Synthesis and reactivity of N-vinyl-1,2,3-dithiazolimines

Article abstract of DOI:10.3987/COM-05-10390

A reaction of 4,5-dichloro-1,2,3-dithiazolium chloride (Appel salt) (1) with aziridines (2a-d) affords the N-vinyl-1,2,3-dithiazolimines (3a-d), which can be transformed into thiazole derivatives.

Full text of DOI:10.3987/COM-05-10390

HETEROCYCLES, Vol. 65, No. 7, 2005
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HETEROCYCLES, Vol. 65, No. 7, 2005, pp. 1601 - 1608
Received, 7th March, 2005, Accepted, 25th April, 2005, Published online, 28th April, 2005
SYNTHESIS AND REACTIVITY OF N-VINYL-1,2,3-DITHIAZOLIMINES
Vladimir N. Yarovenkoa*, Andrey. A. Es'kova, Pavel A. Kondrasheva, Anatolii V.
Ignatenkoa, Igor V. Zavarzina, Lidia G. Vorontsovaa, Igor P. Sedisheva, Mikhail
M. Krayushkina, and Zoya A. Starikovab
aN. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47
Leninsky prosp., 119991 Moscow, Russian Federation. Fax: +7 (095) 135 5328.
E-mail: yarov@ioc.ac.ru
bA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy
of Sciences, 28 ul. Vavilova, 119991 Moscow, Russian Federation. Fax: +7 (095)
135 5085
Abstract – A reaction of 4,5-dichloro-1,2,3-dithiazolium chloride (Appel salt) (1)
with aziridines (2a-d) affords the N-vinyl-1,2,3-dithiazolimines (3a-d), which can
be transformed into thiazole derivatives.
INTRODUCTION
1,2,3-Dithiazolimines are of considerable interest in the synthesis of biologically active compounds.1 In
addition, the reactive 1,2,3-dithiazole ring in dithiazolimines can be transformed into various compounds,
including heterocyclic structures.2
1,2,3-Dithiazolimines are prepared by the reactions of readily accessible 4,5-dichloro-1,2,3-dithiazolium
chloride (1) (Appel salt) with amines.1,2 The reactions are accompanied by elimination of two hydrogens
from one nitrogen atom of the substrate to form dithiazolimines. Poorly known processes involving
elimination of two protons from different atoms of the substrate would be a substantial extension of this
approach. Earlier, we have demonstrated that such reactions occur between N-monosubstituted aldehyde
hydrazones and Appel salt.3
RESULTS AND DISCUSSION
In the present study, we developed a procedure for the synthesis of new N-vinyl-1,2,3-dithiazolimines
from aziridines, which involves elimination of hydrogens from different nitrogen and carbon atoms. The

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HETEROCYCLES, Vol. 65, No. 7, 2005
reaction of Appel salt (1) with aziridinecarboxylic acid ester or amide (2a,b) having the trans-
configuration4 produces one of the possible isomers (Scheme 1). Apparently, the aziridine ring opening
occurs almost in parallel with the formation of the double bond.
The NOESY spectrum of dithiazolimine (3a) shows the H/CH3 (7.08/1.22), H/CH2 (7.08/4.21), and
Hortho/CH (7.61/7.22) correlation peaks, which confirm the cis- orientation of this vinyl proton with
respect to the ester group and the geminal arrangement of the proton and the benzene ring. The cis-
arrangement is also evidenced by the fact that the GATED 13C NMR spectrum shows a doublet of triplets
at δ 124.15 with the constants J(C/CH2)/JC/CH(Ar) = 158.64/5.13 Hz. The GATED 13C NMR spectrum
of dithiazolimine (3b) has a doublet of triplets at δ 141.63 with the constants J(C/NH2)/J(C/CH(Ar)) =
156.89/4.88 Hz, which is indicative of the geminal arrangement of the proton and the benzene ring at the
carbon atom and the cisoid arrangement of the amide group and this proton, as in the above structure (3a).
By contrast, the reaction of Appel salt (1) with aziridine (2c), which also has the trans- configuration,5
affords two isomeric 1,2,3-dithiazolimines (3c) and (3d) with ratio 1:9 according NMR spectra (Scheme
1). The signals in the NMR spectra of the resulting compounds are not contradictory to structures (3c) or
(3d). However, they do not allow us to decide between these structures. The position of the
dithiazolimine fragment was determined based on further transformations of compound (3d) into
thiazolyltetrazole (7d) and thiazole (6d) and the transformation of product (3c) into thiazole (6c) (Scheme
2).
Scheme 1
Cl
S+
Cl
S N
N
(1)
S
R
H
S
Cl
Cl
R N
Cl
DZM
Ph
3a,b
N
Ph
2a,b,c
R
Ph
H H
a: R = COOEt
b: R = CONH2
N
Cl
DZM =
c: R = COPh
S
N
O
O
S
Ph
DZM
Ph
Ph
+
DZM
3d
Ph
3c
We studied the reactivity of the resulting dithiazolimines. Earlier, transformations of compounds, in
which the dithiazole fragment is conjugated with the N-vinyl fragment, in the presence of nucleophiles or
on heating have not been investigated. We found that refluxing of dithiazolimines (3a,b,d) in toluene in

