Synthesis of N-aryl S-alkylthiocarbamates

Article abstract of DOI:10.1002/hc.10163

The synthesis of N-aryl S-alkylthiocarbamates was discussed. The carbamates were synthesized by reactions of isocyanates with LiAlHSH and then with alkyl halides. Melting points were determined by using Yanagimoto micromelting point apparatus and were corrected. It was found that LiAlHSH behaved in a similar fashion as LiAlHSeH.

Full text of DOI:10.1002/hc.10163

Heteroatom Chemistry
Volume 14, Number 4, 2003
Synthesis of N-Aryl S-Alkylthiocarbamates
Mamoru Koketsu, Chikashi Kobayashi, and Hideharu Ishihara
Department of Chemistry, Faculty of Engineering, Gifu University, Gifu 501-1193, Japan
Received 26 January 2003; revised 14 February 2003
isocyanates 1 and alkyl halides 3, using LiAlHSH 2.
ABSTRACT: Several N-aryl S-alkylthiocarbamates
Herein, we report a new method for preparation of S-
alkyl thiocarbamates 4 and confirm the usefulness of
LiAlHSH as a reagent for the introduction of sulfur
atom.
were synthesized by reactions of isocyanates with
ꢀ
C
LiAlHSH and then with alkyl halides.
2003 Wiley
Periodicals, Inc. Heteroatom Chem 14:374–378, 2003; Pub-
lished online in Wiley InterScience (www.interscience.
wiley.com). DOI 10.1002/hc.10163
RESULTS AND DISCUSSION
The reaction leading to N-aryl S-alkylthiocarba-
mates 4 is shown in Scheme 1. Phenyl isocyanate 1a
was added to an anhydrous THF solution of LiAlHSH
2 [9]. The reaction mixture was stirred at room tem-
perature for 1 h under an argon atmosphere. A so-
lution of methyl iodide 3a in THF was added to the
reaction mixture at room temperature. The resulting
reaction mixture was stirred for an additional 3 h.
After workup, S-methyl N-phenylthiocarbamate
4a was obtained in 84% yield. Reactions of three iso-
cyanates 1 with nine alkyl halides 3 also gave the cor-
responding N-aryl S-alkylthiocarbamates 4 (Table 1).
The yield using alkyl halides bearing longer carbon
chains tended to decrease because of their reduced
electrophilicity. These results confirm that LiAlHSH
2 affords a variety of N-aryl S-alkylthiocarbamates,
showing a reactivity similar to LiAlHSeH [8b]. The
13C NMR spectra of 4 in CDCl3 show interesting spec-
tral features at 20◦C. There is significant line broad-
ening of the peaks of C1, C2, C4, C6, and C7, while
those of C3, C5, and alkyl carbons gave typically
sharp peaks (Fig. 1, upper). These spectral features
were highly dependent on the conditions of the NMR
measurement. For example, the broad signals of 4
became sharper when the spectrum was measured
in DMSO-d6 or in CDCl3 at lower temperatures (0
and −20◦C). The 13C NMR spectra measured in CDCl3
at −40◦C showed sharp peaks similar to ordinary
spectra along with new small satellite peaks (Fig. 1,
lower). These interesting observations in the NMR
INTRODUCTION
Thiocarbamates have been used as key intermediates
for the synthesis of ureas [1] and isocyanates [2] and
are very important moieties in pesticides [3]. How-
ever, only a limited number of methods have been
reported for the preparation of the thiocarbamates.
For example, S-allylic thiocarbamates were obtained
from O-allylic thiocarbamates by 1,3-allyl migration
from the oxygen to the sulfur atom [4]. Other routes
are the reactions of alkyl thiocyanates with alcohols
[5], and of amines with elemental sulfur and carbon
monoxide in the presence of selenium [6]. A facile
method for the preparation of thiocarbamates would
certainly be very useful. Recently, we developed a
novel selenating reagent [7], LiAlHSeH which is gen-
erated by the stirring selenium powder with LiAlH4
in THF. This reagent is useful for preparing a variety
of selenium containing compounds [8]. However, ap-
plication of same procedure to the sulfur atom, while
reasonable, has not yet been been demonstrated. In
the present study, we investigated the preparation
of various thiocarbamates from the corresponding
Correspondence to: Mamoru Koketsu; e-mail: koketsu@cc.gifu-
u.ac.jp.
