Anilinolysis of reactive aryl 2,4-dinitrophenyl carbonates: Kinetics and mechanism

Article abstract of DOI:10.1002/kin.20544

The reactions of a series of anilines with phenyl 2,4-dinitrophenyl (1), 4-nitrophenyl 2,4-dinitrophenyl (2), and bis(2,4-dinitrophenyl) (3) carbonates are subjected to a kinetic investigation in 44 wt% ethanol-water, at 25.0 ± 0.1°C and an ionic strength of 0.2 M. Under amine excess pseudo-first-order rate coefficients (k_obs) are obtained. Plots of k_obs against free amine concentration at constant pH are linear, with slopes k_N. The BrAnsted plots (log k_N vs. anilinium pK_a) for the anilinolysis of 1-3 are linear, with slope (β) values of 0.52, 0.61, and 0.63, respectively. The values of these slopes and other considerations suggest that these reactions are ruled by a concerted mechanism. For these reactions, the k_N values follow the reactivity sequence: 3 > 2 > 1. Namely, the reactivity increases as the number of nitro groups attached to the nonleaving group increases. Comparison of the reactions of this work with the stepwise pyridinolysis of carbonates 1-3 indicates that the zwitterionic tetrahedral intermediate (T^±) formed in the pyridinolysis reactions is destabilized by the change of its pyridino moiety by an isobasic anilino group. This is attributed to the superior leaving ability from the T^± intermediate of anilines, relative to isobasic pyridines, which destabilize kinetically this intermediate. The k_N values for the anilinolysis of carbonates 1-3 are similar to those found in the reactions of these carbonates with secondary alicyclic amines. With the kinetic data for the anilinolysis of the title substrates and 4-methylphenyl and 4-chlorophenyl 2,4-dinitrophenyl carbonates, a multiparametric equation is derived for log k_N as a function of the pK_a of the conjugate acids of anilines and nonleaving groups.

Full text of DOI:10.1002/kin.20544

Anilinolysis of Reactive Aryl
2,4-Dinitrophenyl
Carbonates: Kinetics and
Mechanism
´
ENRIQUE A. CASTRO, CLAUDIA DOMECQ, JOSE G. SANTOS
Facultad de Qu´ımica, Pontificia Universidad Cato´lica de Chile, Casilla 306, Santiago 6094411, Chile
Received 4 November 2010; revised 14 December 2010; accepted 14 December 2010
DOI 10.1002/kin.20544
Published online 3 February 2011 in Wiley Online Library (wileyonlinelibrary.com).
ABSTRACT: The reactions of a series of anilines with phenyl 2,4-dinitrophenyl (1), 4-nitrophenyl
2,4-dinitrophenyl (2), and bis(2,4-dinitrophenyl) (3) carbonates are subjected to a kinetic in-
vestigation in 44 wt% ethanol–water, at 25.0 0.1◦C and an ionic strength of 0.2 M. Under
amine excess pseudo-first-order rate coefficients (kobs) are obtained. Plots of kobs against free
amine concentration at constant pH are linear, with slopes kN. The Brønsted plots (log kN vs.
