Electrogeneration of (Z)-α-aroyloxy-β-aroylthiostilbenes and (Z)-4,5-diaryl-2-arylimino-1,3-oxathioles by cathodic reduction of monothiobenzils in the presence of electrophilic reagents. Computational B3LYP and RI-MP2 study on the relative stability of ox

Article abstract of DOI:10.1016/j.tet.2010.12.044

Electrochemical reductions of monothiobenzils in the presence of either aroyl or carbonimidoyl dichlorides were carried out, yielding products with sulfur retention. Electrolyses in the presence of aroyl chlorides led to previously unknown (Z)-α-aroyloxy-

Full text of DOI:10.1016/j.tet.2010.12.044

Tetrahedron 67 (2011) 1083e1090
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Electrogeneration of (Z)-a-aroyloxy-b-aroylthiostilbenes and (Z)-4,5-diaryl-2-
arylimino-1,3-oxathioles by cathodic reduction of monothiobenzils in the
presence of electrophilic reagents. Computational B3LYP and RI-MP2 study on the
relative stability of oxathiole compounds
,
a
a
a
a
Antonio Guirado a , Andres Zapata , Raquel Andreu , Jose I. Lopez Sanchez , María D. Paredes ,
*
ꢀ
ꢀ
ꢀ
ꢀ
a
a
b
c,
*
ꢀ
ꢀ
ꢀ
ꢀ
Juan E. Lopez Sanchez , Delia Bautista , Peter G. Jones , Jesus Galvez
Departamento de Química Organica, Facultad de Química, Universidad de Murcia, Campus de Espinardo, 30071 Murcia, Spain
a
ꢀ
b
€
€
Institut fur Anorganische und Analytische Chemie, Technische Universitat Braunschweig, Postfach 3329, 38023 Braunschweig, Germany
c Departamento de Química Física, Universidad de Murcia, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 30 August 2010
Received in revised form 10 December 2010
Accepted 14 December 2010
Available online 21 December 2010
Electrochemical reductions of monothiobenzils in the presence of either aroyl or carbonimidoyl di-
chlorides were carried out, yielding products with sulfur retention. Electrolyses in the presence of aroyl
chlorides led to previously unknown (Z)-
whereas reactions in the presence of arylcarbonimidoyl dichlorides provided novel 4,5-diaryl-2-ar-
ylimino-1,3-oxathioles in fair to high yields. The molecular structures of (Z)- -benzoyloxy- -benzoylthio-
a-aroyloxy-b-aroylthiostilbenes in high to quantitative yields,
a
b
4,40-dimethylstilbene and (Z)-2-(2,4-dichlorophenylimino)-4,5-diphenyl-1,3-oxathiole were determined
by X-ray crystallography. Also, ab initio HF, density functional B3LYP, and MøllerePlesset RI-MP2 pro-
cedures were applied to oxathiole compounds revealing that (Z)-isomers are more stable than (E)-iso-
mers and that both isomers are separated by a relatively low activation barrier.
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Electrosynthesis
Monothiobenzils
Carbonimidoyl dichlorides
Thiolesters
Oxathioles
1. Introduction
intermediates generated byelectroreduction of benzils,16,17 furils,18 or
anils19 at lower cathodic potentials, yielding 2-arylimino-4,5-diaryl-
Electrochemical reductions of benzils in protic media lead to
benzoins through two-electron, two-proton processes.1e3 However,
electrolyses in aprotic media carried out in the presence of non-
electroactive electrophilic reagents have a demonstrably higher
synthetic interest, since under these conditions the electro-
generated intermediates can attack these reagents instead of un-
dergoing simple protonation.4e7 On this basis we developed
effective preparative processes for enediol diesters by cathodic
reduction in the presence of acylating agents.8e10
With a view to expanding this synthetic methodology, we have
established that carbonimidoyl dichlorides,11 which are inexpensive
and easily available reagents,12,13 show optimal chemical and elec-
trochemical properties to be exploited. They were found to be re-
ducible atrelatively high cathodic potentials, providing isocyanides in
near quantitative yields,14,15 but also showed ability to act exclusively
as geminal dielectrophilic agents, thereby capturing reactive
1,3-dioxoles, 2-arylimino-4,5-di(2-furyl)-1,3-dioxoles or 3,4,5-tri-
aryl-2-aryliminooxazolines, respectively.
Monothiobenzils20e27 are also easily available compounds that
can be prepared from chlorodeoxybenzoins by reaction with so-
dium thiosulfate followed by the treatment with sodium hydrox-
ide. These substances, like thiones,28 exhibit
a remarkable
proclivity to undergo desulfuration in polar reactions, yielding ei-
ther benzils or products that would be expected when starting from
benzils; e.g., in ethanolic solution, monothiobenzil is slowly con-
verted to benzil with evolution of hydrogen sulfide, whereas the
treatment of monothiobenzil with hydroxylamine leads to benzil
dioxime.26 Conversely, cycloaddition reactions, in general, occur
with retention of sulfur, leading to thioheterocyclic compounds.
Consequently, synthetic research has mainly focused on this par-
ticular reactivity.20,21,24,25,27 However, mild electrochemical meth-
odology, seemingly optimal to attempt preparative processes with
sulfur retention, remained unexplored.
Given the good results obtained with the work on electro-
reduction of benzils in the presence of acyl and carbonimidoyl
chlorides, we persevered in expanding our research project,
* Corresponding authors. Tel.: þ34 868 887 490; fax: þ34 868 884 148; e-mail
address: anguir@um.es (A. Guirado).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.12.044

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A. Guirado et al. / Tetrahedron 67 (2011) 1083e1090
studying possible applications of this methodology to mono-
thiobenzils. A preliminary communication on cathodic acylations
leading to monothiostilbenediol derivatives was reported.29 In this
paper, we report full details of that work along with the results of
a number of electroreductive reactions of monothiobenzil in the
presence of carbonimidoyl dichlorides that have been demon-
strated to provide an excellent approach to (Z)-2-arylimino-4,5-
diphenyl-1,3-oxathioles. Spectroscopic properties and X-ray crys-
tallographic molecular structures of novel compounds are also
reported. Finally, a computational B3LYP and RI-MP2 study on the
relative stability of isomeric oxathiole compounds was also carried
out in order to explain the observed stereoselectivity.
