Facile S-alkyl thiocarbamate synthesis by a novel DBU-assisted carbonylation of amines with carbon monoxide and sulfur

Article abstract of DOI:10.1016/S0040-4020(03)00031-0

A novel DBU-assisted carbonylation of amines with carbon monoxide and sulfur has been developed for the synthesis of S-alkyl thiocarbamates. In the presence of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), S-alkyl thiocarbamates are synthesized in excellent yields from amines, carbon monoxide, sulfur, and alkyl halides under mild conditions (1 atm, 20°C). In the absence of DBU, however, no formation of S-alkyl thiocarbamate is observed. The present DBU-assisted carbonylation can also be applied to new synthetic methods for benthiocarb and orthobencarb (herbicides) and carbamoyl chlorides.

Full text of DOI:10.1016/S0040-4020(03)00031-0

Tetrahedron 59 (2003) 1327–1331
Facile S-alkyl thiocarbamate synthesis by a novel DBU-assisted
carbonylation of amines with carbon monoxide and sulfur
b
b
Takumi Mizuno,a Junko Takahashi and Akiya Ogawa
,
*
aOsaka Municipal Technical Research Institute, 1-6-50, Morinomiya, Joto-ku, Osaka 536-8553, Japan
bDepartment of Chemistry, Faculty of Science, Nara Women’s University, Kitauoyanishi-machi, Nara 630-8506, Japan
Received 28 November 2002; accepted 17 December 2002
Abstract—A novel DBU-assisted carbonylation of amines with carbon monoxide and sulfur has been developed for the synthesis of S-alkyl
thiocarbamates. In the presence of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), S-alkyl thiocarbamates are synthesized in excellent yields
from amines, carbon monoxide, sulfur, and alkyl halides under mild conditions (1 atm, 208C). In the absence of DBU, however, no formation
of S-alkyl thiocarbamate is observed. The present DBU-assisted carbonylation can also be applied to new synthetic methods for benthiocarb
and orthobencarb (herbicides) and carbamoyl chlorides. q 2003 Elsevier Science Ltd. All rights reserved.
1. Introduction
Carbonylation of primary amines with carbon monoxide
and sulfur to form urea derivatives was introduced by
Franz and Applegath in 1961.1–3 Furthermore, Grisley and
Stephens developed S-alkyl thiocarbamate (1) synthesis
from secondary amines, carbon monoxide, sulfur, and alkyl
halides in similar manners.4,5 However, these reactions
require high temperature and pressurized carbon monoxide.
In 1989, our research group has found that selenium exhibits
an excellent catalytic activity toward the carbonylation of
amines with carbon monoxide and sulfur. This selenium-
catalyzed carbonylation of amines (2) smoothly proceeds
Therefore, in our strategy, we explored a new and useful
route to the S-alkyl thiocarbamates under mild conditions.
under mild conditions to give thiocarbamate salts (3), and
the alkylation of which leads to the formation of S-alkyl
thiocarbamates (1) in excellent yields.7,8
Recently, we reported the sulfur-assisted carbonylation
of alcohols,12,13 amides,14 and ketones15 with carbon
Owing to the toxicity of elemental selenium, however, use
monoxide using DBU (1,8-diazabicyclo[5.4.0]undec-7-ene)
as a base. Herein, we wish to report a facile synthesis of
S-alkyl thiocarbamates (1) from amines, carbon monoxide,
sulfur, and alkyl halides under mild conditions (1 atm,
208C), strongly assisted by DBU.
of this preparative method is considerably limited for
industrial large-scale production of S-alkyl thiocarbamates,
some of which are used as herbicides (e.g. benthiocarb (1d)
and orthobencarb (1e)).9
2. Results and discussion
Our trial employing DBU as a base, which is cheap and
commercially available, leads to a successful carbonylation
of di-n-propylamine (2a) with carbon monoxide and sulfur.
Di-n-propylamine (2a) easily reacts with carbon monoxide
(1 atm) and sulfur (1.5 equiv.) at 208C for 18 h in the
presence of DBU (1.5 equiv.) in THF. The resulting
Keywords: S-alkyl thiocarbamates; DBU; carbon monoxide; sulfur;
carbonylation.
