Synthesis of N-(3- and 4-substituted phenyl)-O-isobutyl thionocarbamates from O-isobutyl xanthate and amines using a nano-platinum multi-walled carbon nanotube catalyst

Article abstract of DOI:10.1007/s00706-011-0568-5

Twelve N-(3- and 4-substituted phenyl)-O-isobutyl thionocarbamates, eight of which are novel, were synthesized from O-isobutyl xanthate and 3- and 4-substituted anilines in the presence of a nano-platinum aminophenyl modified multi-walled carbon nanotube catalyst. The nano-Pt catalyst was prepared on a carbon nanotube support modified by diazotization, nitro group reduction, and subsequent microwave-assisted nano-Pt precipitation. The catalyst was characterized by Fourier transform infrared (FT-IR) spectroscopy, elemental analysis, thermogravimetric analysis, and transmission electron microscopy. The nano-platinum/modified carbon nanotube catalyst was compared with a commercial Pt/active carbon catalyst in terms of product purity and yield. The results obtained by the use of the catalysts were additionally compared with those obtained by reaction of sodium isobutyl xanthogenacetate and 3- and 4-substituted anilines. Full structure characterization of the synthesized N-(substituted phenyl)-O-isobutyl thionocarbamates was achieved using FT-IR, ¹H and ¹³C NMR, and mass spectrometric methods, and their purity was proved by elemental analysis and gas chromatography. The new catalytic method offers advantages over the commercial method, such as higher yields and no product purification is required, thus conforming to the principles of ecologically friendly syntheses.

Full text of DOI:10.1007/s00706-011-0568-5

Monatsh Chem (2011) 142:1045–1053
DOI 10.1007/s00706-011-0568-5
ORIGINAL PAPER
Synthesis of N-(3- and 4-substituted phenyl)-O-isobutyl
thionocarbamates from O-isobutyl xanthate and amines using
a nano-platinum multi-walled carbon nanotube catalyst
•
Milutin M. Milosavljevic Goran D. Vukovic
•
´
Aleksandar D. Marinkovic Radoslav Aleksic
´
•
•
´
´
´
Petar S. Uskokovic
Received: 26 March 2011 / Accepted: 26 June 2011 / Published online: 19 July 2011
Ó Springer-Verlag 2011
Abstract Twelve N-(3- and 4-substituted phenyl)-O-iso-
butyl thionocarbamates, eight of which are novel, were
synthesized from O-isobutyl xanthate and 3- and 4-substi-
tuted anilines in the presence of a nano-platinum
aminophenyl modified multi-walled carbon nanotube cata-
lyst. The nano-Pt catalyst was prepared on a carbon nanotube
support modified by diazotization, nitro group reduction, and
subsequent microwave-assisted nano-Pt precipitation. The
catalyst was characterized by Fourier transform infrared
(FT-IR) spectroscopy, elemental analysis, thermogravimet-
ric analysis, and transmission electron microscopy. The
nano-platinum/modified carbon nanotube catalyst was
compared with a commercial Pt/active carbon catalyst in
terms of product purity and yield. The results obtained by the
use of the catalysts were additionally compared with those
obtained by reaction of sodium isobutyl xanthogenacetate
and 3- and 4-substituted anilines. Full structure character-
ization of the synthesized N-(substituted phenyl)-O-isobutyl
required, thus conforming to the principles of ecologically
friendly syntheses.
Keywords Amines ꢀ Nanostructure ꢀ
Nucleophilic substitutions ꢀ Heterogeneous catalysis ꢀ
Thionocarbamates ꢀ Nano-Pt/NH2Ph-MWCNT
Introduction
Thio- and thionocarbamates are derivatives of thiocarba-
mic acid, either thiol or thiono esters, respectively [1, 2].
Their structural characteristics, direct bonding of the car-
bonyl and thiocarbonyl group and nitrogen, contribute to
their broad range of biological activities, such as fungicidal
[3, 4], bactericidal [3, 5], herbicidal [6–8], germicidal
and pesticidal [9–11], and insecticidal [12, 13]. In addition,
O-alkylthionocarbamates were used as polymerization
accelerators and selective flotoreagents [14].
1
thionocarbamates was achieved using FT-IR, H and 13C
NMR, and mass spectrometric methods, and their purity was
proved by elemental analysis and gas chromatography. The
new catalytic method offers advantages over the commercial
method, such as higher yields and no product purification is
There are many procedures for the synthesis of alkyl
thionocarbamates, such as aminolysis of alkaline salts of
xanthogenacetic acid with or without a catalyst. As an
example, an alkyl thionocarbamate was synthesized from
diethyl dixanthogenate and xanthate and amines in the
presence of manganese(II) acetate and nickel zeolite cata-
lysts [15]. Thionocarbamates can also be prepared by the
reaction of xanthogenates and amines in the presence of
nickel and palladium salt catalysts [16]. The oxidation of
an amine salt of xanthogenic acid, by hydrogen peroxide
and sodium hypochlorite, led to a high yield of isopropyl
thionocarbamate [14].