O
Ar2COO
Ar1
SOCAr2
Ar1
2e, 2 Ar2COCl
2 Cl
Ar1
Ar1
S
1
2
Ar1
Yield (%)
Ar2
C6H5
4-ClC6H4
4-CH3C6H4
C6H5
4-ClC6H4
4-CH3C6H4
C6H5
4-ClC6H4
4-CH3C6H4
C6H5
entry
C6H5
C6H5
C6H5
a
b
c
d
e
f
89
91
78
80
60
84
88
94
95
89
70
76
4-CH3OC6H4
4-CH3OC6H4
4-CH3OC6H4
4-CH3C6H4
4-CH3C6H4
4-CH3C6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
The chemistry of oxathioles has been extensively reviewed.30e32
Regarding 2-imino-1,3-oxathioles, the standard synthetic pro-
cedure involves the reaction of phenacyl bromides with either
a dithiocarbamate or a thiourea.33 Compounds of this type can also
g
h
i
be synthesized by decomposition of an
a-diazoketone in the
presence of an isothiocyanate.33 Further specific reactions yielding
2-imino-1,3-oxathioles have been reported.34e43
j
k
l
4-ClC6H4
4-CH3C6H4
2. Results and discussion
Monothiobenzils 1 and aroyl chlorides (ratio 1:2) were added
and dissolved in the catholyte. After a short time these solutions
changed to an intensive blue colour because of the change of poly-
merized monothiobenzils to the monomeric state.22,23 Then, elec-
trolyses were carried out at constant cathodic potentials under
which the role of aroyl chlorides, being non-electroactive, is limited
to that of electrophilic agents, which react with the nucleophilic
intermediates electrogenerated from monothiobenzils. The elec-
tricity consumption was 2 F in all cases. Single electrolysis products
were formed and isolated and, after applying the usual instrumental
Scheme 1.
techniques, were identified as (Z)-a-benzoyloxy-b-benzoylth-
iostilbenes 2 (Scheme 1). Yields ranged from fair to quantitative.
Geometrical characteristics of this new class of compounds were
determined by single crystal X-ray crystallography of 2g, showing
that the C]C double bond adopts a (Z) configuration. The molecular
structure found is illustratedin Fig.1. Thestericinteractions force the
p-tolyl rings out of the plane (interplanar angle of the two p-tolyl
rings¼116.5ꢀ, torsion angles: C46eC41eC3eC2¼29.7ꢀ and
C16eC11eC2eC3¼67.1ꢀ). Table 1 shows a comparison between
X-ray selected bond lengths and bond angles and those computed at
three different levels of theory, the ab initio HF/6-31G(d), and two
density functional procedures, the well known B3LYP/6-31G(d), and
the newer, but computationally more demanding, wB97X-D/6-31G
(d). This Table shows an excellent agreement between experimental
Fig. 1. Thermal ellipsoid plot (50% level) of compound 2g in the crystal.
Table 1
Selected bond lengths and bond angles of crystal and calculated structures in crystal structure of 2g
a
b
c
ꢁ
ꢁ
ꢁ
ꢁ
Bond
Crystal structure (A)
Calculated structure (A)
Calculated structure (A)
Calculated structure (A)
S1eC2
C2eC3
O2eC3
O2eC4
C2eC11
S1eC1
1.783 (2)
1.339 (3)
1.408 (3)
1.369 (3)
1.484 (3)
1.795 (2)
1.789
1.325
1.383
1.337
1.493
1.795
1.792
1.352
1.400
1.370
1.484
1.831
1.780
1.344
1.388
1.361
1.482
1.814
Bond angle
Crystal structure (ꢀ)
Calculated structure (ꢀ)a
Calculated structure (ꢀ)b
Calculated structure (ꢀ)c
C3eC2eS1
C4eO2eC3
C2eC3eO2
C2eS1eC1
C3eC2eC11
C2eC3eC41
119.50 (17)
116.43 (17)
117.7 (17)
98.77 (11)
124.0 (2)
119.93
120.25
119.98
101.46
123.55
126.09
120.38
118.98
119.26
101.55
123.97
126.88
120.48
119.14
119.40
101.67
123.33
126.48
128.1 (2)
Geometries optimized at the following levels of theory.
a
HF/6-31G(d).
B3LYP/6-31G(d).
wB97X-D/6-31G(d).
b
c

A. Guirado et al. / Tetrahedron 67 (2011) 1083e1090
1085
X-ray crystallography data and the calculated molecular structures
of 2g, which confirms the accuracy of the computational method-
ology applied to envisage molecular geometries (the small differ-
ences might be ascribed to molecular distortion in the crystal
structure induced by packing effects).
As in the case of electroreductions of diaryl-1,2-diketones, these
reactions showed stereoselectivity toward the formation of Z iso-
mers. This seems to be attributable to chelation of electrogenerated
intermediates with electrolyte metal cations.44 This is the first
electrochemical synthetic process developed from mono-
thiobenzils. Considering the pronounced proclivity of mono-
thiobenzils to undergo desulfuration reactions, these findings are
notable.
In view of the good results obtained by studying electro-
reductive acylations of monothiobenzils, our objective was to
explore the possibility of formation of 2-arylimino-4,5-diphenyl-
1,3-oxathioles by electrochemical reduction of monothiobenzil
in the presence of arylcarbonimidoyl dichlorides (Scheme 2).
Fig. 2. Thermal ellipsoid plot (50% level) of compound 3c in the crystal.
Ar
N
O
is a good agreement between experimental X-ray crystallography
data and the calculated molecular structures of 3c (the RI-MP2
procedure is significantly more elaborate than the others but, as we
show below, the use of this high level method is necessary to ex-
plain why the (Z)-isomers are the exclusive species).
2e, ArN=CCl2
2 Cl
Ph
S
O
Ph
S
Ph
Ph
1
3
The exclusive isolation of products 3 with (Z) stereochemistry
can be explained on the basis of our conclusions from previous
work on electrosynthesis and topomerization of aryliminodiox-
oles.18,46 These compounds exhibit a remarkably low configura-
tional stability around the carbonenitrogen double bond causing
topomerization processes that were studied by HF and B3LYP
computational methodology, showing relatively small Ea and
entry
Ar
Yield (%)
C6H5
53
74
71
63
75
56
a
b
c
d
e
f
4-ClC6H4
2,4-Cl2C6H3
2,6-Cl2C6H3
4-BrC6H4
4-NCC6H4
D
Gs298 values, close to 12 and 13 kcal/mol, respectively. With this
purpose, and in order to gain further insights into the isomeriza-
tion process of compounds 3, the transition state (TS) optimized
structures for the thermal (Z)e(E) interconversion of products 3a
and 3f were determined at the B3LYP/6-31G(d) level of theory and
characterized by vibrational frequency calculations that gave a sole
imaginary frequency for the TS structure. The computed TSs for 3a
and 3f are shown in Fig. 4. The CNC angles are 176.4ꢀ and 162.3ꢀ,
respectively, and this reveals that there is a small deviation from
the inversion mechanism in favor of the rotational one,46 espe-
cially for 3f. Also, it is interesting to note that the aryl group
changes its configuration to almost orthogonal with the five-
membered ring in the transition state (82.9ꢀ for 3a and 88.2ꢀ for
3c), which can be attributed to a gain of stabilization by orbital
overlapping and also by lessening of steric hindrance. In addition,
there is a shortening of the bond C]N in the TS with respect to the
Scheme 2.