Contract grant sponsor: Ministry of Education, Culture, Sports,
Science and Technology of Japan.
Contract grant number: 14540490.
2003 Wiley Periodicals, Inc.
c
ꢀ
374

Synthesis of N-Aryl S-Alkylthiocarbamates 375
over sodium sulfate and evaporated to dryness. The
residue was purified by flash chromatography on
silica gel with dichloromethane/hexane (1:2) to give
4a 0.14 g (84%) as white crystals; mp 71.2–72.8◦C;
1
IR (KBr) 1661, 3288 cm−1; H NMR (CDCl3); δ 2.42
(3H, s, CH3), 7.11 (1H, t, J = 7.2 Hz, Ar), 7.12 (1H,
br s, NH), 7.31 (2H, t, J = 7.2 Hz, Ar), 7.41 (2H,
d, J = 7.2 Hz, Ar); 13C NMR (CDCl3); δ 12.6, 119.8,
124.4, 129.1, 137.7, (Ar), 162.6; MS (CI): m/z = 168
[M+ + 1].
SCHEME 1
spectra are predicted based on equilibrium in 4, be-
tween the major s-trans and the minor s-cis forms
(Scheme 2), as was previously observed in the NMR
spectra of Se-aryl N-alkylselenocarbamates [8b].
In conclusion, various S-aryl N-alkylthiocar-
bamates have been synthesized by reacting iso-
cyanates 1 with LiAlHSH 2 and then with alkyl
halides. It was confirmed that LiAlHSH 2 behaves
similar to LiAlHSeH [7], and represents an excellent
reagent for the introduction of sulfur.
S-Ethyl N-phenylthiocarbamate 4b. White crys-
1
tals; mp 63.9–65.1◦C; IR (KBr) 1651, 3281 cm−1; H
NMR (CDCl3); δ 1.33 (3H, t, J = 7.2 Hz, CH3), 2.98
(2H, q, J = 7.2 Hz, CH2), 7.09 (1H, t, J = 7.2 Hz, Ar),
7.21 (1H, br s, NH), 7.30 (2H, t, J = 7.2 Hz, Ar), 7.41
(2H, d, J = 7.2 Hz, Ar); 13C NMR (CDCl3); δ 15.5,
24.7, 119.7, 124.4, 129.1, 137.6 (Ar), 165.8; MS (CI):
m/z = 182 [M+ + 1].
EXPERIMENTAL
S-Propyl N-phenylthiocarbamate 4c. White crys-
Melting points were determined by use of Yanagi-
moto micromelting point apparatus and are uncor-
rected. IR spectra were measured on Perkin-Elmer
1600 spectrometer. 1H and 13C spectra were recorded
on a JEOL-JNM-ꢀ400 (400 MHz) spectrometer. Mass
spectra were obtained on a Shimadzu 9020-DF mass
spectrometer. Tetrahydrofuran was distilled from
sodium-benzophenone immediately prior to use.
1
tals; mp 73.2–75.6◦C; IR (KBr) 1653, 3280 cm−1; H
NMR (CDCl3); δ 1.00 (3H, t, J = 7.6 Hz, CH3), 1.67
(2H, m, CH2), 2.95 (2H, t, J = 7.6 Hz, CH2), 7.02 (1H,
br s, NH), 7.10 (1H, t, J = 7.6 Hz, Ar), 7.31 (2H, t,
J = 7.6 Hz, Ar), 7.41 (2H, d, J = 7.6 Hz, Ar); 13C NMR
(CDCl3); δ 13.2, 23.6, 32.2, 119.7–137.7 (Ar), 165.9;
MS (CI): m/z = 196 [M+ + 1].
S-Butyl N-phenylthiocarbamate 4d. White crys-
S-Methyl N-phenylthiocarbamate 4a. Phenyl
isocyanate 1a (0.22 ml, 2.0 mmol) was added to a
THF solution (10 ml) of LiAlHSH 2 (1.0 mmol). The
reaction mixture was stirred at room temperature
for 1 h. Methyl iodide 3a (0.06 ml, 1.0 mmol) was
added to the reaction mixture. The resulting reaction
mixture was stirred at room temperature for 3 h.
