2-Oxo-2-polyfluoroalkylethane-1-sulfones and -sulfamides in the Biginelli and 'retro-Biginelli' reactions

Article abstract of DOI:10.1016/j.tetlet.2011.09.143

2-Oxo-2-polyfluoroalkylethane-1-sulfones and -sulfamides react with aryl aldehydes and urea under Biginelli reaction conditions to yield 4-hydroxy-4-polyfluoroalkyl-5-sulfonyl-6-aryl-tetrahydropyrimidinones. The latter compounds on reaction with hexamethy

Full text of DOI:10.1016/j.tetlet.2011.09.143

Tetrahedron Letters 52 (2011) 6619–6622
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Tetrahedron Letters
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2-Oxo-2-polyfluoroalkylethane-1-sulfones and -sulfamides in the Biginelli
and ‘retro-Biginelli’ reactions
⇑
Vadim M. Timoshenko , Yuriy M. Markitanov, Yuriy G. Shermolovich
Institute of Organic Chemistry, NAS of Ukraine, Murmanska St. 5, 02660 Kyiv, Ukraine
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 28 July 2011
Revised 12 September 2011
Accepted 30 September 2011
Available online 6 October 2011
2-Oxo-2-polyfluoroalkylethane-1-sulfones and -sulfamides react with aryl aldehydes and urea under
Biginelli reaction conditions to yield 4-hydroxy-4-polyfluoroalkyl-5-sulfonyl-6-aryl-tetrahydropyrimidi-
nones. The latter compounds on reaction with hexamethylenetetramine (HMTA) under thermal condi-
tions undergo ‘retro-Biginelli’ reaction involving replacement of the 6-aryl substituent of the
pyrimidinone cycle with a hydrogen atom donated by HMTA. Hexamethylenetetramine was employed
for the first time in place of formaldehyde in the reported one-step Biginelli protocol for the synthesis
of fluorinated sulfonyl-containing 6-unsubstituted tetrahydropyrimidinones.
Keywords:
Biginelli reaction
Tetrahydropyrimidinone
Polyfluoroalkyl
Ó 2011 Elsevier Ltd. All rights reserved.
Ketosulfone
Ketosulfamide
Hexamethylenetetramine
Multicomponent reactions are powerful synthetic tools in or-
ganic chemistry allowing the construction of complex heterocyclic
compounds from several simple functional substrates in a one-pot
procedure.1 The Biginelli reaction represents a widely studied
three-component condensation which provides an easy and eco-
nomic route to a pyrimidine core.2 Interest in this reaction has
been rekindled because of the pharmaceutical applications of the
products formed.3 A large variety of b-dicarbonyl compounds as
well as diverse catalysts have been tested in the Biginelli proce-
dure,2c but attention on this topic persists.
In this Letter we report on the application of 2-oxo-2-poly-
fluoroalkylethane-1-sulfones and -sulfamides as b-dicarbonyl
surrogates in the Biginelli reaction for the preparation of pyrimid-
inones substituted with a sulfonyl or sulfamide moiety. The prod-
ucts underwent a ‘retro-Biginelli’ reaction when treated with
hexamethylenetetramine (HMTA).
We found that 2-oxo-2-polyfluoroalkylethane-1-sulfones 1a,b
and -sulfamides 1c,d underwent a three-component reaction with
aryl aldehydes and urea to give the expected substituted tetrahy-
dropyrimidinones 2a–h (Table 1). In our case, 4-hydroxy-contain-
ing pyrimidinones were formed, similarly to the Biginelli reaction
of related fluoroalkyl keto compounds described in the literature.4
Favorable reaction conditions involved heating the starting
compounds in a mixture of acetic anhydride and acetic acid as sol-
vent. The use of acetic anhydride derived from the necessity to trap
water, evolved during the condensation, because the starting poly-
fluoroalkyl keto compounds easily form hydrates and become
unreactive.