´
´
´
A. D. Marinkovic (&) ꢀ R. Aleksic ꢀ P. S. Uskokovic
Faculty of Technology and Metallurgy, University of Belgrade,
Karnegijeva 4, P. O. Box 3503, 11120 Belgrade, Serbia
e-mail: marinko@tmf.bg.ac.rs
´
M. M. Milosavljevic
Economics Institute, Kralja Milana 16, 11000 Belgrade, Serbia
N-Phenyl thionocarbamate was synthesized from phenyl
chlorothionoformate and corresponding amines in dioxane
[17]. Raney nickel and platinum or palladium on a carbon
support were used in the reaction of sodium alkyl
´
G. D. Vukovic
Faculty of Technology and Metallurgy, Nanotechnology and
Functional Materials Centre, University of Belgrade,
Karnegijeva 4, P. O. Box 3503, 11120 Belgrade, Serbia
123

´
M. M. Milosavljevic et al.
1046
xanthogenate and amine in order to obtain thionocarba-
mates [18].
The second protocol involved in situ diazotization with
4-nitroaniline, affording direct coupling on the graphitic
surface, and subsequent reduction of the nitro group with
lithium aluminum hydride to produce terminal amino
functionality (NH2Ph-MWCNT). Modification of the
MWCNT by these two pathways should influence catalyst
synthesis and their activity in the synthesis of N-(3- and
4-substituted phenyl)-O-isobutyl thionocarbamates. Nano-
platinum precipitation on NH2Ph-MWCNT and PDA-
MWCNT surfaces was performed by microwave-assisted
chloroplatinic acid reduction in the presence of ethylene
glycol to afford Pt/NH2Ph-MWCNT and Pt/PDA-MWCNT
catalysts. The results of the thionocarbamate synthesis in
the presence of catalyst were compared with those obtained
from isobutyl xanthogenacetic acid sodium salt and 3- and
4-substituted anilines (Scheme 1). An additional benefit of
this method, which gives moderate yields of the products,
is the isolation of sodium thioglycolate as a by-product,
which is used as a component in cosmetic products.
The synthesis of N,O-diphenyl thionocarbamates was
achieved from aniline and aryl chlorothioformate in ace-
tonitrile [19], and aromatic isothiocyanates reacted with
equimolar quantities of primary and secondary alcohols or
diols to give good yields of O-alkyl thiocarbamate [20].
S-aryl (alkyl) thiocarbamates were synthesized from
isocyanate and disulfide in the presence of Zn/AlCl3 as
catalyst [21], as well as starting from thiol and isocyanate
under catalyst- and solvent-free conditions [22]. Moreover,
thermal rearrangement of thionocarbamates to thiocarba-
mates, or the process at ambient temperature in the presence
of a catalyst, is a useful method for such interconversions
[23, 24].
Organic reactions in aqueous media have attracted
considerable attention in recent years, because they offer a
powerful tool for minimizing waste production and harm-
ful organic solvent disposal. Some particular properties of
water make this solvent very attractive (i.e., non-toxicity,
non-inflammability, high heat capacity, possibility of con-
trolling pH, isolation of insoluble solid products by
filtration, and the recycling of inorganic catalysts and the
water itself), allowing organic processes in aqueous med-
ium to be safer, very efficient, and highly selective [25].
The main goal of the present study was to develop a new
catalyst, compare it with a commercial Pt/active carbon
catalyst as well as with the results of a commercial syn-
thesis of thionocarbamates [15].
Results and discussion
In the presented work, a new synthesis of N-(3- and
4-substituted phenyl)-O-isobutyl thionocarbamates 1a–1l
was performed, starting from sodium isobutyl xanthate and
3- and 4-substituted anilines in the presence of Pt/NH2Ph-
MWCNT and Pt/PDA-MWCNT catalyst. The optimal
reaction conditions were defined with respect to the
reaction time, temperature, and catalyst concentration
achieving optimal catalyst activity and product purity (data
not presented). Two modifications of the MWCNT were
performed in order to study their catalytic efficiency, as
well as the effect of such modified graphitic supports on
their catalytic ability. The success of the catalyst-promoted
synthesis of N-(3- and 4-substituted phenyl)-O-isobutyl
thionocarbamates was compared with the results obtained
using Pt/active carbon and a well-known commercial
method [15].
Amino-functionalized multi-walled carbon nanotubes
(MWCNT) were prepared by two protocols. The first
procedure was based on the chemical transformation of
carboxylic acid residues, introduced onto the MWCNT
surface by chemical oxidation, by direct coupling of 1,4-
phenylenediamine (PDA) with the carboxylic groups to
introduce amino terminal groups (PDA-MWCNT). Pre-
activation of the carboxylic groups with N,N-diisopropyl-
ethylamine (DIEA) and subsequent formation of an active
ester using O-(7-azabenzotriazol-1-yl)-N,N,N0,N0-tetra-
methyluronium hexafluorophosphate (N-HATU) enabled
amide bond formation [26].
