93
(20), 65 (36), 63 (13), 57 (24), 56 (9).
Anal. Calcd for C24H41NO2: C, 76.75; H, 11.00; N, 3.73. Found: C,
76.84; H, 11.05; N, 3.78.
Methyl Butylcarbamate (3e)
1H NMR: d = 0.87 (t, J = 6.5 Hz, 3 H, CH3CH2), 1.20–1.33 (m, 2 H,
CH3CH2), 1.33–1.50 (m, 2 H, CH3CH2CH2), 3.11 (d, J = 6.0 Hz,
2 H, CH2NH), 3.61 (s, 3 H, OCH3), 4.89 (m, 1 H, NH). Similar to
that reported.19
Benzyl Benzylcarbamate (3m)
1H NMR: d = 4.40 (d, J = 5.8 Hz, 2 H, CH2NH), 5.16 (s, 2 H,
OCH2), 5.24 (m, 1 H, NH), 7.10–7.50 (m, 10 H, ArH). Similar to
that reported.21
MS (EI, 70 eV): m/z (%) = 131 (10) [M+], 89 (7), 88 (100), 76 (6),
59 (10), 57 (6), 44 (21).
Synthesis 2008, No. 18, 2919–2924 © Thieme Stuttgart · New York