*
Corresponding author. Tel.: þ81-6-6963-8051; fax: þ81-6-6963-8049;
e-mail: tmizuno@omtri.city.osaka.jp
0040–4020/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4020(03)00031-0

1328
T. Mizuno et al. / Tetrahedron 59 (2003) 1327–1331
Table 1. Influence of bases (1.5 equiv.) on the synthesis of 1a
pylthiocarbamate (1a) is obtained in excellent yields
(93–99%) (entries 1, 3, and 4). Shorter reaction time (4 h)
provides the almost same yield (88%) of 1a (entry 2).
K2CO3 also affords 1a in fairly good yields (68%) (entry 5).
In contrast, the use of other bases (Dabco (1,4-diazabicyclo-
[2.2.2]octane), Et3N, N-methylpyrrolidine, NaOH, KOH,
Na2CO3, NaHCO3, and none) results in the poor yields
(0–39%) of the desired 1a (entries 6–13).
Entry
Base
Yield (%)
1
2
3
DBUa
DBU
DBNc
93
88b
94
99
68
11
0
4
5
6
7
DBA–DBUd
K2CO3
Dabcoe
Et3N
In the presence of 1.5 equiv. of DBU under 1 atm of carbon
monoxide at 208C for 18 h, S-alkyl thiocarbamates (1a–l)
are synthesized from the corresponding amines (2a–i) and
alkyl halides (Eq. (2), Table 2).
8
9
10
11
12
13
N-Methylpyrrolidine
NaOH
KOH
Na2CO3
NaHCO3
None
0
39
0
0
0
0f
a
1,8-Diazabicyclo[5.4.0]undec-7-ene.
4 h.
1,5-Diazabicyclo[4.3.0]non-5-ene.
6-Dibutylamino-1,8-diazabicyclo[5.4.0]undec-7-ene.
1,4-Diazabicyclo[2.2.2]octane.
Di-n-propylamine (2a) (2.0 equiv.) was used.
b
c
d
e
f
thiocarbamate salt (3a) in THF solution is esterified by
methyl iodide (1.5 equiv.) under an ambient pressure at
208C for 2 h. Finally, S-methyl N,N-di-n-propylthiocarba-
mate (1a) is obtained in 93% yield. In the absence of DBU,
however, 1a is not obtained at all (Eq. (1)).
ð2Þ
S-Alkyl thiocarbamates (1a–j) from secondary amines
(2a–g) are prepared in excellent yields under mild
conditions (1 atm, 208C) (entries 1–11), even in consider-
ably large scale (entries 2–4). EPTC (1b),8,10 benthiocarb
(1d),8,11 and orthobencarb (1e)8 used as herbicides, can also
be synthesized in good yields (entries 3, 5, and 6). The yield
of S-methyl N-n-butylthiocarbamate (1k) from the primary
amine (n-butylamine, 2h) is slightly lowered, accompanied
with the formation of the corresponding urea derivative
(entry 12).16 Furthermore, in spite of the low basicity of
aniline (2i), S-methyl N-phenylthiocarbamate (1l) is
obtained in good yield (entry 13).
ð1Þ
The influence of bases on this carbonylation of di-n-
propylamine (2a) with carbon monoxide and sulfur is
examined (Table 1). When strong bases such as DBU,
DBN (1,5-diazabicyclo[4.3.0]non-5-ene), and DBA–DBU
(6-dibutylamino-1,8-diazabicyclo[5.4.0]undec-7-ene) are
employed for this carbonylation, S-methyl N,N-di-n-pro-
Next, the chlorination of S-alkyl thiocarbamate (1) by
sulfuryl chloride is successfully performed to afford the
Table 2. Synthesis of S-alkyl thiocarbamates (1a–l)
Entry
R1
R2
R3
X
Yield (%)a
1
2
3
4
5
n-Pr
n-Pr
n-Pr
Et
n-Pr
n-Pr
n-Pr
Et
2a
2a
2a
2b
2b
Me
Me
Et
I
I
I
I
Cl
1a
93
1a
91b
91b
94b
87
1bc
1c
Me
Et
Et
1dd
6
Et
Et
2b
Cl
1ee
88
7
8
9
10
11
12
13
n-Bu
i-Pr
–(CH2)4–
–(CH2)5–
–(CH2)2O(CH2)2–
n-Bu
i-Pr
2c
2d
2e
2f
2g
2h
2i
Me
Me
Me
Me
Me
Me
Me
I
I
I
I
I
I
I
1f
1g
1h
1i
1j
1k
1l
93
83
84
84
95
78 (14)f
81
n-Bu
Ph
H
H
a
Reaction conditions: amine (10 mmol), sulfur (481 mg, 15 mmol), DBU (2.24 mL, 15 mmol), alkyl halide (15 mmol), THF (10 mL).