The catalysts were prepared by two protocols: the first
method included MWCNT oxidation/amidation and the
Scheme 1
123

Synthesis of N-(3- and 4-substituted phenyl)-O-isobutyl thionocarbamates
1047
and C–N bond stretching, respectively. Oxidation, the
N-HATU-promoted amidation of MWCNT by the phen-
ylenediamine method, and characterization of the obtained
material (PDA-MWCNT) were presented elsewhere [26].
TEM study
The morphology of the NH2Ph-MWCNT and Pt/NH2Ph-
MWCNT materials was analyzed by high resolution TEM
(HRTEM) and high angle annular dark field (HAADF)
images are shown in Fig. 2. The sidewalls of raw-MWCNT
are integrated and smooth with a trace of impurities and
metallic nanoparticles of various shapes and dimensions
found inside the nanotubes [26]. Most of the catalyst residue
was removed by purification, as was determined by induc-
tively coupled plasma mass spectrometry (ICP-MS) of a
nitric acid extract [28]. Compared with those of the raw-
MWCNT, the sidewalls of NO2Ph-MWCNT and NH2Ph-
MWCNT (Fig. 2a) are more corrugated and there are
detectable amorphous prominences on the outer graphite
sheets and inside the nanotubes. Obvious morphological
differences between these two samples were not observed.
The modified MWCNT still had a similar cylinder wall
structure like that of the raw-MWCNT, and the interplanar
spacing was similar [26]. Representative HRTEM and
HAADF images of the Pt/NH2Ph-MWCNT show a satis-
factory homogenous distribution of Pt nanoparticles over
the NH2Ph-MWCNT surface (Fig. 2b, d). The mean Pt
particle diameter was less then 3 nm. The electron dif-
fraction pattern of the Pt nanoparticles, shown in Fig. 2c,
indicates the presence of mainly twinned platinum particles.
Fig. 1 FT-IR transmission spectra of a raw-MWCNT, b NO2Ph-
MWCNT, and c NH2Ph-MWCNT
second diazotization/reduction; both methods introduced
terminal amino groups. Diazotization/reduction is the
method of choice as it gave a catalyst with better perfor-
mance. The selected catalyst was used in thionocarbamate
synthesis and its performance was compared with that of a
commercial Pt/active carbon catalyst to estimate its feasi-
bility for commercial implementation. The synthesized
Pt/NH2Ph-MWCNT catalyst and intermediary products
were characterized by FT-IR spectroscopy, transmission
electron microscopy (TEM), thermogravimetric analysis
(TGA), and elemental analysis.
FT-IR spectroscopy
Thermogravimetric analysis
The FT-IR spectra of the raw MWCNT (raw-MWCNT)
and the nitrophenyl (NO2Ph-MWCNT) and aminophenyl
(NH2Ph-MWCNT) modified MWCNT (Fig. 1) confirm
that nitrophenyl groups were introduced by diazotization
(Fig. 1b), and subsequent reduction produced amino ter-
minal groups (Fig. 1c). A broad band at ca. 3,452 cm-1 is
attributed to the hydroxyl stretching vibration (mOH) and the
peak at ca. 1,630 cm-1 is assigned to the C=C skeletal
graphitic stretching vibration (Fig. 1a) [27]. The FT-IR
transmission spectrum of NO2Ph-MWCNT (Fig. 1b) shows
the appearance of a band at ca. 1,580 cm-1 (broad band
overlapped with the C=C stretching vibration), which is
ascribed to the asymmetric nitro group stretch vibration, as
TGA not only gives useful information about the thermal
stability of the groups present on the MWCNT surface, but
also enables the determination of Pt content in the Pt/
NH2Ph-MWCNT catalyst. TGA weight loss curves
obtained by heating the raw-MWCNT, NO2Ph-MWCNT,
and NH2Ph-MWCNT in nitrogen and the Pt/NH2Ph-
MWCNT in air are presented in Fig. 3. As shown in Fig. 3,
the weight loss curves of modified samples overlap below
200 °C. Absorbed water and traces of the reactants used in
the purification and modification processes were desorbed
below 200 °C [29, 30]. These processes are followed by
defragmentation of the nitro- and aminophenyl groups
present on the MWCNT walls; these processes occur
between 200 and 500 °C [31]. At temperatures over
500 °C, the graphitic structure shows considerable stability
with no significant weight loss. On the other hand, the TG
curves for Pt/NH2Ph-MWCNT in air showed that oxidative
thermal degradation completely removes the organic
material leaving 6.15% residue of PtO2. According to this
well as the symmetric nitro group vibration at 1,342 cm-1
.
