A facile KF/Al2O3-mediated, one-pot synthesis of symmetrical trithiocarbonates from alkyl halides and carbon disulfide

Article abstract of DOI:10.1246/cl.2008.22

A facile, efficient, and convenient method has been developed for the one-pot synthesis of symmetrical trithiocarbonates from carbon disulfide and various alkyl halides in the presence of KF/Al₂O₃ in DMF at room temperature. Copyright

Full text of DOI:10.1246/cl.2008.22

22
Chemistry Letters Vol.37, No.1 (2008)
A Facile KF/Al2O3-mediated, One-pot Synthesis of Symmetrical Trithiocarbonates
from Alkyl Halides and Carbon Disulfide
Barahman Movassagh,ꢀ1;2 Mohammad Soleiman-Beigi,1 and Mohammad Nazari1
1Department of Chemistry, K. N. Toosi University of Technology, P. O. Box 16315-1618, Tehran, Iran
2Kermanshah Oil Refining Company, Kermanshah, Iran
(Received September 10, 2007; CL-070977)
A facile, efficient, and convenient method has been devel-
room temperature in an aerial atmosphere catalyzed by KF (40%
by weight)/Al2O3.
oped for the one-pot synthesis of symmetrical trithiocarbonates
from carbon disulfide and various alkyl halides in the presence
of KF/Al2O3 in DMF at room temperature.
The experiments were initially conducted with benzyl bro-
mide and carbon disulfide, as a model reaction, at various molar
ratios, solvents, and temperatures under an aerial atmosphere. It
was found that equimolar amounts (3 mmol) of benzyl bromide
and CS2 in dry dimethylformamide (DMF) produced the desired
product in 68% yield within 17 h at room temperature. Under the
same reaction conditions, another experiment was also carried
out with molar ratio of benzyl bromide:CS2 = 1:1.5, for which
the isolated yield of the product was 92%. Therefore, we decided
to perform our study at this molar ratio in dry DMF at 25 ꢁC.
To establish the generality of this process, various alkyl
halides were added to stirred mixture of carbon disulfide and
In recent years, synthesis of symmetrical and unsymmetrical
dialkyl trithiocarbonates has attracted much attention, since they
represent an important class of key compounds that have been
used for various applications, especially for the preparation of
insecticides, pesticides in agriculture and as lubricating addi-
tives.1 Furthermore, radical polymerization with thiocarbonyl-
thio reversible addition–fragmentation chain-transfer (RAFT)
agents2–4 is arguably one of the most versatile processes for liv-
ing free-radical polymerization displaying superior flexibility
with respect to monomers and reaction conditions. For instance,
dibenzyl trithiocarbonate (DBTTC) derivatives are focused as
RAFT agents,4,5 which enables controlled free-radical polymer-
ization of various vinyl monomers to afford polymers with nar-
row polydispersities and controlled molecular weights.
Some procedures for preparation of trithiocarbonates have
been developed including reactions of thiols with thiophosgene,6
arylchlorothioformates with alkanethiols,7 sodium trithiocarbon-
ates with alkyl halides,8 benzenethiols and alkyl halides with
carbon disulfide in the presence of a phase-transfer catalyst.9
Another general method involves the dialkylation of the trithio-
carbonate anion with halides, using phase-transfer catalysts or at
elevated temperature.10 However, various disadvantages such as
