The [3 + 2] cycloaddition reaction of thiazole carbene-derived C-C-Se 1,3-dipoles: A concise and highly efficient strategy for the construction of multifunctional dihydroselenophenes and selenopheno[2,3-b]pyrazines

Article abstract of DOI:10.1039/b904575a

The first study on the reaction of C⁺-C-Se^- 1,3-dipoles with electron-deficient alkenes and alkyne is reported. 2-Arylselenocarbamoylthiazolium inner salts, the unique thiazole carbene-derived C⁺-C-Se^- 1,3-dipol

Full text of DOI:10.1039/b904575a

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
The [3 + 2] cycloaddition reaction of thiazole carbene-derived C-C-Se
1,3-dipoles: a concise and highly efficient strategy for the construction of
multifunctional dihydroselenophenes and selenopheno[2,3-b]pyrazines†
Jian-Hong Zhang and Ying Cheng*
Received 5th March 2009, Accepted 22nd May 2009
First published as an Advance Article on the web 29th June 2009
DOI: 10.1039/b904575a
The first study on the reaction of C+-C-Se- 1,3-dipoles with electron-deficient alkenes and alkyne is
reported. 2-Arylselenocarbamoylthiazolium inner salts, the unique thiazole carbene-derived C+-C-Se-
1,3-dipoles, reacted efficiently with methoxycarbonylallenes or dimethyl acetylenedicarboxylate to
produce dihydroselenophenes or selenopheno[2,3-b]pyrazines, respectively, in high yields. Both
reactions probably proceeded via a [3 + 2] cycloaddition of C+-C-Se- 1,3-dipoles with alkenes or alkyne
followed by different transformations of the thiazole-spiro-selenophene intermediates. This work
provides a concise and efficient strategy for the construction of multifunctional dihydroselenophenes
and selenopheno[2,3-b]pyrazines, which are not easy accessible by other methods.
ular cyclization of selenium substituted aromatic compounds.7,12
Although numerous syntheses of selenophene derivatives have
Introduction
Selenophene1 and fused selenophene derivatives have attracted
been reported, further development of concise and efficient strat-
continued interest owing to their rich chemical and biological
egy for the construction of selenophenes and fused selenophenes
activities, and important physical properties. 2,5-Bis(selenophen-
is of great importance.
2-yl)-N-methylpyrrole, for example, is a antineoplastic agent
Nucleophilic N-heterocyclic carbenes are known to react with
aryl isocyanates13 or isothiocyanates14–19 to form stable zwitterionic
inner salts. In 2006, we reported for the first time that the
2-thiocarbamoylbenzimidazolium or -imidazolinium salts pre-
pared from the reaction of benzimidazole or imidazoline carbenes
with aryl isothiocyanates are unique ambident C+-C-S- and
C+-C-N- bis-dipolar compounds.16 Since then, we have developed
ambident 1,3-dipoles derived from N-heterocyclic carbenes and
isothiocyanates into versatile synthons in the construction of
novel spiro- and fused thiophene and pyrrole derivatives.16–19
Although N-heterocyclic carbene-derived C+-C-S- dipoles have
been intensively investigated, their selenium analogues, the
C+-C-Se- dipoles are still not explored. We envisioned that the
reaction of N-heterocyclic carbenes with isoselenocyanates would
form 2-selenocarbamoyl N-heterocyclic inner salts that might
act as C+-C-Se- dipoles for the construction of selenophene
derivatives. Therefore, we undertook the current study on the
reaction of 2-selenocarbamoyl thiazolium salts with dimethyl
acetylenedicarboxylate and methoxycarbonylallenes.
with a broad spectrum of antitumoral activity against several
human cancer cells,2 while a series of 2-(selenophen-2-yl)pyrroles,
2-(selenophen-2-yl)thiophenes, 2-(selenophen-2-yl)selenophenes
and 2,5-bis(selenophen-2-yl)thiophenes strongly inhibit liver can-
cer cells.3 2,5-Diphenylselenophene and other organoselenium
compounds have been reported to induce phase II enzyme
activities,4 and selenophenyl ketones or thioketones could be
used in the treatment of diseases related to protein aging.5 Some
benzoselenophene derivatives exhibit antibacterial and antifungal
activity.6 In addition to the potential applications in pharmaceu-
ticals, selenophene derivatives can also be utilized in the area of
functional materials due to their important optical and electronic
properties. Aromatic ring-fused selenophenes,7,8 or polymers of
selenophenes9 and fused selenophenes,10 for instance, are good
organic semiconductors for various optoelectronic devices such as
organic field-effect transistors and light-emitting diodes. Because
of the wide applications, the interest in the synthesis of selenophene
and fused selenophene derivatives remains undiminished. The
known methods for the construction of selenophenes are mainly
based on the ring-closure reactions of acetylenes, olefins, b-diketo
compounds and a,b-unsaturated acetonitriles with selenium
reagents, including selenium chloride, sodium selenide, elemental
selenium, or dimethyl diselenide (MeSeSeMe).6,11 Preparation of
aromatic ring fused selenophenes generally starts from intramolec-
Results and discussion
Bis(1,3-diphenyl-2-imidazolidinylidene), which was regarded as an
equivalent or a precursor of 1,3-diphenyl imidazoline carbene, is
known to react with aryl isoselenocyanates to form 1 + 2 adducts,
spiro[imidazolidine-2,4¢-imidazolidine]-2¢,5¢-diselenones (1,3,6,9-
tetraazaspiro[4.4]nonane-2,4-diselones).14 However, the stable 1,3-
dipolar adducts of N-heterocyclic carbenes with isoselenocyanates
have not been reported before. According to our experiences
in the preparation of 1,3-dipolar adducts from the reaction
of N-heterocyclic carbenes with aryl isothiocyanates,16–19 we
attempted the preparation of stable C+-C-Se- dipoles, namely
College of Chemistry, Beijing Normal University, Beijing, 100875, China.