Amino groups, obtained by reduction of nitro groups, are
evidenced by the peaks at ca. 3,495 and 3,361 cm-1, which
are due to the asymmetric and symmetric NH2 stretch
vibrations, respectively, overlapped with the mOH vibration
(Fig. 1c). In addition, the band at ca. 1,587 cm-1 and a
new one at ca. 1,180 cm-1 correspond to N–H in-plane
123

´
M. M. Milosavljevic et al.
1048
Fig. 2 HRTEM images of
a NH2Ph-MWCNT and b Pt/
NH2Ph-MWCNT; c electron
diffraction pattern of Pt
nanoparticles; d HAADF image
of Pt/NH2Ph-MWCNT
result, it could be calculated that 5.28% of Pt nanoparticles
were deposited on the NH2Ph-MWCNT support. Also,
TGA analysis showed a 4.95% Pt nanoparticle loading on
PDA-MWCNT (not presented).
Elemental analysis
The attachment of surface functional groups on the sidewall
of the MWCNT was further confirmed by elemental analysis
(Table 1). No nitrogen was detected in the analysis of the
raw-MWCNT but a significant amount of nitrogen (1.61%)
was observed for NO2Ph-MWCNT which is due to diazoti-
zation, and an even higher nitrogen content of 2.16% after
reduction of the nitro group. Based on the results presented in
Table 1, the nitrogen content (2.16%) of NH2Ph-MWCNT
provides an estimation of the amount of attached amino-
phenyl groups (around 14 wt%), which is in good accordance
with the TGA results. Furthermore, the increased oxygen
content for NO2Ph-MWCNT (6.98%) and the subsequently
Fig. 3 TGA curves of
c
under air
a
NH2Ph-MWCNT under nitrogen; and
raw-MWCNT,
b
NO2Ph-MWCNT,
Pt/NH2Ph-MWCNT
d
123

Synthesis of N-(3- and 4-substituted phenyl)-O-isobutyl thionocarbamates
1049
implementation of optimized laboratory technology on a
semi-industrial scale. In addition, it was found that no
dangerous by-products were found in the wastewater
effluent, and the simple wastewater treatment for the
removal of organic residues indicates this method to be an
alternative option to existing processes. Somewhat lower
yields were obtained by the use of Pt/PDA-MWCNT cat-
alyst which indicates low suppressing influence of the
amide bridging group in Pt/PDA-MWCNT on catalyst
activity, comparing to direct bonding in Pt/NH2Ph-
MWCNT. From this point of view, the goals of future
studies will be focused on new syntheses of MWCNT
supports and a method for catalyst precipitation or, alter-
natively, the synthesis of catalysts based on other active
metals with the intention of producing catalysts with higher
activities.
Table 1 Elemental analysis of raw-MWCNT, NO2Ph-MWCNT, and
NH2Ph-MWCNT
Sample
C/%
H/%
N/%
O/%a
raw-MWCNT
NO2Ph-MWCNT
NH2Ph-MWCNT
a
97.46
90.23
93.89
0.32
1.18
1.76
0
2.22b
6.98
2.19
1.61
2.16
Calculated as difference (catalyst percent was found to be negli-
gible [32])
b
Oxygen present due to oxidative purification performed by supplier
decreased content for NH2Ph-MWCNT (2.19%) also provide
direct evidence for the reduction of the nitro groups.
According to the established optimal synthesis methods
A–D, described in the ‘‘Experimental’’, a series of N-(3-
and 4-substituted phenyl)-O-isobutyl thionocarbamates
1a–1l were obtained and the results are given in Table 2.
Somewhat lower yields of the N-(3- and 4-substituted
phenyl)-O-isobutyl thionocarbamates were obtained when
method A was employed (Table 2). The results indicate
that method A, the reaction of thioacyl nucleophilic sub-
stitution of NaEtXAc by 3- and 4-substituted anilines, does
not offer the possibility for scale-up, as was found for
N-alkyl and N,N-dialkyl-O-ethyl thionocarbamate [15].
These results strongly indicate that the significantly lower
basicity of 3- and 4-substituted anilines is a factor of pri-
mary significance, which limits the achievement of
acceptable conversion to the desired product. The data
from MS, FT-IR, 1H, and 13C NMR spectroscopy of the N-
(3- and 4-substituted phenyl)-O-isobutyl thionocarbamates
1a–1l, presented in the ‘‘Experimental’’, undoubtedly cor-
roborate the structure of the synthesized compounds.
The satisfactory reaction yields obtained by method B
and the simple work-up offer the possibility for the
In conclusion, the presented work describes the optimal
synthesis of N-(3- and 4-substituted phenyl)-O-isobutyl
thionocarbamates from O-ethyl isobutyl xanthate and 3-
and 4-substituted anilines in the presence of nano-platinum
multi-walled carbon nanotube catalysts. Satisfactory con-
versions of the starting materials into products using Pt/
NH2Ph-MWCNT (34.0–80.9%) and somewhat lower yields
in the presence of a Pt/PDA-MWCNT and Pt/active carbon
catalysts (20.9–78.5% and 20.8–70.1%, respectively) were
achieved. The techno-economic aspect of the new method B
is satisfactory, especially regarding catalyst recyclability
and simple product purification to achieve acceptable
commercial purity. Considering possible applications of the
nano-Pt/NH2Ph-MWCNT catalyst, it provides an accept-
able and versatile method for the preparation of N-(3- and
4-substituted phenyl)-O-isobutyl thionocarbamates. This
method has several unique merits, namely, simple opera-
tion, mild reaction conditions, avoidance of hazardous
Table 2 Yields and purities of N-(3- and 4-substituted phenyl) O-isobutyl thionocarbamates obtained by methods A–D
Comp.