anilinium pKa) for the anilinolysis of 1–3 are linear, with slope (β) values of 0.52, 0.61, and 0.63,
respectively. The values of these slopes and other considerations suggest that these reactions
are ruled by a concerted mechanism. For these reactions, the kN values follow the reactivity
sequence: 3 > 2 > 1. Namely, the reactivity increases as the number of nitro groups attached
to the nonleaving group increases. Comparison of the reactions of this work with the stepwise
pyridinolysis of carbonates 1–3 indicates that the zwitterionic tetrahedral intermediate (T )
formed in the pyridinolysis reactions is destabilized by the change of its pyridino moiety by an
isobasic anilino group. This is attributed to the superior leaving ability from the T intermediate
of anilines, relative to isobasic pyridines, which destabilize kinetically this intermediate. The kN
values for the anilinolysis of carbonates 1–3 are similar to those found in the reactions of these
carbonates with secondary alicyclic amines. With the kinetic data for the anilinolysis of the title
substrates and 4-methylphenyl and 4-chlorophenyl 2,4-dinitrophenyl carbonates, a multipara-
metric equation is derived for log kN as a function of the pKa of the conjugate acids of anilines
and nonleaving groups. ꢀ 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 191–197, 2011
C
less is known on the aminolysis of diaryl carbonates [6–
17]. Some of the latter reactions have been described
as stepwise, mainly due to the nonlinear Brønsted-type
plots obtained, usually consisting of two linear por-
tions (at low and high pKa values) and a curvature in
between. These biphasic plots have been explained by
the existence of a zwitterionic tetrahedral intermedi-
ate (T ) on the reaction pathway, and a change in the
rate-determining step, from T formation to its decom-
position to products, as the amine basicity increases
[6–12]. On the other hand, other aminolysis reactions
INTRODUCTION
Although the kinetics and mechanisms of the aminoly-
sis of alkyl aryl carbonates are well documented [1–5],
Correspondence to: Jose G. Santos; e-mail: jgsantos@uc.cl.
Contract grant sponsor: MECESUP.
Contract grant number: UCH-06011.
Contract grant sponsor: FONDECYT.
Contract grant number: 1060593.
Supporting Information is available in the online issue at
wileyonlinelibrary,com.
c
ꢀ
2011 Wiley Periodicals, Inc.

192
CASTRO, DOMECQ, AND SANTOS
of diaryl carbonates have been found to be concerted,
that is, with no intermediate, in a single step. One of the
evidences to reach this conclusion has been the linear
Brønsted-type plots of slopes 0.4–0.7 found [13–17].
Examples of the above reactions are the pyridinoly-
sis of phenyl and 4-nitrophenyl 2,4-dinitrophenyl car-
bonates (1 and 2, respectively), bis-(2,4-dinitrophenyl)
carbonate (3), and 4-methylphenyl and 4-chlorophenyl
2,4-dinitrophenyl carbonates (4 and 5, respectively),
which were found to be driven by a stepwise mecha-
nism [12]. In contrast, the reactions of secondary ali-
cyclic (SA) amines with the same diaryl carbonates are
ruled by a concerted mechanism [13,16,17]. Likewise,
the reactions of anilines with carbonates 4 and 5 are
also governed by a concerted process [13].
It is obvious that the mechanism (stepwise vs. con-
certed) of the above reactions depends on the stability
of the T intermediate, which in turn depends on the
groups attached to its central carbon atom [6,7]. With
the aim to clarify the mechanism of the aminolysis of
diaryl carbonates and to assess the effect of the amino
and the other groups involved in the T intermediate
on its stability, in this work we report a kinetic inves-
tigation of the reactions of a series of anilines with
carbonates 1–3.
were initiated by the addition of 10 μL of an acetoni-
trile substrate solution into the spectrophotometric cell
containing 3 mL of a thermostated solution of the cor-
responding aniline at the desired concentration and pH.
All the reactions were examined under excess of
amine over the substrate. The initial substrate concen-
tration was about 5 × 10−5 M, and in most cases the
pH was maintained by the use of an external buffer
(0.01 M phosphate).
Pseudo-first-order rate coefficients (kobs) were
found throughout and determined by means of the ki-
netics software for first-order reactions of the spec-
trophotometer. Errors in the kobs values were less than
3%. The experimental conditions of the reactions and
the values of kobs are shown in Tables S1–S3 of the
Supporting Information.
Product Studies
One of the products of the reactions under scrutiny
was identified as 2,4-dinitrophenoxide by comparison
of the UV–vis spectra after completion of the reac-
tions with that of an authentic sample under the same
experimental conditions.