Electrolyses were carried out following an experimental procedure
similar to that applied in electroreductive acylation reactions but
using the geminal dielectrophilic agents in ratio 1:1. These pro-
cesses also consumed 2 F, leading to products that were identified
as the targeted compounds. Yields ranged from moderate to high.
The stereochemical arrangements of products 3a and 3c were
established by X-ray crystallographic analysis showing that the C]
N double bond adopt a (Z) configuration. The molecular structure
found for 3c is illustrated in Fig. 2. The oxathiole ring is planar
ꢁ
ꢁ
ꢁ
ꢁ
ground state (1.262 A/1.221 A for 3a and 1.266 A/1.232 A for 3c).
This fact supports the view that a rotation process taking place
through a polar mechanism is not involved in the isomerization
process since under these conditions these bonds might be
expected to lengthen. Finally, the activation energies (Ea) including
ZPE and thermal corrections for 3a and 3f were obtained at the
same level as geometry optimizations as the difference between
the total molecular energy of the transition state TS and that of the
ground state. The values found were small, just 12.41 and
ꢁ
(mean deviation 0.009 A) and the dimensions of the ring agree well
with average values of four other 2-imino-1,3-oxathioles (refcodes:
BEQCEG, HEJCEE, JUTJAJ, VEYRUM) found in theꢀCambridge Data-
base;45 maximum deviations are 0.01 A and 1.3 . The substituent
ꢁ
rings C11e16, C21e26 and C31e36 subtend interplanar angles of
78.0, 35.7, and 39.1ꢀ with the central ring, all rotated in the same
sense. The packing (Fig. 3) involves layers of molecules parallel to
3
the yz plane at xz¼,
/
; molecules are linked by the weak hy-
11.38 kcal/mol, whereas the values of D
Gs298 were 12.09 and
4
drogen bonds C24eH24/N (H/N 2.66 A, angle 172ꢀ) and
11.57 kcal/mol. It should be noted that these kinds of processes are
so fast that the resulting isomers cannot be separated at room
temperature.47 The values of Ea for rotational barriers around a C]
N bond range between very low (<10 kcal/mol) and extremely high
(>70 kcal/mol) values.46 We have found values of z12 kcal/mol,
which reveals the easy isomerization around the C]N bond.
ꢁ
ꢀ
ꢁ
C34eH34/S (H/S 2.97 A, angle 127 ). Table 2 shows a comparison
between X-ray selected bond lengths and bond angles of 3c and
those computed at three different levels of theory, the ab initio HF/
6-31G(d), the density functional B3LYP/6-31G(d), and the modified
MøllerePlesset RI-MP2/6-31G(d). As previously found for 2g, there

1086
A. Guirado et al. / Tetrahedron 67 (2011) 1083e1090
Fig. 3. Packing diagram of compound 3c showing weak hydrogen bonds (dashed lines).
Table 2
Selected bond lengths and bond angles of crystal and calculated structures in crystal structure of 3c
a
b
c
ꢁ
ꢁ
ꢁ
ꢁ
Bond
Crystal structure (A)
Calculated structure (A)
Calculated structure (A)
Calculated structure (A)
SeC1
SeC2
C1eO
OeC3
C2eC3
1.754 (2)
1.763 (2)
1.361 (2)
1.398 (2)
1.339 (3)
1.769
1.776
1.338
1.371
1.326
1.794
1.783
1.361
1.388
1.353
1.772
1.762
1.367
1.389
1.358
Bond angle
Crystal structure (ꢀ)
Calculated structure (ꢀ)a
Calculated structure (ꢀ)b
Calculated structure (ꢀ)c
C1eSeC2
SeC2eC3
C2eC3eO
C3eOeC1
OeC1eS
90.29 (10)
110.7 (2)
115.0 (2)
112.9 (2)
111.17 (14)
89.67
110.23
115.07
115.07
109.94
89.89
110.49
114.89
114.74
109.92
89.90
110.88
114.93
113.05
111.22
Geometries optimized at the following levels of theory.
a
HF/6-31G(d).
B3LYP/6-31G(d).
RI-MP2/6-31G(d).
b
c
Relative stabilities and population distribution of 3-(Z),(E) ste-
reoisomeric pairs have been computed at two different levels of
theory, B3LYP/6-31G(d) and RI-MP2/6-31G(d), and the results are
shown in Table 3. These results make it clear that (Z)-isomers show
a higher stability than (E)-isomers, such that in all cases (Z)-isomers
are the predominant population at both levels of theory. However,
values of the Z/E ratio computed at the B3LYP level show some
scatter and for this reason a higher level procedure, the RI-MP2
method, was also used. The Z/E-values obtained with this pro-
cedure demonstrate that (Z)-isomers are always in a ratio ꢁ80%,
which, in turn, gives rise to its exclusive crystallization by a con-
tinuous shift of the equilibrium toward the Z-form as crystallization
progresses.
In order to get experimental evidence to confirm that the for-
mation of electrolysis products involves radical anion nucleophilic
intermediates electrogenerated from monothiobenzils and the
subsequent chemical reaction with the added electrophiles, some
electroanalytical experiments were carried out. Thus, the reduction
of 1a is a quasireversible 1e process when cyclic voltammetry is
performed by switching the direction of the scan at ꢂ0.85 V (under
these conditions a second 1e wave that appears at more negative
potential (ꢂ1.1 V) is prevented). As has been reported,48 this second
wave is due to the formation of a dianion, which avoids the ap-
pearance of the wave of the first process. The peak potential, Ep, for
the first process corresponds to ꢂ0.72 V at 1 V/s. In turn, the
electrophile shows a single wave with Ep¼ꢂ1.81 V (PheN¼CCl2).

A. Guirado et al. / Tetrahedron 67 (2011) 1083e1090
1087
and some other biological activities recently detected in certain
members of the family,57e59 the progress on the synthesis of ary-
liminooxathioles is a subject of renewed interest. In this context, it
is noteworthy that novel and effective methods for the stereo-
selective synthesis of the previously unattainable families of com-
pounds 2 and 3 are reported. These are the first examples of
electroorganic synthesis from monothiobenzils. Given the re-
tention of sulfur, these reactions provide evidence of a great po-
tential for expanding the chemistry of this class of compounds.