Substituent
Method A
Yield/%
Method B
Yield/%
Method C
Yield/%
Method D
Yield/%
Puritya/%
Puritya/%
Puritya/%
Puritya/%
1a
1b
1c
1d
1e
1f
1g
1h
1i
H
32.1
45.9
44.5
30.3
52.1
18.3
51.4
40.6
18.8
44.2
41.3
67.6
99.2
99.0
99.0
98.7
98.7
98.7
98.7
98.7
98.8
98.8
99.2
99.0
40.1
63.1
61.0
48.9
72.3
34.0
74.5
56.2
34.1
69.1
60.2
80.9
99.3
99.2
99.5
99.6
99.4
99.3
99.7
99.7
99.8
99.2
98.9
99.3
39.4
52.2
49.8
45.6
66.4
30.4
70.8
55.6
20.9
68.2
54.6
78.5
99.0
99.1
99.4
99.0
98.4
99.0
99.1
99.1
99.2
99.0
98.8
99.4
38.2
50.1
48.2
36.1
59.3
20.8
61.8
43.3
21.3
48.6
44.8
70.1
99.4
98.9
98.8
99.1
99.4
99.5
98.7
99.6
99.3
98.8
99.7
99.6
4-OCH3
4-OH
4-CH3
4-I
4-F
4-Br
4-Cl
3-Cl
1j
1k
1l
3-Br
3-OCH3
4-N(CH3)2
a
Determined by GC method
123

´
M. M. Milosavljevic et al.
1050
organic solvents, employment of moderately toxic and
inexpensive reagents, short reaction times, and high product
yields. This new environmentally benign process represents
a suitable alternative to existing methods, and contributes to
the protection of the environment.
[33]. All other reagents, such as 3- and 4-substituted ani-
lines (Sigma Aldrich), 1,4-phenylenediamine (PDA, Sigma
Aldrich), isopentyl nitrite (Sigma Aldrich), lithium alumi-
num hydride (LiAlH4, Sigma Aldrich), ethylene glycol
(EG, Alfa Aesar), solutions of H2PtCl6 (Alfa Aesar) and
KOH (Sigma Aldrich), were used as received. The com-
mercial Pt on active carbon catalyst was supplied by Acros
Organics. Millipore deionized water (DI, 18 MX cm) was
used for sample washing and solution preparation.
Experimental
FT-IR spectra were recorded in the transmission mode using
a BOMEM (Hartmann & Braun) spectrometer. TEM mea-
surements were performed using FEI-CM200 super-twin
and CM300 ultra-twin microscopes (Philips Electronic
Instruments) operating at 200 and 300 kV and equipped with
Gatan 1 k 9 1 k and 2 k 9 2 k CCD cameras, respectively.
The particle shapes were determined by real space crystal-
lography using high-resolution images taken from particles
near or at the edge of the carbon black substrate, and/or by
numerical Fourier filtering of the digitized image intensity
spectrum of particles on the top of the carbon. TGA was
performed using a TA Instruments SDT Q600 at a heating
rate of 20 °C min-1 and a nitrogen or air flow of
100 cm3 min-1. Elemental analyses were performed using a
Diazotization of MWCNT (Fig. 4)
The initial solvent-free functionalizations were performed
on purified MWCNT [31] under an inert atmosphere [34,
35]. Raw-MWCNT (110 mg) and 400 mg 4-nitroaniline
were added to a flask equipped with a reflux condenser and
a magnetic stirrer. Then, 6 cm3 isoamyl nitrite was slowly
added via a syringe. Heating (60 °C) under vigorous stir-
ring resulted in the commencement of paste formation.
After 3 h, the paste was diluted with DMF and filtered
through
a polytetrafluoroethylene (PTFE) (0.05 lm)
membrane filter. The collected solid was washed with
DMF until the filtrate became colorless. DMF was removed
by washing with diethyl ether, and the product NO2Ph-
MWCNT was dried in a vacuum oven at 60 °C for 6 h.
1
VARIO EL III elemental analyzer. The H and 13C NMR
spectral measurements were recorded on a Bruker AC 250
spectrometer, at 250 MHz for the 1H NMR and 62.89 MHz
for the 13C NMR spectra. The spectra were recorded at room
temperature in dimethyl sulfoxide-d6 (DMSO-d6) in 5-mm
tubes. The chemical shifts are expressed as d values in parts
per million referenced to the tetramethylsilane reference
standard signal. The mass spectra were recorded on a Ther-
moFinnigan Polaris Q ion trap mass spectrometer, including
TraceGC 2000 (ThermoFinnigan, Austin, TX, USA), inte-
grated GC–MS/MS system.