For the reaction of carbonate 1 with aniline, the
other product was identified as phenyl carbamate, by
HPLC comparison of a sample at the end of the re-
action with that of the product of the reaction of
phenyl chloroformate with aniline. HPLC conditions:
Y
NO
2
O
C
®
X
O
O
NO
2
LiChroCART 250-4 HPLC-RP-18e (5 μm) HPLC
®
Cartridge LiCrhorsphere 100 RP 8, mobile phase 50%
v/v CH3CN: phosphate buffer (0.01 M/pH = 7.00),
1: X = Y = H
2: X = NO ; Y = H
flow rate 1.0 mL/min, r.t. = 19.3 min.
2
3: X = Y = NO
2
4: X = Me ; Y = H
5: X = Cl ; Y = H
RESULTS AND DISCUSSION
All the reactions studied were carried out under excess
aniline over the carbonate, pseudo-first-order coeffi-
cients (kobs) being obtained throughout. The values of
kobs and the experimental conditions of the reactions
are detailed in Tables S1–S3 of the Supporting Infor-
mation. The ranges of kobs values and aniline concen-
trations are summarized in Tables I–III.
The rate law obtained for all the reactions inves-
tigated is given by Eqs. (1) and (2), where P, S, and
[amine] represent the product 2,4-dinitrophenoxide an-
ion, the substrate, and the free aniline concentration,
respectively; k0 is the rate coefficient for solvolysis
of the substrate and kN is the rate coefficient for its
aminolysis.
EXPERIMENTAL
Materials
Anilines were distilled or recrystallized before use.
Carbonates 1 [6], 2 [12], and 3 [18], were prepared by
the methods described and identified by their melting
points and spectroscopic properties.
Kinetic Measurements
These were carried out by means of a Hewlett–
Packard 8453 diode array spectrophotometer (300–
500-nm range) in 44 wt% ethanol aqueous solution, at
25.0 0.1◦C and an ionic strength of 0.2 M (KCl). The
reactions were studied by monitoring the appearance
of 2,4-dinitrophenoxide anion at 360 nm. The reactions
d[P]
= kobs[S]
(1)
(2)
dt
kobs = k0 + kN[amine]
International Journal of Chemical Kinetics DOI 10.1002/kin

ANILINOLYSIS OF ARYL 2,4-DINITROPHENYL CARBONATES: KINETICS AND MECHANISM
193
Table I Experimental Conditions and kobs Values for the Reactions of Anilines with Phenyl 2,4-Dinitrophenyl
Carbonate (1)a
Aniline Substituent
4-Amino
pH
FNb
103[N]tot (M)c
103kobs (s−1
)
Number of Runs
6.5
7.0
7.0
7.5
8.0
6.5
7.0
7.5
6.5
7.0
7.5
6.5
7.0
7.5
7.0
7.5
0.5287
0.7801
0.9800
0.9936
0.9980
0.9755
0.9921
0.9975
0.9910
0.9971
0.9991
0.9943
0.9982
0.9994
0.9999
1
0.186–1.86
0.186–1.86
0.341–3.41
0.341–3.41
0.341–3.07
0.401–4.01
0.401–4.01
0.401–4.01
0.877–21.9
0.877–21.9
0.877–21.9
0.450–4.50
0.450–4.50
0.900–4.50
0.442–4.42
0.442–4.42
0.894–5.69
0.812–6.48
0.482–5.51
0.486–3.48
0.542–3.17
0.328–2.44
0.363–2.38
0.334–2.33
0.316–4.80
0.334–5.72
0.416–5.15
0.151–0.658
0.151–0.638
0.250–0.681
0.148–0.292
0.169–0.326
7
7
7
7
5
6
6
6
7
7
7
6
7
6
7
7
4-Methoxy
4-Methyl
None
3-Methoxy
3-Acetyl
aIn 44 wt% ethanol–water, at 25.0◦C, ionic strength 0.2 M (KCl), 0.01 phosphate buffer.
bFree amine fraction.
cConcentration of total amine (free base plus protonated forms).
The values of k0 and kN for all the reactions were
determined as the intercept and slope, respectively, of
the linear plots of kobs versus [amine] and were found
to be pH independent. The value of k0 was much lower
than that of kN[amine] in Eq. (2). The kN values are
presented in Table IV, together with the pKa values of
the conjugate acids of the series of anilines employed.