HETEROCYCLES, Vol. 65, No. 7, 2005
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the presence of triethylamine afford 4-benzoyl-2-cyano-5-phenyl-1,3-thiazoles (4a,b,d). The reactions of
dithiazoles (3a-d) with ammonia or aminoethanol in tetrahydrofuran produce thiazoles (5a,b,d,d’)
containing amido groups, whereas the reactions with ethylenediamine give dihydroimidazolylthiazoles
(6c,d). Earlier, it has been demonstrated that the reactions of amines with iminodithiazoles containing no
adjacent substituents afforded only products of the dithiazole ring cleavage.2 The reactions of
dithiazolimines with azidoacetate at 10 kbar and 110оC or in the presence of dibutyltin oxide Bu2SnO at
70 - 80 °C and 5 kbar give tetrazoles (7a,d). Apparently, azide reacts with the imine fragment of the
dithiazole ring activated by the chlorine atom rather than with the nitrile group, because our attempts to
prepare the tetrazole moiety from compound (4d) by the reaction with azidoacetate under the same
conditions failed.
Scheme 2
R
NHR1
R
N
S
O
O
N
CN
O
S
4a,b,d
Ph
5a,b,d,d'
Ph
a: R = OEt
b: R = NH2
d: R = Ph
NH2R1
a: R = OCH2CH3, R1 =H
b: R = NH2, R1 = H
Et3N
PhMe
d: R = Ph, R1 = H
d': R = Ph, R1 = CH2CH2OH
3a,b,c,d
N3CH2CO2Me
NH2(CH2)2NH2
Pressure
NH2(CH2)2NH2
Ph
CO2Me
N N
Ph
N
R
O
O
N
N
O
N
N
N
N
H
Ph
S
S
S
N
Ph
7a,d
Ph
6d
6c
HN
a: R = OEt
d: R = Ph
The structures of thiazolyltetrazoles (7a,d) were established by spectroscopic methods. The structure of
compound (7d) was confirmed by X-Ray diffraction analysis (Figure 1) The tetrazole and thiazole rings
in compound (7d) are planar and are twisted with respect to each other by 20о. The ethylacetate group in
the tetrazole fragment is in the ortho position with respect to the thiazole substituent. Apparently, the
electronic systems of the heterocycles participate is the π-conjugation.

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Figure 1. ORTEP drawing of 7d
To summarize, we developed a procedure for the synthesis of new dithiazolimine and thiazole derivatives.
It should be noted that published methods for the synthesis of these thiazoles (for example, the Hantzsch
reaction) are difficult to use because the synthesis of most thioamides required for these reactions was not
described and is a rather complex problem. It should also be noted that the reactions involving azides can
also be considered as a new approach to the synthesis of tetrazole derivatives.
EXPERIMENTAL
1
13
The H and C NMR spectra were recorded on Bruker WM-200 (200 MHz) and Bruker WM-250 (250
MHz) instruments in DMSO-d6 and CDCl3 relative to HMDS. The MS spectra were obtained on a Varian
MATCH-6 instrument with direct sample injection into the ion source; the ionization energy was 70 eV;
the accelerating voltage was 1.75 kV. The melting points were measured on a Boetius hot-stage apparatus.
The reactions at high pressure were carried out in Teflon tubes on an apparatus described earlier.6
Synthesis of dithiazolimines (3a-c). Pyridine (790 mg, 10 mmol) was added dropwise with stirring to a
mixture of aziridine (2a-c) (5 mmol) and Appel salt (1) (1.04 g, 5 mmol) in dichloromethane (30 mL) at rt
for 5 min. Then the reaction mixture was stirred for 3 h, the solvent was removed in vacuo, and the
residue was purified by column chromatography (SiO2, petroleum ether/ethyl acetate 1:20).