Amine (50 mmol), sulfur (2.40 g, 75 mmol), DBU (11.2 mL, 75 mmol), alkyl halide (75 mmol), THF (20 mL).
EPTC.
Benthiocarb.
Orthobencarb.
Yield of N,N0-di-n-butylurea.
b
c
d
e
f

T. Mizuno et al. / Tetrahedron 59 (2003) 1327–1331
1329
Scheme 1.
corresponding carbamoyl chloride (4) under mild con-
ditions.18,19,21 The slow addition of sulfuryl chloride to
S-methyl N,N-di-n-propylthiocarbamate (1a) at 08C fol-
lowed by vigorous stirring at 208C for 1 h gave N,N-di-n-
propylcarbamoyl chloride (4a) in quantitative yield after
purification by vacuum distillation (Eq. (3)). N,N-Di-n-
propylcarbamoyl chloride (4a) from 1b and N,N-diethyl-
carbamoyl chloride (4b) from 1c are also prepared in good
yields, by the chlorination using sulfuryl chloride.
thiocarbamates 3,25 we suggest a plausible pathway for
this DBU-assisted carbonylation of amines with carbon
monoxide and sulfur as follows (Scheme 1). Elemental
sulfur is readily subject to S–S bond fission by the reaction
with amines strongly assisted by DBU, to form DBU salts of
thiolate anions 6. The reaction of 6 with carbon monoxide
gives the carbonylated species 7. Through an intramolecular
rearrangement of 7 (path A) or elimination of carbonyl
sulfide from 7 (path B), DBU salts of thiocarbamates 3 are
generated.
It seems that main role of DBU on this carbonylation is the
acceleration on the formation of thiolates 6.
3. Conclusion
ð3Þ
A useful synthetic method for S-alkyl thiocarbamates (1)
has been developed under mild conditions, in which the
carbonylation of amines with carbon monoxide and sulfur is
powerfully assisted by DBU, DBN, and DBA–DBU. This
carbonylation is employed successfully for the synthesis
of benthiocarb (1d), orthobencarb (1e) (herbicides), and
carbamoyl chlorides (4).
In regard to the role of DBU on this carbonylation with
carbon monoxide and sulfur, we assumed DBU contributes
to the efficiency of the formation of carbonyl sulfide in situ
from carbon monoxide and sulfur at an early reaction stage.
We have found that carbonyl sulfide, when is blown into the
DMF solution of DBU at room temperature, affords white
solid, COS–DBU complex (5), which is thermally unstable
and regenerates carbonyl sulfide on warming to 458C.22,23
From the viewpoint of application to actual industrial
production of S-alkyl thiocarbamates (1) as herbicides, the
present reaction is very significant, in terms of the use of
easily available carbon monoxide, sulfur and DBU, and
mild reaction conditions.
4. Experimental
4.1. General
However, COS–DBU complex (5) was not generated from
DBU and sulfur in THF solution under the atmosphere of
carbon monoxide at 208C, although the conditions are
similar to those of the present carbonylation. This result
shows that no formation of carbonyl sulfide from carbon
monoxide and sulfur, even in the presence of DBU, when
primary or secondary amines are not present in situ.