The mixture was extracted with dichloromethane
and washed with water. The organic layer was dried
1
tals; mp 64.3–65.0◦C; IR (KBr) 1652, 3287 cm−1; H
NMR (CDCl3); δ 0.92 (3H, t, J = 7.6 Hz, CH3), 1.42
(2H, m, J = 7.6 Hz, CH2), 1.64 (2H, quint, J = 7.6
Hz, CH2), 2.97 (2H, t, J = 7.6 Hz, CH2), 7.09 (1H,
t, J = 7.2 Hz, Ar), 7.13 (1H, br s, NH), 7.30 (2H,
t, J = 7.2 Hz, Ar), 7.40 (2H, d, J = 7.2 Hz, Ar); 13C
NMR (CDCl3); δ 13.6, 21.8, 29.9, 32.3, 119.6–137.8
(Ar), 166.0; MS (CI): m/z = 210 [M+ + 1].
TABLE 1 Synthesis of N-Aryl S-Alkylthiocarbamate
Thiocarbamate (4), Yield (%)a
Ar = C6H5
Ar = 4-CH3C6H4
(4j–4r)
Ar = 4-ClC6H4
(4s–4v)
RX ( 3)
(4a–4i)
b
CH3I
C2H5I
84
71
66
54
50
25
55
44
36
59
51
50
46
52
24
36
32
44
–
47
b
CH3(CH2)2I
CH3(CH2)3I
(CH3)2CH(CH2)2I
CH3(CH2)7Br
C H5CH2Br
C6H5(CH ) Br
C6H5(CH2)2Br
–
b
–
b
–
b
–
35
24
23
6
2 3
aIsolated yield.
bNot tried.

376 Koketsu, Kobayashi, and Ishihara
FIGURE 1 13C NMR spectra of compounds 4 at 20◦C (upper) and −40◦C (lower).
Hz, Ar); 13C NMR (CDCl3); δ 22.1, 27.4, 28.3, 30.8,
39.1, 119.6–137.7 (Ar), 165.9; MS (CI): m/z = 224
[M+ + 1].
S-Isopentyl N-phenylthiocarbamate 4e. White
crystals; mp 66.1–69.3◦C; IR (KBr) 1655, 3290 cm−1;
1H NMR (CDCl3); δ 0.92 (6H, t, J = 6.8 Hz, CH3), 1.54
(2H, q, CH2), 1.68 (1H, m, CH), 2.97 (2H, t, J = 8.0
Hz, CH2), 7.09 (1H, t, J = 7.2 Hz, Ar), 7.19 (1H, br s,
NH), 7.30 (2H, t, J = 7.2 Hz, Ar), 7.41 (2H, d, J = 7.2
S-Octyl N-phenylthiocarbamate 4f. White crys-
1
tals; mp 56.1–58.9◦C; IR (KBr) 1658, 3328 cm−1; H

Synthesis of N-Aryl S-Alkylthiocarbamates 377
SCHEME 2
NMR (CDCl3); δ 0.86 (3H, t, J = 6.8 Hz, CH3), 1.33
(10H, d, J = 6.8, CH2), 1.65 (2H, m, CH2), 2.96 (2H,
t, J = 6.8 Hz, CH2), 7.09 (1H, t, J = 7.2 Hz, Ar), 7.10
(1H, br s, NH), 7.30 (2H, t, J = 7.2 Hz, Ar), 7.41 (2H,
d, J = 7.2 Hz, Ar); 13C NMR (CDCl3); δ 14.0, 22.6,
28.7, 29.0, 29.1, 30.2, 30.3, 31.7, 119.6–137.7 (Ar),
165.9; MS (CI): m/z = 266 [M+ + 1].
S-Ethyl N-(4-methylphenyl)thiocarbamate 4k.
White crystals; mp 81.0–81.5◦C; IR (KBr) 1654, 3260
1
cm−1; H NMR (CDCl3); δ 1.33 (3H, t, J = 7.2 Hz,
CH3), 2.30 (3H, s, CH3), 2.96 (2H, q, J = 7.2 Hz,
CH2), 7.10 (1H, d, J = 8.4 Hz, Ar) , 7.21 (1H, br s,
NH), 7.28 (2H, t, J = 8.4 Hz, Ar); 13C NMR (CDCl3);
δ 15.5, 20.8, 119.8–134.6 (Ar), 165.8; MS (CI): m/z =
196 [M+ + 1].
