Stepwise formation of 1,3-diazolium-4-thiolates by Muenchnone cycloadditions: Promising candidates for nonlinear optics

Article abstract of DOI:10.1021/jo500349g

An improved preparation of mesoionic heterocycles 1,3-diazolium-4-thiolates by [3 + 2] cycloadditions of muenchnones with aryl isothiocyanates is reported. The process takes place with high or complete regioselectivity, and fast and clean transformations are observed under microwave heating in DMF. DFT calculations support that this cycloaddition proceeds preferably through a stepwise mechanism. Given the pattern substitution around the mesoionic ring resulting in a push-pull system, theoretical estimations predict large hyperpolarizabilities in some cases, which is typical of molecules exhibiting nonlinear optical responses.

Full text of DOI:10.1021/jo500349g

Note
pubs.acs.org/joc
̈
Stepwise Formation of 1,3-Diazolium-4-thiolates by Munchnone
Cycloadditions: Promising Candidates for Nonlinear Optics
†
†
†
†
‡
David Cantillo,*,†,§ Martín Avalos, Reyes Babiano, Pedro Cintas, Jose L. Jimenez, Mark E. Light,
́
́
́
Juan C. Palacios,† and Rocío Porro†
†Departamento de Química Organ
E-06006, Badajoz, Spain
́ ́
ica e Inorganica, QUOREX Research Group, Facultad de Ciencias, Universidad de Extremadura,
‡Department of Chemistry, University of Southampton, Highfield, Southampton, U.K., SO17 1BJ
S
* Supporting Information
ABSTRACT: An improved preparation of mesoionic heterocycles 1,3-
diazolium-4-thiolates by [3 + 2] cycloadditions of munchnones with aryl
̈
isothiocyanates is reported. The process takes place with high or complete
regioselectivity, and fast and clean transformations are observed under
microwave heating in DMF. DFT calculations support that this
cycloaddition proceeds preferably through a stepwise mechanism. Given
the pattern substitution around the mesoionic ring resulting in a push−pull
system, theoretical estimations predict large hyperpolarizabilities in some
cases, which is typical of molecules exhibiting nonlinear optical responses.
esoionic rings, by virtue of their dipolar nature, are not
Monly suitable partners in cycloaddition reactions but also
promising candidates for optoelectronic applications combining
donor and acceptor moieties. In the course of our studies
directed toward the preparation of stable mesoionic hetero-
cycles that could be regarded as precursors of new NLO
materials, we have described recently the synthesis of 2-amino-
1,3-thiazolium-4-thiolate systems by stepwise thionation of 2-
heating, decomposition of the starting munchnone was a
̈
common drawback, partly accounting for poor yields of the
isolated products. Thus, we decided to move to a polar solvent
such as DMF, susceptible of dielectric heating, at higher
temperatures to enhance the reaction and minimize decom-
position of the starting material. Gratifyingly, when DMF was
used as solvent in combination with rapid heating at 140 °C in
a microwave (MW) oven, clean reactions were obtained in very
short times (<10 min) (see the Experimental Section for
details).
aminothioisomunchnones with aryl isothiocyanates.1 In this
̈
context, the reaction of munchnones (1,3-oxazolium-5-olates)
̈
with other heterocumulenes (CS2) leading to 1,3-thiazolium-5-
thiolate derivatives has also been revisited.2 In this case,
however, it was found that both the concerted cycloaddition
and the retrocycloaddition tandem reactions compete favorably
with the stepwise thionation. It is noteworthy that, within
The results obtained for the reactions of munchnones 1a−1c
̈
with aryl isothiocyanates (2a−2c) are collected in Table 1.