Melting points were determined on a Mettler FP 5
instrument and were uncorrected. FT-IR spectra were
recorded on a Nicolet Magna-IR 550 instrument. H and
13C NMR spectra were obtained on a JEOL JNM-AL300
(300 MHz, 75 MHz) instrument. Chemical shifts were
reported in ppm relative to tetramethylsilane (d-units).
Mass and exact mass spectra were recorded on a JEOL JMS-
600 spectrometer. Amines (2a–i), alkyl halides, THF, DBU,
1
Based on our finding on the smooth reaction for salts of
thiolates 6 with carbon monoxide to convert into salts of

1330
T. Mizuno et al. / Tetrahedron 59 (2003) 1327–1331
other bases, sulfur (99.5%), carbon monoxide (99.9%), and
sulfuryl chloride were used as purchased.
167.9; MS (m/z, %) 203 (Mþ, 57), 156 (100), 132 (33), 100
(39), 75 (34), 57 (98).
4.2. Typical procedure for the synthesis of S-methyl N,N-
di-n-propyl thiocarbamate (1a) from di-n-propylamine
(2a), methyl iodide, carbon monoxide and sulfur
4.2.6. S-Methyl N,N-diisopropylthiocarbamate (1g). Oil;
IR (neat) 2970, 1660, 1280 cm21 1H NMR (300 MHz,
;
CDCl3) d 1.30 (brs, 12H), 2.30 (s, 3H), 3.51 (brs, 1H), 4.08
(brs, 1H); 13C NMR (75 MHz, CDCl3) d 12.4, 20.5, 47.2,
49.0, 166.2; MS (m/z, %) 175 (Mþ, 25), 128 (100), 86 (76),
75 (30). Exact MS calcd for C8H17NOS: 175.1031. Found:
175.1027.
A THF (10 mL) solution containing di-n-propylamine (2a)
(1.37 mL, 10 mmol), powdered sulfur (481 mg, 15 mmol)
and DBU (2.24 mL, 15 mmol) was vigorously stirred under
carbon monoxide (1 atm) at 208C for 18 h. Into the THF
solution of thiocarbamate salt, methyl iodide (0.93 mL,
15 mmol) was added slowly at 08C under argon atmosphere.
The reaction mixture was stirred for additional 2 h at 208C.
The resulting mixture was then poured into 1N HCl
(100 mL), and extracted with t-butyl methyl ether
(100 mL, 50 mL£2). After evaporation of solvents and
purification by short-column chromatography (silica gel,
toluene/AcOEt¼1:1), S-methyl N,N-di-n-propylthiocarba-
mate (1a) was afforded in an 93% yield (1.63 g). S-Methyl
N,N-di-n-propylthiocarbamate (1a)6–8,25: oil; IR (neat)
4.2.7. S-Methyl pyrrolidinecarbothioate (1h).8,25 Oil; IR
1
(neat) 2975, 2875, 1660, 1370 cm21; H NMR (300 MHz,
CDCl3) d 1.86–1.97 (m, 4H), 2.35 (s, 3H), 3.37 (t, J¼7 Hz,
2H), 3.53 (t, J¼7 Hz, 2H); 13C NMR (75 MHz, CDCl3) d
12.5, 24.5, 25.5, 45.8, 47.0, 166.2; MS (m/z, %) 145 (Mþ,
75), 98 (100), 55 (50).
4.2.8. S-Methyl piperidinecarbothioate (1i).6–8 Oil; IR
1
(neat) 2935, 1650, 1410, 1210 cm21; H NMR (300 MHz,
CDCl3) d 1.56–1.64 (m, 6H), 2.33 (s, 3H), 3.49 (brs, 4H);
13C NMR (75 MHz, CDCl3) d 12.8, 24.5, 25.6, 45.7, 167.2;
MS (m/z, %) 159 (Mþ, 55), 112 (100), 69 (51).
1
2965, 1655, 1405, 1225, 1125 cm21; H NMR (300 MHz,
CDCl3) d 0.90 (t, J¼7 Hz, 6H), 1.60 (brs, 4H), 2.32 (s, 3H),
3.28 (brs, 4H); 13C NMR (75 MHz, CDCl3) d 11.2, 12.8,
21.4, 49.3, 168.2; MS (m/z, %) 175 (Mþ, 100), 128 (89), 86
(79), 75 (65). Exact MS calcd for C8H17NOS: 175.1031.