Compounds 2 were isolated as single diastereomers in 70–85%
yields.5 Their stereochemistry was deduced from NMR data and
by comparison with the data of other reported similar
compounds.4a,b
Table 1
Biginelli reaction of 2-oxo-2-polyfluoroalkylethane-1-sulfones 1a,b and -sulfamides
1c,d
Ar
Ar
O
RSO2
RF
Ac2O/AcOH
80 oC, 5 h
6
RSO2
RF
NH
4N
H
O
NH2
O
HO
O
H2N
2a-h
1a-d
Ketone
RF
R
Ar
Product
Yielda (%)
1a
1a
1b
1b
1c
1c
1d
1d
CF3
CF3
HCF2CF2
HCF2CF2
CF3
CF3
HCF2CF2
HCF2CF2
p-Tol
p-Tol
p-Tol
p-Tol
Et2N
Et2N
Et2N
Et2N
Ph
2a
2b
2c
2d
2e
2f
85
74
77
70
76
82
72
70
p-MeOC6H4
Ph
p-MeOC6H4
Ph
p-MeOC6H4
Ph
p-MeOC6H4
2g
2h
⇑
Corresponding author. Tel.: +380 44 499 4938; fax: +380 44 573 2643.
E-mail address: vadim@ioch.kiev.ua (V.M. Timoshenko).
a
Isolated yield.
0040-4039/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2011.09.143

6620
V. M. Timoshenko et al. / Tetrahedron Letters 52 (2011) 6619–6622
istics were similar to those of compound 3a.7 The 1H NMR spectra
Ar
NH
Ar
N
RSO2
RF
N
RSO2
6
of the substituted hexamines 4 displayed similar sets of signals,
two AB systems due to the four methylene groups, a singlet for
the fifth CH2-group and a singlet resulting from the CH–Ar proton.7
Compounds 4a,b were isolated as viscous oils and were soluble
in polar solvents such as chloroform, acetonitrile, and ethanol.
They appeared unstable in CDCl3 solution and over 1–2 days
underwent partial conversion into an aryl aldehyde and HMTA
according to the 1H NMR data. This transformation is probably in-
duced by the acidic chloroform, since acidification of a chloroform
solution of 4a with 35% hydrochloric acid in an NMR tube caused
complete decomposition into benzaldehyde and HMTA as was evi-
dent from the 1H NMR spectrum. This instability of compounds 4
explains their low isolated yields (20% for 4a and 16% for 4b) but
their isolation and characterization are useful for clarification of
the outcome of this retro-reaction.
As can be seen from the mechanism proposed in Scheme 2, for-
mal displacement of the aryl substituent at C-6 of the tetrahydro-
pyrimidinone 2 by a hydrogen atom, donated from a molecule of
the hexamine, occurs. The aryl group in turn is transferred to the
hexamine to give the 2-aryl substituted derivative. We assume that
the formation of 3 proceeds through acyclic intermediate A, gener-
ated via thermal cleavage of the pyrimidinone core in 2. In this
intermediate the carbanion adjacent to the sulfonyl substituent is
stabilized by the presence of a strong electron-withdrawing group,
while the iminium cation is postulated as an intermediate in the
condensation of aldehydes with urea in the course of the classical
Biginelli reaction. The arylidene group is transferred to HMTA
releasing the methylidene moiety to afford the intermediate B,
subsequent cyclization of which results in the 6-unsubstituted tet-
rahydropyrimidinone 3.
i)
NH
O
+
4N
H
+
N
N
N
N
RF
HO
N
N
N
H
O
HO
2a-h
3a-d
4a,b
3: RF = CF3, R = p-Tol (a); RF = HCF2CF2, R = p-Tol (b);
RF = CF3, R = Et2N (c); RF = HCF2CF2, R = Et2N (d);
4: Ar = Ph (a); p-MeO-C6H4 (b)
Scheme 1. Reagents and conditions: (i) PhCH3, reflux, 5 h.
Our further efforts were directed to the dehydration of hydroxy
derivatives 2 to give dihydropyrimidinones which are classical
Biginelli products from the condensation of nonfluorinated keto
compounds.2a The use of p-toluenesulfonic acid, a known dehy-
drating agent for compounds of this type,4a led to no results. We
tested several different dehydrating agents but our attempts
proved unsuccessful. During the search for methods to modify
our synthesized Biginelli products we serendipitously found that
heating compound 2a with HMTA in a solvent led to tetrahydro-
pyrimidinone 3a which did not contain an aryl substituent at C-6
of the heterocyclic framework. We examined this unprecedented
transformation more carefully and found that it was general for
all our fluorinated tetrahydropyrimidinones 2 bearing both sulfo-
nyl and sulfamide moieties. The optimal conditions for this trans-
formation were refluxing a suspension of equimolar amounts of
reactants in toluene. After separation of solid compounds 3 the
mother liquor was evaporated, and after purification of the residue
by chromatography on silica gel, we obtained the other product of
this reaction, compound 4 (Scheme 1). The reaction also takes
place in refluxing acetonitrile, but in this case more careful purifi-
cation of the final products was required and the yields of 3 were
lower.