E-mail: ycheng2@bnu.edu.cn; Fax: +86 1058805558; Tel: +86 1058805558
† Electronic supplementary information (ESI) available: Experimental
procedure for the preparation of 2-arylselenocarbamoyl thiazolium salts
4 and full characterization for compounds 4. CCDC reference numbers
721793 (6a) and 721794 (8j). For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/b904575a
3264 | Org. Biomol. Chem., 2009, 7, 3264–3270
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Table 1 Preparation of 2-selenocarbamoylthiazolium inner salts 4a
Table 2 The reaction of 3-benzyl-2-(4-methoxphenyl)selenocarbamoyl-
4-methylthiazolium salt 4g with DMAD 5 under different conditionsa
Entry
1: R
3: Ar
Yield of 4b
Entry
4g:5
Solvent
Yield of 6g (%)b
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1a: Bn
3a: Ph
4a: 65
4b: 69
4c: 73
4d: 76
4e: 61
4f: 65
4g: 55
4h: 80
4i: 88
4j: 65
4k: 55
4l: 71
4m: 66
4n: 68
4o: 61
4p: 81
1a: Bn
3b: 4-ClPh
3c: 3,4-Cl2Ph
3d: 4-CF3Ph
3b: 4-ClPh
3d: 4-CF3Ph
3a: Ph
1
2
3
4
5
6
7
8
1:1
benzene
benzene
benzene
benzene
CH2Cl2
THF
57
68
78
90
86
84
88
77
1a: Bn
1a: Bn
1.1.5
1.2.0
1.2.5
1.2.5
1.2.5
1.2.5
1.2.5
1b: 4-MeBn
1b: 4-MeBn
1c: 4-MeOBn
1c: 4-MeOBn
1c: 4-MeOBn
1d: 4-ClBn
1d: 4-ClBn
1d: 4-ClBn
1e: 4-BrBn
1e: 4-BrBn
1e: 4-BrBn
1f: Et
3b: 4-ClPh
3d: 4-CF3Ph
3a: Ph
3b: 4-ClPh
3d: 4-CF3Ph
3a: Ph
3b: 4-ClPh
3c: 3,4-Cl2Ph
3c: 3,4-Cl2Ph
CH3COCH3
CH3CN
a At room temp. for 0.5 h. b Isolated yield.
stituents. It was found that the 1,3-dipoles 4 with either an electron-
rich or an electron-deficient benzyl and phenyl groups on the thia-
zole ring and on the selenocarbamoyl moiety, respectively, reacted
with DMAD efficiently to afford selenopheno[2,3-b]pyrazines 6
in 80–93% yields (Scheme 2 and Table 3). The reaction of 3-ethyl
and 3-butyl thiazolium salts 4 with DMAD gave high yields of
products, though these products were not fully characterized due
to their instability.
a Reaction conditions: THF, -20 ◦C, 2.5–3.5 h. b Isolated yield.
2-selenocarbamoyl thiazolium inner salts, from the reaction of
thiazole carbenes with aryl isoselenocyanates at low temperature.
Thus, thiazole carbenes 2, which were generated in situ from
the thiazolium salts 1 with sodium hydride, reacted with aryl
isoselenocyanates 3 in dry THF at -20 ◦C to produce the
desired 2-selenocarbamoylthiazolium inner salts 4 in 55–88%
yields (Scheme 1 and Table 1). It should be pointed out that
the reaction between thiazole carbene 2 and an electron-rich
aryl substituted isoselenocyanate 3, such as 4-tolyl or 4-anisyl
isoselenocyanates, did not give stable dipolar adducts. It is most
probably due to the anion centers of dipoles 4 not being efficiently
stabilized by the electron-rich aryl rings.
Scheme 2 The reaction of 2-arylselenocarbamoylthiazolium salts 4 with
DMAD.
To further extend the applications of the N-heterocyclic
carbene-derived C-C-Se 1,3-dipoles, we investigated the reaction
between 2-arylselenocarbamoylthiazolium salts 4 and methoxy-
carbonylallenes 7. Under similar conditions as for the reaction
with DMAD, the reaction of 4 with methoxycarbonylallenes 7
proceeded very slowly. To promote the reaction, the non-polar
solvent benzene was replaced by THF to increase the solubility of
thiazolium salts 4, and the reaction temperature was elevated to
the boiling point of THF. Under these conditions, the reaction of
thiazolium salts 4 with allenes 7 proceeded smoothly to produce
products 8 in 61–78% yields in about 3 h (Scheme 3 and Table 4).
Scheme 1 The reaction of thiazolium salts 1 with aryl isoselenocyanates
3 in the presence of sodium hydride.
We then studied the reaction between 2-selenocarbamoyl thi-
azolium salts 4 and dimethyl acetylenedicarboxylate (DMAD),
a strong dipolarophile that gave spiro-thiophenes16,17 or fused
thiophenes19 in the reactions with N-heterocyclic carbene-
derived C+-C-S- dipoles. Firstly, the reaction of N-benzyl 2-(4-
methoxyphenyl)selenocarbamoylthiazolium salt 4g with DMAD
was optimized by varying the ratio of starting materials and
solvents at ambident temperature (Table 2). It was found that
the reaction of 4g with DMAD proceeded very rapidly and
efficiently. No matter whether in a polar or non-polar solvent,
such as benzene, THF, dichloromethane, acetone and acetonitrile,
the reaction finished in half a hour at room temperature to give
product selenopheno[2,3-b]pyrazine 6g in good to excellent yields.
Although thiazolium salt 4g was only slightly soluble in benzene,
the reaction took place immediately when DMAD was added, and
the highest yield (90%) of 6g was obtained from the reaction of 4g
with 2.5 equivalent of DMAD in benzene at room temperature.
The scope of the reaction was then examined under optimized
conditions by using thiazolium salts 4 bearing different sub-
Table 3 The reaction of 2-arylselenocarbamoylthiazolium salts 4 with
DMAD under optimized conditions
Entry
4
R
Ar
6
Yield (%)a
1
2
3
4
5
6
7
8
9
4a
4b
4d
4e
4f
4g
4h
4i
Bn
Bn
Bn
Ph
6a
6b
6d
6e
6f
6g
6h
6i
82
89
87
84
87
90
90
90
93
89
80
4-ClPh
4-CF3Ph
4-ClPh
4-CF3Ph
Ph
4-ClPh
4-CF3Ph
Ph
4-MeBn
4-MeBn
4-MeOBn
4-MeOBn
4-MeOBn
4-ClBn
4-ClBn
4-ClBn
4j
4k
4l
6j
6k
6l
10
11
4-ClPh
4-CF3Ph
a Isolated yield.