Found: 175.1012.
4.2.9. S-Methyl morpholinecarbothioate (1j).25,26 Mp
71.88C (71–738C26); IR (melt) 2930, 2870, 1650, 1405,
1
1220 cm21; H NMR (300 MHz, CDCl3) d 2.28 (s, 3H),
3.49 (brs, 4H), 3.61 (t, J¼5 Hz, 4H); 13C NMR (75 MHz,
CDCl3) d 12.7, 44.9, 66.5, 168.2; MS (m/z, %) 161 (Mþ,
63), 114 (100), 70 (56).
4.2.1. S-Ethyl N,N-di-n-propylthiocarbamate (1b).6–8
;
Oil; IR (neat) 2965, 1650, 1405, 1220, 1125 cm21 1H
NMR (300 MHz, CDCl3) d 0.90 (t, J¼7 Hz, 6H), 1.28 (t,
J¼7 Hz, 3H), 1.59 (brs, 4H), 2.90 (q, J¼7 Hz, 2H), 3.27
(brs, 4H); 13C NMR (75 MHz, CDCl3) d 11.2, 15.3, 21.5, 24.6,
47.8, 167.7; MS (m/z, %) 189 (Mþ, 47), 128 (100), 86 (59).
4.2.10. S-Methyl N-butylthiocarbamate (1k).7,8 Oil; IR
(neat) 3320, 2960, 1655, 1520, 1215 cm21 1H NMR
;
(300 MHz, CDCl3) d 0.93 (t, J¼7 Hz, 3H), 1.31–1.41 (m,
2H), 1.46–1.53 (m, 2H), 2.35 (s, 3H), 3.30 (d, J¼5 Hz, 2H),
5.31 (brs, 1H); 13C NMR (75 MHz, CDCl3) d 12.1, 13.5,
19.7, 31.6, 41.1, 167.5; MS (m/z, %) 147 (Mþ, 77), 100 (99),
75 (31), 57 (100).
4.2.2. S-Methyl N,N-diethylthiocarbamate (1c).6–8 Oil;
1
IR (neat) 2975, 1650, 1405, 1250 cm21; H NMR (300
MHz, CDCl3) d 1.17 (t, J¼7 Hz, 6H), 2.32 (s, 3H), 3.38 (brs,
4H); 13C NMR (75 MHz, CDCl3) d 12.6, 13.3, 41.8, 167.4;
MS (m/z, %) 147 (Mþ, 53), 100 (100), 72 (72).
4.2.11. N,N0-Dibutylurea.2 Mp 68.28C (67–698C2); IR
(KBr) 3330, 2960, 1620, 1580, 1460, 1235 cm21; 1H NMR
(300 MHz, CDCl3) d 0.85 (t, J¼7 Hz, 6H), 1.20–1.36 (m,
8H), 2.95 (q, J¼6 Hz, 4H), 5.68 (brs, 2H); 13C NMR
(75 MHz, CDCl3) d 13.6, 19.5, 32.1, 38.8, 158.0; MS (m/z,
%) 172 (Mþ, 100), 130 (17), 101 (15), 74 (14), 57 (14).
4.2.3. S-4-Chlorobenzyl N,N-diethylthiocarbamate
(1d).7,8 Oil; IR (neat) 2975, 1650, 1410, 1250, 1115 cm21
;
1H NMR (300 MHz, CDCl3) d 1.16 (t, J¼7 Hz, 6H), 3.37
(brs, 4H), 4.10 (s, 2H), 7.23–7.30 (m, 4H); 13C NMR
(75 MHz, CDCl3) d 13.2, 33.7, 42.1, 128.5, 130.2, 132.7,
137.1, 166.2; MS (m/z, %) 257 (Mþ, 34), 125 (21), 100
(100), 72 (35).