Reduction of NO2Ph-MWCNT (Fig. 4)
NO2Ph-MWCNT (100 mg) was dispersed in anhydrous
THF by sonication for 30 min. After the sonication, 10 mg
of LiAlH4 was added to the dispersion and the sonication
continued for 1 h. The reaction mixture was then slowly
added to 200 cm3 of methanol and vacuum-filtered through
a 0.05-lm-pore-size PTFE membrane filter. The product
NH2Ph-MWCNT was dried in a vacuum oven at 60 °C for
6 h [36].
Materials
Commercially available MWCNT (raw-MWCNT, Sigma
Aldrich), prepared by a chemical vapor deposition method,
was used as received without further purification. N,N-
dimethylformamide (DMF) and tetrahydrofuran (THF)
were purified and dried to remove any trace of moisture
Catalyst synthesis—nano-Pt/NH2Ph-MWCNT
from NH2Ph-MWCNT (Fig. 4)
The preparation of Pt/NH2Ph-MWCNT was carried out
from 2.2 cm3 of a 0.01 mol dm-3 aqueous solution of
Fig. 4 Pt/NH2Ph-MWCNT catalyst preparation: a diazotization of purified MWCNT; b reduction of NO2Ph-MWCNT; c microwave-assisted
precipitation of nano-Pt on NH2Ph-MWCNT
123

Synthesis of N-(3- and 4-substituted phenyl)-O-isobutyl thionocarbamates
1051
H2PtCl6 and 80 mg of NH2Ph-MWCNT in 50 cm3 of EG
using microwave heating by a method described elsewhere
[37, 38].
method B in the presence of Pt/PDA-MWCNT. The results
of the synthesis are given in Table 2.
Synthesis of N-(3- and 4-substituted phenyl)-O-isobutyl
thionocarbamates in the presence of Pt/active carbon
(method D)
Catalyst synthesis—nano-Pt/PDA-MWCNT
from PDA-MWCNT
Nano-Pt/PDA-MWCNT was synthesized from PDA-
MWCNT analogously to the preparation of nano-Pt/
NH2Ph-MWCNT.
The synthesis of N-(3- and 4-substituted phenyl)-O-isobu-
tyl thionocarbamateswas performed analogously to method
B in the presence of a Pt/active carbon catalyst. The results
of the synthesis are given in Table 2.
Synthesis of N-(3- and 4-substituted phenyl)-O-isobutyl
thionocarbamates [15] (method A)
Catalyst regeneration
The synthesis of N-(3- and 4-substituted phenyl)-O-isobu-
tyl thionocarbamates was performed analogously to the
published method, except that 50 cm3 of an ethanolic
solution of 4-substituted aniline (0.34 mol) was added to an
aqueous solution of isobutyl xanthogenacetic acid sodium
salt (0.34 mol). After heating at 80 °C for 5 h, the ethanol
was evaporated and the precipitate was dissolved in
dichloromethane. The organic layer was washed with 5%
hydrochloric acid, then with water until neutral, and dried
over sodium sulfate. After removal of the solvent, the crude
product was crystallized from ethanol. The results of
the synthesis are given in Table 2. The pure N-(3- and
4-substituted phenyl)-O-isobutyl thionocarbamates had
The Pt/NH2Ph-MWCNT, Pt/PDA-MWCNT, and Pt/active
carbon catalysts were regenerated by refluxing in a short-
chain aliphatic alcohol, because the substances adsorbed
onto the catalyst surface are readily soluble in the alcohol.
The regenerated catalyst was used in ten cycles without
significant activity loss. Characterization of regenerated
catalyst showed that the applied experimental method has
no influence on the properties of the catalyst [39].
N-Phenyl-O-isobutyl thionocarbamate (1a)
M.p.: 74 °C (Ref. [40] 75 °C).
N-(4-Methoxyphenyl)-O-isobutyl thionocarbamates
(1b, C12H17NO2S)
1
1
satisfactory elemental analysis and MS, H, and 13C NMR
M.p.: 72 °C; H NMR (250 MHz, DMSO-d6): d = 0.95
spectral data.
(6H, d, J = 6.8 Hz, (CH3)2CH), 2.07 (1H, m, CHCH2O),
3.79 (3H, s, PhOCH3), 4.33 (2H, d, J = 6.2 Hz, CH2O),
6.86 and 7.18 (4H, AA0XX0, J = 8.6 Hz, Ph), 8.74 (1H, bs,
NH) ppm; 13C NMR (62.89 MHz, DMSO-d6): d = 19.1,
27.7, 55.4, 78.7, 114.0, 126.0, 130.0, 157.3, 188.7 ppm;
FT-IR (KBr): vꢀ = 3,471, 3,214, 3,122, 3,050, 2,996, 2,955,
2,830, 2,061, 2,010, 1,870, 1,600, 1,550, 1,509, 1,459,
1,413, 1,358, 1,302, 1,251, 1,206, 1,173, 1,041, 961,
828 cm-1; MS (70 eV): m/z = 239.3 (M?).