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Table 4 The reaction of 2-arylselenocarbamoylthiazolium salts 4 with
methoxycarbonylallenes 7a
tions. In the former case, the thiazoline-spiro-dihydroselenophene
intermediate 9 derived from cycloaddition of C-C-Se dipole 4
with DMAD probably underwent cleavage of the S–C bond
of the thiazole ring to give a zwitterion 10. Electrocyclization
of 10 followed by isomerization formed the selenopheno[2,3-
b]pyrazine intermediate 12. S-Nucleophilic addition of 12 to
DMAD affords product 6 (Scheme 4, equ. 1). In the latter case,
[3 + 2] cycloaddition of dipole 4 with methoxycarbonylallenes
7 formed a thiazoline-spiro-tetrahydroselenophene intermediate
13. Deprotonation of tetrahydroselenophene and cleavage of S–C
bond of thiazoline of 13 gave rise to the formation of an enamine
substituted dihydroselenophene 14. Hydrolysis of enamine 14
with a trace amount of water in solvent and/or in the eluent
of column chromatography produced products 8 (Scheme 4,
equ. 2). Apparently, the aromatization of dihydroselenophenes 9
to selenophenes 11 or the conversion of tetrahydroselenophenes
13 to highly conjugated dihydroselenophenes 14 was, respectively,
the driving force in the transformation of spiro intermediates 9
or 13 that lead to the formation of fused selenophenes or mono
dihydroselenophenes.
Entry
4
R
Ar
7
R1
8
Yield (%)b
1
2
3
4
5
6
7
8
9
4c
4o
4a
4i
4m
4n
4o
4p
4n
4o
Bn
4-BrBn
Bn
4-MeOBn
4-BrBn
4-BrBn
4-BrBn
Et
4-BrBn
4-BrBn
3,4-Cl2Ph
3,4-Cl2Ph
Ph
4-CF3Ph
Ph
4-ClPh
3,4-Cl2Ph
3,4-Cl2Ph
4-ClPh
3,4-Cl2Ph
7a Et
8a
8b
8c
8d
8e
8f
67
78
72
61
73
76
71
71
68
72
7a Et
7b i-Pr
7b i-Pr
7b i-Pr
7b i-Pr
7b i-Pr
7b i-Pr
7c Bn
7c Bn
8g
8h
8i
10
8j
a Reaction conditions: 4:7 = 1:2, THF, reflux, 2.5–3 h. b Isolated yield.
Scheme 3 The reaction of 2-arylselenocarbamoylthiazolium salts 4 with
methoxycarbonylallenes 7.
In sharp contrast to the reaction with DMAD that afforded fused
selenophenes 6, dipoles 4 reacted with allenes to give monocyclic
compounds, the dihydroselenophene derivatives 8.
The structures of all products were fully characterized by
1
spectroscopic data and microanalysis. The H NMR, MS and
microanalysis data indicated that products 6 were the 1 + 2 adducts
of dipoles 4 with DMAD, while compounds 8 were derived from
=
1 + 1 addition of two reactants with the loss of a CH3C CHS
moiety. Although spectroscopic data did not allow full verification
of the structures of products, X-ray diffraction analysis determined
unambiguously that compound 6a was (E)-dimethyl 1-benzyl-
3-(1,2-dimethoxycarbonylvinylthio)-2-methyl-4-phenyl-1,4-dihy-
droselenopheno[2,3-b]pyrazine-6,7-dicarboxylate, while 8j was
(2Z,5Z)-methyl 4-(4-bromobenzylamino)-5-(3,4-dichlorophenyl-
imino)-2-(2-phenylethylidene)-2,5-dihydroselenophene-3-carbox-
ylate (Fig. 1).20 It is worth noting that both the exocyclic C C
=
=
and C N bonds of dihydroselenophene 8 adopt the Z-con-
figurations to avoid the steric repulsion among the substituents of
selenophene ring.
Fig. 1 Ortep drawings of X-ray structures of 6a and 8j (50% probability
was chosen for the ellipsoids).
Both the formation of selenopheno[2,3-b]pyrazines 6 and
dihydroselenophenes 8 can be best explained by the [3 + 2]
cycloaddition between the C-C-Se dipolar specie of 4 and DMAD
or methoxycarbonylallene 7 followed by different ring transforma-
Scheme 4 The proposed mechanisms for the formation of seleno-
pheno[2,3-b]pyrazines 6 and dihydroselenophenes 8.
3266 | Org. Biomol. Chem., 2009, 7, 3264–3270
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(E)-Dimethyl 1-benzyl-4-(4-chlorophenyl)-3-(1,2-dimethoxycar-
bonylvinylthio)-2-methyl-1,4-dihydroselenopheno[2,3-b]pyrazine-
6,7-dicarboxylate (6b). 89%, red crystals, mp 175–176 ◦C;
Conclusions
In conclusion, we have demonstrated that the 2-arylsel-
enocarbamoylthiazolium salts derived from thiazole carbenes
and aryl isoselenocyanates are unique C+-C-Se- 1,3-dipoles
being able to react efficiently with DMAD or methoxycar-
bonylallenes to produce selenopheno[2,3-b]pyrazine or dihydrose-
lenophene derivatives respectively in good to excellent yields. Both
reactions were proposed to proceed via a [3 + 2] cycloaddition
of C+-C-Se- 1,3-dipoles with the alkyne or alkenes followed
by different transformation of the thiazole-spiro-selenophene
intermediates. The easy availability and high reactivity render
the 2-arylselenocarbamoylthiazolium salts powerful 1,3-dipoles
in the synthesis of novel multifunctional dihydroselenophene
and selenopheno[2,3-b]pyrazine derivatives, which are not ready
accessible by other methods.
v
max/cm-1 1741, 1718, 1701; dH (400 MHz, CD3COCD3) 7.21–
7.26 (m, 3H, Ar-H), 7.19 (d, J 8.8, 2H, Ar-H), 7.09 (dd, J 7.6
and 1.5, 2H, Ar-H), 6.54 (d, J 8.8, 2H, Ar-H), 5.66 (s, 1H,
=
CH C), 4.27 (s, 2H, CH2Ph), 3.80 (s, 3H, OCH3), 3.64 (s, 3H,
OCH3), 3.54 (s, 3H, OCH3), 3.53 (s, 3H, OCH3), 1.99 (s, 3H,
pyrazinyl-CH3); dC (125 MHz, CD3COCD3) 165.7, 164.3, 163.3,
161.7, 152.1, 147.4, 144.1, 142.1, 136.4, 135.9, 131.9, 130.0, 129.4,
129.1, 128.6, 128.1, 126.9, 121.2, 118.4, 115.6, 55.8, 52.4, 52.3,
51.8, 51.3, 17.3; MS (ESI) m/z: 690 (M), 713 (M + Na+). Anal.