Reactions of 1a with either 2a or 2c led to mixtures of two
isomeric products (3a + 3a′ and 3c + 3c′), although 3b was the
only product isolated from the reaction of 1a with 2b.
mesoionic heterocycles, munchnones still attract considerable
̈
However, the corresponding reactions of munchnones 1b and
̈
attention as their regio- and stereochemical outcome cannot
easily be predicted, and recent theoretical studies provide
further insight into the actual mechanistic pathway.3,4
1c with the same isothiocyanates (2a−2c) occurred in a
regiospecific manner, and only one mesoionic product (3d−3i)
could be detected and isolated. The structure of 3e could be
confirmed by X-ray diffraction (see Figure S1a, Supporting
Information). Likewise, the solid-state structure of 3a′, which
corresponds to the regioisomer of the expected 1,3-diazolium-
4-thiolate 3a, was also unequivocally assigned by single-crystal
X-ray diffraction (Figure S1b, Supporting Information). In
compound 3a′, the aryl group linked to carbon atoms adopts a
coplanar arrangement with the mesoionic core, thereby
favoring electron delocalization, while the aryl group joined
to the nitrogen atom shows a perpendicular disposition with
the heterocyclic ring. Such structural features are also shared by
Herein, we report an experimental and theoretical study
aimed at designing a new series of 1,3-diazolium-4-thiolates
from the corresponding munchnones and aryl isothiocyanates.
̈
Although an example of this transformation was first reported
by Huisgen and co-workers more than four decades ago,5
neither has the procedure in question been synthetically
explored in detail nor has its rationale been assessed.
Syntheses of 1,3-diazolium-4-thiolates (3a−3i) were carried
out by reaction of the corresponding munchnones (1a−1c)2,6
̈
with an excess of the corresponding para-substituted aryl
isothiocyanate (2a−2c) (Scheme 1). In agreement with the
seminal protocol,5 reactions were first attempted in refluxing
toluene, but most reactions were sluggish, often low yielding,
and required at least 6 h for completion. Under prolonged
Received: February 24, 2014
Published: April 10, 2014
© 2014 American Chemical Society
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Note
Scheme 1
process for which we have located two transition states and the
corresponding zwitterionic intermediate. The cycloadduct
formation is slightly exergonic, although the retrocycloaddition
of carbon dioxide is very exergonic and releases more than 30
kcal mol−1 relative to the starting materials (see Table S1,
Supporting Information). Remarkably, the formation of
cycloadduct 4a′ derived from 1a and 2a through pathway (b)
proceeds by a concerted process characterized by an energy
barrier similar to that found for route (a) (ΔΔG⧧ < 3 kcal
mol−1). This fact suggests that, in such a case, and presumably
others with a similar substitution pattern, both routes might
coexist, in agreement with the experimental results (see Table
1). However, for the reaction of 1b with 2a, route (b) would
only be feasible after overcoming an energy barrier of ∼10 kcal
mol−1 higher than that estimated for route (a). This energy
difference accounts for the regiospecificity observed exper-
imentally in the reactions of dipoles 1b and 1c with 2a−2c. The
presence of NO2 and MeO substituents at the C-2 and C-4
Table 1. Reactions of Munchnones 1a−1c with
̈
a
Isothiocyanates 2a−2c
b
reactants
time (min)
product
yield (%)
1a + 2a
1a + 2b
1a + 2c
1b + 2a
1b + 2b
1b + 2c
1c + 2a
1c + 2b
1c + 2c
10
10
6
3a + 3a′
30 + 42
58
3b
3c + 3c′
39 + 55
57
10
10
5
3d
3e
3f
23
48
3
3g
3h
3i
49
2.5
1
24
80
a
Conditions: 0.8 mmol of 1, 1 mL of DMF, 4.0 mmol of 2. MW
b
irradiation at 140 °C. Isolated yield.