Synthesis of N-(3- and 4-substituted phenyl)-O-isobutyl
thionocarbamates in the presence of the nano-Pt/
NH2Ph-MWCNT catalyst (method B)
To a 50 cm3 three-necked flask containing 25 cm3 DI
water and equipped with a magnetic mixer, dropping fun-
nel, condenser, and thermometer was added 8.41 g of 75%
active commercial sodium isobutyl xanthate (0.038 mol).
After the xanthate had completely dissolved, 20 mg Pt/
NH2Ph-MWCNT catalyst was added followed by 3.95 cm3
70% ethylamine. The reaction mixture was heated to 80 °C
and maintained at that temperature for 6 h. After cooling to
room temperature, the reaction mixture was filtered to
remove catalyst and the reaction product was purified by
two successive washings with DI water and then dried. The
results of the synthesis are given in Table 2.
N-(4-Hydroxyphenyl)-O-isobutyl thionocarbamate
(1c, C11H15NO2S)
1
M.p.: 92 °C; H NMR (250 MHz, DMSO-d6): d = 0.93
(6H, d, J = 6.6 Hz, (CH3)2CH), 2.05 (1H, m, CHCH2O),
4.32 (2H, d, J = 6.2 Hz, CH2O), 6.82 and 7.08 (4H,
J = 9 Hz, Ph), 7.93 (1H, s, NH), 8.67 (1H, bs, OH) ppm;
13C NMR (62.89 MHz, DMSO-d6): d = 19.0, 27.7, 78.8,
115.7, 124.6, 129.8, 153.6, 188.7 ppm; FT-IR (KBr):
vꢀ = 3,346, 3,230, 3,056, 2,959, 1,878, 1,603, 1,556,
1,510, 1,470, 1,437, 1,386, 1,302, 1,271, 1,193,1,044,
831, 736 cm-1; MS (70 eV): m/z = 225.3 (M?).
Synthesis of N-(3- and 4-substituted phenyl)-O-isobutyl
thionocarbamates in the presence of the nano-Pt/PDA-
MWCNT catalyst (method C)
N-(4-Methylyphenyl)-O-isobutyl thionocarbamates
(1d, C12H17NOS)
1
The synthesis of N-(3- and 4-substituted phenyl)-O-isobu-
tyl thionocarbamates was performed analogously to
M.p.: 70 °C; H NMR (250 MHz, DMSO-d6): d = 0.97
(6H, d, J = 6.8 Hz, (CH3)2CH), 2.09 (1H, m, CHCH2O),
123

´
M. M. Milosavljevic et al.
1052
2.31 (3H, s, PhCH3), 4.34 (2H, d, J = 6.2 Hz, CH2O), 7.14
(4H, s, Ph), 8.96 (1H, bs, NH) ppm; 13C NMR (62.89 MHz,
DMSO-d6): d = 19.1, 20.8, 27.6, 78.3, 121.8, 129.4, 134.5,
188.6 ppm; FT-IR (KBr): vꢀ = 3,436, 3,222, 3,040,
2,971, 1,889, 1,597, 1,542, 1,509, 1,463, 1,405, 1,355,
1,315, 1,288, 1,201, 1,036, 964, 801 cm-1; MS (70 eV):
m/z = 223.3 (M?).
DMSO-d6): d = 19.1, 27.6, 79.0, 122.4, 124.9, 128.2,
130.2, 138.2, 188.7 ppm; FT-IR (KBr): vꢀ = 3,217, 3,038,
2,967, 1,919, 1,588, 1,536, 1,470, 1,400, 1,358, 1,329,
1,279, 1,071, 1,023, 918, 859, 761, 669, 603 cm-1; MS
(70 eV): m/z = 287.1 (M?).
N-(3-Methoxyphenyl)-O-isobutyl thionocarbamates
(1k, C12H17NO2S)
1
N-(4-Iodophenyl)-O-isobutyl thionocarbamate
(1e, C11H14INOS)
M.p.: 60 °C; H NMR (250 MHz, DMSO-d6): d = 0.99
(6H, d, J = 6.6 Hz, (CH3)2CH), 2.12 (1H, m, CHCH2O),
3.78 (3H, s, Ph-OCH3), 4.34 (2H, d, J = 6.2 Hz, CH2O),
6.70 (1H, dd, J = 2.4, 6.0 Hz, Ph), 6.90 (2H, bs, Ph), 7.22
(1H, t, J = 8.2 Hz, Ph), 9.06 (1H, bs, NH) ppm; 13C NMR
(62.89 MHz, DMSO-d6): d = 19.1, 27.6, 55.2, 77.0, 107.6,
110.9, 113.9, 129.6, 138.1, 159.9, 188.6 ppm; FT-IR
(KBr): vꢀ = 3,217, 2,963, 2,871, 2,835, 1,901, 1,596,
1,539, 1,464, 1,407, 1,327, 1,254, 1,056, 933, 766,
682 cm-1; MS (70 eV): m/z = 239.3 (M?).