Calcd for C30H27ClN2O8SSe: C 52.22, H 3.94, N 4.06; Found:
C 52.60, H 3.88, N 3.85.
(E)-Dimethyl 1-benzyl-3-(1,2-dimethoxycarbonylvinylthio)-2-
methyl-4-(4-trifluoromethylphenyl)-1,4-dihydroselenopheno[2,3-b]-
pyrazine-6,7-dicarboxylate (6d). 87%, yellow crystals, mp
149–150 ◦C; vmax/cm-1 1740, 1721, 1702, 1613; dH (400 MHz,
CD3COCD3) 7.49 (d, J 8.4, 2H, Ar-H), 7.05–7.11 (m, 3H, Ar-H),
7.01 (dd, J 7.6 and 1.2, 2H, Ar-H), 6.86 (d, J 8.4, 2H, Ar-H),
Experimental
Melting points are uncorrected. 1H NMR (500 or 400 MHz) and
13C NMR (125 or 100 MHz) spectra were recorded in the indicated
solvents. J values are reported in Hz. IR spectra were recorded
using an AVATAR 360 FT-IR spectrometer. Mass spectra were
recorded on a Trace MS (EI) or Surveyor MSQ Plus (ESI) instru-
ment and elemental analyses were performed on a GMBH Vario
EL instrument. Column chromatography was performed using
200–300 mesh silica gel or neutral Al2O3. Thiazolium salts 1 were
prepared according to literature.21 For the experimental procedure
for the preparation of 2-arylselenocarbamoyl thiazolium salts 4 see
Electronic Supplementary Information.†
=
5.69 (s, 1H, CH C), 4.38 (s, 2H, CH2Ph), 3.81 (s, 3H, OCH3),
3.68 (s, 3H, OCH3), 3.51 (s, 3H, OCH3), 3.50 (s, 3H, OCH3),
2.05 (s, 3H, pyrazinyl-CH3); dC (100 MHz, CD3COCD3) 166.5,
165.3, 164.2, 162.6, 149.4, 149.0, 148.6, 148.3, 137.4, 135.6, 134.7,
129.4, 129.3, 128.8, 127.3, 127.27, 127.23, 127.19, 127.0, 126.7,
125.5, 123.9, 123.1, 116.6, 115.9, 55.4, 53.4, 53.2, 52.9, 52.1, 17.9;
MS (ESI) m/z: 725 (M + 1), 747 (M + Na+). Anal. Calcd for
C31H27F3N2O8SSe: C 51.46, H 3.76, N 3.87; Found: C 51.48, H
3.79, N 3.51.
(E)-Dimethyl
4-(4-chlorophenyl)-3-(1,2-dimethoxycarbonyl-
vinylthio)-2-methyl-1-(4-methylbenzyl)-1,4-dihydroselenopheno-
[2,3-b]pyrazine-6,7-dicarboxylate (6e). 84%, red crystals,
mp 109–110 ◦C; vmax/cm-1 1736, 1714, 1602; dH (400 MHz,
CD3COCD3) 7.17 (d, J 8.8, 2H, Ar-H), 7.03 (d, J 7.8, 2H, Ar-H),
6.94 (d, J 8.0, 2H, Ar-H), 6.52 (d, J 8.8, 2H, Ar-H), 5.65 (s, 1H,
1. General procedure for the reaction of 2-arylselenocarbamoyl-
thiazolium salts 4 with DMAD
Under nitrogen atmosphere and at room temperature, DMAD
(2.5 mmol) was added dropwise to the suspension of 2-
arylselenocarbamoylthiazolium salts 4 (1 mmol) in benzene
(40 mL). The mixture was then stirred at room temperature
for 0.5 hour. After removal of the solvent under vacuum at a
temperature below 35 ◦C, the residue was chromatographed on a
neutral Al2O3 column eluting with a mixture of petroleum ether
(30–60 ◦C) and ethyl acetate (from ◦5:1 to 3:1). The eluent was
evaporated under vacuum below 35 C, and the products 6 were
isolated in 80–93% yields.
=
CH C), 4.22 (s, 2H, CH2Ph), 3.79 (s, 3H, OCH3), 3.64 (s, 3H,
OCH3), 3.53 (s, 3H, OCH3), 3.52 (s, 3H, OCH3), 2.22 (s, 3H,
CH3Ph), 1.97 (s, 3H, pyrazinyl-CH3); dC (100 MHz, CD3COCD3)
166.6, 165.2, 164.2, 162.6, 153.0, 148.2, 145.2, 143.0, 138.6, 136.9,
134.1, 132.7, 131.2, 130.2, 129.99, 129.98, 127.6, 122.2, 119.4,
116.6, 56.5, 53.3, 53.2, 52.6, 52.2, 21.2, 18.2; HRMS (TOF-EI):
704.0504, Anal. Calcd for C31H29ClN2O8SSe: 704.0498.