S-Benzyl N-phenylthiocarbamate 4g. White
powder; mp 92.1–94.2◦C; IR (KBr) 1653, 3250 cm−1;
1H NMR (CDCl3); δ 4.22 (2H, s, CH2), 7.08–7.40
(10H, m, Ar), 7.10 (1H, br s, NH); 13C NMR (CDCl3);
δ 34.4, 119.8–137.8 (Ar), 165.1; MS (CI): m/z = 244
[M+ + 1].
S-Propyl N(4-methylphenyl)thiocarbamate 4l.
White crystals; mp 74.2–75.8◦C; IR (KBr) 1653, 3294
1
cm−1; H NMR (CDCl3); δ 1.00 (3H, t, J = 7.6 Hz,
CH3), 1.68 (2H, m, CH2), 2.30 (3H, s, CH3), 2.95 (2H,
t, J = 7.6 Hz, CH2), 7.03 (1H, br s, NH), 7.10 (1H,
d, J = 8.4 Hz, Ar) , 7.28 (2H, t, J = 8.4 Hz, Ar); 13C
NMR (CDCl3); δ 13.2, 20.8, 23.6, 32.1, 119.9–135.2
(Ar), 166.0; MS (CI): m/z = 210 [M+ + 1].
S-Phenetyl N-phenylthiocarbamate 4h. White
crystals; mp 108.1–110.3◦C; IR (KBr) 1652, 3382
1
cm−1; H NMR (CDCl3); δ 2.96 (2H, t, J = 6.8 Hz,
CH2), 3.21 (2H, t, J = 7.7 Hz, CH2), 7.08–7.40 (10H,
m, Ar), 7.43 (1H, br s, NH); 13C NMR (CDCl3); δ 31.5,
36.6, 119.7–139.9 (Ar), 165.5; MS (CI): m/z = 258
[M+ + 1].
S-Butyl N-(4-methylphenyl)thiocarbamate 4m.
White crystals; mp 73.9–75.1◦C; IR (KBr) 1651, 3297
1
cm−1; H NMR (CDCl3); δ 0.91 (3H, t, J = 7.6 Hz,
CH3), 1.40 (2H, m, J = 7.6 Hz, CH2), 1.62 (2H, quint,
J = 7.6 Hz, CH2), 2.29 (3H, s, CH3), 2.95 (2H, t,
J = 7.6 Hz, CH2), 7.08 (1H, d, J = 8.4 Hz, Ar), 7.23
(1H, br s, NH), 7.28 (2H, t, J = 8.4 Hz, Ar); 13C NMR
(CDCl3); δ 13.5, 20.7, 21.8, 29.9, 32.3, 119.9–135.1
(Ar), 166.0; MS (CI): m/z = 224 [M+ + 1].
S-3-Phenyl-propyl N-phenylthiocarbamate 4i.
White crystals; mp 78.3–79.8◦C; IR (KBr) 1652, 3386
1
cm−1; H NMR (CDCl3); δ 1.99 (2H, quint, J = 7.2
Hz, CH2), 2.73 (2H, t, J = 7.2 Hz, CH2), 2.99 (2H,
t, J = 7.2 Hz, CH2), 7.08–7.41 (10H, m, Ar), 7.17
(1H, br s, NH); 13C NMR (CDCl3); δ 29.7, 31.8, 34.7,
119.6–141.5 (Ar), 165.7; MS (CI): m/z = 272 [M+ + 1].
S-Isopentyl N-(4-methylphenyl)thiocarbamate 4n.
White crystals; mp 33.1–35.6◦C; IR (KBr) 1657, 3318
1
S-Methyl N-(4-methylphenyl)thiocarbamate 4j.
Yellow crystals; mp 102.1–103.5◦C; IR (KBr) 1654,
cm−1; H NMR (CDCl3); δ 0.92 (6H, t, J = 6.8 Hz,
CH3), 1.53 (2H, q, CH2), 1.67 (1H, m, CH), 2.30 (3H,
s, CH3), 2.96 (2H, t, J = 7.2 Hz, CH2), 7.06 (1H, br
s, NH), 7.10 (1H, d, J = 8.4 Hz, Ar), 7.28 (2H, t,
J = 8.4 Hz, Ar); 13C NMR (CDCl3); δ 20.8, 22.1, 27.4,
28.3, 30.8, 39.1, 120.0–135.1 (Ar), 164.2; MS (CI):
m/z = 238 [M+ + 1].