1
M.p.: 115 °C; H NMR (250 MHz, DMSO-d6): d = 0.96
(6H, d, J = 6.8 Hz, (CH3)2CH), 2.10 (1H, m, CHCH2O),
4.34 (2H, d, J = 6.2 Hz, CH2O), 7.11 (2H, bs, Ph), 7.64
(2H, d, J = 9.0 Hz, Ph), 8.86 (1H, bs, NH) ppm; 13C NMR
(62.89 MHz, DMSO-d6): d = 19.1, 27.5, 78.9, 89.2, 126.8,
136.8, 137.9, 188.8 ppm; FT-IR (KBr): vꢀ = 3,454, 3,220,
3,095, 3,040, 2,969, 2,869, 1,890, 1,591, 1,538, 1,485,
1,393, 1,355, 1,278, 1,204, 1,033, 822 cm-1; MS (70 eV):
m/z = 335.2 (M?).
N-[4-(N,N-Dimethylamino)phenyl]-O-isobutyl-
thionocarbamate (1l, C13H20N2OS)
N-(4-Fluorophenyl)-O-isobutyl thionocarbamate
(1f, C11H14FNOS)
1
M.p.: 61 °C; H NMR (250 MHz, DMSO-d6): d = 0.95
1
M.p.: 49 °C; H NMR (250 MHz, DMSO-d6): d = 0.96
(6H, d, J = 6.8 Hz, (CH3)2CH), 2.07 (1H, m, CHCH2O),
2.94 (6H, m, N(CH3)2), 4.32 (2H, d, J = 6.8 Hz, CH2O),
6.68 (2H, t, J = 8.2 Hz, Ph), 7.13 (2H, m, Ph), 8.53 (1H,
bs, NH) ppm; 13C NMR (62.89 MHz, DMSO-d6):
d = 19.1, 27.7, 40.5, 77.0, 112.3, 123.5, 126.4, 127.3,
148.5, 188.5 ppm; FT-IR (KBr): vꢀ = 3,428, 3,184,
3,019, 2,961, 2,800, 1,615, 1,523, 1,445, 1,412, 1,347,
1,215, 1,169, 1,046, 948, 821, 724 cm-1; MS (70 eV):
m/z = 252.3 (M?).
(6H, d, J = 6.6 Hz, (CH3)2CH), 2.08 (1H, m, CHCH2O),
4.33 (2H, d, J = 6.2 Hz, CH2O), 7.03 (2H, m, Ph), 7.27
(2H, s, Ph), 9.18 (1H, bs, NH) ppm; 13C NMR (62.89 MHz,
DMSO-d6): d = 19.0, 27.6, 78.8, 115.8, 127.8, 133.4,
163.6, 188.7 ppm; FT-IR (KBr): vꢀ = 3,181, 3,017, 2,964,
2,875, 1,871, 1,610, 1,550, 1,509, 1,469, 1,409, 1,384,
1,353, 1,288, 1,214, 1,156, 1,034, 1,089, 828 cm-1; MS
(70 eV): m/z = 227.2 (M?).
N-(4-Bromophenyl)-O-isobutyl thionocarbamate
(1g, C11H14BrNOS)
Acknowledgments This work was supported by the Ministry of
Education and Science of the Republic of Serbia (Project Number
1
´
172013 and III45019). Goran Vukovic is grateful to the project FP7
M.p.: 59 °C; H NMR (250 MHz, DMSO-d6): d = 0.95
REGPOT NANOTECH FTM, GRANT AGREEMENT 245916 for
financial support. The authors gratefully thank Professor Velimir
(6H, d, J = 6.8 Hz, (CH3)2CH), 2.10 (1H, m, CHCH2O),
4.34 (2H, d, J = 6.8 Hz, CH2O), 7.26 (2H, bs, Ph), 7.45
(2H, d, J = 9.0 Hz, Ph), 8.88 (1H, bs, NH) ppm; 13C NMR
(62.89 MHz, DMSO-d6): d = 19.1, 27.6, 78.9, 123.8,
126.8, 132.7, 136.1, 188.7 ppm; FT-IR (KBr): vꢀ = 3,218,
3,102, 3,043, 2,967, 2,871, 1,889, 1,592, 1,541, 1,489,
1,417, 1,397, 1,353, 1,204, 1,075, 1,035, 824 cm-1; MS
(70 eV): m/z = 287.1 (M?).
´
Radmilovic from the National Centre for Electron Microscopy,
Lawrence Berkeley National Laboratory, for the electron microscopy
characterization. Electron microscopy characterization was supported
by the US Department of Energy, Office of Basic Energy Sciences,
Division of Materials Sciences and Engineering under Contract No.
DE-AC02 05CH11231.
N-(4-Chlorophenyl)-O-isobutyl thionocarbamate (1h)
M.p.: 58 °C (Ref. [41] 68–69 °C).
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