3. Experimental
3.1. General
NMR spectra were determined on Bruker AV-200, Bruker AV-
300 or Bruker AV-400 with tetramethylsilane as internal reference.
Electron-impact mass spectra were obtained on Thermoquest trace
MS spectrometer under an ionizing voltage of 70 eV. IR spectra
(Nujol emulsions) were recorded on a Nicolet Impact 400 Spec-
trometer. Microanalyses were performed on a Carlo Erba EA-1108
Fig. 4. Optimized TS structures for 3a and 3f computed at the B3LYP/6-31G(d) level of
theory.
Table 3
€
analyzer. Melting points were determined on a Buchi Melting point
Relative stabilities and Z/E ratio-values of the isomers of compounds 3 computed at
the B3LYP/6-31G(d) and RI-MP2/6-31G(d) levels of theory
B-540 and are uncorrected. Preparative electrochemical experi-
ments were performed with an Amel 552 potentiostat coupled to
an Amel 721 integrator. Voltammetric measurements were per-
formed at 298 K with a potentiostat/galvanostat AUTOLAB-100
(Eco-Chemie, Utrecht) using a one compartment three electrode
system with a hanging mercury drop electrode. A Ag/AgCl/KCl
(saturated) electrode was the reference and a platinum plate was
the auxiliary electrode. Monothiobenzils 1 were prepared starting
from the corresponding benzoins, which were halogenated, treated
with sodium thiosulfate, and finally with sodium hydroxide
according to the protocol described by Bak and Praefcke.20,21 Car-
Compound
B3LYP/6-31G(d)
G0298
RI-MP2/6-31G(d)
G0298
D
E
D
Z/E
D
E
D
Z/E
3a
3b
3c
3d
3e
3f
ꢂ0.41
þ0.02
ꢂ0.88
ꢂ0.52
ꢂ0.03
ꢂ0.03
ꢂ0.30
ꢂ0.46
ꢂ2.10
ꢂ0.15
ꢂ0.69
ꢂ0.18
62:38
69:31
97:3
56:44
76:24
58:42
ꢂ1.31
ꢂ0.90
ꢂ0.79
ꢂ0.79
ꢂ0.88
ꢂ0.76
ꢂ1.45
ND
ND
ND
ND
92:8
82:18
79:21
79:21
82:18
84:16
ꢂ0.97
D
D
E¼difference between the total molecular energy of the isomers Z and E (kcal/mol)
G0298¼difference between the free energy of the isomers Z and E at 298 K (kcal/
mol). ND: not determined. The population of both isomers in the equilibrium was
bonimidoyl dichlorides
2
were prepared by standard
D
G0
NZ
NE
G
computed at 298 K by applying the Boltzmann distribution
expressed as values of the Z/E ratio (in those cases where the
available, the corresponding values of E were used).
¼ eꢂ =RT, and
procedures.12,60
D
0 values were not
All computations were performed with the Spartan’08 package
program.61 The most stable conformers were determined by using
the MMFF molecular mechanics method. Next, these conformers
were used as input for ab initio molecular orbital, density functional
theory, and MøllerePlesset calculations of geometry optimizations
at the HartreeeFock, B3LYP, wB97X-D, and RI-MP2 levels of theory
with the 6-31G(d) basis set. Frequency calculations were performed
at the same level of theory as the geometry optimizations to
characterize the stationary points as local minima (equilibrium
structures) and to evaluate the zero-point energy (ZPE). No scaling
procedures were used.
D
Addition of PheN¼CCl2 to solutions of monothiobenzil results in
the disappearance with time of the wave corresponding to the
electrophilic reagent, while the first wave remains due to the for-
mation at the same potential of an active reaction intermediate (A-
EClꢃ) see Scheme 3. Cyclic voltammograms obtained at different
scan rates without and in the presence of electrophilic agents
support the idea that process takes place through an ECEC mech-
anism. On the other hand, (PhCOCl) exhibits a peak potential at
ꢂ1.42 V, showing that the only electroactive compound is mono-
thiobenzil under the preparative electrolysis conditions. It should
be noted that in a related work on cathodic acylation of 1,2-dike-
tones we found clear evidence for the electrogeneration of radical
anion intermediates.10
3.2. Electrogeneration of products 2 and 3
The electrochemical generation of products 2 was performed in
a cylindrical cell62 following the experimental procedure pre-
viously reported.29,63 Products 3 were generated by a similar pro-
cedure but using dimethylformamide instead of acetone.
Monothiobenzils 1 (5 mmol) were reduced under nitrogen atmo-
sphere, in the presence of either aroyl chlorides (10 mmol) or
Summarizing, it can be stated that over the years, the prepara-
tion of 2-arylimino-1,3-oxathioles has been encouraged by a ver-
satile reactivity, providing them with a notable usefulness as
synthetic intermediates.32,34,36,49e53 In view of the anticancer54e56
ECl
Cl
ECl
Cl
+ e
Products 2
A-E
A-E
A
A + e
ECl2
Cl
+ e
Cl
A= ArCOCSAr
ECl= ArCOCl
ECl2= ArNCCl2
Products 3
A-ECl
Scheme 3.

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A. Guirado et al. / Tetrahedron 67 (2011) 1083e1090
carbonimidoyl dichlorides (5 mmol) at cathodic potentials ranging
between ꢂ0.70 and ꢂ1.0 V versus SCE. These potentials were se-
lected in order to provide operative current intensities. The average
current densities were close to 15 mA/cm2 at the beginning and
0.9 mA/cm2 at the end. The cell voltage values remained below 5 V
in all cases. The electricity consumption was 2 F for all cases. All
electrolysis products were isolated by dropping the catholyte so-
lution into cold brine (200 mL) and filtering or extracting the
mixture with diethyl ether. The isolated products were crystallized
from the appropriate solvent.
2H, J¼9.0 Hz), 7.04 (d, 2H, J¼9.0 Hz), 7.13e7.21 (m, 6H), 7.61 (d, 2H,
J¼8.7 Hz), 7.84 (d, 2H, J¼8.7 Hz); 13C NMR
d (CDCl3, 75.4 MHz):
55.11, 113.68, 113.77, 126.65, 127.55, 128.89, 129.01, 130.05, 130.50,
131.55, 131.61, 134.95, 140.00, 140.31, 152.00, 159.20, 160.06, 163.60,
187.64; MS, m/z (%): 566 (Mþþ2, 8), 564 (Mþ,11), 409 (23), 393 (30),
286 (9), 155 (11), 151 (31), 139 (100), 135 (46), 113 (36), 111 (48), 77
(22); IR (Nujol): 1743, 1680, 1603, 1504, 1462, 1253, 1171, 1080, 1012,
898, 831 cmꢂ1
.