3e, which shows the expected regiochemistry for these
cycloadditions.
positions of the parent munchnone 1a most likely enhances its
̈
From a mechanistic standpoint, the formation of 1,3-
diazolium-4-thiolates 3 and 3′ may be rationalized by two
possible approaches of the aryl isothiocyanate to the mesoionic
heterocycle (Figure 1). The first approach (a) involves binding
of the nucleophilic carbon atom (C-4) of 1 to the thiocarbonyl
carbon of 2 to yield cycloadduct 4, whereas the second
approach (b) would lead to 4′ through the linkage of
electrophilic C-2 and CS carbon atoms of 1 and 2,
respectively. Both pathways would afford, after the loss of
carbon dioxide, the regioisomeric heterocycles 3 and 3′ that can
only be differentiated by the relative position of the thiolate
group with respect to the two para-substituted aryl groups at
the mesoionic ring. To shed light into the origin of the
regioselectivity, we optimized at the M06-2X/6-311+G(d,p)
level7/basis set8 the structures of all stationary states involved in
reactivity toward the concerted pathway, thereby decreasing the
corresponding energy barrier. The cycloadditions of 1a and 1b
with 2a were also computationally assessed using DMF as
solvent in the calculations. Notably, this solvent switching had
no effect on the concertedness, and analogous energy profiles
were obtained for both reactions (see Figure S2, Supporting
Information). Data collected in Table S1 (Supporting
Information) summarize the energy landscape for the cyclo-
addition of munchnones 1a and 1b with aryl isothiocyanates
̈
2a−2c. 4-Nitrophenyl isothiocyanate 2c exhibits the highest
reactivity with the munchnones, in close agreement with
̈
Sustmann’s type I dipolar cycloaddtions (i.e., HOMO(dipole)-
LUMO(dipolarophile)-controlled reactions).11 Moreover, the
computational data are also in agreement with the experimental
results, as the reactions of the munchnones with 2c proceeded
̈
the two reaction channels (a) and (b) of munchnones 1a and
̈
faster than those of electron-rich aryl isothiocyanates 2a and 2b
(cf. Table 1) and adequately predict the regioselectivity in all
cases except for the reaction of 1a with 2b. In this case, the
calculated barriers point to a nonregioselective reaction, albeit
only a product could be experimentally observed. Alternative
concerted or stepwise mechanisms for pathways (a) and (b)
1b with aryl isothiocyanates 2a−2c. Solvent effects were
included in all geometry optimizations and frequency analyses,
using the SMD method9 and either toluene or DMF (vide
infra) as solvents.10
Figure 1 shows the free energy profiles for the reaction of 1a
and 1b with 2a. In both cases, pathway (a) involves a stepwise
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Figure 1. Free energy profiles for the formation of regioisomeric cycloadducts in the 1,3-dipolar cycloaddition of 1a (black) and 1b (blue) with 2a.
For the sake of clarity, the saddle points show the corresponding bond-forming processes only (dashed lines).
a
Table 2. β(0)tot and β(ω)tot (×10−30 esu) Calculated for 3a−3i by the FF and CPHF Methods
b
c
b
c
FF
CPHF
FF
CPHF
compound
β(0)tot
β(0)tot
β(ω)tot
compound
β(0)tot
β(0)tot
β(ω)tot
3a
366.8
114.4
363.8
355.8
88.8
112.6
29.3
109.9
106.9
21.4
9.2
149.7
36.0
3e
3f
35.3
23.0
39.4
34.6
34.0
52.3
8.9
10.4
17.6
11.1
15.8
21.0
13.0
12.4
21.6
21.5
22.9
27.1
3a′
3b
3c
146.5
141.8
26.4
3g
3h
3i
3c′
3d
d
29.1
11.7
3j
a
b
c
d
ω = 1064 nm. B3LYP/6-31+G(d). HF/6-31+G(d). 3j: R1 = R2 = R3 = R4 = H.