We have found that the above-mentioned transformation only
occurs on heating and does not proceed at room temperature. No
intermediates were detected by monitoring the reaction by NMR.
We observed either a mixture of the initial tetrahydropyrimidi-
none 2 and HMTA with no final products after 1–1.5 h or a mixture
of 2, 3, 4 and HMTA after a longer period and, finally, full conver-
sion of 2 into 3.
The stereochemistry of tetrahydropyrimidinone 3a was deter-
mined by X-ray diffraction (Fig. 1).6 The structures of derivatives
3b–d were supported by NMR data; their spectroscopic character-
In attempts to support the proposed assumption concerning the
mechanistic features of the described retro-reaction we synthe-
sized adduct 5 by reaction of ketosulfone 1a with urea in CH3CN
and then reacted it with several aryl aldehydes and with HMTA
(Scheme 3).
The adduct 5 was a crystalline compound isolated in 45% yield8
because only 50% conversion of the ketosulfone 1a was achieved in
the reaction with urea. However isolation of this adduct as an indi-
vidual compound and its subsequent reactions with aldehydes and
with HMTA yielding tetrahydropyrimidinones 2a,b and 3a serves
as an additional argument in support of the suggested pathway
for the retro-reaction. Moreover, this adduct can be considered as
a possible intermediate in the Biginelli condensation of poly-
fluoroalkyl keto derivatives. A number of mechanisms have been
proposed for the Biginelli reaction, and recently9 it was shown that
an iminium pathway, consisting of initial condensation of an alde-
hyde with urea in acidic media followed by addition of the enol
form of the ketone to the resulting iminium ion, is the most favor-
able. In our case, the product of initial addition of urea to the highly
electrophilic C@O group of the fluoroalkyl ketones, adduct 5, is
acidic enough to promote the final cyclization into the pyrimidi-
none in reactions with aldehydes or with HMTA. The Biginelli reac-
tion sequence, involving the initial condensation of urea with
acetoacetate, supported by isolation of the corresponding
intermediate (enamine pathway), was also proposed for the non-
fluorinated series.10
The reaction of 5 with hexamethylenetetramine led us to antic-
ipate that HMTA can be used in the Biginelli condensation as a
Figure 1. X-ray crystal structure of 3a.

V. M. Timoshenko et al. / Tetrahedron Letters 52 (2011) 6619–6622
6621
Ar
RSO2
NH
O
+
Ar
H
Ar
NH
RF
O
RSO2
RF
H2N
N
RSO2
RF
RSO2
RSO2
RF
NH
O
NH
O
NH
O
H
RF
HO
N
H
HO
N
H
O
N
N
HO
HO
H
NH
O
H
3
2
A
H2N
B
N
N
N
N
Ar
N
N
N
4
Scheme 2. Proposed ‘retro-Biginelli’ reaction pathway.
Ar
p-TolSO2
CF3
ii)
NH
O
N
HO
H
2a: Ar = Ph (52%)
2b: Ar = p-MeO-C6H4 (48%)
p-TolSO2
CF3
O
O
i)
NH2
O
SO2Tol- p
+
H2N NH2
CF3
N
HO
H
1a
p-TolSO2
iii)
5 (45%)
NH
O
CF3
HO
N
H
3a (44%)
Scheme 3. Reagents and conditions: (i) CH3CN, reflux, 2 h; (ii) ArCHO, CH3CN, rt, 8 h; (iii) HMTA, CH3CN, rt, 8 h.
