Reactions of O-aryl S-aryl dithiocarbonates with pyridines in aqueous ethanol: Kinetics and mechanism

Article abstract of DOI:10.1002/poc.1553

The reactions of O-(4-methylphenyl) S-(4-nitrophenyl) dithiocarbonate (1), O-(4-chlorophenyl) S-(4-nitrophenyl) dithiocarbonate (2), and O-(4-chlorophenyl) S-phenyl) dithiocarbonate (3) with a series of pyridines were subjected to a kinetic investigation

Full text of DOI:10.1002/poc.1553

Research Article
Received: 29 January 2009,
Revised: 3 March 2009,
Accepted: 3 March 2009,
Published online in Wiley InterScience: 28 April 2009
(www.interscience.wiley.com) DOI 10.1002/poc.1553
Reactions of O-aryl S-aryl dithiocarbonates
with pyridines in aqueous ethanol: kinetics
and mechanism
a
a
a
*
´
Enrique A. Castro , Marcela Gazitu´a and Jose G. Santos
The reactions of O-(4-methylphenyl) S-(4-nitrophenyl) dithiocarbonate (1), O-(4-chlorophenyl) S-(4-nitrophenyl)
dithiocarbonate (2), and O-(4-chlorophenyl) S-phenyl) dithiocarbonate (3) with a series of pyridines were subjected
to a kinetic investigation in 44 wt% ethanol–water, at 25.0 -C and an ionic strength of 0.2 M. The reactions were
followed spectrophotometrically. Under amine excess, pseudo-first-order rate coefficients (kobs) were determined. For
the studied reactions, plots of kobs versus free pyridine concentration at constant pH were linear, with the slope (kN)
independent of pH. The Brønsted-type plots for (1) and (2) were biphasic, suggesting a stepwise mechanism with a
change in the rate-determining step, from breakdown to the formation of a tetrahedral intermediate (TW), as the
basicity of the pyridines increases. For the reactions of (3), at the pKa range of the pyridines studied, only the
breakdown to products of TW was observed. Copyright ß 2009 John Wiley & Sons, Ltd.
Keywords: diaryl dithiocarbonates; kinetics; mechanism; pyridinolysis
carbonate (1), O-(4-chlorophenyl) S-(4-nitrophenyl) dithiocarbo-
INTRODUCTION
nate (2), and O-(4-chlorophenyl) S-phenyl dithiocarbonate (3)
with a series of pyridines. By comparing the kinetic results of this
work with those of the aminolysis of related compounds, we
evaluate the effects of the electrophilic moiety and the
non-leaving and leaving groups of the substrate on the kinetics
and mechanism.
The kinetics and mechanisms of the aminolysis of O-alkyl S-aryl
dithiocarbonates are well documented.[1–10] The reactions of
O-ethyl S-(2,4,6-trinitrophenyl) dithiocarbonate (ETNPDTC) with
secondary alicyclic (SA) amines[1,5] and quinuclidines (QUI),[7] and
those of O-ethyl S-(2,4-dinitrophenyl) dithiocarbonate (EDNPDTC)
with QUI,[7] in aqueous ethanol at 44 wt%, proceed by a
concerted mechanism. Other reactions have been found to be
stepwise, through a zwitterionic tetrahedral intermediate. Among
these are those of O-ethyl S-(4-nitrophenyl) dithiocarbonate
(ENPDTC) with SA amines, both in water[2] and in aqueous
ethanol,[4] as well as those of EDNPDTC with pyridines[8] in water
and with SA amines, both in water[1] and aqueous ethanol.[4] Also,
the reactions of ETNPDTC with pyridines[8] and SA amines in
water[1] are driven by a stepwise mechanism. The reactions of
O-ethyl S-(4-X-phenyl) dithiocarbonates with SA amines (X ¼ H,
CH3O, CH3, and Cl)[2,3,6] have also been found to be stepwise,
through two tetrahedral intermediates, one zwitterionic and the
other anionic.
RESULTS AND DISCUSSION
On the other hand, Lee and co-workers have examined the
kinetics of the reactions of O-ethyl S-aryl dithiocarbonates with
anilines[9] and benzylamines[10] in acetonitrile, and concluded
that these reactions are concerted.