3.2.6. (Z)- -(4-Methylbenzoyloxy)-b
a
-(4-methylbenzoylthio)-4,40-di-
methoxystilbene (2f). Yield 84%; crystallization from ether/hexane
gave white prisms mp 149e152 ꢀC. (Found: C, 73.37; H, 5.30; S, 6.16.
3.2.1. (Z)-
a
-Benzoyloxy-
b
-benzoylthiostilbene
(2a). Yield
89%;
crystallization from methanol gave white needles mp 123e124 ꢀC.
C32H28O5S requires: C, 73.26; H, 5.38; S, 6.11); 1H NMR
d (CDCl3,
(Found: C, 76.96; H, 4.68; S, 7.31. C28H20O3S requires: C, 77.04; H,
300 MHz): 2.35 (s, 3H), 2.38 (s, 3H), 3.73 (s, 3H), 3.76 (s, 3H), 6.68 (d,
2H, J¼8.7 Hz), 6.76 (d, 2H, J¼8.7 Hz), 7.14e7.27 (m, 6H), 7.37 (d, 2H,
J¼8.7 Hz), 7.77 (d, 2H, J¼8.1 Hz), 8.00 (d, 2H, J¼8.1 Hz); 13C NMR
4.62; S, 7.35); 1H NMR
d (CDCl3, 300 MHz): 7.12e7.25 (m, 6H),
7.30e7.60 (m, 10H), 7.88 (d, 2H, J¼7.2 Hz), 8.12 (d, 2H, J¼7.2 Hz); 13C
NMR
d
(CDCl3, 75.4 MHz): 119.98, 127.54, 127.82, 128.03, 128.12,
d (CDCl3, 75.4 MHz): 21.69, 21.75, 55.21, 113.62, 113.73, 118.20,
128.53, 128.58, 128.94, 129.05, 129.09, 130.21, 130.29, 133.51, 133.65,
134.41, 136.49, 137.77, 152.74, 164.27, 188.43; MS, m/z (%): 436 (Mþ,
29), 300 (50), 315 (43), 299 (72), 121 (46), 106 (61), 105 (100), 77
(84); IR (Nujol): 1732, 1673, 1450, 1248, 1206, 1085, 1066, 902,
126.61, 127.25, 127.72, 129.30, 130.38, 130.58, 130.69, 131.61, 134.38,
144.33,144.49,144.51,151.99,159.08,159.91,164.58,188.59; MS, m/z
(%): 524 (Mþ, 21), 389 (31), 373 (39), 286 (9), 151 (34), 135 (43), 119
(100), 91 (83), 65 (35); IR (Nujol): 1736, 1603, 1510, 1463, 1251, 1173,
695 cmꢂ1
.
1081, 897, 828, 746 cmꢂ1
.
3.2.2. (Z)-
a
-(4-Chlorobenzoyloxy)-
b
-(4-chlorobenzoylthio)stilbene
3.2.7. (Z)- -Benzoyloxy-b
a
-benzoylthio-4,40-dimethylstilbene
(2b). Yield 91%; crystallization from methanol gave white needles
(2g). Yield 88%; crystallization from methanol gave white plates
mp 159e161 ꢀC. (Found: C, 77.58; H, 5.15; S, 6.84. C30H24O3S re-
mp 139e140 ꢀC. (Found: C, 66.66; H, 4.03; S, 6.31. C28H18Cl2O3S
requires: C, 66.54; H, 3.59; S, 6.34); 1H NMR
d
(CDCl3, 300 MHz):
quires: C, 77.56; H, 5.21; S, 6.90); 1H NMR
d (CDCl3, 300 MHz): 2.25
7.10e7.50 (m, 14H), 7.81 (d, 2H, J¼8.7 Hz), 8.04 (d, 2H, J¼8.7 Hz); 13C
(s, 3H), 2.28 (s, 3H), 6.96e7.04 (m, 4H), 7.22 (d, 2H, J¼8.1 Hz),
NMR
d (CDCl3, 75.4 MHz): 119.84, 127.44, 128.11, 128.24, 128.29,
7.33e7.43 (m, 6H), 7.46e7.57 (m, 2H), 7.87 (d, 2H, J¼7.8 Hz), 8.11 (d,
128.97, 129.07, 129.16, 129.34, 130.37, 131.67, 134.25, 134.86, 137.57,
140.18, 140.46, 152.91, 163.50, 187.26; MS, m/z (%): 504 (Mþ, 3), 349
(12), 33 (46), 140 (72), 139 (100), 121 (29), 111 (54), 77 (31); IR
(Nujol): 1737, 1679, 1464, 1378, 1256, 1210, 1172, 1084, 1015,
2H, J¼7.8 Hz); 13C NMR
d (CDCl3, 75.4 MHz): 21.35, 21.42, 119.27,
127.64, 128.58, 128.64, 128.90, 128.97, 129.04, 129.28, 130.23, 130.31,
131.80, 133.47, 133.62, 135.15, 136.82, 137.64, 139.11, 152.58, 164.42,
188.71; MS, m/z (%): 465 (Mþþ1, 24), 464 (Mþ, 52), 343 (53), 327
(71), 135 (60), 119 (62), 106 (74), 91 (61), 77 (100), 65 (20), 51 (43);
IR (Nujol): 1738, 1658, 1605, 1510, 1462, 1254, 1173, 1088, 1034, 904,
902 cmꢂ1
.
3.2.3. (Z)-
a
-(4-Methylbenzoyloxy)-
b
-(4-methylbenzoylthio)stilbene
835 cmꢂ1
.
(2c). Yield 78%; crystallization from methanol gave white prisms
mp 129e130 ꢀC. (Found: C, 77.50; H, 5.24; S, 6.96. C30H24O3S re-
3.2.8. (Z)-
a
-(4-Chlorobenzoyloxy)-b
-(4-chlorobenzoylthio)-4,40-di-
quires: C, 77.56; H, 5.21; S, 6.90); 1H NMR
d
(CDCl3, 200 MHz): 2.33
methylstilbene (2h). Yield 94%; crystallization from methanol gave
(s, 3H), 2.37 (s, 3H), 7.11e7.24 (m, 10H), 7.29e7.34 (m, 2H), 7.41e7.47
white prisms mp 154e156 ꢀC. (Found: C, 67.63; H, 4.10; S, 5.94.