1
3242 cm−1; H NMR (CDCl3); δ 2.30 (3H, s, CH3),
2.39 (3H, s, CH3), 7.10 (1H, d, J = 8.4 Hz, Ar), 7.27
(1H, br s, NH), 7.28 (2H, t, J = 8.4 Hz, Ar); 13C NMR
(CDCl3); δ 12.5, 20.7, 119.9–135.0, (Ar), 166.3; MS
(CI): m/z = 182 [M+ + 1].

378 Koketsu, Kobayashi, and Ishihara
S-Octyl N-(4-methylphenyl)thiocarbamate 4o.
Yellow crystals; mp 61.0–62.1◦C; IR (KBr) 1650,
31.6, 36.5, 120.8–139.8 (Ar), 165.6; MS (CI): m/z =
292 [M+ + 1].
1
3301 cm−1; H NMR (CDCl3); δ 0.87 (3H, t, J = 6.8
Hz, CH3), 1.31 (10H, d, J = 6.8, CH2), 1.64 (2H,
quint, J = 6.8 Hz, CH2), 2.30 (3H, s, CH3), 2.95 (2H,
t, J = 6.8 Hz, CH2), 7.02 (1H, br s, NH), 7.10 (1H,
d, J = 8.4 Hz, Ar), 7.28 (2H, t, J = 8.4 Hz, Ar); 13C
NMR (CDCl3); δ 14.0, 20.8, 22.6, 28.7, 29.0, 29.1,
30.2, 30.3, 31.7, 119.8–135.1 (Ar), 165.9; MS (CI):
m/z = 280 [M+ + 1].
S-3-Phenyl-propyl N-(4-chlorophenyl)thiocarba-
mate 4v. White crystals; mp 85.3–86.0◦C; IR (KBr)
1655, 3328 cm−1; 1H NMR (CDCl3); δ 1.99 (2H, quint,
J = 7.6 Hz, CH2), 2.73 (2H, t, J = 7.6 Hz, CH2), 2.98
(2H, t, J = 7.6 Hz, CH2), 7.06 (1H, br s, NH), 7.17–
7.37 (9H, m, Ar); 13C NMR (CDCl3); δ 29.7, 31.7, 34.7,
120.8–141.0 (Ar), 165.8; MS (CI): m/z = 306 [M+ + 1].
S-Benzyl N-(4-methylphenyl)thiocarbamate 4p.
White powder; mp 109.1–110.3◦C; IR (KBr) 1653,
ACKNOWLEDGMENT
1
3250 cm−1; H NMR (CDCl3); δ 2.30 (3H, s, CH3),
The authors thank Professor Robert J. Linhardt for
his critical reading of this manuscript.
4.21 (2H, s, CH2), 7.02 (1H, br s, NH), 7.09–7.36 (9H,
m, Ar); 13C NMR (CDCl3); δ 20.8, 34.4, 119.9–137.9
(Ar), 166.2; MS (CI): m/z = 258 [M+ + 1].
REFERENCES
S-Phenetyl N-(4-methylphenyl)thiocarbamate 4q.
White crystals; mp 97.5–98.7◦C; IR (KBr) 1651, 3270
cm−1; 1H NMR (CDCl3); δ 2.29 (3H, s, CH3), 2.71 (2H,
t, J = 7.8 Hz, CH2), 2.97 (2H, t, J = 7.8 Hz, CH2),
7.08–7.29 (9H, m, Ar), 7.13 (1H, br s, NH); 13C NMR
(CDCl3); δ 20.8, 29.6, 31.8, 119.9–141.1 (Ar), 167.7;
MS (CI): m/z = 272 [M+ + 1].
[1] (a) Mizuno, T.; Kino, T.; Ito, T.; Miyata, T. Synthetic
Commun 2000, 30, 3081–3089; (b) Anbazhagan, M.;
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C. F. J Agr Entomol 1990, 7, 293–304; (c) Iwata,
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[4] (a) Bo¨hme, A.; Gais, H.-J. Tetrahedron: Asymmetry
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(c) Sakamoto, M.; Yoshiaki, M.; Takahashi, M.; Fujita,
T.; Watanabe, S. J Chem Soc, Perkin Trans 1 1995, 373–
377.