Although the kinetics of the aminolysis of O-alkyl S-aryl
dithiocarbonates has been extensively investigated (see above),
that of O-aryl S-aryl dithiocarbonates has not drawn much
attention.[11] We are aware of only a single work on this subject:
the aminolysis (SA amines) of O-phenyl S-(4-nitrophenyl)
dithiocarbonate in aqueous ethanol, which shows the presence
of two tetrahedral intermediates, one zwitterionic and one
anionic.[11]
Under amine excess, pseudo-first-order rate constants (kobs) were
found for all the reactions. These were obtained by means of the
spectrophotometer kinetics software for first-order reactions. The
experimental conditions of the reactions and the values of kobs
are summarized in Tables 1–3
For the studied reactions, the pseudo-first-order rate constants
(kobs), obtained under amine excess, obey Eqn (1), where k0 and
*
Correspondence to: J. G. Santos, Facultad de Qu´ımica, Pontificia Universidad
´
Catolica de Chile, Casilla 306, Santiago 6094411, Chile.
E-mail: jgsantos@uc.cl
In order to shed more light on the mechanism of the
pyridinolysis of diaryl dithiocarbonates, we report a kinetic study
of the reactions of O-(4-methylphenyl) S-(4-nitrophenyl) dithio-
a
E. A. Castro, M. Gazitu´a, J. G. Santos
Facultad de Qu´ımica, Pontificia Universidad Catolica de Chile, Casilla 306,
Santiago 6094411, Chile
´
J. Phys. Org. Chem. 2009, 22 1003–1008
Copyright ß 2009 John Wiley & Sons, Ltd.

´
E. A. CASTRO, M. GAZITUA AND J. G. SANTOS
Table 1. Experimental conditions and kobs values for the reactions of pyridines with O-(4-methylphenyl) S-4-nitrophenyl dithio-
carbonate (1)a
b
Pyridine substituent
4-Oxy
pH
FN
103[N]tot (M)c
103kobs (sꢀ1)
Number of runs
11.2
11.5
11.8
0.333
0.500
0.667
0.333
0.500
0.667
0.333
0.500
0.667
0.333
0.500
0.667
0.9995
0.9998
0.99995
1
3.03–30.3
1.02–10.2
2.18–21.8
3.74–37.4
10.0–100
3.97–39.7
3.40–34.9
3.69–36.9
3.78–37.8
10.3–103
5.38–53.8
8.80–88.0
10.4–104
10.6–106
10.3–41.4
12.7–139
12.6–126
13.4–93.6
8.30–98.7
3.40–38.8
12.0–114
10.6–59.1
25.0–188
7
7
7
7
7
7
7
7
7
7
7
7
7
7
3
7
7
5
3,4-Diamino
4-Dimethylamino
4-Amino
9.15
9.45
9.75
8.84
9.14
8.44
8.68
8.98
9.28
9.0d
9.5d
10.0d
9.0d
9.5d
10.0d
14.9–92.2
7.50–41.6
8.90–55.5
10.4–72.4
15.1–76.4
12.7–72.2
18.6–131
0.0647–1.04
0.221–0.931
0.272–0.440
0.201–1.61
0.199–1.51
0.223–0.930
3,4-Dimethyl
None
1
1
a In 44 wt% ethanol–water, at 25.0 8C, and ionic strength 0.2 M (KCl).
b Free amine fraction.
c Concentration of total amine (free base plus protonated forms).
d Under the presence of borate buffer 0.01 M.
Table 2. Experimental conditions and kobs values for the reactions of pyridines with O-(4-chlorophenyl) S-4-nitrophenyl dithio-
carbonate (2)a
b
Pyridine substituent
4-Oxy
pH
FN
103[N]tot (M)c
103kobs (sꢀ1
)
Number of runs
11.2
11.5
11.8
0.333
0.500
0.667
0.333
0.500
0.667
0.333
0.500
0.667
0.333
0.50
3.03–30.3
1.02–10.2
2.18–21.8
3.74–37.4
10.0–100
3.97–39.7
3.40–34.9
3.69–36.9
3.78–37.8
10.3–103
5.38–53.8
8.80–48.4
10.5–89.4
10.3–104
12.7–108
12.6–126
13.4–114
18.2–202
6.50–86.7
24.0–259
21.6–124
56.0–357
24.0–188
14.1–90.5
19.6–124
23.5–162
34.6–172
24.8–155
38.8–157
0.218–0.964
0.272–1.14
0.0637–0.144
0.345–1.95
0.599–1.83
7
7
7
7
7
7
7
7
7
7
7
4
6
7
6
7
6
3,4-Diamino
4-Dimethylamino
4-Amino
9.15
9.45
9.75
8.84
9.14
8.44
8.68
8.98
9.28
9.0d
0.667
0.9995
0.99995
1
3,4-Dimethyl
None
10.0d
9.0d
9.5d
1
1
10.0d
a In 44 wt% ethanol–water, at 25.0 8C, and ionic strength 0.2 M (KCl).