(m, 2H), 7.78 (d, 2H, J¼8.2 Hz), 8.01 (d, 2H, J¼8.3 Hz); 13C NMR
C30H22Cl2O3S requires: C, 67.54; H, 4.16; S, 6.01); 1H NMR
d (CDCl3,
d
(CDCl3, 50.3 MHz): 21.71, 21.77, 120.17, 126.40, 127.73, 127.81,
300 MHz): 2.26 (s, 3H), 2.29 (s, 3H), 6.96e7.05 (m, 4H), 7.20 (d, 2H,
J¼8.1 Hz), 7.30e7.41 (m, 6H), 7.81 (d, 2H, J¼8.7 Hz), 8.03 (d, 2H,
128.08, 128.15, 129.02, 129.20, 129.32, 130.39, 130.42, 134.18, 134.71,
138.10, 144.46, 144.55, 152.81, 164.42, 188.15; MS, m/z (%): 464 (Mþ,
9), 329 (10), 313 (56), 120 (18), 119 (100), 105 (13), 91 (99), 77 (16),
65 (30); IR (Nujol): 1732, 1669, 1604, 1461, 1248, 1209, 1176, 1090,
J¼8.7 Hz); 13C NMR
d (CDCl3, 75.4 MHz): 21.27, 21.34, 118.92, 127.54,
128.89, 128.93, 130.08, 131.40, 131.54, 134.72, 134.93, 137.77, 139.27,
139.94, 140.24, 152.52, 163.43, 187.34; MS, m/z (%): 534 (Mþþ2, 30),
532 (Mþ, 39), 377 (55), 361 (76), 141 (100), 119 (72), 111 (88), 91
(64), 75 (48); IR (Nujol): 1736, 1675, 1595, 1463, 1259, 1202, 1172,
903 cmꢂ1
.
3.2.4. (Z)-
a
-Benzoyloxy-
b
-benzoylthio-4,40-dimethoxystilbene
1091, 906 cmꢂ1
.
(2d). Yield 80%; crystallization from methanol gave white needles
mp 150e153 ꢀC. (Found: C, 72.51; H, 4.90; S, 6.50. C30H24O5S re-
3.2.9. (Z)- -(4-Methylbenzoyloxy)-b
a
-(4-methylbenzoylthio)-4,40-di-
quires: C, 72.56; H, 4.87; S, 6.46); 1H NMR
d
(CDCl3, 300 MHz): 3.74
methylstilbene (2i). Yield 95%; crystallization from methanol gave
(s, 3H), 3.76 (s, 3H), 6.49 (d, 2H, J¼9.0 Hz), 6.57 (d, 2H, J¼9.0 Hz),
white prisms mp 169e171 ꢀC. (Found: C, 77.93; H, 5.75; S, 6.45.
7.21e7.42 (m, 10H), 7.81 (d, 2H, J¼8.6 Hz), 8.04 (d, 2H, J¼8.6 Hz); 13C
C32H28O3S requires: C, 78.02; H, 5.73; S, 6.51); 1H NMR
d (CDCl3,
NMR
d
(CDCl3, 75.4 MHz): 55.20, 113.72, 113.83, 127.71, 128.93,
300 MHz): 2.24 (s, 3H), 2.27 (s, 3H), 2.33 (s, 3H), 2.36 (s, 3H),
129.03, 130.10, 130.54, 131.58, 131.64, 135.03, 140.05, 140.35, 152.05,
159.25, 160.10, 163.62, 188.94; MS, m/z (%): 497 (Mþþ1, 9), 496 (Mþ,
22), 375 (9), 359 (20), 151 (16), 135 (20), 105 (100), 77 (33); IR
(Nujol): 1738, 1658, 1605, 1510, 1462, 1254, 1173, 1088, 1034, 904,
6.94e7.03 (m, 4H), 7.13e7.23 (m, 6H), 7.34 (d, 2H, J¼8.1 Hz), 7.77 (d,
2H, J¼8.1 Hz), 8.00 (d, 2H, J¼8.4 Hz); 13C NMR
d (CDCl3, 75.4 MHz):
21.34, 21.39, 21.67, 21.74, 119.33, 126.57, 127.71, 128.84, 128.92,
129.03, 129.27, 130.23, 130.36, 131.94, 134.33, 135.33, 137.49, 138.97,
144.31, 144.41, 152.50, 164.48, 188.36; MS, m/z (%): 492 (Mþ, 8), 357
(11), 341 (47), 135 (11), 119 (100), 91 (67), 65 (14); IR (Nujol): 1732,
835, 707 cmꢂ1
.
3.2.5. (Z)- -(4-Chlorobenzoyloxy)-
a
b
-(4-chlorobenzoylthio)-4,40-di-
1672, 1605, 1462, 1455, 1377, 1262, 1176, 1095, 901 cmꢂ1
.
methoxystilbene (2e). Yield 60%; crystallization from hexane gave
yellow prisms mp 139e141 ꢀC. (Found: C, 63.65; H, 3.90; S, 5.72.
3.2.10. (Z)-a-Benzoyloxy-b
-benzoylthio-4,40-dichlorostilbene
C30H22Cl2O5S requires: C, 63.72; H, 3.92; S, 5.67); 1H NMR
d
(CDCl3,
(2j). Yield 89%; crystallization from methanol gave white powder
300 MHz): 3.53 (s, 3H), 3.56 (s, 3H), 6.50 (d, 2H, J¼8.9 Hz), 6.57 (d,
mp 136e138 ꢀC. (Found: C, 66.50; H, 4.06; S, 6.28. C28H18Cl2O3S

A. Guirado et al. / Tetrahedron 67 (2011) 1083e1090
1089
requires: C, 66.54; H, 3.59; S, 6.34); 1H NMR
d
(CDCl3, 200 MHz):
226 (3), 203 (1), 165 (8), 121 (100), 105 (86), 77 (67); IR (Nujol):
1656,1650,1620,1494,1449,1311,1262,1219,1185,1133,1088,1071,
7.15e7.61 (m, 14H), 7.87 (d, 2H, J¼7.3 Hz), 8.10 (d, 2H, J¼7.3 Hz); 13C
NMR
d
(CDCl3, 50.3 MHz): 127.68, 128.68, 128.71, 128.79, 130.35,
1053, 1030, 873, 847, 828, 782, 767, 752, 706, 690, 592 cmꢂ1
.
130.50, 131.68, 132.86, 133.83, 133.96, 134.11, 135.38, 136.20, 136.44,
152.16, 164.27, 188.21; MS, m/z (%): 506 (Mþþ2, 14), 504 (Mþ, 19),
385 (31), 383 (36), 369 (41), 367 (47), 157 (38), 155 (50), 139 (49),
105 (100), 77 (87); IR (Nujol): 1737, 1678, 1489, 1462, 1246, 1210,
3.2.16. (Z)-2-(2,6-Dichlorophenylimino)-4,5-diphenyl-1,3-oxathiole
(3d). Yield 63%; crystallization from acetonitrile gave white nee-
dles mp 207e210 ꢀC. (Found: C, 63.12; H, 3.32; N, 3.50; S, 7.94.