were also explored. However, in both cases, stationary points
accounting for a single reaction channel could be located. To
further rationalize the concerted vs stepwise mechanisms for
coupled perturbed Hartree−Fock (CPHF) and the finite-field
(FF) methods implemented in the Gaussian 09 software
package.13 To establish an adequate level of theory for the
estimation of the NLO properties, we performed a series of
calculations for the hyperpolarizabilities of two model
compounds, 4-nitroaniline (pNA) and 4-dimethylamino-4′-
nitrostilbene (DANS), known for their good NLO properties
(see Table S2 in the Supporting Information). Using the finite-
field (FF) method, good results, close to the experimental
values, were obtained when the B3LYP density functional was
employed in conjunction with a basis set containing diffuse
functions. Also, the CPHF method worked well when diffuse
functions were added. Thus, we decided to calculate the
hyperpolarizabilities of compounds 3a−3i using both the FF
and the CPHF methods at the B3LYP/6-31+G(d) and HF/6-
31+G(d) levels, respectively. High hyperpolarizabilities (Table
2) were obtained for 1,3-diazolium-4-thiolates (regioisomers 3)
possessing an electron-withdrawing group attached to the C-2
atom and an electron-releasing group at the C-5 carbon atom.
This effect is particularly relevant when the electron-deficient
substituent is a nitro group. In contrast, the nature of the
the cycloadditions of munchnones with isothiocynates, we
̈
constructed the potential energy surfaces for the approaches (a)
and (b). A simple mathematical analysis12 of theoretical data
demonstrated the stepwise character leading to cycloadduct
formation through pathway (a), and a concerted, yet a very
asynchronous mechanism, for pathway (b) (see the Supporting
Information for a more detailed discussion on other plausible
reaction channels and PES analyses).
In contrast with their parent munchnones, which are
̈
relatively unstable and decompose when stored for long
periods, 1,3-diazolium-4-thiolates (3a−3i) are very stable as
solid materials or in solution. Furthermore, the presence of
electron-donating and electron-withdrawing groups at the ends
of the 1,3-diazolium-4-thiolate ring with extended π-conjuga-
tion suggests that such substances could be a new family of
nonlinear optical materials. Second-order NLO properties of
the aforementioned mesoionic compounds were estimated by
calculating their molecular hyperpolarizabilities using the
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Note
imaginary frequency, respectively. All of the presented relative energies
are free energies at 298.15 K with respect to the reactants.
substituent linked to the N-3 position, which comes from the
isothiocyanate moiety, has little or no influence on the
magnitude of the hyperpolarizability. However, the β value of
3d is remarkably smaller than that calculated for 3a′, thus
reflecting the importance of the position occupied by the
electron-withdrawing substituent. Although the 1,3-diazolium-
4-thiolate ring substituted with simple phenyl groups (3j) also
exhibits a certain hyperpolarizability, the push−pull character of
the mesoionic system is greatly enhanced by the introduction of
electron-withdrawing and electron-donating groups. Analysis of
the frontier molecular orbitals for 3c (Figure S4, Supporting
Information), one of the three 1,3-diazolium-4-thiolates
showing a high hyperpolarizability, revealed that the HOMO
is formerly located on the ring fragment where the negative
charge (MeO-C6H4-CC-S−) exists, whereas the LUMO
orbital is located on the acceptor fragment of the push−pull
system (O2N-C6H4-CN+−). This spatial separation of
frontier orbitals unveils the charge transfer of the HOMO−
LUMO transition as well as the required overlapping through
the C-2 carbon atom to obtain large nonlinear responses.14 It is
worth pointing out that some β values collected in Table 2 for
mesoionic compounds 3 are significantly higher than those of
standard compounds taken as NLO references, pNA and
DANS, calculated at the same levels of theory (see Table S2,
Supporting Information).
Reactions of 1,3-Oxazolium-5-olates with Aryl Isothiocya-
nates. A mixture of munchnone (0.8 mmol), aryl isothiocyanate (4.0
̈
mmol), and DMF (1 mL) was placed in a pyrex 10 mL flask and
heated in a MW oven (max. 500 W) (Milestone Ethos) at 140 °C
(open vessel, internal probe temperature measurement) until the
disappearance of the starting heterocycle (TLC analysis, benzene:a-
cetonitrile, 2:1). The reaction mixture was cooled to room
temperature, the solvent was evaporated to dryness, and the resulting
residue was purified by column chromatography (benzene/acetoni-
trile).