In conclusion, we have found that 4-hydroxy-4-polyfluoroalkyl-
5-tolylsulfonyl(diethylsulfamido)-6-aryl-tetrahydropyrimidin-
2(1H)-ones, obtained via Biginelli condensation of 2-oxo-2-poly-
fluoroalkylethane-1-sulfones and -sulfamides with aryl aldehydes
and urea, undergo a ‘retro-Biginelli’ reaction to give 6-unsubstitut-
ed tetrahydropyrimidin-2(1H)-ones on heating with hexamethy-
lenetetramine. We have also demonstrated for the first time that
HMTA can be used in Biginelli reactions as a masked form of form-
aldehyde providing direct access to 6-unsubstituted tetrahydro-
pyrimidin-2(1H)-ones.
N
N
N
N
RSO2
CF3
i)
NH
O
RSO2
CF3
NH2
O
N
HO
O
H2N
H
1a,c
3a: 44%
3c: 41%
Scheme 4. Reagents and conditions: (i) TMSCl (cat.), CH3CN, reflux, 3 h, ratio of 1-
HMTA–urea–TMSCl = 1:0.5:1:0.2.
Acknowledgment
masked equivalent of formaldehyde for the synthesis of 6-unsub-
stituted pyrimidinones of type 3. Only a few publications report
on the effective utilization of formaldehyde11 or its carbonyl equiv-
alents (1,3-oxazinanes as masked formaldehyde)12 in Biginelli con-
densations to prepare dihydropyrimidinones. Our attempts to use
paraformaldehyde and urea together with trifluoromethyl keto-
sulfone 1a as a model substrate in the acid-catalyzed Biginelli con-
densation in order to obtain the desired pyrimidinone proved
fruitless, the reactions being accompanied with the formation of
undefined complex mixtures. HMTA is known to be a formylating
agent in a number of organic reactions, but has never been utilized
in the multicomponent Biginelli synthesis instead of formalde-
hyde, therefore, the use of HMTA in this reaction seemed promis-
ing. Indeed, when ketones 1a,c were subjected to the Biginelli
reaction with urea and HMTA we obtained the expected tetrahy-
dropyrimidinones 3a,c (Scheme 4).
The reactions of 1a,c with HMTA and urea proceeded under re-
flux in acetonitrile over 3 h. Catalytic amounts of TMSCl were used
to accelerate the cyclocondensation, however, we found that the
reaction could proceed without any catalyst, thus it is self-cata-
lyzed. Tetrahydropyrimidinone 3a precipitated from the reaction
mixture whereas compound 3c was obtained after removal of the
solvent and recrystallization.
We thank Dr. V. V. Trachevsky, Common Usage Center of Radio-
spectroscopy, NAS of Ukraine, Kyiv for recording the NMR spectra.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2011.09.143.
References and notes
1. (a) Zhu, J., Bienaymé, H., Eds.Multicomponent reactions; Wiley-VCH: Weinheim,
2005; (b) Simon, C.; Constantieux, T.; Rodriguez, J. Eur. J. Org. Chem. 2004, 4957–
4980.
2. (a) Kappe, C. O. Acc. Chem. Res. 2000, 33, 879–888; (b) Wan, J.-P.; Liu, Y.
Synthesis 2010, 3943–3953; (c) Vdovina, S. V.; Mamedov, V. A. Russ. Chem. Rev.
2008, 77, 1017–1053.
3. (a) Kappe, C. O. Eur. J. Med. Chem. 2000, 35, 1043–1052; (b) Singh, K.; Arora, D.;
Singh, K.; Singh, S. Mini-Rev. Med. Chem. 2009, 9, 95–106; (c) Kumar, B. R. P.;
Sankar, G.; Baig, R. B.; Chandrashekaran, S. Eur. J. Med. Chem. 2009, 44, 4192–
4198.
4. (a) Kappe, C. O.; Falsone, S. F.; Fabian, W. M. F.; Belaj, F. Heterocycles 1999, 51,
77–84; (b) Saloutin, V. I.; Burgart, Y. V.; Kuzueva, O. G.; Kappe, C. O.;
Chupakhin, O. N. J. Fluorine Chem. 2000, 103, 17–23; (c) Azizian, J.; Mirza, B.;
Mojtahedi, M. M.; Saeed Abaee, M.; Sargordan, M. J. Fluorine Chem. 2008, 129,
1083–1089; (d) Burgart, Ya. V.; Kuzueva, O. G.; Pryadeina, M. V.; Kappe, C. O.;
Saloutin, V. I. Russ. J. Org. Chem 2001, 37, 869–880.