The k0 values obtained ranged between 3 × 10−2 and
1 × 10−4
s
−1. (The individual values are summarized
in Table S4 in the Supporting Information.)
Table II Experimental Conditions and kobs Values for the Reactions of Anilines with 4-Nitrophenyl 2,4-Dinitrophenyl
Carbonate (2)a
Aniline Substituent
4-Amino
pH
FNb
103[N]tot (M)c
103kobs (s−1
)
Number of Runs
6.5
7.0
7.5
6.5
7.0
7.5
6.5
7.0
7.5
6.5
7.0
7.5
6.5
7.0
7.5
6.5
7.5
0.5287
0.7801
0.9182
0.9394
0.9800
0.9936
0.9755
0.9921
0.9975
0.9910
0.9971
0.9991
0.9943
0.9982
0.9994
0.9996
1
0.186–1.86
0.186–1.86
0.186–0.931
0.341–3.41
0.341–3.41
0.341–3.41
0.401–1.20
0.401–4.01
0.401–4.01
0.877–17.5
0.877–21.9
0.877–21.9
0.450–4.05
0.450–4.50
0.450–3.15
0.442–4.42
0.442–4.42
13.3–76.0
9.39–88.4
11.3–37.1
6.68–38.2
6.10–32.0
6.72–32.8
5.14–10.3
4.27–21.3
5.41–21.5
4.50–37.3
4.36–46.2
6.38–48.0
2.71–7.44
3.00–8.78
3.56–7.36
2.09–3.64
2.07–3.66
7
7
4
7
6
6
3
7
7
6
6
7
6
7
5
7
7
4-Methoxy
4-Methyl
None
3-Methoxy
3-Acetyl
aIn 44 wt% ethanol–water, at 25.0◦C, ionic strength 0.2 M (KCl), 0.01 phosphate buffer.
bFree amine fraction.
cConcentration of total amine (free base plus protonated forms).
International Journal of Chemical Kinetics DOI 10.1002/kin

194
CASTRO, DOMECQ, AND SANTOS
Table III Experimental Conditions and kobs Values for the Reactions of Anilines with Bis-(2,4-dinitrophenyl)
Carbonate (3)a
Aniline Substituent
4-Amino
pH
FNb
103[N]tot (M)c
103kobs (s−1
)
Number of Runs
6.5
7.0
7.0
7.5
6.5
7.0
7.5
6.5
7.0
7.5
6.5
7.5
6.5
7.0
7.5
0.5287
0.7801
0.9800
0.9936
0.9755
0.9921
0.9975
0.9910
0.9971
0.9991
0.9943
0.9994
0.9996
0.9999
1
0.186–1.30
0.186–0.931
0.341–3.07
0.341–2.39
0.401–4.01
0.401–4.01
0.401–4.01
0.439–3.95
0.439–4.39
0.439–4.39
0.450–4.50
0.450–4.50
0.442–4.42
0.884–3.98
0.442–4.42
83.2–412
73.8–293
40.6–236
51.5–221
27.8–164
31.3–168
36.2–178
21.6–71.0
25.4–82.7
26.5–81.9
20.0–50.7
26.5–57.6
16.0–25.2
18.6–25.3
15.4–27.4
5
4
5
5
6
7
7
6
7
7
6
7
7
5
7
4-Methoxy
4-Methyl
None
3-Methoxy
3-Acetyl
aIn 44 wt% ethanol–water, at 25.0 ◦C, ionic strength 0.2 M (KCl), 0.01 phosphate buffer.
bFree amine fraction.
cConcentration of total amine (free base plus protonated forms).
Figure 1 shows the Brønsted plots obtained for the
reactions of carbonates 1–3 with the series of anilines.
In these plots, the kN values, as well as those of the pKa
of the conjugate acids of these amines, were statisti-
cally corrected with q = 2 for phenylendiamine (q = 1
for the other anilines) and p = 3 for all the conjugate
acids of the anilines [13]. The parameter q is the num-
ber of equivalent basic sites in the free amine, and p
is the number of equivalent dissociable protons in the
conjugate acid of the amine [19].
of carbonates, esters, and their thio analogues [20].