4.2.12. S-Methyl N-phenylthiocarbamate (1k).7,8,27 Mp
84.68C (78–78.58C,8 808C27); IR (KBr) 3290, 1660, 1600,
1
1540, 1445, 1245, 1165, 755 cm21; H NMR (300 MHz,
4.2.4. S-2-Chlorobenzyl N,N-diethylthiocarbamate (1e).8
Oil; IR (neat) 2975, 1650, 1410, 1250, 1115 cm21; 1H NMR
(300 MHz, CDCl3) d 1.16 (t, J¼7 Hz, 6H), 3.38 (brs, 4H),
4.28 (s, 2H), 7.16–7.22 (m, 2H), 7.34–7.37 (m, 1H), 7.50–
7.53 (m, 1H); 13C NMR (75 MHz, CDCl3) d 13.3, 32.3,
42.0, 126.9, 128.5, 129.4, 131.2, 134.1, 136.3, 166.4; MS
(m/z, %) 257 (Mþ, 12), 222 (56), 189 (32), 128 (72), 100
(100), 86 (40), 72 (39).
CDCl3) d 2.35 (s, 3H), 7.08 (t, J¼7 Hz, 1H), 7.34 (t,
J¼8 Hz, 2H), 7.55 (d J¼8 Hz, 2H), 10.5 (s, 1H); 13C NMR
(75 MHz, CDCl3) d 11.7, 118.9, 123.2, 128.8, 139.0, 165.2;
MS (m/z, %) 167 (Mþ, 80), 119 (100), 92 (27), 77 (25).
4.3. General procedure for the synthesis of N,N-di-n-
propylcarbamoyl chloride (4a) by the chlorination of
S-methyl N,N-di-n-propylthiocarbamate (1a) with
sulfuryl chloride
4.2.5. S-Methyl N,N-di-n-butylthiocarbamate (1f).6–8
Oil; IR (neat) 2960, 1655, 1410, 1205, 1125 cm21
;
1H
Into neat S-methyl N,N-di-n-propylthiocarbamate (1a)
(3.51 g, 20 mmol), sulfuryl chloride (2.41 mL, 30 mmol)
was added slowly at 08C under argon atmosphere. The
reaction mixture was stirred for additional 1 h at 208C. After
NMR (300 MHz, CDCl3) d 0.94 (t, J¼7 Hz, 6H), 1.26–1.38
(m, 4H), 1.55 (brs, 4H), 2.32 (s, 3H), 3.30 (brs, 4H); 13C
NMR (75 MHz, CDCl3) d 12.7, 13.7, 20.0, 30.1, 47.3,

T. Mizuno et al. / Tetrahedron 59 (2003) 1327–1331
1331
8. Mizuno, T.; Nishiguchi, I.; Sonoda, N. Tetrahedron 1994, 50,
5669–5680.
purification by vacuum distillation, N,N-di-n-propyl-carba-
moyl chloride (4a) was given in 100% yield (3.27 g).
N,N-Di-n-propylcarbamoyl chloride (4a)6: oil; IR (neat)
9. A series of S-alkyl thiocarbamates (1) is well known as useful
herbicides.6,8,10,11
1
2965, 1735, 1405, 1220, 1125 cm21; H NMR (300 MHz,
10. Sanders, H. J. Chem. Engng News 1981, 59, 20–35.
11. Sugiyama, H. J. Synth. Org. Chem. Jpn 1980, 38, 555–563.
12. Mizuno, T.; Nishiguchi, I.; Hirashima, T.; Ogawa, A.; Kambe,
N.; Sonoda, N. Tetrahedron Lett. 1988, 29, 4767–4768.
13. Mizuno, T.; Takahashi, J.; Ogawa, A. Tetrahedron Lett. 2002,
43, 7765–7767.
CDCl3) d 0.90–0.96 (m, 6H), 1.58–1.73 (m, 4H), 3.29–
3.39 (m, 4H); 13C NMR (75 MHz, CDCl3) d 10.9, 20.6,
21.6, 51.4, 52.7, 148.9; MS (m/z, %) 165 (9), 163 (Mþ, 26),
136 (32), 134 (100), 128 (31), 92 (31). Exact MS calcd for
C7H14NOCl: 163.0764. Found: 163.0751.