1-Methyl-5-(4-methoxyphenyl)-2-(4-nitrophenyl)-3-phenyl-
1,3-diazolium-4-thiolate (3a). This compound was hardly soluble
in typical deuterated solvents, and as a result, a suitable 13C NMR
spectrum could not be recorded; (100 mg, 30%); mp 228−231 °C; 1H
NMR (400 MHz, CDCl3) δ 8.27 (d, J = 8.0 Hz, 2H), 8.11 (s, 2H),
7.32−7.14 (m, 7H), 6.83 (d, J = 8.0 Hz, 2H), 3.75 (s, 3H), 3.62 (s,
3H); IR (KBr, cm−1) 1525, 1345, 1248. Anal. Calcd for C23H19N3O3S:
C, 66.17; H, 4.59; N, 10.07; S, 7.68. Found: C, 65.87; H, 4.68; N, 9.90;
S, 7.75.
1-Methyl-2-(4-methoxyphenyl)-5-(4-nitrophenyl)-3-phenyl-
1,3-diazolium-4-thiolate (3a′). (140 mg, 42%); mp 192−194 °C;
1H NMR (400 MHz, DMSO-d6) δ 8.31 (s, 4H), 7.47−7.30 (m, 7H),
6.99 (d, J = 8.0 Hz, 2H), 3.76 (s, 3H), 3.60 (s, 3H); 13C NMR (100
MHz, DMSO-d6) δ 161.4, 152.7, 145.2, 142.8, 137.7, 136.2, 132.8,
130.0, 129.6, 129.1, 124.7, 123.6, 116.1, 114.7, 55.8, 36.4; IR (KBr,
cm−1) 1531, 1348, 1230. Anal. Calcd for C23H19N3O3S: C, 66.17; H,
4.59; N, 10.07; S, 7.68. Found: C, 65.76; H, 4.81; N, 9.83; S, 7.70.
1-Methyl-3,5-bis(4-methoxyphenyl)-2-(4-nitrophenyl)-1,3-
In summary, the experimental results show that 1,3-
diazolium-4-thiolates, described for the first time several
decades ago, can advantageously be obtained with high
regioselectivity using a polar solvent such as DMF at high
temperatures. DFT calculations suggest that the cycloaddition
1
diazolium-4-thiolate (3b). (207 mg, 58%); mp 230−231 °C; H
NMR (400 MHz, DMSO-d6) δ 8.30 (s, 4H), 7.47 (d, J = 8.0 Hz, 2H),
7.22 (d, J = 8.0 Hz, 2H), 7.01 (d, J = 8.0 Hz, 2H), 6.93 (d, J = 8.0 Hz,
2H), 3.78 (s, 3H), 3.76 (s, 3H), 3.60 (s, 3H); 13C NMR (100 MHz,
DMSO-d6) δ 161.4, 159.5, 145.2, 143.0, 137.8, 132.8, 130.7, 129.9,
128.8, 124.6, 123.5, 116.3, 114.7, 114.2, 55.8, 55.8, 36.3; IR (KBr,
cm−1) 1516, 1333, 1251. Anal. Calcd for C24H21N3O4S: C, 64.41; H,
4.73; N, 9.39; S, 7.17. Found: C, 64.03; H, 4.97; N, 9.31; S, 7.19.
1-Methyl-5-(4-methoxyphenyl)-2,3-bis(4-nitrophenyl)-1,3-
of munchnones 1a or 1b with phenyl isothiocyanate (2a)
̈
proceeds through a stepwise mechanism involving two
transition states plus a zwitterionic intermediate. A competing
concerted process may still occur for the cycloaddition of 1a
and 2a, consistent with the experimental detection of both
1
diazolium-4-thiolate (3c). (144 mg, 39%); mp 206−207 °C; H
regioisomers. Reactions of munchnones 1b and 1c with aryl
̈
NMR (400 MHz, DMSO-d6) δ 8.34−8.26 (m, 6H), 7.66 (d, J = 12.0
Hz, 2H), 7.50 (d, J = 8.0 Hz, 2H), 7.02 (d, J = 8.0 Hz, 2H), 3.77 (s,
3H), 3.63 (s, 3H); 13C NMR (100 MHz, DMSO-d6) δ 161.7, 147.6,
145.4, 142.7, 141.8, 137.3, 132.9, 131.4, 130.1, 128.8, 125.0, 124.3,
123.7, 115.6, 114.9, 55.9, 36.4; IR (KBr, cm−1) 1522, 1344, 1251. Anal.