HETEROCYCLES, Vol. 65, No. 7, 2005
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1
Ethyl 2-(4-chloro-[1,2,3]-dithiazol-5-ylideneamino)-3-phenylacrylate (3a). Yield 72%; oil; H-NMR
δ: 1.24 (t, 3 H, J=7.21 Hz, CH3), 4.22 (q, 2 H, J=7.21 Hz, CH2), 7.13 (s, 1 H, CH), 7.38 (m, 3 H, Harom),
7.66 (m, 2 H, Harom); 13C-NMR (50 MHz) δ: 14.09 (CH3), 61.64 (O-CH2), 124.15 (Ph-CH=), 128.69 (o),
129.30 (p), 130.37 (m), 133.50 (i), 138.09 (=C-N=), 145.68 (C-4), 161.58 (C=O), 162.28 (C-5). Anal.
Calcd for C13H11N2O2ClS2: C, 47.78; H, 3.39; N, 8.57; Cl, 10.85; S, 19.62. Found: C, 47.88; H, 3.42; N,
8.46; Cl, 10.73; S, 19.75. MS, m/z 326 (M+).
2-(4-Chloro-[1,2,3]-dithiazol-5-ylideneamino)-3-phenylacrylamide (3b).Yield 58%; mp 174-176 °C;
1H-NMR δ: 5.93 (s, 1 H, NH), 6.51 (s, 1 H, NH), 7.23 (s, 1 H, Harom), 7.26-7.53 (m, 5 H, Harom);
13C-NMR (50 MHz) δ: 119.18 (=C-N=), 128.61 (o), 130.37 (p), 130.65 (m), 133.31(i), 141.63 (Ph-CH=),
148.97 (C-4), 171.35 (C-5), 172.51 (C=O). Anal. Calcd for C11H8N3OClS2: C, 44.37; H, 2.71; N, 14.11;
Cl, 11.91; S, 21.53. Found: C, 44.51; H, 2.73; N, 14.16; Cl, 11.87; S, 21.65. MS, m/z 297 (M+).
1
2-(4-Chloro-[1,2,3]-dithiazol-5-ylideneamino)-1,3-diphenylpropenone (3d). Yield 63%; oil; H-NMR
13
δ: 6.81 (s, 1 H, Harom), 7.36-7.89 (m, 10 H, Harom); C-NMR (50 MHz) δ: 128.02 (Ph-CH=), 128.55,
128.67, 129.37, 129.52, 130.84, 133.03, 133.81, 136.81, 145.03 (C-N=), 145.94 (C-4), 161.18 (C-5),
190.95 (C=O). Anal. Calcd for C17H11N2OClS2: C, 56.90; H, 3.09; N, 7.81; Cl, 9.88; S, 17.87. Found: C,
57.12; H, 3.07; N, 7.88; Cl, 9.77; S, 17.95. MS, m/z 359 (M+). The assignment of the 13C chemical shifts
was made based on the published data.7
General procedure for the synthesis of cyanothiazoles (4a,b,d). A mixture of toluene (5 mL),
triethylamine (2.18 g, 23 mmol, 3 mL) and dithiazolimine (3a,b,d) (100 mg) was refluxed for 8 h. Then
the toluene was removed in vacuo and the residue was purified by column chromatography (SiO2,
petroleum ether/ethyl acetate 1:4).
Ethyl 2-cyano-5-phenylthiazole-4-carboxylate (4a). Yield 83%; mp 108-109 °C; 1H-NMR δ: 1.14 (t, 3
13
H, J=7.09 Hz, CH3), 4.23 (q, 2 H, J=7.11 Hz, CH2), 7.44-7.60 (m, 5 H, Harom); C-NMR (50 MHz) δ:
13.62, 61.35, 112.38, 128.47, 128.98, 129.21, 129.88, 138.08, 141.79, 150.85, 160.143. Anal. Calcd for
C13H10N2O2S: C, 60.45; H, 3.90; N, 10.85; S, 12.41 Found: C, 60.57; H, 3.92; N, 10.71; S, 12.58. MS,
m/z 258 (M+).
2-Cyano-5-phenylthiazole-4-carboxamide (4b). Yield 75%; mp 163-165 °C; 1H-NMR δ: 7.48-7.66 (m,
13
5 H, Harom), 7.99 (s, 2 H, NH2); C-NMR (50 MHz), δ: 112.60, 128.20, 128.46 129.74, 129.91, 132.70,
145.78, 146. 87, 162.21. Anal. Calcd for C11H7N3OS: C 57.63, H 3.08, N 18.33, S 13.99. Found: C 57.81,
H 3.05, N 18.23, S 14.08. MS, m/z 229 (M+).
4-Benzoyl-5-phenylthiazole-2-carbonitrile (4d). Yield 90%; mp 65-67 °C; 1H-NMR δ: 7.41-7.89 (m, 10
H, Harom); 13C-NMR (50 MHz) δ: 112.75, 127.09, 127.85, 128.74, 129.15, 129.47, 130.11, 130.39, 133.74,
134.23, 135.89, 148.75, 188.71. Anal. Calcd for C17H10N2OS: C, 70.33; H, 3.47; N, 9.65; S, 11.04.
Found: C, 70.46; H, 3.45; N, 9.56; S, 11.21. MS, m/z 290 (M+).