C21H13Cl2NOS requires: C, 63.32; H, 3.29; N, 3.52; S, 8.05); 1H NMR
1085, 902, 687 cmꢂ1
.
d
(CDCl3, 200 MHz): 7.00 (t, 1H, J¼7.78 Hz), 7.24e7.37 (m, 10H), 7.46
3.2.11. (Z)- -(4-Chlorobenzoyloxy)-
a
b
-(4-chlorobenzoylthio)-4,40-di-
(s, 2H); 13C NMR
d
(CDCl3, 50.4 MHz): 164.17, 143.01, 142.43, 129.48,
chlorostilbene (2k). Yield 70%; crystallization from methanol gave
white powder mp 146e148 ꢀC. (Found: C, 58.64; H, 2.80; S, 5.65.
129.38, 129.09, 129.04,129.02, 128.60,128.42,127.96,127.58,127.46,
125.13, 114.52; MS, m/z (%): 399 (Mþþ2, 0.4), 397 (Mþ, 0.6), 226 (3),
203 (1), 151 (1), 138 (1), 109 (2), 105 (77), 89 (4), 77 (57), 73 (2), 50
(4); IR (Nujol): 1666, 1634, 1441, 1436, 1224, 1130, 1084, 1065, 1030,
C28H16Cl4O3S requires: C, 58.56; H, 2.81; S, 5.58); 1H NMR
d (CDCl3,
200 MHz): 7.16e7.26 (m, 6H), 7.29e7.46 (m, 6H), 7.81 (d, 2H,
J¼8.6 Hz), 8.03 (d, 2H, J¼8.6 Hz); 13C NMR
d
(CDCl3, 50.3 MHz):
962, 790, 761, 714, 696, 674, 650 cmꢂ1
.
127.06, 128.75, 128.78, 128.97, 129.18, 130.41, 131.62, 131.66, 132.50,
134.29,134.57,135.57,135.80,140.73,152.13,163.38,186.96; MS, m/z
(%): 572 (Mþ, 6), 419 (15), 405 (24), 401 (38), 246 (11), 155 (36), 139
(100),111 (54), 75 (36); IR (Nujol): 1744,1681,1585,1486,1463,1255,
3.2.17. (Z)-2-(4-Bromophenylimino)-4,5-diphenyl-1,3-oxathiole
(3e). Yield 75%; crystallization from acetonitrile gave colorless
plates mp 122e123 ꢀC. (Found: C, 61.90; H, 3.48; N, 3.39; S, 7.89.
C21H14BrNOS requires: C, 61.77; H, 3.46; N, 3.43; S, 7.85); 1H NMR
1206, 1087, 1012, 903 cmꢂ1
.
d
(CDCl3, 300 MHz): 6.99 (d, 2H, J¼8.4 Hz), 7.26e7.31 (m, 9H),
3.2.12. (Z)- -(4-Methylbenzoyloxy)-
a
b
-(4-methylbenzoylthio)-4,40-
7.45e7.48 (m, 3H); 13C NMR
d
(CDCl3, 75.4 MHz): 113.42, 117.45,
dichlorostilbene (2l). Yield 76%; crystallization from methanol gave
122.78, 127.44, 127.96,128.39,128.94,128.99,129.03,129.27,129.69,
132.56, 142.04, 147.42, 161.33; MS, m/z (%): 407 (Mþ, 2), 226 (2), 165
(8), 121 (100), 105 (70), 77 (47); IR (Nujol): 1657, 1651, 1622, 1582,
1495, 1481, 1449, 1219, 1180, 1130, 1086, 1007, 960, 845, 829, 760,
white needles mp 112e114 ꢀC. (Found: C, 67.49; H, 4.20; S, 5.96.
C30H22Cl2O3S requires: C, 67.54; H, 4.16; S, 6.01); 1H NMR
d (CDCl3,
300 MHz): 2.32 (s, 3H), 2.37 (s, 3H), 7.14e7.26 (m, 10H), 7.36 (d, 2H,
J¼8.4 Hz), 7.76 (d, 2H, J¼8.1 Hz), 7.98 (d, 2H, J¼8.1 Hz); 13C NMR
715, 706, 690, 660, 645, 614 cmꢂ1
.
d
(CDCl3, 75.4 MHz): 21.75, 21.81, 120.03, 126.00, 127.75, 128.62,
128.65, 129.42, 130.40, 130.46, 131.68, 132.97, 133.88, 133.96, 135.24,
136.34, 144.83, 144.90, 152.02, 164.35, 187.91; MS, m/z (%): 534
(Mþþ2, 0.4), 532 (Mþ, 1), 397 (1), 383 (5), 381 (7), 120 (24), 119
(100), 91 (40); IR (Nujol): 1739, 1673, 1606, 1487, 1463, 1257, 1206,
3.2.18. (Z)-2-(4-Cianophenylimino)-4,5-diphenyl-1,3-oxathiole
(3f). Yield 56%; crystallization from methanol gave white needles
mp 140e141 ꢀC. (Found: C, 74.25; H, 4.02; N, 7.87; S, 9.11.
C22H14N2OS requires: C, 74.55; H, 3.98; N, 7.90; S, 9.05); 1H NMR
1174, 1083, 1012, 897 cmꢂ1
.
d
(CDCl3, 200 MHz): 7.18e7.43 (m, 12H), 7.65 (d, 2H, J¼8.51 Hz); 13
C
NMR
d (CDCl3, 50.4 MHz): 107.68, 113.53, 118.93, 121.95, 127.41,
3.2.13. (Z)-2-(Phenylimino)-4,5-diphenyl-1,3-oxathiole (3a). Yield
53%; crystallization from acetonitrile gave white needles mp
137e138 ꢀC. (Found: C, 76.70; H, 4.63; N, 4.19; S, 9.79. C21H15NOS
127.72, 128.48, 128.95, 129.13, 129.20, 129.27, 129.47, 133.71, 142.32,
152.28, 162.24; MS, m/z (%): 354 (Mþ, 2), 282 (1), 247 (1), 198 (1),
165 (9), 121 (100), 105 (80), 77 (48); IR (Nujol): 2231, 1650, 1623,
1596, 1499, 1446, 1221, 1175, 1131, 1089, 1072, 1032, 961, 860, 764,
requires: C, 76.57; H, 4.59; N, 4.25; S, 9.73); 1H NMR
d
(CDCl3,
200 MHz): 7.09e7.49 (m, 15H); 13C NMR
d
(CDCl3, 75.4 MHz):
747, 696, 691 cmꢂ1
.