Calcd for C23H18N4O5S: C, 59.73; H, 3.92; N, 12.11; S, 6.93. Found:
C, 59.45; H, 4.13; N, 12.02; S, 6.99.
isothiocyanates follow apparently stepwise mechanisms based
on energy considerations and supported by the stereochemical
outcome. As inferred from theoretical calculations too,
compounds 3a−3i possess high hyperpolarizabilities that
depend on the nature and position of electron-withdrawing
substituents at the heterocyclic ring. These and previous results
suggest that mesoionic systems constitute a promising, yet
underestimated, family of molecules with large NLO responses
waiting for practical applications.
1-Methyl-2-(4-methoxyphenyl)-3,5-bis(4-nitrophenyl)-1,3-
1
diazolium-4-thiolate (3c′). (203 mg, 55%); mp 221−223 °C; H
NMR (400 MHz, DMSO-d6) δ 8.27 (dd, J = 4.0 Hz, 12.0 Hz, 4H),
7.79 (t, J = 8.0 Hz, 4H), 7.68 (d, J = 8.0 Hz, 2H), 7.09 (d, J = 8.0 Hz,
2H), 3.83 (s, 3H), 3.58 (s, 3H); 13C NMR (100 MHz, DMSO-d6)
159.2, 159.2, 148.7, 147.7, 147.6, 132.8, 132.8, 132.2, 131.2, 124.3,
114.1, 55.7; IR (KBr, cm−1) 1349, 1265. Anal. Calcd for C23H18N4O5S:
C, 59.73; H, 3.92; N, 12.11; S, 6.93. Found: C, 59.67; H, 4.02; N,
12.23; S, 6.94.
EXPERIMENTAL SECTION
■
General Remarks. Solvents and reagents were purchased from
standard commercial suppliers and used without further purification.
1,3-Oxazolium-5-olates (munchnones) 1a−1c were prepared in a
̈
1-Methyl-2-(4-methoxyphenyl)-5-(4-nitrophenyl)-3-phenyl-
1,3-diazolium-4-thiolate (3d). (190 mg, 57%); mp 112−115 °C;
1H NMR (400 MHz, CDCl3) δ 8.59 (s, 1H), 8.42 (d, J = 8.0 Hz, 1H),
8.19 (d, J = 8.0 Hz, 1H), 7.58 (t, J = 8.0 Hz, 1H), 7.40−7.28 (m, 5H),
7.22 (d, J = 8.0 Hz, 2H), 6.89 (d, J = 8.0 Hz, 2H), 3.81 (s, 3H), 3.66
(s, 3H); 13C NMR (100 MHz, CDCl3) δ 161.7, 148.2, 136.8, 135.3,
131.8, 129.7, 129.3, 129.1, 128.7, 128.3, 124.6, 122.5, 115.2, 114.8,
113.7, 55.5, 35.5; IR (KBr, cm−1) 1505, 1346, 1255. Anal. Calcd for
C23H19N3O3S: C, 66.17; H, 4.59; N, 10.07; S, 7.68. Found: C, 66.09;
H, 4.71; N, 10.19; S, 7.55.
three-step sequence as reported previously.6 The identity of the
unknown compounds 3a−3i was confirmed by their elemental
analyses, mp’s, and NMR data (Supporting Information).