6622
V. M. Timoshenko et al. / Tetrahedron Letters 52 (2011) 6619–6622
5. For selected data and the data for other procedures and compounds, see:
Supplementary data.
7.80 (4H, dd, J = 8.4 Hz, C6H4-para), 4.17 (1H, m, H-5), 3.81 (1H, ABm,
JAB = 14.4 Hz, HA-6), 3.36 (1H, ABd, JAB = 14.4 Hz, J = 3.3 Hz, HB-6), 2.40 (3H, s,
CH3). 13C NMR (DMSO-d6, 100 MHz): d 153.02 (s, C@O), 143.82 (s, CAr-CH3),
137.85 (s, CAr-SO2), 129.06, 128.34, (s, 2CAr-H), 122.43 (q, JCF = 288.5 Hz, CF3),
General procedure for the Biginelli reaction of 2-oxo-2-polyfluoroalkylethane-1-
sulfones 1a,b and -sulfamides 1c,d. Preparation of 2a–h: To a mixture of urea
(66 mg, 1.1 mmol) and the corresponding aryl aldehyde (1.1 mmol), a solution
of ketosulfone 1a,b (1 mmol) or ketosulfamide 1c,d (1 mmol) in a mixture of
Ac2O (1.5 ml, 1.5 mmol) and glacial AcOH (1 ml) was added. The mixture was
heated at 80 °C for 5 h, allowed to cool, diluted with Et2O (2 ml) and the
precipitate filtered, washed with H2O, Et2O, and dried to give
tetrahydropyrimidinones 2a–h as colourless or white solids which were
crystallized from an appropriate solvent. Analytical data for compound 2a.
Yield 0.35 g (85%), mp 206 °C (CH3CN). Colourless cubes. IR (KBr): 3420, 3350,
3240, 3100, 1690 (C@O). 19F NMR (DMSO-d6, 188 MHz): d À83.05 (3F, s, CF3).
1H NMR (DMSO-d6, 300 MHz): d 7.40 and 7.88 (4H, dd, J = 8.1 Hz, C6H4-para),
7.64 (2H, m, NH-1 + OH), 7.27–7.37 (5H, m, C6H5), 6.96 (1H, s, NH-3), 5.47 (1H,
d, J = 4.5 Hz, H-6), 4.16 (1H, s, H-5), 2.41 (3H, s, CH3). 13C NMR (DMSO-d6,
100 MHz): d 153.95 (s, C@O), 144.07 (s, CAr-CH3), 140.57 (s, CPh-ipso), 138.00 (s,
2
80.92 (q, JCF = 30.1 Hz, C-4), 58.21 (s, C-5), 36.30 (s, C-6), 20.80 (s, CH3). MS
APCI (m/z): 339 ([M+H]+, 100%). Anal. Calcd for C12H13F3N2O4S: C, 42.60; H,
3.87; N, 8.28; S, 9.48. Found: C, 42.50; H, 3.95; N, 8.50; S 9.60. Analytical data for
compound 4a. Yield 43 mg (20%) from 2a (eluent MeOH–CH2Cl2, 1:1, Rf = 0.50).
Yellowish oil. 1H NMR (CDCl3, 400 MHz): d 7.37–7.53 (5H, m, C6H5), 5.65 (1H, s,
H-2), 4.90 (2H, AB, JAB = 12.4 Hz, CHAHB), 5.01 (2H, JAB = 12.4 Hz, CHAHB), 4.78 s
(2H, H-6), 4.65 (2H, AB, JAB = 12.8 Hz, CHAHB), 4.50 (2H, AB, JAB = 12.8 Hz,
CHAHB). 13C NMR (CDCl3, 100 MHz): d 138.18 (s, CPh-ipso), 128.95, 127.86,
126.43 (s, 3CPh), 79.79 (s, C-2), 76.49 (s, 2CH2), 74.52 (s, 2CH2), 68.40 (s, C-5).
GC/MS (m/z): 216 (M+, 21%), 118 (100%), 91 (52%), 42 (75%). Anal. Calcd for
C
12H16N4: C, 66.64; H, 7.46; N, 25.90. Found: C, 66.34; H, 7.60; N, 25.75.