(E)-Dimethyl 3-(1,2-dimethoxycarbonylvinylthio)-2-methyl-1-
(E)-Dimethyl 1-benzyl-3-(1,2-dimethoxycarbonylvinylthio)-2-
methyl-4-phenyl-1,4-dihydroselenopheno[2,3-b]pyrazine-6,7-dicar-
boxylate (6a). 82%, red crystals, mp 108–109 ◦C; vmax/cm-1 1742,
1728, 1687; dH (500 MHz, CD3COCD3) 7.37–7.42 (m, 3H, Ar-H),
7.32 (t, J 7.8, 2H, Ar-H), 7.25–7.28 (m, 3H, Ar-H), 6.69 (d, J 7.6,
(4-methylbenzyl)-4-(4-trifluoromethylphenyl)-1,4-dihydroseleno-
pheno[2,3-b]pyrazine-6,7-dicarboxylate
(6f). 87%,
yellow
crystals, mp 122–123 ◦C; vmax/cm-1 1737, 1716, 1611; dH
(500 MHz, CD3COCD3) 7.62 (d, J 8.3, 2H, Ar-H), 7.02 (s, 4H,
=
Ar-H), 6.99 (d, J 8.4, 2H, Ar-H), 5.84 (s, 1H, CH C), 4.47 (s,
=
2H, Ar-H), 5.80 (s, 1H, CH C), 4.40 (s, 2H, CH2Ph), 3.94 (s,
2H, CH2Ph), 3.96 (s, 3H, OCH3), 3.84 (s, 3H, OCH3), 3.66 (s, 3H,
OCH3), 3.64 (s, 3H, OCH3), 2.25 (s, 3H, CH3Ph), 2.20 (s, 3H,
pyrazinyl-CH3); dC (125 MHz, CD3COCD3) 165.6, 164.4, 163.3,
161.7, 148.9, 148.3, 147.7, 147.3, 137.5, 134.8, 134.1, 133.4, 129.0,
128.4, 126.23, 126.21, 125.9, 125.6, 125.5, 124.7, 123.3, 122.0,
115.7, 115.3, 54.4, 52.5, 52.3, 52.0, 51.3, 20.1, 17.0; MS (ESI)
m/z: 738 (M), 761 (M + Na+). Anal. Calcd for C32H29F3N2O8SSe:
C 52.11, H 3.96, N 3.80; Found: C 52.30, H 3.95, N 3.64.
3H, OCH3), 3.77 (s, 3H, OCH3), 3.69 (s, 3H, OCH3), 3.68 (s, 3H,
OCH3), 2.12 (s, 3H, pyrazinyl-CH3); dC (100 MHz, CD3COCD3)
166.7, 165.2, 164.3, 162.7, 154.2, 148.6, 144.0, 143.9, 137.4, 137.0,
130.3, 130.1, 129.9, 129.4, 128.9, 128.3, 126.5, 120.8, 120.0, 116.2,
57.0, 53.3, 53.2, 52.6, 52.2, 18.2. MS (ESI) m/z: 657 (M + 1), 679
(M + Na+). Anal. Calcd for C30H28N2O8SSe: C 54.96, H 4.30, N
4.27; Found: C 55.03, H 4.70, N 4.19.
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(E)-Dimethyl 1-(4-methoxybenzyl)-3-(1,2-dimethoxycarbonyl-
vinylthio)-2-methyl-4-phenyl-1,4-dihydroselenopheno[2,3-b]-
pyrazine-6,7-dicarboxylate (6g). 90%, red crystals, mp 118–
119 ◦C; vmax/cm-1 1737, 1714; dH (500 MHz, C6D6) 7.17 (d, J 8.0,
2H, Ar-H), 7.09 (t, J 7.4, 2H, Ar-H), 6.97 (t, J 7.1, 1H, Ar-H), 6.87
(E)-Dimethyl 1-(4-chlorobenzyl)-4-(4-chlorophenyl)-3-(1,2-dime-
thoxycarbonylvinylthio)-2-methyl-1,4-dihydroselenopheno[2,3-b]-
pyra◦zine-6,7-dicarboxylate (6k). 89%, red crystals, mp 159–
160 C; vmax/cm-1 1739, 1711, 1695; dH (500 MHz, CD3COCD3)
7.40 (d, J 8.1, 2H, Ar-H), 7.36 (d, J 8.5, 2H, Ar-H), 7.23 (d, J
=
=
(d, J 7.7, 2H, Ar-H), 6.80 (d, J 8.0, 2H, Ar-H), 5.83 (s, 1H, CH C),
8.2, 2H, Ar-H), 6.74 (d, J 8.5, 2H, Ar-H), 5.81 (s, 1H, CH C),
4.46 (s, 2H, CH2Ph), 3.82 (s, 3H, OCH3), 3.64 (s, 3H, OCH3), 3.40
(s, 3H, OCH3), 3.395 (s, 3H, OCH3), 3.31 (s, 3H, OCH3), 2.02
(s, 3H, pyrazinyl-CH3); dC (125 MHz, C6D6) 166.5, 164.6, 163.5,
162.1, 159.9, 154.2, 148.3, 143.5, 142.9, 137.0, 130.7, 129.3, 129.2,
128.7, 127.3, 126.3, 120.5, 120.0, 115.5, 114.0; MS (EI) m/z: 508
(100), 686 (M+, 2%). Anal. Calcd for C31H30N2O9SSe: C 54.31, H
4.41, N 4.09; Found: C 54.37, H 4.60, N 3.88.
4.42 (s, 2H, CH2Ph), 3.95 (s, 3H, OCH3), 3.79 (s, 3H, OCH3),
3.68 (s, 3H, OCH3), 3.67 (s, 3H, OCH3), 2.14 (s, 3H, pyrazinyl-
CH3); dC (125 MHz, CD3COCD3) 165.7, 164.3, 163.3, 161.7,
152.2, 147.3, 144.1, 142.0, 135.8, 135.0, 133.6, 131.8, 130.8, 129.8,
129.5, 128.6, 126.4, 121.5, 118.9, 115.8, 55.1, 52.5, 52.3, 51.8, 51.3,
17.3; MS (ESI) m/z: 724 (M), 747 (M + Na+). Anal. Calcd for
C30H26ClN2O8SSe: C 49.74, H 3.62, N 3.87; Found: C 49.97, H
3.63, N 3.66.