Computational Details. All of the calculations reported in this
work were carried out using the Gaussian 09 package.13 The M06-2X7
density functional method in conjunction with the 6-311+G(d,p) basis
set was selected for all the geometry optimizations and frequency
analysis. The geometries were optimized including solvation effects.
For this purpose, the SMD9 solvation method was employed, using
toluene as solvent. Frequency calculations at 298.15 K on all the
stationary points were carried out at the same level of theory as the
geometry optimizations to ascertain the nature of the stationary points.
Ground and transition states were characterized by none and one
1-Methyl-2,3-bis(4-methoxyphenyl)-5-(4-nitrophenyl)-1,3-
diazolium-4-thiolate (3e). (83 mg, 23%); mp 209−211 °C; 1H
NMR (400 MHz, CDCl3) δ 8.59 (s, 1H), 8.44 (d, J = 8.0 Hz, 1H),
8.17 (t, J = 4.0 Hz, 1H), 7.21 (d, J = 8.0 Hz, 4H), 6.90 (t, J = 8.0 Hz,
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Note
4H), 3.82 (s, 3H), 3.78 (s, 3H), 3.65 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ 161.6, 159.8, 148.2, 141.5, 136.8, 131.8, 131.4, 129.7, 129.6,
127.9, 124.6, 122.4, 115.3, 114.8, 114.4, 55.5, 55.5, 35.6; IR (KBr,
cm−1) 1513, 1344, 1252. Anal. Calcd for C24H21N3O4S: C, 64.41; H,
4.73; N, 9.39; S, 7.17. Found: C, 64.20; H, 4.85; N, 9.55; S, 6.71
1-Methyl-2-(4-methoxyphenyl)-3,5-bis(4-nitrophenyl)-1,3-
COMPUTAEX for allowing us the use of supercomputing
facilities (LUSITANIA).
REFERENCES
(1) (a) Cantillo, D.; Avalos, M.; Babiano, R.; Cintas, P.; Jimen
■
́
́
ez, J.
1
L.; Light, M. E.; Palacios, J. C. Org. Lett. 2008, 10, 1079−1082.
diazolium-4-thiolate (3f). (177 mg, 48%); mp 139−141 °C; H
́
(b) Cantillo, D.; Avalos, M.; Babiano, R.; Cintas, P.; Jimen
́
ez, J. L.;
NMR (400 MHz, DMSO-d6) δ 8.94 (d, 1H), 8.32−8.17 (m, 4H), 7.79
(t, J = 8.0 Hz, 1H), 7.66 (d, J = 12.0 Hz, 2H), 7.50 (d, J = 8.0 Hz, 2H),
7.02 (d, J = 8.0 Hz, 2H), 3.77 (s, 3H), 3.61 (s, 3H); 13C NMR (100
MHz, DMSO-d6) δ 161.6, 148.0, 147.6, 141.7, 136.1, 132.9, 131.3,
129.9, 129.3, 124.7, 124.3, 121.9, 115.6, 114.9, 113.9, 55.9, 35.9; IR
(KBr, cm−1) 1509, 1346, 1253. Anal. Calcd for C23H18N4O5S: C,
59.73; H, 3.92; N, 12.11; S, 6.93. Found: C, 59.63; H, 4.03; N, 12.08;
S, 7.03.
1-Methyl-5-(4-nitrophenyl)-2,3-diphenyl-1,3-diazolium-4-
thiolate (3g). (152 mg, 49%); mp 230−231 °C; 1H NMR (400 MHz,
CDCl3) δ 8.62 (s, 1H), 8.42 (d, J = 8.0 Hz, 1H), 8.19 (d, J = 8.0 Hz,
1H), 7.68 (t, J = 8.0 Hz, 1H), 7.46−7.28 (m, 10H), 3.67 (s, 3H); 13C
NMR (100 MHz, CDCl3) δ 13C NMR (101 MHz, CDCl3) δ 148.2,
140.9, 136.9, 135.1, 131.4, 131.2, 130.2, 129.7, 129.4, 129.3, 129.1,
128.7, 124.8, 123.5, 122.6, 35.5; IR (KBr, cm−1) 1525, 1343. Anal.