113.53, 121.06, 124.68, 127.58, 128.27, 128.48, 128.99, 129.10, 129.28,
129.66, 130.07,142.01,148.59,161.07; MS, m/z (%): 329 (Mþ, 71), 330
(17), 226 (24),165 (36),121 (98),105 (92), 77 (100); IR (Nujol): 1659,
1621, 1591, 1487, 1447, 1246, 1164, 1121, 1070, 960, 831, 764, 691,
3.3. X-ray structure determination of compound 2g
Crystal data: C30H24O3S, Mr¼464.55, monoclinic, space group
646 cmꢂ1
.
P21/n, a¼11.1663 (8), b¼12.1181 (11), c¼18.2901 (12) A,
b
¼93.196
ꢁ
3
(5) , U¼2471.1 (3) A at ꢂ100 ꢀC; Z¼4, Dx¼1.249 g cmꢂ3, F(000)¼
ꢀ
ꢁ
3.2.14. (Z)-2-(4-Chlorophenylimino)-4,5-diphenyl-1,3-oxathiole
(3b). Yield 74%; crystallization from methanol gave white needles
mp 116e117 ꢀC. (Found: C, 69.58; H, 3.92; N, 3.80; S, 8.79.
C21H14ClNOS requires: C, 69.32; H, 3.88; N, 3.85; S, 8.81); 1H NMR
976,
m
¼0.16 mmꢂ1
.
Data collection:
A
colorless prism
0.54ꢄ0.42ꢄ0.19 mm was mounted in inert oil on a glass fiber and
transferred to the cold gas stream of the diffractometer (Siemens
P4). Measurements were performed to 2qmax 50ꢀ with mono-
d
(CDCl3, 200 MHz): 7.04 (d, 2H, J¼8.7 Hz), 7.24e7.34 (m, 10H), 7.46
chromated Mo Ka radiation. Of 5193 measured reflections, 4350
(dd, 2H, J¼1.5, 7.5 Hz); 13C NMR
d
(CDCl3, 50.4 MHz): 113.46, 122.40,
were unique (Rint¼0.033) and were used for all calculations.
Structure refinement: The structures were refined anisotropically
against F2 (program SHELXL-97)1 The hydrogen atoms were refined
using rigid methyl groups or a riding model. The final wR2 value
was 0.0898 for all reflections and 309 parameters, with R1 0.0417
127.49,128.04,128.43,129.00,129.02,129.07,129.07,129.30,129.65,
129.77, 142.09, 146.99, 161.46; MS, m/z (%): 365 (Mþþ2, 0.6), 363
(Mþ, 2), 226 (3), 165 (7), 137 (2), 121 (100), 105 (72), 77 (55); IR
(Nujol): 1658, 1651, 1615, 1587, 1484, 1456, 1377, 1217, 1175, 1130,
1086, 1069, 962, 846, 831, 761, 720, 706, 691 cmꢂ1
.
for reflections with I>2s(I); max. Dr 0.19 e/A , S 0.85.
3
ꢁ
Complete crystallographic data (excluding structure factors)
have been deposited at the Cambridge Crystallographic Data Centre
under the number CCDC 753391. Copies may be requested free of
charge from The Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, England (e-mail: deposit@ccdc.cam.ac.uk).
3.2.15. (Z)-2-(2,4-Dichlorophenylimino)-4,5-diphenyl-1,3-oxathiole
(3c). Yield 71%; crystallization from methanol gave white needles
mp 128e129 ꢀC. (Found: C, 63.42; H, 3.25; N, 3.49; S, 8.02.
C21H13Cl2NOS requires: C, 63.32; H, 3.29; N, 3.52; S, 8.05); 1H NMR
d
(CDCl3, 200 MHz): 7.06 (d, 1H, J¼8.5 Hz), 7.21 (d, 1H, J¼2.2 Hz),
7.25e7.36 (m, 8H), 7.45 (d, 3H, J¼2.1 Hz); 13C NMR
d
(CDCl3,
3.4. X-ray structure determination of compound 3c
50.4 MHz): 114.01, 122.52, 127.63, 127.72, 127.99, 128.18, 128.54,
129.09, 129.19, 129.21, 129.49, 129.60, 130.10, 130.19, 142.53, 144.54,
163.28; MS, m/z (%): 399 (Mþþ2, 0.7), 397 (Mþ,1), 362 (MþꢂCl, 0.3),
Crystal data: C21H13Cl2NOS, Mr¼398.28, triclinic, space group P1,
ꢁ
a¼8.493 (2), b¼9.925 (3), c¼11.358 (3) A,
a
¼94.78 (2), ¼97.72 (2),
b

1090
A. Guirado et al. / Tetrahedron 67 (2011) 1083e1090
3
ꢀ
ꢀ
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19. Guirado, A.; Zapata, A.; Jones, P. G. Tetrahedron 1995, 51, 10375.
g
¼110.02 (2) , U¼882.8 (4) A at ꢂ130 C; Z¼2, Dx¼1.498 g cmꢂ3, F
(000)¼408,
m
¼0.5 mmꢂ1
. Data collection: A colorless tablet
0.7ꢄ0.4ꢄ0.2 mm was mounted in inert oil on a glass fiber and
transferred to the cold gas stream of the diffractometer (Stoe
STADI-4). Measurements were performed to 2qmax 50ꢀ with mon-
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ochromated Mo Ka radiation. Of 3987 measured reflections, 3117
were unique (Rint¼0.016) and were used for all calculations.
Structure refinement: The structures were refined anisotropically
against F2 (program SHELXL-97).64 Hydrogen atoms were included
with a riding model. The final wR2 value was 0.0869 for all re-
flections and 235 parameters, with R1 0.0340 for reflections with
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3
ꢁ
I>2s(I); max. Dr 0.26 e/A , S 1.07.
2075.
Complete crystallographic data (excluding structure factors)
have been deposited at the Cambridge Crystallographic Data Centre
under the number CCDC 243017. Copies may be requested free of
charge from The Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, England (e-mail: deposit@ccdc.cam.ac.uk).
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We gratefully acknowledge the financial support of the
ꢀ
ꢀ
ꢀ
ꢀ
Fundacion Seneca of the Comunidad Autonoma de la Region de
Murcia (project 08755/PI/08).
Supplementary data
X-ray structural data of compounds 2g and 3c and several rep-
resentative voltammograms. Supplementary data associated with
this article can be found in the online version, at doi:10.1016/
j.tet.2010.12.044.
49. Baudy, M.; Robert, A. Tetrahedron Lett. 1980, 21, 2517.
50. Merijanian, A.; Sharma, G. M.; Moushati, J.; Gunderson, K. J. Org. Chem. 1986, 51,
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References and notes
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€
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