(E)-Dimethyl 4-(4-chlorophenyl)-1-(4-methoxybenzyl)-3-(1,2-
dimethoxycarbonylvinylthio)-2-methyl-1,4-dihydroselenopheno-
[2,3-b]pyrazine-6,7-dicarboxylate (6h). 90%, red crystals, mp
108–109 ◦C; vmax/cm-1 1736, 1709; dH (400 MHz, CD3COCD3)
7.16 (d, J 8.8, 2H, Ar-H), 6.99 (d, J 8.7, 2H, Ar-H), 6.76 (d, J
(E)-Dimethyl
1-(4-chlorobenzyl)-3-(1,2-dimethoxycarbonyl-
vinylthio)-2-methyl-4-(4-trifluoromethylphenyl)-1,4-dihydrosel-
enopheno[2,3-b]pyrazine-6,7-dicarboxylate (6l). 80%, yellow
crystals, mp 129–130 ◦C; vmax/cm-1 1743, 1733, 1716, 1706, 1605;
dH (500 MHz, CD3COCD3) 7.66 (d, J 8.5, 2H, Ar-H), 7.23 (d,
J 8.3, 2H, Ar-H), 7.16 (d, J 8.3, 2H, Ar-H), 7.03 (d, J 8.4, 2H,
=
8.6, 2H, Ar-H), 6.58 (d, J 8.8, 2H, Ar-H), 5.65 (s, 1H, CH C),
4.20 (s, 2H, CH2Ph), 3.80 (s, 3H, OCH3), 3.68 (s, 3H, OCH3),
3.64 (s, 3H, OCH3), 3.53 (s, 3H, OCH3), 3.52 (s, 3H, OCH3), 1.97
(s, 3H, pyrazinyl-CH3); dC (100 MHz, CD3COCD3) 166.6, 165.2,
164.2, 162.6, 160.7, 153.0, 148.2, 145.4, 143.1, 136.8, 132.6, 131.3,
131.2, 130.2, 129.3, 127.6, 122.3, 119.4, 116.5, 114.7, 56.1, 55.6,
53.3, 53.2, 52.7, 52.2, 18.2; MS (ESI) m/z: 720 (M), 743 (M +
Na+). Anal. Calcd for C31H29ClN2O9SSe: C 51.71, H 4.06, N 3.89;
Found: C 51.77, H 3.95, N 3.46.
=
Ar-H), 5.85 (s, 1H, CH C), 4.52 (s, 2H, CH2Ph), 3.97 (s, 3H,
OCH3), 3.84 (s, 3H, OCH3), 3.66 (s, 3H, OCH3), 3.64 (s, 3H,
OCH3), 2.21 (s, 3H, pyrazinyl-CH3); dC (125 MHz, CD3COCD3)
165.6, 164.4, 163.3, 161.7, 148.6, 147.6, 147.1, 135.1, 134.8, 133.6,
133.4, 130.2, 128.5, 126.4, 126.3, 126.0, 125.8, 125.4, 124.8, 123.3,
121.8, 116.0, 115.9, 53.9, 52.6, 52.3, 52.0, 51.3, 17.0; MS (-c ESI)
m/z: 757 (M - 1). Anal. Calcd for C34H30N4O2S: C 49.12, H 3.46,
N 3.70; Found: C 49.30, H 3.31, N 3.49.
(E)-Dimethyl 1-(4-methoxybenzyl)-3-(1,2-dimethoxycarbonyl-
vinylthio)-2-methyl-4-(4-trifluoromethylphenyl)-1,4-dihydrose-
lenopheno[2,3-b]pyrazine-6,7-dicarboxylate (6i). 93%, yellow
crystals, mp 117–118 ◦C; vmax/cm-1 1734, 1707; dH (500 MHz,
CD3COCD3) 7.61 (d, J 8.2, 2H, Ar-H), 7.05 (d, J 7.8, 2H, Ar-
H), 7.00 (d, J 8.2, 2H, Ar-H), 6.74 (d, J 7.7, 2H, Ar-H), 5.83 (s,
2. General procedure for the reaction of 2-arylselenocar-
bamoylthiazolium salts 4 with methoxycarbonylallenes 7
Under nitrogen atmosphere, 2-arylselenocarbamoylthiazolium
salts 4 (1 mmol) were mixed with methoxycarbonylallenes 7
(2 mmol) in dry THF (50 mL). The mixture was then stirred
in refluxing THF for 2.5–3 h. After removal of the solvent under
vacuum, the residue was chromatographed on a silicon gel column
to give products 8 in 61–78% yields (petroleum ether (30–60 ◦C) :
ethyl acetate = 9:1).
(2Z,5Z)-Methyl 4-(benzylamino)-5-(3,4-dichlorophenylimino)-
2-propylidene-2,5-dihydrose◦lenophene-3-carboxylate (8a). 67%,
yellow crystals, mp 64–65 C; vmax/cm-1 3288, 1649, 1605, 1579;
dH (400 MHz, CDCl3) 8.24 (brs, 1H, NH), 7.36 (d, J 8.5, 1H,
Ar-H), 7.20–7.29 (m, 5H, Ar-H), 6.97 (d, J 2.4, 1H, Ar-H), 6.72
=
1H, CH C), 4.44 (s, 2H, CH2Ph), 3.96 (s, 3H, OCH3), 3.83 (s,
3H, OCH3), 3.71 (s, 3H, OCH3), 3.65 (s, 3H, OCH3), 3.64 (s, 3H,
OCH3), 2.19 (s, 3H, pyrazinyl-CH3); dC (125 MHz, CD3COCD3)
165.7, 164.5, 163.4, 161.8, 159.6, 148.9, 148.5, 147.8, 147.3, 134.9,
134.1, 129.7, 128.5, 126.23, 126.21, 125.9, 125.6, 125.4, 124.6,
123.3, 122.1, 115.6, 115.4, 113.7, 54.5, 54.1, 52.6, 52.3, 52.1, 51.3,
17.1; MS (ESI) m/z: 754 (M), 777 (M + Na+). Anal. Calcd for
C32H29F3N2O9SSe: C 51.00, H 3.88, N 3.72; Found: C 51.17, H
3.62, N 3.61.