b Free amine fraction.
c Concentration of total amine (free base plus protonated forms).
d Under the presence of borate buffer 0.01 M.
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Copyright ß 2009 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2009, 22 1003–1008

REACTIONS OF O-ARYL S-ARYL DITHIOCARBONATES
Table 3. Experimental conditions and kobs values for the reactions of pyridines with O-(4-chlorophenyl) S-phenyl dithiocarbonate
(3)a
b
Pyridine substituent
4-Oxy
pH
FN
103[N]tot (M)c
104kobs(sꢀ1
)
Number of runs
9.0d
9.5d
10.0d
9.15
9.45
9.75
8.84
9.14
9.44
8.68
8.98
9.28
0.003152
0.01
4.77–43.4
4.63–46.3
4.57–45.7
4.72–47.2
20.7–37.6
9.76–39.0
11.0–44.2
4.32–43.2
4.14–41.4
7.27–72.7
18.6–74.3
6.53–65.3
2.80–8.14
5.14–29.0
11.4–81.0
7
7
7
7
4
6
6
7
5
7
6
7
0.03065
0.333
0.500
0.667
0.333
0.500
0.667
0.333
0.500
0.667
3,4-Diamino
4-Dimethylamino
4-Amino
0.815–6.36
4.62–8.53
1.89–8.00
3.14–10.4
2.09–15.8
2.18–19.0
1.97–7.84
3.99–14.8
1.39–16.3
a In 44 wt% ethanol–water, at 25.0 8C, and ionic strength 0.2 M (KCl).
b Free amine fraction.
c Concentration of total amine (free base plus protonated forms).
d Under the presence of borate buffer 0.01 M.
kN are the rate coefficients for solvolysis and aminolysis of the
substrates, respectively, and [N] is the free amine concentration.
The values of k0 and kN showed no dependence on pH within the
pH range employed. These values were obtained as the intercept
and slope, respectively, of linear plots of kobs against free amine
concentration at constant pH
Scheme 1).[12] A similar equation has been reported by Gresser
and Jencks.[13]
Equation 2 contains four parameters: b1 and b2, which are the
Brønsted slopes at high and low pKa, respectively, and kN0 and pKa0,
which are the corresponding values at the center of the Brønsted
curvature.
ꢀ
ꢁ
ꢀ
ꢁ
kN
kN0
1 þ a
kobs ¼ k0 þ kN ½Nꢁ
(1)
log
¼ b2ðpKa ꢀ pKa0Þ ꢀ log
(2)
2
For these reactions, k0 values were much smaller than the
aminolysis term, kN [N], in Eqn (1). The kN values are summarized
in Table 4.