8. Compound 5: A mixture of ketosulfone 1a (133 mg, 0.5 mmol) and urea (30 mg,
0.5 mmol) in acetonitrile (2 ml) was stirred under reflux for 2 h. After cooling
the yellow solution to room temperature, unreacted urea crystallized and was
removed by filtration. The mother liquor was evaporated under vacuum, and
the viscous oil in the residue was treated with Et2O to form a white solid which
was filtered and dried to give compound 5. Yield 73 mg (45%), mp 92 °C with
decomposition. 19F NMR (DMSO-d6, 188 MHz): d À83.97 (3F, s, CF3). 1H NMR
(DMSO-d6, 400 MHz): d 8.99 (1H, br s, NH), 7.41 and 7.78 (4H, dd, J = 8.4 Hz,
C6H4-para), 7.32 (1H, s, OH), 6.22 (2H, br s, NH2), 3.92 (2H, s, CH2), 2.39 (3H, s,
CH3). 13C NMR (DMSO-d6, 100 MHz): d 159.73 (s, C@O), 144.31 (s, CAr-CH3),
138.37 (s, CAr-SO2), 129.57, 128.12 (s, 2CAr-H), 123.31 (q, JCF = 293.4 Hz, CF3),
C
Ar-SO2), 129.28, 128.86, 128.37, 127.24 (s, 4CAr-H), 125.58 (s, CAr-ortho),
122.39 (q, JCF = 285.4 Hz, CF3), 80.90 (q, 2JCF = 33.0 Hz, C-4), 66.05 (s, C-5), 49.76
(s, C-6), 21.12 (s, CH3). MS APCI (m/z): 415 ([M+H]+, 100%). Anal. Calcd for
C18H17F3N2O4S: C, 52.17; H, 4.13; N, 6.76; S, 7.74. Found: C, 52.11; H, 4.16; N,
6.89; S, 7.83.
6. Selected X-ray crystallographic data for compound 3a:
C12H13F3N2O4S,
monoclinic, a = 21.411(5) Å, b = 6.8914(17) Å, c = 21.721(6) Å, b = 116.923(7),
V = 2857.7(13) Å3, space group C2/c. CCDC-749283 contains the Supplementary
crystallographic data for the structure reported in this Letter. These data can be
obtained free of charge from the Cambridge Crystallographic Data Centre via
http://www.ccdc.cam.ac.uk/data_request/cif.
2
82.06 (q, JCF = 31.2 Hz, C-4), 56.25 (s, CH2), 21.19 (s, CH3). MS APCI (m/z): 327
([M+H]+, 100%). Anal. Calcd for C11H13F3N2O4S: C, 40.49; H, 4.02; N, 8.59; S,
9.83. Found: C, 40.63; H, 4.12; N, 8.69; S, 9.90.
7. Compounds 3a–d and 4a,b. General procedure:
A
suspension of
tetrahydropyrimidinone 2a–h (1.0 mmol) and hexamethylenetetramine
(140 mg, 1.0 mmol) in toluene (3 ml) was refluxed at 110 °C for 5 h. After
cooling to room temperature the resulting solid was filtered, washed with hot
H2O then cold acetone and dried to give pure compounds 3a–d. The mother
liquor, after filtration of compounds 3a–d, was evaporated under reduced
pressure and the residue was purified by column chromatography on silica gel
giving 4a,b. Analytical data for compound 3a. Yield 0.25 g (75%) from 2a, mp
240–242 °C (1,4-dioxane–H2O). Colourless solid. IR (KBr): 3380, 3230, 3090,
2950, 2910, 1710 (C@O). 19F NMR (DMSO-d6, 188 MHz): d À82.48 (3F, s, CF3).
1H NMR (DMSO-d6, 100 MHz): d 7.44, 7.02, 6.72 (3H, s, 2NH + OH), 7.40 and
9. De Souza, R. O. M. A.; da Penha, E. T.; Milagre, H. M. S.; Garden, S. J.; Esteves, P.
M.; Eberlin, M. N.; Antunes, O. A. C. Chem. Eur. J. 2009, 15, 9799–9804.
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Peppe, C. Tetrahedron 2002, 58, 4801–4808; (c) Wang, M.; Jiang, H.; Wang, Z. J.
Chem. Res., Synop. 2005, 691–693; (d) Kassaee, M. Z.; Masrouri, H.; Movahedi,
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