In fact, the concerted reactions of SA amines with
carbonates 1, 2, 3, and 5 show β values of 0.39, 0.51,
0.48, and 0.44, respectively [13,16,17]. Similarly, the
concerted reactions of quinuclidines with carbonates 4
and 5 exhibit a β value of 0.57 [14]. The linear Brønsted
plots found in the reactions of the latter carbonates with
anilines show slopes slightly larger (β = 0.68 and 0.66,
respectively) [13], but still within the β range expected
for concerted mechanisms.
The Brønsted slopes (β) of the linear plots in Fig. 1
are 0.52, 0.61, and 0.63 for the anilinolysis reactions of
carbonates 1, 2, and 3, respectively. These β values are
in accordance with the values usually obtained (β =
0.4–0.7) for concerted mechanisms in the aminolysis
It is known that the β value alone is not sufficient
to conclude that a mechanism is concerted. It is also
necessary to make sure that the expected pKa value at
the center of the Brønsted curvature (pKa0) for a hypo-
thetical stepwise mechanism is within the pKa range
Table IV Values of pKa for the Conjugate Acids of Anilines and kN Values for the Reactions of Anilines with
Phenyl(2,4-dinitrophenyl) Carbonate (1), 4-Nitrophenyl(2,4-dinitrophenyl) Carbonate (2), and Bis(2,4-dinitrophenyl)
Carbonate (3)a,b
kN(s1M1)
Aniline Substituent
pK
1
2
3
a
4-Amino
4-Methoxy
4-Methyl
None
3-Methoxy
3-Acetyl
6.45
5.31
4.90
4.46
4.26
3.1
2.4 0.1
0.98 0.02
0.57 0.01
0.23 0.01
0.12 0.01
0.044 0.002
43
9.2 0.5
4.5 0.1
2.0 0.1
1.40 0.08
0.36 0.04
1
300 24
75
39
6
1
15.0 0.6
7.3 0.5
2.4 0.2
aBoth the pKa and kN values were determined in 44 wt% ethanol–water, at 25.0◦C, ionic strength 0.2 M (KCl).
bErrors shown are standard deviations.
International Journal of Chemical Kinetics DOI 10.1002/kin

ANILINOLYSIS OF ARYL 2,4-DINITROPHENYL CARBONATES: KINETICS AND MECHANISM
195
4
2
1
1
2
0
–2
4
2
2
q
0
0
k
k
4
3
-1
2
0
3
6
9
12
3
4
5
6
7
pKa + log(p/q)
pKa + log (p/q)
Figure 2 Brønsted plots obtained for the reactions of car-
Figure 1 Brønsted-type plots for the aminolysis (anilines)
bonates 1–3 with a series of SA amines ( , [16,17]), quinu-
◦
of carbonates 1 ( ), 2 (o), and 3 (ꢀ) in 44 wt% ethanol–water,
•
clidines (ꢀ, [14]) and anilines ( , this work).
•
25.0 0.1◦C, ionic strength 0.2 mol · dm−3 (KCl).
ber of nitro groups attached to the nonleaving group
increases. The greater electron-withdrawing power of
the nonleaving group as more nitro groups are added
leaves the carbonyl carbon of the carbonate more pos-
itive and therefore more prone to the aniline attack.
The same sequence of reactivity was reported for the
concerted reactions of carbonates 1–3 with SA amines
[16,17].
employed [21,22]. The pyridinolysis reactions of car-
bonates 1–3 are stepwise, as judged by the biphasic
Brønsted plots obtained, with pKa0 values in the range
7.2–8.0 [12]. It is known that anilines are better nu-
cleofuges than isobasic pyridines from the tetrahedral
intermediate T [23]. This means that the pKa0 value
for the reactions of anilines with carbonates 1–3 for
a hypothetical stepwise mechanism would be larger
than 7.2–8.0 [6], which is outside the pKa range of the
anilines employed. Nevertheless, we are more inclined
toward a concerted mechanism for the following rea-
sons: (i) If the studied anilinolysis reactions were step-
wise, the slopes of the Brønsted plots in Fig. 1 would
correspond to those for rate-determining breakdown
of T to products (β2), since the pKa0 value would
be larger than that of the most basic aniline [6,7,20].