log a ¼ ðb2 ꢀ b1ÞðpKa ꢀ pKa0Þ
The Brønsted-type plots of Fig. 1 were obtained with the data
in Table 4. For the pyridinolysis of 1 and 2, the biphasic Brønsted
plots can be explained by the existence of a tetrahedral
intermediate (Tꢂ) and a change in the rate-determining step,
from that for k2 to that for k1 (see Scheme 1), as the amine
becomes more basic.[12–14]
These curves were calculated by means of a semi-empirical
equation, Eqn (2), based on the existence of a zwitterionic
tetrahedral intermediate (Tꢂ) on the reaction pathway (see
The Brønsted curves were calculated by means of the following
parameters: log kN0 ¼ 0.33, pKa0 ¼ 9.0, b1 ¼ 0.12 and b2 ¼ 0.83
(n ¼ 6, R2 ¼ 0.99991) for the reactions of 1 and log kN0 ¼ 0.71,
pKa0 ¼ 9.1, b1 ¼ 0.11 and b2 ¼ 0.89 (n ¼ 6, R2 ¼ 0.9995) for the
reactions of 2. The errors of the slopes are ꢂ 0.1, and those of pKa0
and log k0N are ꢂ 0.2 and ꢂ 0.1, respectively. These values of b1
and b2 are in accordance with those reported for other
aminolyses governed by stepwise mechanisms: b1 ¼ 0.1–0.3
and b2 ¼ 0.8–1.1[1,2,4,7,8,12–14]
Table 4. Values of pKa for the conjugate acids of pyridines and kN values for the reactions of pyridines with O-(4-methylphenyl)
S-(4-nitrophenyl) dithiocarbonate (1), O-(4-chlorophenyl) S-(4-nitrophenyl) dithiocarbonate (2) and O-(4-chlorophenyl) S-phenyl
dithiocarbonate (3)a
kN (sꢀ1 Mꢀ1
)
Pyridine substituent
pKa
1
2
3
4-Oxy
11.5
9.45
9.14
8.98
5.68
4.63
8.8 ꢂ 0.4
3.4 ꢂ 0.1
19.3 ꢂ 0.8
6.6 ꢂ 0.2
6.1 ꢂ 0.2
4.7 ꢂ 0.2
5.6 ꢂ 0.1
3,4-Diamino
4-Dimethylamino
4-Amino
3,4-Dimethyl
None
0.032 ꢂ 0.002
0.068 ꢂ 0.002
0.037 ꢂ 0.001
2.8 ꢂ 0.1
2.1 ꢂ 0.1
0.0083 ꢂ 0.0001
0.0011 ꢂ 0.00005
0.0088 ꢂ 0.0005
0.0012 ꢂ 0.00007
a Both the pKa and kN values were determined in 44 wt% ethanol–water, at 25.0 8C, and ionic strength 0.2 M (KCl).
J. Phys. Org. Chem. 2009, 22 1003–1008
Copyright ß 2009 John Wiley & Sons, Ltd.
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´
E. A. CASTRO, M. GAZITUA AND J. G. SANTOS
with the curvature center at pKa0 ¼ 9.0. This result indicates a
greater leaving ability (greater k2 in Scheme 1) of
4-nitrobenzenethiolate, relative to 4-nitrophenoxide, from the
corresponding intermediates Tꢂ (see below). Although phen-
oxides are better nucleofuges than isobasic benzenethiolates,[16]
the above result can be explained by the rather large difference in
basicity of the groups involved (pKa ¼ 4.5 and 7.5 in aqueous
ethanol for 4-nitrobenzenethiol and 4-nitrophenol, respectively).
On the other hand, the pyridinolysis of aryl chlorothionofor-
mates[17] is stepwise with the formation of the intermediate Tꢂas
the rate-determining step for the whole pKa range of the
pyridines studied, showing that chloride is a better nucleofuge
than 4-nitrobenzenethiolate from the corresponding tetrahedral
intermediate.
Figure 1. Brønsted plots obtained for the pyridinolysis of dithiocarbo-
nates 1 (~), 2 (*), and 3 (*) in 44 wt% ethanol–water, at 25.0 8C, ionic
strength 0.2 M (KCl)
Effect of the non-leaving group
For the pyridinolysis of dithiocarbonate 3, a linear Brønsted
plot with a slope of 0.88 was obtained (see Fig. 1), which indicates
that for these reactions decomposition to products of the
intermediate, Tꢂ is the rate-limiting step.[12–14]
It can be observed from Table 4 and Fig. 1 that the kN values for
the reactions with pyridines of pKa > 9.0 are greater for 2 than for
1. For the reactions of both substrates with 4-oxypyridine (an
amine with pKa greater than pKa0 for the reactions of both
substrates), the first step is rate-determining, and kN ¼ k1.
Therefore, Table 4 shows that the k1 value for 2 is twice as
great as that for 1. This result can be explained by the greater
electron-withdrawing effect of Cl than CH3 (sP values are 0.23 and
Effect of the leaving group
The pyridinolysis of 2 shows a biphasic Brønsted plot with the
curvature center (pKa0) at a pKa of 9.1. Nevertheless, for the
reactions of the same amines with 3, the linear Brønsted plot with
high slope shows that the k2 step is rate-determining for the
whole pKa range. This means that for the reactions of this
substrate, the pKa0 value is greater than 11.5. The lower pKa0 value
for the pyridinolysis of 2 is reasonable, in view of the greater
nucleofugality (greater k2 value) of 4-nitrobenzenethiolate in 2
compared with benzenethiolate in 3. It is known that a greater k2/
ꢀ0.17, respectively),[18] which leads to
a more positive
thiocarbonyl group for 2 and, therefore, leaves it more prone
to nucleophilic attack by the amine.