=
(dd, J 8.5 and 2.4, 1H, Ar-H), 6.43 (t, J 7.4, 1H, HC C), 4.87
(E)-Dimethyl
1-(4-chlorobenzyl)-3-(1,2-dimethoxycarbonyl-
(s, 2H, CH2Ph), 3.77 (s, 3H, OCH3), 2.04–2.12 (m, 2H, CH2CH3),
0.99 (t, J 7.4, 3H, CH2CH3); dC (100 MHz, CDCl3) 166.4, 163.6,
154.4, 150.7, 138.3, 132.2, 130.2, 127.9, 127.7, 127.6, 126.4, 126.3,
126.2, 120.3, 117.8, 107.5, 50.5, 48.3, 27.1, 13.0; MS (ESI) m/z:
495 (M + 1). Anal. Calcd for C22H20Cl2N2O2Se: C 53.46, H 4.08,
N 5.67; Found: C 53.18, H 4.55, N 5.18.
vinylthio)-2-methyl-4-phenyl-1,4-dihydroselenopheno[2,3-b]-
pyra◦zine-6,7-dicarboxylate (6j). 93%, red crystals, mp 131–
132 C; vmax/cm-1 1739, 1729, 1697; dH (500 MHz, CD3COCD3)
7.42 (d, J 8.3, 2H, Ar-H), 7.36 (t, J 7.9, 2H, Ar-H), 7.30 (t, J 7.2,
1H, Ar-H), 7.24 (d, J 8.3, 2H, Ar-H), 6.71 (d, J 7.7, 2H, Ar-H),
=
5.79 (s, 1H, CH C), 4.40 (s, 2H, CH2Ph), 3.94 (s, 3H, OCH3),
3.77 (s, 3H, OCH3), 3.69 (s, 3H, OCH3), 3.68 (s, 3H, OCH3),
2.12 (s, 3H, pyrazinyl-CH3); dC (125 MHz, CD3COCD3) 165.8,
164.3, 163.3, 161.8, 153.4, 147.5, 143.0, 142.7, 136.1, 135.1, 133.6,
130.9, 129.5, 128.6, 127.4, 125.3, 120.1, 119.7, 115.5, 55.4, 52.4,
52.3, 51.7, 51.3, 17.4; MS (ESI) m/z: 691 (M + 1), 713 (M +
Na+). Anal. Calcd for C30H27ClN2O8SSe: C 52.22, H 3.94, N 4.06;
Found: C 52.44, H 3.55, N 3.94.
(2Z,5Z)-Methyl 4-(4-bromobenzylamino)-5-(3,4-dichlorophen-
ylimino)-2-propylidene-2,5-dihydroselenophene-3-carboxylate (8b).
78%, yellow crystals, mp 105–106 ◦C; vmax/cm-1 3288, 1648, 1606,
1582; dH (400 MHz, CDCl3) 8.43 (brs, 1H, NH), 7.46 (d, J 8.4, 2H,
Ar-H), 7.44 (d, J 8.5, 1H, Ar-H), 7.18 (d, J 8.4, 2H, Ar-H), 7.04
(d, J 2.4, 1H, Ar-H), 6.77 (dd, J 8.5 and 2.4, 1H, Ar-H), 6.54 (t, J
=
7.4, 1H, HC C), 4.93 (d, J 4.6, 2H, CH2Ph), 3.86 (s, 3H, OCH3),
3268 | Org. Biomol. Chem., 2009, 7, 3264–3270
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2.12–2.19 (m, 2H, CH2CH3), 1.06 (t, J 7.5, 3H, CH2CH3); dC
(100 MHz, CDCl3) 167.5, 164.6, 155.5, 151.6, 138.5, 133.3, 131.7,
131.2, 129.0, 128.82, 128.75, 127.7, 121.2, 121.1, 118.8, 108.8, 51.5,
48.5, 28.1, 14.0; MS (ESI) m/z: 573 (M + 1). Anal. Calcd for
C22H19BrCl2N2O2Se: C 46.10, H 3.34, N 4.89; Found: C 46.46, H
3.68, N 4.75.
(2Z,5Z)-Methyl
4-(4-bromobenzylamino)-5-(3,4-dichloro-
phenylimino)-2-(2-methylpropylidene)-2,5-dihydroselenophene-
3-carboxylate (8g). 71%, yellow crystals, mp 139–140 ◦C;
v
max/cm-1 3286, 1648, 1597, 1583, 1574; dH (400 MHz, CDCl3)
8.36 (brs, 1H, NH), 7.39 (d, J 8.5, 2H, Ar-H), 7.36 (d, J 8.5, 1H,
Ar-H), 7.09 (d, J 8.4, 2H, Ar-H), 6.96 (d, J 2.4, 1H, Ar-H), 6.69
=
(dd, J 8.5 and 2.4, 1H, Ar-H), 6.30 (d, J 9.3, 1H, HC C), 4.85 (s,
(2Z,5Z)-Methyl
4-(benzylamino)-2-(2-methylpropylidene)-5-
2H, CH2Ph), 3.78 (s, 3H, OCH3), 2.11–2.20 (m, 1H, CH(CH3)2),
0.98 (d, J 6.6, 6H, CH(CH3)2); dC (100 MHz, CDCl3) 167.4,
164.7, 155.6, 151.7, 138.6, 133.3, 133.1, 131.7, 131.2, 129.0, 128.8,
127.0, 121.2, 121.1, 118.8, 108.7, 51.5, 48.5, 35.3, 22.9; MS (ESI)
m/z: 587 (M + 1). Anal. Calcd for C23H21BrCl2N2O2Se: C 47.05,
H 3.60, N 4.77; Found: C 47.30, H 3.89, N 4.79.
(phenylimino)-2,5-dihydroselenophene-3-carboxylate (8c). 72%,
◦
yellow crystals, mp 92–93 C; vmax/cm-1 3291, 1651, 1612, 1584;
dH (400 MHz, CDCl3) 8.27 (brs, 1H, NH), 7.31 (t, J 7.6, 2H,
Ar-H), 7.24–7.27 (m, 5H, Ar-H), 7.10 (t, J 7.4, 1H, Ar-H), 6.88
(d, J 7.6, 2H, Ar-H), 6.24 (d, J 9.2, 1H, HC C), 4.92 (s, 2H,
CH2Ph), 3.77 (s, 3H, OCH3), 2.11–2.20 (m, 1H, CH(CH3)2), 0.97
(d, J 6.6, 6H, CH(CH3)2); dC (100 MHz, CDCl3) 167.6, 162.6,
155.8, 152.6, 139.5, 131.7, 129.4, 128.6, 127.5, 127.4, 127.2, 125.4,
119.1, 107.8, 51.4, 49.3, 35.1, 22.9; MS (EI) m/z: 91 (100), 440
(M+, 10%). Anal. Calcd for C23H24N2O2Se: C 62.87, H 5.51, N
6.38; Found: C 63.11, H 5.31, N 6.28.