synthetic inconvenience, unavailability of starting materials,
use of large excess of highly toxic or stinky chemicals, and for-
mation of unwanted side products such as sulfides, etc. encoun-
tered in the reported methodologies necessitate the development
of a more efficient and convenient method. Very recently, Wood
and co-workers reported the synthesis of symmetrical trithiocar-
bonates using 1,10-thiocarbonyl diimidazole (TCDI) and primary
thiols;11 this method, however, needs an inert atmosphere and
elevated temperature (60 ꢁC) and gives moderate yields of the
product. In a recent report, symmetrical trithiocarbonates were
obtained from various alkyl halides with carbon disulfide and
cesium carbonate under ambient conditions;12 but, this reagent
is rather expensive.
KF/Al2O3 in DMF at 25 ꢁC (Scheme 1).
2ꢂ 18
The trithiocarbonate anion (CS3
)
is known to be pre-
pared by reacting ammonium sulfide, strong aqueous ammonia,
aqueous alkali-metal hydroxide, or alkali-metal sulfide with car-
bon disulfide. When carbon disulfide was added to the suspen-
sion of KF/Al2O3 in dry DMF, and the mixture was stirred vig-
orously at 25 ꢁC, the colorless mixture changed to blood red so-
lution within 15 min, indicating the formation of trithiocarbonate
anion.18 In situ alkylation with alkyl halides for the appropriate
time (Table 1) followed by filtration, evaporation of DMF, addi-
tion of water, and extraction with Et2O afforded the crude sym-
metrical trithiocarbonates; further purification can be achieved
by preparative TLC.19 The structures of all the products were
established from their analytical and spectral (IR, 1H and
13C NMR) properties. Potassium fluoride and alumina are both
inexpensive and commercially available. We found that this
method was applicable for trithiocarbonation of benzyl, allyl,
primary, and secondary halides. The results are summarized in
Table 1. The procedure worked fine with primary, benzyl
(PhCH2) as well as allyl halides (Entries 1, 2, and 5–10,
Table 1) to give symmetrical trithiocarbonates in high to excel-
lent yields. The results clearly show the need for longer reaction
times for secondary halides (Entries 3, 11, and 12, Table 1),
giving the products with lower yields. Under the same reaction
conditions, tertiary halides (Entries 4 and 13, Table 1) does
not produce the expected trithiocarbonate even after 40–48 h.
This represents the SN2 type nucleophilic reaction.
The potassium fluoride on alumina continues to attract much
interest from organic chemists due to the versatility of use in
synthetic chemistry.13 Its benefit have been achieved by taking
advantage of the strongly basic nature of KF/Al2O3 which has
allowed it to replace organic bases in a number of reactions.14–17
The high efficacy and ease of product isolation prompted us to
investigate its use for preparation of a variety of trithiocarbon-
ates. We report here an efficient one-pot synthesis of symmetrical
dialkyl trithiocarbonates by reaction of alkyl halides with CS2 at
To conclude, we have developed a new convenient and effi-
cient protocol for the one-pot synthesis of symmetrical trithio-
carbonates from carbon disulfide and various alkyl halides in
S
KF/Al2O3
R
R
2 R-X + 3 CS2
S
S
DMF, 25 °C, air
Scheme 1.
Copyright Ó 2008 The Chemical Society of Japan