On the other hand, for amines with pKa < pKa0 the rate-
determining step is expulsion of the leaving group from the Tꢂ
intermediate (k2 in Scheme 1); for these amines, kN ¼ k1k2/kꢀ1. It
can be observed from Fig. 1 that for pyridines with pKa lower than
pKa0, the kN values for the reactions of 1 and 2 are closely similar.
Since the k1 values are larger for the pyridinolysis of 2, necessarily
the k2/kꢀ1 values must be larger for the pyridinolysis of 1; this is in
accordance with an equation derived from the hypothesis of the
tetrahedral intermediate (Eqn 3),[8,19] which predicts a larger k2
value for a smaller pKa0.
k
ratio shifts the center of the Brønsted curvature towards
ꢀ1
lower values (see below).[12–14]
In the same line, the reaction of 4-methylphenyl 4-nitrophenyl
thionocarbonate (4) with pyridines, at the same experimental
conditions as those of this study, is governed by a stepwise
mechanism, being the expulsion of the nucleofuge, the
rate-determining step for the whole pKa range.[15] This suggests
that the pKa0 must be greater than 9.1.[15] Nevertheless,
pyridinolysis of 1 (this study) shows a biphasic Brønsted plot
ꢀ
ꢁ
k
ꢀ1
log
¼ ðb2 ꢀ b1Þ ðpKa0 ꢀ pKaÞ
(3)
k2
Scheme 1.
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J. Phys. Org. Chem. 2009, 22 1003–1008

REACTIONS OF O-ARYL S-ARYL DITHIOCARBONATES
Effect of the electrophilic group
synthesized by the reaction of phenyl chlorodithioformate with
4-chlorophenoxide, as reported.[23] The solid products showed
the following characteristics.
1: m.p. 93–94 8C. 1HNMR (400 MHz, CDCl3) d PPM: 2.36 (s, 3H);
6.96 (d, 2H J ¼ 8.4 Hz); 7.21 (d, 2H, J ¼ 8.4 Hz); 7.80 (d, 2H
J ¼ 8.8 Hz); 8.30 (d ,2H J ¼ 8.8 Hz). 13CNMR (200 MHz,CDCl3) d ppm:
21.18, 121.58, 124.52, 130.45, 136.06, 137.03, 138.24, 148.95,
152.31, 210.28.
The pyridinolysis of dithiocarbonate 2 (this study) and that of
4-clorophenyl S-(4-nitrophenyl) thiolcarbonate (5),[20] under the
same experimental conditions, are driven by
a stepwise
mechanism, as judged by the biphasic Brønsted plots found
with pKa0 9.1 and 7.9, respectively. It is known that the change of
thiocarbonyl by carbonyl as the electrophilic group, enlarges
both kꢀ1 and k2, due to the greater energy of the p bond of CO as
compared with that of CS (by 40 kcal/mol), which enhances the
driving force of Oꢀ (relative to Sꢀ) in the intermediate to form a
double bond and expel both the amine and the leaving group of
the substrates.[14,21] The fact that the pKa0 value for the
pyridinolysis of thiolcarbonate 5 (7.9) is smaller than that for 2
(9.1) indicates that k2 increases more than kꢀ1 by the change of
CS in the latter substrate by CO in the former (see Eqn 3).
The reaction of 4-oxypyridine with thiolcarbonate 5 is about 15
times faster than that with 2 (for both reactions kN ¼ k1),[20] which
means that pyridine attack to the CO group is faster than that to
CS, when formation of the intermediate Tꢂ is rate-limiting. This is
in accordance with the larger k1 values found for the pyridinolysis
of S-(2,4-dinitrophenyl) and S-(2,4,6-trinitrophenyl) ethyl thiol-
carbonates (6 and 7, respectively)[22] , compared with those for
the same aminolysis of the corresponding dithiocarbonates.[8]
2: m.p. 107–108 8C (lit[23] 109–111 8C). 1HNMR (400 MHz, CDCl3)
d PPM: 7.03 (d, 2H, J ¼ 8.4 Hz); 7.38(d, 2H, J ¼ 8.4 Hz); 7.79(d, 2H,
J ¼ 8.4 Hz); 8.31 (d, 2H, J ¼ 8.4 Hz); 13CNMR (200 MHz, CDCl3) d
PPM: 123.64, 124.60, 130.03, 132.76, 136.17, 137.85, 149.06,
152.70, 210.02.