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General procedure for the synthesis of 2-thiazolecarboxamides (5a,b,d,d’). A 25% aqueous ammonia
solution (5 mL) was added with stirring to a solution of dithiazolimine (3a,b,d) (100 mg) in THF (10 mL).
The reaction mixture was stirred at rt for 3 h. Then water and THF were removed in vacuo and the residue
was purified by column chromatography (SiO2, petroleum ether/ethyl acetate 1:4).
1
Ethyl 2-carbamoyl-5-phenylthiazole-4-carboxylate (5a). Yield 77%; mp 153-155°C; H-NMR δ: 1.12
(t, 3 H, J=7.22 Hz, CH3), 4.19 (q, 2 H, J=7.22 Hz, CH2), 7.48-7.54 (m, 5 H, Harom), 9.82 (s, 1 H, NH),
10.26 (s, 1 H, NH); 13C-NMR (50 MHz) δ: 13.24, 60.54, 127.96, 129.17, 140.65, 148.81, 159.86, 160.82,
161.90. Anal. Calcd for C13H12N2O3S: C, 56.51; H, 4.38; N, 10.14; S, 11.60. Found: C, 56.62; H, 4.40; N,
10.07; S, 11.79. MS, m/z 276 (M+).
5-Phenylthiazole-2,4-dicarboxylic acid diamide (5b). Yield 56%; mp 54-56 °C; 1H-NMR δ: 7.49 (m, 5
H, Harom), 9.91 (s, 1 H, NH), 10.32 (s, 1 H, NH); 13C-NMR (50 MHz) δ: 128.48, 129.57, 129.71, 141.43,
152.21, 161.46, 166.53, 185.77. Anal. Calcd for C11H9N3O2S: C, 53.43; H, 3.67; N, 16.99; S, 12.97.
Found: C, 53.54; H, 3.65; N, 16.84; S, 13.08. MS, m/z 247 (M+).
4-Benzoyl-5-phenylthiazole-2-carboxamide (5d). Yield 78%; mp 119-121 °C; 1H-NMR δ: 7.28-7.88 (m,
10 H, Harom), 7.99 (s, 1 H, NH), 8.26 (s, 1 H, NH); 13C-NMR (50 MHz) δ: 128.79, 128.99, 129.14, 129.41,
129.61, 130.11, 134.02, 136.18, 146.45, 148.15, 160.52, 162.28, 189.90. Anal. Calcd for C17H12N2O2S: C,
66.22; H, 3.92; N, 9.08; S, 10.40. Found: C, 66.34; H, 3.89; N, 8.93; S, 10.51. MS, m/z 308 (M+).
Synthesis of 4-benzoyl-N-(2-hydroxyethyl)-5-phenyl-1,3-thiazole-2-carboxamide (5d’). Ethanolamine
(860 mg, 14mmol, 1 mL) was added with stirring to a solution of dithiazolimine (3d) (100 mg, 0.28
mmol) in THF (10 mL). The reaction mixture was stirred at rt for 8 h, after which THF was removed in
vacuo and the residue was purified by column chromatography (SiO2, petroleum ether/ethyl acetate 1:4).
1
13
Yield 79%; oil; H-NMR δ: 3.58 (br s, 4 H, 2CH2), 7.27-7.88 (m, 10 H, Harom); C-NMR (50 MHz) δ:
42.06, 59.33, 128.15, 128.51, 128.94, 129.51, 130.00, 133.14, 136.13, 148.04, 156.71, 158.69, 161.94,
164.91, 189.99. Anal. Calcd for C19H16N2O3S: C, 64.76; H, 4.58; N, 7.95; S, 9.10. Found: C, 64.89; H,
4.56; N, 7.88; S, 9.22. MS, m/z 352 (M+).
[2-(4,5-Dihydro-1H-imidazol-2-yl)-5-phenylthiazol-4-yl]phenylmethanone (6d).
A
mixture of
dithiazolimine (3d) (200 mg, 0.55 mmol) and ethylenediamine (500 mg, 0.56 mL, 8.3 mmol) in THF (10
mL) was stirred at rt for 20 h, after which THF was removed in vacuo and the residue was purified by
column chromatography (SiO2, petroleum ether/ethyl acetate 1:4). Yield 73%; mp 167-169 °C; 1H-NMR
13
δ: 3.98 (s, 4 H, 2CH2), 7.41-7.92 (m, 10 H, Harom); C-NMR (50 MHz) δ: 45.92 (-CH2-CH2-), 128.14,
128.49, 129.00 (p), 129.27, 129.49, 132.67 (=N-C=), 133.64 (p), 133.37 (i), 136.64 (i), 156.86 (=C-Ph),
158.55 (-N=C-NH-), 160.63 (-N=C-S-), 188.91 (C=O). Anal. Calcd for C19H15N3OS: C, 68.45; H, 4.53;
N, 12.60; S, 9.62. Found: C, 68.58; H, 4.51; N, 12.45; S, 9.74. MS, m/z 333 (M+).