Calcd for C22H17N3O2S: C, 68.20; H, 4.42; N, 10.85; S, 8.28. Found:
C, 67.90; H, 4.38; N, 10.85; S, 8.24.
1-Methyl-3-(4-methoxyphenyl)-5-(4-nitrophenyl)-2-phenyl-
1,3-diazolium-4-thiolate (3h). (80 mg, 24%); mp 119−120 °C; 1H
NMR (400 MHz, CDCl3) δ 8.59 (s, 1H), 8.45 (d, J = 8.0 Hz, 1H),
8.20 (d, J = 8.0 Hz, 1H), 7.68 (t, J = 8.0 Hz, 1H), 7.48−7.41 (m, 3H),
7.31 (d, J = 4.0 Hz, 2H), 7.23 (d, J = 8.0 Hz, 2H), 6.88 (d, J = 8.0 Hz,
2H), 3.78 (s, 3H), 3.67 (s, 3H); 13C NMR (100 MHz, CDCl3) δ
159.9, 148.2, 141.1, 136.9, 131.4, 131.2, 130.2, 129.7, 129.7, 129.3,
127.7, 124.7, 123.6, 122.6, 114.4, 55.4, 35.5; IR (KBr, cm−1) 1515,
1342, 1253. Anal. Calcd for C23H19N3O3S: C, 66.17; H, 4.59; N, 10.07;
S, 7.68. Found: C, 66.39; H, 4.81; N, 10.38; S, 7.63.
1-Methyl-3,5-bis(4-nitrophenyl)-2-phenyl-1,3-diazolium-4-
thiolate (3i). (275 mg, 80%); mp 135−136 °C; 1H NMR (400 MHz,
CDCl3) δ 8.64 (s, 1H), 8.30 (d, J = 8.0 Hz, 1H), 8.23−8.19 (m, 3H),
7.68 (t, J = 8.0 Hz, 1H), 7.59 (d, J = 8.0 Hz, 2H), 7.50 (t, J = 8.0 Hz,
1H), 8.45 (t, J = 8.0 Hz, 2H), 7.33 (d, J = 8.0 Hz, 2H), 3.69 (s, 3H);
13C NMR (100 MHz, CDCl3) δ 148.2, 147.7, 140.5, 136.6, 131.9,
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P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.;
Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima,
T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.;
Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin,
K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.;
Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega,
N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.;
Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.;
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130.7, 130.2, 130.1, 129.8, 129.7, 126.2, 124.9, 124.3, 122.9, 35.6; IR
(KBr, cm−1) 1527, 1347. Anal. Calcd for C22H16N4O4S: C, 61.10; H,
3.73; N, 12.96; S, 7.41. Found: C, 61.02; H, 3.72; N, 13.13; S, 7.57.
ASSOCIATED CONTENT
■
S
* Supporting Information
Supplementary figures and tables, copies of H and 13C NMR
1
spectra for all new compounds, crystallographic data for 3e and
3a′, and Cartesian coordinates and electronic energies for all
calculated structures. This material is available free of charge via
the Internet at http://pubs.acs.org.
̈
Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O;
Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09,
Revision D.01; Gaussian, Inc.: Wallingford, CT, 2009.
(14) Kanis, D. R.; Ratner, M. A.; Marks, T. J. Chem. Rev. 1994, 94,
195−242.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: david.cantillo@uni-graz.at.
Present Address
§Institute of Chemistry, Karl-Franzens-University Graz, Hein-
richstrasse 28, A-8010 Graz, Austria.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This research was supported by the Ministry of Science and
Innovation (Grant CTQ2010-18938/BQU), the Junta de
Extremadura (Ayuda a Grupos Consolidados, Grant
́
GRU10049) and FEDER. We are also grateful to CenitS and
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dx.doi.org/10.1021/jo500349g | J. Org. Chem. 2014, 79, 4201−4205