1
3: m.p. 68–69 8C (lit[23] 68–69 8C). HNMR (400 MHz, CDCl3) d
PPM: 7.02 (d, 2H J ¼ 8.8 Hz); 7.7.46(d, 2H J ¼ 8.8 Hz); 7.47 (m, 3H);
7.61(m, 2H); 13CNMR (200 MHz, CDCl3): 123.65, 129.77,
129.86,130.32,130.69, 132.38, 135.39, 153.01, 213.23.
Kinetic measurements
The kinetics of the reactions was analyzed through a diode array
spectrophotometer in 44 wt% ethanol–water, at 25.0ꢂ 0.1 8C and
an ionic strength of 0.2 M (maintained with KCl). The reactions
were followed at 420 nm (appearance of 4-nitrobenzenethiolate
anion) for thereactions of1 and 2, and at 325–350 nm (appearance
of the corresponding 1-(4-chlorophenoxy)thiocarbonylpyridinium
cation) for the reactions of 3.
The reactions were studied under at least 10-fold amine excess
over the substrate, the initial concentration of the latter being
2.5 ꢃ 10ꢀ5 M. Under these conditions, pseudo-first-order rate
coefficients (kobs) were found throughout, and the reactions were
followed for at least five half-lives. For all the reactions, the pH was
maintained constant (three pH values for each amine), either by
the buffer formed by partial protonation of the amine or by the
addition of an external buffer.
The experimental conditions of the reactions are shown in
Tables 1–3.
CONCLUDING REMARKS
Product studies
4-Nitrobenzenethiolate anion was identified as one of the
products of the reactions of 1 and 2. This was carried out by
comparison of the UV–Vis spectra after completion of these
reactions with that of an authentic sample of 4-nitrobenzenethiol,
under the same experimental conditions.
For the reactions of 3, an increase and decrease of absorbance
at 325–350 nm was observed, attributed to the formation and
hydrolysis of the corresponding pyridiniumcarbamate cation, by
analogy with the pyridinolysis of aryl chlorothionoformates.[17]
From the results obtained in this work, several conclusions can be
drawn: (i) The mechanism of the pyridinolysis of 1–3 is stepwise.
The k1 value for 2 is twice of that for 1, in line with the greater
electron-withdrawing ability of 4-chloro than 4-methyl in the
non-leaving group. (ii) The pyridinolysis of 2 shows a smaller pKa0
value than that for the same aminolysis of the corresponding
thionocarbonate due to the faster nucleofugality from the
intermediate Tꢂ of 4-nitrobenzenethiolate relative to
4-nitrophenoxide. (iii) The pyridinolyses of 2 and the correspond-
ing thiolcarbonate are stepwise with pKa0 values of 9.1 and 7.9,
respectively, showing that the kꢀ1/k2 ratio is larger for the former
reactions. (iv) For the pyridinolysis of 3, the rate-limiting step is
the decomposition of Tꢂ to products.
Acknowledgements
The authors thank MECESUP of Chile (Project RED QUIMICA
UCH-0408) and FONDECYT of Chile (project 1060593). M.G.
thanks CONICYT of Chile for a doctoral fellowship.
EXPERIMENTAL
Materials
REFERENCES
The substrates 1 and 2 were synthesized by the reaction of the
corresponding aryl chlorothionoformate with 4-nitrobenzene-
thiolate, as previously described for the preparation of O-phenyl
˜
[1] E. A. Castro, F. Ibanez, M. Salas, J. G. Santos, P. Sepulveda, J. Org. Chem.
1993, 58, 459–463.
[2] E. A. Castro, M. Salas, J. G. Santos, P. Sepulveda, J. Org. Chem. 1991, 56,
5324–5328.
S-(2,4-dinitrophenyl) dithiocarbonate.[11] Compound
3
was
J. Phys. Org. Chem. 2009, 22 1003–1008
Copyright ß 2009 John Wiley & Sons, Ltd.
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´
E. A. CASTRO, M. GAZITUA AND J. G. SANTOS
˜
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