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[2-(4,5-Dihydro-1H-imidazol-2-yl)-4-phenylthiazol-5-yl]phenylmethanone (6c). A mixture of two
dithiazolimines (3d) and (3c) (1 g, 2.8 mmol), which were prepared according to the above-described
procedure, was dissolved in tetrahydrofuran (30 mL) and then ethylenediamine (2 g, 2.24 mL, 33.2
mmol) was added. The reaction mixture was stirred at rt for 20 h and worked up analogously to
compound (6d). Compounds (6d) and (6c) were prepared in yields of 610 mg (66%), and 66 mg, (7%),
respectively; mp 108-110 °C; 1H-NMR δ: 3.69 (s, 4 H, 2CH2), 7.24-7.69 (m, 10 H, Harom); 13C-NMR (50
MHz) δ: 45.91(-CH2-CH2-), 128.42 (-S-C=), 128.99, 129.39, 130.33, 130.43, 134.50, 136.01, 148.14,
148.43 (-N=C-S-), 148.98, 157.41 (-N=C-NH-), 189.57 (C=O). Anal. Calcd for C19H15N3OS: C, 68.45; H,
4.53; N, 12.60; S, 9.62. Found: C, 68.56; H, 4.50; N, 12.47; S 9.71. MS, m/z 333 (M+).
Synthesis of thiazolyltetrazoles (7a,d). A mixture of dithiazolimine (3a) or (3d) (100 mg) and methyl
azidoacetate (160 mg, 1.4 mmol) in acetonitrile (3 mL) was kept at 110 °C and 10 kbar for 8 h. Tetrazoles
were purified by thin layer chromatography (SiO2, ethyl acetate/hexane 1:1) and crystallized from
acetone.
Ethyl 2-(1-methoxycarbonylmethyl-1H-tetrazol-5-yl)-5-phenylthiazole-4-carboxylate (7a). Yield
1
63%; mp 91-93 °C; H-NMR δ: 1.19 (t, 3 H, J=7.20 Hz, CH3), 3.89 (s, 3 H, CH3), 4.21 (q, 2 H, J=7.22
13
Hz, CH2), 5.87 (s, 2 H, CH2), 7.51-7.62 (m, 5 H, Harom); C-NMR (50 MHz) δ: 13.63, 50.25, 52.80,
61.16, 128.35, 128.46, 129.83, 129.99, 141.72, 147.87, 148.34, 148.46, 160.59, 166.56. Anal. Calcd for
C16H15N5O4S: C, 51.47; H, 4.05; N, 18.76; S, 8.59. Found: C, 51.53; H, 4.07; N, 18.82; S, 8.63. MS, m/z
373 (M+).
Methyl [5-(4-benzoyl-5-phenylthiazol-2-yl)tetrazol-1-yl]acetate (7d). Yield 76%; mp 170-171°C;
13
1H-NMR δ: 2.51 (s, 3 H, CH3), 5.75 (s, 2 H, CH), 7.47-7.91 (m, 10 H, Harom); C-NMR (50 MHz) δ:
50.08, 52.37 128.38, 128.61, 129.06, 129.38, 129.95, 130.05, 133.96, 136.11, 146.45, 148.09. 148.53,
166.46, 188.95. Anal. Calcd for C20H15N5O3S: C, 59.25; H, 3.73; N, 17.27; S, 7.91. Found: C, 59.43; H,
3.71; N, 17.15; S, 8.22. MS, m/z 405 (M+).
X-Ray diffraction study of thiazolyltetrazole (7d). Colorless transparent single crystals of compound
(7d) of composition C20H15N5O3S were grown from a solution in acetone. The unit cell parameters and
intensities of 5452 independent reflections were measured at 295 К on a “CAD4 Enraf-Nonius”
diffractometer (MoKα radiation, λ = 0.711 Ǻ, graphite monochromator, q –5/3q-scanning technique in the
angle range 2.04 ≥ θ ≤ 29.97°). The crystallographic data for compound (7d): molecular weight М =
405.43, monoclinic system, space group Р21/n, a 9.000 (4), b 12.366 (5), c 16.901 (6) Å, β 92.28 (3)˚, V
1879.5 (13) Å3 , Z = 4, ρcalcd = 1.433 g/cm3. The structure was solved by direct methods, which revealed
all nonhydrogen atoms. The hydrogen atoms were located from difference electron density maps. The
structure was solved by the full-matrix least-squares method with anisotropic displacement parameters for
nonhydrogen atoms. The hydrogen atoms were refined isotropically by the least-squares method. The