The experimental values (β = 0.52–0.63) are too small
compared with the expected β2 values for stepwise re-
actions, which are in the 0.8–1.1 range [6,20]. (ii) The
anilinolysis of carbonate 4 is concerted [13]; therefore,
the reactions of these amines with carbonate 1 should
also be concerted since the change of 4-methylphenyl
in 4 by phenyl in 1, as the nonleaving group, should
destabilize the putative T intermediate [7,20]. More-
over, the anilinolysis of carbonates 2 and 3 should also
be concerted due to the stronger electron-withdrawing
substituents in the nonleaving group of these carbon-
ates [7,20]. Therefore, the most likely mechanism for
the reactions under the present investigation is the con-
certed process depicted in Scheme 1.
Amine Effect
The concerted mechanism for the anilinolysis of 1–
3 is in contrast to the stepwise process found for the
pyridinolysis of the same carbonates under the same
experimental conditions [12]. This can be attributed to
the known fact that anilines are better nucleofuges than
isobasic pyridines from a tetrahedral intermediate (T )
and, therefore, destabilize this intermediate relative to
pyridines. Consequently, the intermediate formed with
anilines could not exist, or it could exist, but being so
unstable that the concerted process would become of
lower free energy of activation relative to that of the
stepwise mechanism [24–26].
The reactions of carbonates 1–3 with SA amines
and that of 1 with quinuclidines are also concerted
[14,16,17]. Figure 2 summarizes the Brønsted plots
obtained for the reactions of 1–3 with these series of
amines and anilines.
As seen in Fig. 2, SA amines and quinuclidines
seem to be more reactive than anilines toward carbon-
ate 1. Nevertheless, the reactions of the two former
series of amines were carried out in water [14,16],
whereas those of anilines were performed in aqueous
ethanol (this work). Since the reactions of SA amines
From the kN values in Table IV and from Fig. 1,
the following reactivity sequence can be observed: 3
> 2 > 1. Namely, the reactivity increases as the num-
International Journal of Chemical Kinetics DOI 10.1002/kin

196
CASTRO, DOMECQ, AND SANTOS
Y
NO
Y
NO
2
2
O
C
O
C
-
X
O
O
NO
X
O
+
O
NO
2
2
+
ArNH
+
2
+
ArNH
2
Fast
– H
Y
O
X
O
C
ArNH
Scheme 1
and anilines are of similar reactivity toward carbon-
ates 2 and 3 (see Fig. 2, these reactions are both in
44 wt% ethanol–water), it is possible that the appar-
ent greater reactivity of SA amines and quinuclidines
toward carbonate 1 is due only to the change of sol-
vent. It is expected that these reactions be faster in
water than in aqueous ethanol due to the greater po-
larity of the transition state compared with reactants
[6]. The similar reactivity of these amine series toward
carbonates 1–3 is in contrast to the results found for
the stepwise reactions of these amines series with 4-
methylphenyl 4-nitrophenyl carbonate (6) in 44 wt%
ethanol–water, whereby SA amines are more reactive
than anilines [11]. The similar reactivity of these series
of amines toward carbonates 1–3 could be attributed to
the lower selectivity shown by the more reactive car-
bonates (1–3) compared with carbonate 6, according
to the reactivity–selectivity principle [27,28].
2
0
q
k
-2
-2
0
2
log (kNq-1/s-1 M-1)calcd
Figure 3 Double logarithmic plot of the experimental kN/q
values against those calculated by means of Eq. (3), for the
reactions of anilines with carbonates (ꢀ, 1), ( , 2), ( , 3),
( , 4), and ( , 5). The line has unity slope and zero intercept.