Chemistry Letters Vol.37, No.1 (2008)
23
Table 1. Trithiocarbonylation of various alkyl halides
Soc. Jpn. 1984, 57, 3353.
10 a) A. W. M. Lee, W. H. Chan, H. C. Wong, Synth. Commun.
1988, 18, 1531. b) M.-K. Leung, D.-T. Hsieh, K.-H. Lee,
J.-C. Liou, J. Chem. Res., Synop. 1995, 478.
11 M. R. Wood, D. J. Duncalf, S. P. Rannard, S. Perrier, Org.
Lett. 2006, 8, 553.
Entry
Alkyl halide
Time/h
Yielda/%
1
2
3
4
5
6
7
8
9
10
11
12
13
PhCH2Br
PhCH2Cl
12
18
20
48
17
20
17
20
18
18
35
35
40
92
90
PhCH(CH3)Br
PhC(CH3)2Br
CH2=CHCH2Br
CH2=CHCH2Cl
CH3CH2I
79
No reaction
12 N. Aoyagi, B. Ochiai, H. Mori, T. Endo, Synlett 2006, 636.
13 B. E. Blass, Tetrahedron 2002, 58, 9301.
85
84
93
87
94
95
70
14 B. Movassagh, S. Shokri, Tetrahedron Lett. 2005, 46, 6923.
15 B. Movassagh, Y. Zakinezhad, J. Chem. Res. 2006, 369.
16 B. Movassagh, S. Shokri, Synth. Commun. 2005, 35, 887.
17 a) G. W. Kabalka, L. Wang, V. Namboodiri, R. M. Pagni,
Tetrahedron Lett. 2000, 41, 5151. b) V. K. Yadav, K. G.
Babu, M. Mittal, Tetrahedron 2001, 57, 7047. c) G. W.
Kabalka, L. Wang, R. M. Pagni, Synlett 2001, 108. d)
B. E. Blass, C. L. Harris, D. E. Portlock, Tetrahedron Lett.
2001, 42, 1611.
CH3I
CH3(CH2)5Br
CH3(CH2)7I
(CH3)2CHBr
CH3CH2CH(CH3)Br
(CH3)3CBr
75
No reaction
aIsolated yields.
18 E. Wertheim, J. Am. Chem. Soc. 1926, 48, 826.
the presence of KF/Al2O3 at room temperature. This method
offers significant advantages over earlier reported procedures
in that it avoids the need to apply thiol and toxic thiophosgen,
features a simple reaction procedure and mild conditions, easy
work-up, ready availability of the reagent, and high yields of
the products.
19 General procedure: A mixture of KF/Al2O3 (2 g, 40% by
weight)16 and carbon disulfide (3 mmol) in DMF (5 mL)
was vigorously stirred at 25 ꢁC for 15 min; then, alkyl halide
(2 mmol) was added to the red blood mixture. The color
of the mixture immediately changed from red to yellow.
Stirring of the resulting reaction mixture was continued at
25 ꢁC for the appropriate time (Table 1). The progress of
the reaction was monitored by TLC. After completion of
the reaction, the mixture was filtered and the filtrate was
evaporated, Et2O (30 mL) was added and washed with water
(2 ꢃ 15 mL) and dried over anhydrous Na2SO4. The solvent
was evaporated to give the crude trithiocarbonate, which was
purified by preparative TLC (silica gel, eluent, n-hexane).\
Dibenzyl trithiocarbonate: IR (neat): ꢀmax 1602, 1494,
The authors thank the K. N. Toosi University of Technology
Research Council and Kermanshah Oil Refining Company for
financial support.
References and Notes
1
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Degani, R. Fochi, A. Gatti, V. Regondi, Synthesis 1986,
894, and references therein.
1062 (C=S) cmꢂ1 1H NMR (500 MHz, CDCl3): ꢁ 7.31–
.
7.20 (m, 10H), 4.58 (s, 4H). 13C NMR (125 MHz, CDCl3):
ꢁ 223.2, 135.4, 129.7, 129.2, 128.3, 42.0.
Diallyl trithiocarbonate: IR (neat): ꢀmax 1638, 1062 (C=S)
cmꢂ1 1H NMR (500 MHz, CDCl3): ꢁ 5.86–5.77 (m, 2H),
.
2
J. Chiefari, B. Y. K. Chong, F. Ercole, J. Krstina, J. Jeffery,
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5.27 (dd, 2H, J ¼ 17:0, 1.3 Hz), 5.14 (dd, 2H, J ¼ 10:0,
1.3 Hz), 3.98 (d, 4H, J ¼ 6:8 Hz). 13C NMR (125 MHz,
CDCl3): ꢁ 222.9, 131.4, 120.1, 40.1.
Diethyl trithiocarbonate: IR (neat): ꢀmax 1078 (C=S) cmꢂ1
.
3
4
5
1H NMR (500 MHz, CDCl3): ꢁ 3.31 (q, 4H, J ¼ 7:4 Hz),
1.29 (t, 6H, J ¼ 7:4 Hz). 13C NMR (125 MHz, CDCl3): ꢁ
224.8, 31.5, 13.5.
Di-n-octyl trithiocarbonate: IR (neat): ꢀmax 1062 (C=S)
cmꢂ1
.
1H NMR (500 MHz, CDCl3): ꢁ 3.29 (t, 4H, J ¼
7:3 Hz), 1.63 (quin, 4H, J ¼ 7:3 Hz), 1.34 (quin, 4H, J ¼
7:0 Hz), 1.24–1.20 (m, 16H), 0.82 (t, 6H, J ¼ 6:2 Hz).
13C NMR (125 MHz, CDCl3): ꢁ 225.1, 37.3, 32.2, 29.6,
29.5, 29.4, 28.5, 23.1, 14.6.
6
7
8
F. Runge, Z. El-Hewehi, J. Prakt. Chem. 1959, 10, 268.
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Diisopropyl trithiocarbonate: IR (neat): ꢀmax 1078 (C=S)
1
cmꢂ1. H NMR (500 MHz, CDCl3): ꢁ 4.14 (sept, 2H, J ¼
6:9 Hz), 1.34 (d, 12H, J ¼ 6:9 Hz). 13C NMR (125 MHz,
CDCl3): ꢁ 223.9, 42.1, 22.5.
9
A. Sugawara, M. Shirahata, S. Sato, R. Sato, Bull. Chem.
Published on the web (Advance View) December 1, 2007; doi:10.1246/cl.2008.22