S-3-Phenyl-propyl N-(4-methylphenyl)thiocarba-
mate 4r. White crystals; mp 85.3–86.0◦C; IR (KBr)
1653, 3274 cm−1; 1H NMR (CDCl3); δ 1.98 (2H, quint,
J = 7.6 Hz, CH2), 2.29 (3H, s, CH3), 2.71 (2H, t,
J = 7.6 Hz, CH2), 2.97 (2H, t, J = 7.6 Hz, CH2), 7.08–
7.29 (9H, m, Ar), 7.13 (1H, br s, NH); 13C NMR
(CDCl3); δ 20.8, 29.6, 31.8, 34.7, 119.9–141.1 (Ar),
167.7; MS (CI): m/z = 286 [M+ + 1].
[5] Riemschneider, R. J Am Chem Soc 1956, 78 844–847.
[6] (a) Mizuno, T.; Nishiguchi, I.; Sonoda, N. Tetrahedron
1994, 50, 5669–5680; (b) Sonoda, N.; Mizuno, T.;
Murakami, S.; Kondo, K.; Ogawa, A.; Ryu, I.; Kambe,
N. Angewandte Chem 1989, 101, 476–477; (c) Koch, P.
Tetrahedron Lett 1975, 2087–2088.
S-Ethyl N-(4-chlorophenyl)thiocarbamate 4s.
White crystals; mp 95.1–96.2◦C; IR (KBr) 1651, 3271
1
cm−1; H NMR (CDCl3); δ 1.33 (3H, t, J = 7.6 Hz,
CH3), 2.98 (2H, q, J = 7.6 Hz, CH2), 7.13 (1H, br s,
NH), 7.26 (2H, t, J = 8.4 Hz, Ar), 7.36 (2H, t, J =
8.4 Hz, Ar); 13C NMR (CDCl3); δ 15.4, 24.7, 120.8–
136.2 (Ar), 166.0; MS (CI): m/z = 216 [M+ + 1].
[7] Ishihara, H.; Koketsu, M.; Fukuta, Y.; Nada, F. J Am
Chem Soc 2001 123, 8408–8409.
[8] (a) Koketsu, M.; Fukuta, Y.; Ishihara, H. J Org Chem
2002, 67, 1008–1011; (b) Koketsu, M.; Ishida, M.;
Takakura, N.; Ishihara, H. J Org Chem 2002, 67,
486–490; (c) Koketsu, M.; Nada, F.; Hiramatsu, S.;
Ishihara, H. J Chem Soc, Perkin Trans 1, 2002, 737–
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[9] Preparation of LiAlHSH 2: To a solution of sulfur pow-
der (0.3 g, 10 mmol) in dry THF (100 ml) was added
lithium aluminum hydride (0.38 g, 10.0 mmol) at 0◦C
under an argon atmosphere. The mixture was stirred
for 30 min. The sulfur powder was consumed within
10 min. The reaction mixture became a heterogeneous
grayish suspension. The reagent, formed in situ in this
way, was used for further reaction.
S-Benzyl N-(4-chlorophenyl)thiocarbamate 4t.
White powder; mp 115.0–116.3◦C; IR (KBr) 1649,
1
3244 cm−1; H NMR (CDCl3); δ 4.21 (2H, s, CH2),
7.07 (1H, br s, NH), 7.11–7.35 (9H, m, Ar); 13C NMR
(CDCl3); δ 34.4, 121.0–137.6 (Ar), 165.4; MS (CI):
m/z = 278 [M+ + 1].
S-Phenetyl N-(4-chlorophenyl)thiocarbamate 4u.
White crystals; mp 120.1–121.9◦C; IR (KBr) 1651,
1
3293 cm−1; H NMR (CDCl3); δ 2.96 (2H, t, J = 7.8
Hz, CH2), 3.22 (2H, t, J = 7.8 Hz, CH2), 7.03 (1H, br
s, NH), 7.23–7.37 (9H, m, Ar); 13C NMR (CDCl3); δ