ꢁ
ꢂ
◦
•
Multiparametric Study
nonleaving group becomes more basic (larger pKnlg
)
With the corrected kN values (kN/q) obtained for the
anilinolysis of carbonates 1–5, all of these reactions
corresponding to concerted mechanisms, and the cor-
rected pKa of the conjugate acids of the anilines, pKa
+ log(p/q), and that of the nonleaving group (pKnlg),
the multiparametric relation shown in Eq. (3) was ob-
tained.
less positive becomes the carbonyl carbon atom of the
carbonate and less prone results to the amine attack.
The good correlation shown by the concerted anili-
nolysis of carbonates 4 and 5 with the anilinolysis of
carbonates 1–3 (Fig. 3) indicates that the latter reac-
tions are also concerted.
log kN/q = −0.64 + 0.65 [pKa
CONCLUSIONS
+ log(p/q)] − 0.33 pKnlg
(3)
i. The kinetic results for the anilinolysis reactions
of carbonates 1–3 are in accordance with a con-
certed mechanism.
ii. The greater kN values as more nitro groups are at-
tached to the nonleaving group of the carbonate is
due to the greater electron withdrawal from this
group, which leaves the carbonyl carbon more
Figure 3 shows a log–log plot of the experimental
kN values versus those calculated by Eq. (3). The line
has unity slope and zero intercept, showing the good
fit obtained.
The negative value of the nonleaving group sen-
sitivity (βnlg = −0.33) is due to the fact that as the
International Journal of Chemical Kinetics DOI 10.1002/kin

ANILINOLYSIS OF ARYL 2,4-DINITROPHENYL CARBONATES: KINETICS AND MECHANISM
197
positive and, therefore, more prone to amine
attack.
8. Um, I.-H.; Kim, E. Y.; Park, H.-R.; Jeon, S.-E. J Org
Chem 2006, 71, 2302–2306.
9. Um, I.-H.; Yoon, S.; Park, H.-R.; Han, H.-J. Org Biol
Chem 2008, 6, 1618–1624.
10. Castro, E. A.; Andujar, M.; Toro, A.; Santos, J. G. J Org
Chem 2003, 68, 3608–3613.
11. Castro, E. A.; Gazitu´a, M.; Santos, J. G. J Org Chem
2005, 70, 8088–8092.
12. Castro, E. A.; Acun˜a, M.; Soto, C.; Trujillo, C.; Va´squez,
B.; Santos, J. G. J Phys Org Chem 2008, 21, 816–822.
13. Castro, E. A.; Campodo´nico, P.; Toro, A.; Santos, J. G.
J Org Chem 2003, 68, 5930–5935.
iii. The T intermediate formed in the pyridinoly-
sis reactions is destabilized by the change of its
pyridino moiety by an isobasic anilino group, due
to the superior leaving ability of anilines, relative
to isobasic pyridines.
iv. The kN values for the anilinolysis of carbonates
1–3 are similar to those found in the reactions of
these carbonates with SA amines.
14. Castro, E. A.; Campodo´nico, P.; Contreras, R.;
Fuentealba, P.; Santos, J. G.; Leis, J. R.; Garc´ıa-R´ıo, L.;
Saez, J. A.; Domingo, L. Tetrahedron 2006, 62, 2555–
2562.
15. Castro, E. A.; Ramos, M.; Santos, J. G. J Org Chem
2009, 74, 6374–6377.
We thank the program “Mejoramiento de la calidad y la
equidad de la Educacio´n Superior” (MECESUP) of Chile
(project UCH-06011) and Fondo Nacional de Desarrollo
Cient´ıfico y Tecnolo´gico (FONDECYT) of Chile (project
1060593) for financial support.
16. Castro, E. A.; Aliaga, M.; Campodo´nico, P.; Santos, J.
G. J Org Chem 2002, 67, 8911–8916.
17. Castro, E. A.; Soto, C.; Va´squez, B.; Santos, J. G.
Arkivoc 2008, X, 151–160.
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