4.3.1. N,N-Diethylcarbamoyl chloride (4b).28 Oil; IR
;
(neat) 2980, 1735, 1405, 1250, 1210, 1120 cm21 1H
NMR (300 MHz, CDCl3) d 1.19–1.26 (m, 6H), 3.38–3.52
(m, 4H); 13C NMR (75 MHz, CDCl3) d 12.7, 13.6, 44.4,
45.6, 148.5; MS (m/z, %) 137 (29), 135 (Mþ, 90), 122 (32),
120 (100), 100 (90), 92 (40), 72 (46).
14. Miyata, T.; Mizuno, T.; Nagahama, Y.; Nishiguchi, I.;
Hirashima, T.; Sonoda, N. Heteroat. Chem. 1991, 2, 473–475.
15. Mizuno, T.; Nishiguchi, I.; Hirashima, T.; Ogawa, A.; Kambe,
N.; Sonoda, N. Synthesis 1988, 257–259.
16. Ammonium salts of thiocarbamates from primary amines were
easily subject to the oxidation by molecular oxygen to form
urea derivatives.17
17. Mizuno, T.; Matsumoto, M.; Nishiguchi, I.; Hirashima, T.
Heteroat. Chem. 1993, 4, 455–458.
Acknowledgements
18. Generally, carbamoyl chlorides (3) were synthesized from
amines and phosgene.6
We thank SAN-APRO LTD. (Kyoto, Japan) for the gift of
DBA–DBU (6-dibutylamino-1,8-diazabicyclo[5.4.0]undec-
7-ene).
19. The chlorination of S-alkyl thiocarbamates (1) by benzene-
sulfenyl chloride or gaseous chlorine to form the correspond-
ing carbamoyl chlorides (3) was reported.20
20. Sitzmann, M. E.; Gilligan, W. E. J. Org. Chem. 1985, 50,
5879–5881.
References
21. Very recently, we reported benzyl chloroformate synthesis by
the carbonylation of benzyl alcohol with carbon monoxide and
sulfur, and the chlorination using sulfuryl chloride.13
22. Ogawa, A.; Kambe, N.; Murai, S.; Sonoda, N. Tetrahedron
1985, 41, 4813–4819.
1. Franz, R. A.; Applegath, F. J. Org. Chem. 1961, 26,
3304–3305.
2. Franz, R. A.; Applegath, F.; Morriss, F. V.; Baiocchi, F. J. Org.
Chem. 1961, 26, 3306–3308.
23. Recently, DBU–CO2 complex was synthesized and used for
the synthesis of N-alkyl carbamates.24
´
24. Perez, E. R.; da Silva, M. O.; Costa, V. C.; Rodrigues-Filho,
3. Franz, R. A.; Applegath, F.; Morriss, F. V.; Baiocchi, F.;
Bolze, C. J. Org. Chem. 1961, 26, 3309–3312.
4. Grisley, D. W., Jr.; Stephens, J. A. J. Org. Chem. 1961, 26,
3568.
U. P.; Franco, D. W. Tetrahedron Lett. 2002, 43, 4091–4093.
25. Mizuno, T.; Daigaku, T.; Nishiguchi, I. Tetrahedron Lett.
1995, 36, 1533–1536.
5. Many methods for the synthesis of S-alkyl thiocarbamates (1)
have been reported. Among them, the reaction of amines with
thiols and phosgene or with carbonyl sulfide, followed by
alkylation with alkyl halides has been known as the general
routes.6
26. Muehlbauer, E.; Pelster, H. German Patent 1161255, 1964;
Chem. Abstr. 1964, 60, 10559.
27. Jackson, H. E. British Patent 599177, 1948; Chem. Abstr.
1948, 42, 7331.
6. Tilles, H. J. Am. Chem. Soc. 1959, 81, 714–727.
7. Sonoda, N.; Mizuno, T.; Murakami, S.; Kondo, K.; Ogawa, A.;
Ryu, I.; Kambe, N. Angew. Chem., Int. Ed. Engl. 1989, 28,
452–453.
28. Identification of 4a was performed by comparison of the
spectra of 4a with those of commercially available authentic
sample.