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final R factors for 1714 reflections with I > 2σ(I) were R1 0.068 , wR2 0.115. The R factors based on all
independent reflections were R1 0.301, wR2 0.163. The calculations were carried out using the Bruker
SMART8, SHELXL-97, and Bruker SHELXTL9 program packages. The atomic coordinates,
displacement parameters, and geometric characteristics of molecule (7d) were deposited at the Cambridge
Crystallographic Data Center as supplementary publication numbers 266185.
REFERENCES
1. a) V. Thiéry, C. W. Rees, T. Besson, G. Cottenceau, and A.-M. Pons, Eur. J. Med. Chem., 1998, 33,
149. b) P. K. Montana and K. Kim, Tetrahedron Lett., 2002, 43, 3993.
2. a) K. Kim, Sulfur Reports, 1998, 21, 147. b) H.-S. Lee, Y.-G. Chang, and K. Kim, J. Heterocycl.
Chem., 1998, 35, 659. c) J. Guillard and T. Besson, Tetrahedron, 1999, 55, 5139. d). T. Besson, J.
Guillard, and C. W. Rees, Tetrahedron Lett., 2000, 41, 1027. e) T. Besson, C. W. Rees, D. G. Roe,
and V. Thiéry, J. Chem. Soc., Perkin Trans. 1, 2000, 555.
3. V. Yarovenko, A. Es’kov, G. Zatonsky, I. Zavarzin, M. Krayushkin, B. Averkiev, and M. Antipin, J.
Heterocycl. Chem., 2004, 41, 37
4. W. J. Kruper and A. H. Emmons, J. Org. Chem., 1991, 56, 3323
5. X. L. Jin, H. Sugihara, K. Daikai, H. Tateishi, Y. Z. Jin, H. Furuno, and J. Inanaga, Tetrahedron,
2002, 58, 8321.
6. G. I. Nikishin, S. S. Spector, G. P. Shakhovskoi, V. G. Glukhovtsev, and V. M. Zhulin, Bull. Acad.
Sci. USSR Div. Chem. Sci. (Engl.Transl.), 1977, 26, 1534.
7. P. A. Koutentis and C. W. Rees, J. Chem. Soc., Perkin Trans. 1, 1998, 2505.
8. Bruker. SMART. Bruker Molecular Analysis Research Tool. Version 5.059. Bruker AXS, Madison,
Wisconsin, USA. 1998.
9. G. M. Sheldrick SHELXTL Version 5.10, Structure Determination Software Suite, Bruker AXS,
Madison, Wisconsin, USA. 1998.