=
(2Z,5Z)-Methyl 5-(3,4-dichlorophenylimino)-4-(ethylamino)-2-
(2-methylpropylidene)-2,5-dihydroselenophene-3-carboxylate (8h).
71%, yellow crystals, mp 126–127 ◦C; vmax/cm-1 3250, 1647, 1610,
1586; dH (400 MHz, CDCl3) 7.44 (d, J 8.5, 1H, Ar-H), 7.12 (d, J
2.4, 1H, Ar-H), 6.87 (dd, J 8.5 and 2.4, 1H, Ar-H), 6.27 (d, J 9.3,
=
1H, HC C), 3.86 (s, 3H, OCH3), 3.68 (q, J 7.2, 2H, CH2CH3),
(2Z,5Z)-Methyl 4-(4-methoxybenzylamino)-2-(2-methylpropyl-
idene)-5-(4-trifluoromethylphenylimino)-2,5-dihydroselenophene-
3-carboxylate (8d). 61%, yellow crystals, mp 89–90 ◦C; vmax/cm-1
3289, 1653, 1618, 1593; dH (400 MHz, CDCl3) 8.12 (brs, 1H, NH),
7.57 (d, J 8.3, 2H, Ar-H), 7.17 (d, J 8.8, 2H, Ar-H), 6.96 (d, J 8.2,
2.16–2.25 (m, 1H, CH(CH3)2), 1.24 (t, J 7.2, 3H, CH2CH3), 1.03
(d, J 6.6, 6H, CH(CH3)2); dC (100 MHz, CDCl3) 167.4, 165.0,
155.4, 151.9, 133.2, 131.9, 131.2, 128.7, 127.2, 121.4, 118.9, 107.4,
51.4, 40.4, 35.2, 23.0, 16.0; MS (-c ESI) m/z: 446 (M - 1). Anal.
Calcd for C18H20Cl2N2O2Se: C 48.45, H 4.52, N 6.28; Found:
C 48.81, H 4.75, N 6.34.
=
2H, Ar-H), 6.81 (d, J 8.7, 2H, Ar-H), 6.26 (d, J 9.2, 1H, HC C),
4.80 (s, 2H, CH2Ph), 3.78 (s, 3H, OCH3), 3.74 (s, 3H, OCH3),
2.09–2.18 (m, 1H, CH(CH3)2), 0.97 (d, J 6.6, 6H, CH(CH3)2); dC
(100 MHz, CDCl3) 167.3, 164.6, 159.0, 155.5, 155.3, 132.4, 131.3,
128.9, 127.4, 127.2, 127.0, 126.82, 126.78, 126.75, 126.71, 125.5,
122.8, 119.4, 114.1, 108.3, 55.3, 51.4, 48.9, 35.3, 22.9; MS (-c ESI)
m/z: 537 (M - 1). Anal. Calcd for C25H25F3N2O3Se: C 55.87, H
4.69, N 5.21; Found: C 55.89, H 4.86, N 5.17.
(2Z,5Z)-Methyl 4-(4-bromobenzylamino)-5-(4-chlorophenyl-
imino)-2-(2-phenylethylidene)-2,5-dihydroselenophene-3-carboxy-
◦
late (8i). 68%, yellow crystals, mp 101–102 C; vmax/cm-1 3439,
1655, 1589, 1564; dH (400 MHz, CDCl3) 8.66 (brs, 1H, NH), 7.47
(d, J 8.4, 2H, Ar-H), 7.36 (d, J 8.7, 2H, Ar-H), 7.29 (t, J 7.0, 2H,
Ar-H), 7.18–7.23 (m, 5H, Ar-H), 6.88 (d, J 8.7, 2H, Ar-H), 6.71 (t,
=
J 7.6, 1H, HC C), 4.99 (s, 2H, NHCH2Ph), 3.81 (s, 3H, OCH3),
(2Z,5Z)-Methyl
4-(4-bromobenzylamino)-2-(2-methylpro-
=
3.48 (d, J 7.6, 2H, C CHCH2Ph); dC (100 MHz, CDCl3) 167.6,
pylidene)-5-(phenylimino)-2,5-dihydroselenophene-3-carboxylate
(8e). 73%, yellow crystals, mp 99–100 ◦C; vmax/cm-1 3285, 1647,
1605, 1585, 1574; dH (400 MHz, CDCl3) 8.44 (brs, 1H, NH), 7.38
(d, J 8.4, 2H, Ar-H), 7.31 (t, J 7.6, 2H, Ar-H), 7.12 (d, J 8.5, 2H,
Ar-H), 7.09–9.13 (m, 1H, Ar-H), 6.85 (dd, J 7.4 and 1.2 Hz, 2H,
163.0, 156.4, 150.7, 139.6, 138.6, 131.7, 131.0, 130.4, 129.7, 129.1,
128.6, 128.4, 126.4, 123.6, 121.1, 120.5, 108.2, 51.6, 48.5, 40.8; MS
(ESI) m/z: 601 (M + 1). Anal. Calcd for C27H22BrClN2O2Se: C
53.98, H 3.69, N 4.66; Found: C 53.66, H 3.69, N 4.36.
=
Ar-H), 6.26 (d, J 9.2, 1H, HC C), 4.90 (s, 2H, CH2Ph), 3.77 (s,
(2Z,5Z)-Methyl 4-(4-bromobenzylamino)-5-(3,4-dichlorophen-
ylimino)-2-(2-phenylethylidene)-2,5-dihydroselenophene-3-car-
boxylate (8j). 72%, yellow crystals, mp 121–122 ◦C; vmax/cm-1
3204, 1662, 1584; dH (400 MHz, CDCl3) 8.51 (brs, 1H, NH), 7.39
(d, J 8.3, 2H, Ar-H), 7.36 (d, J 8.5, 1H, Ar-H), 7.19–7.23 (m,
2H, Ar-H), 7.08–7.15 (m, 5H, Ar-H), 6.97 (d, J 2.4, 1H, Ar-H),
3H, OCH3), 2.11–2.20 (m, 1H, CH(CH3)2), 0.96 (d, J 6.6, 6H,
CH(CH3)2); dC (100 MHz, CDCl3) 167.7, 162.6, 156.0, 152.6,
138.8, 132.1, 131.6, 129.5, 129.2, 127.2, 125.5, 121.0, 119.1, 108.1,
51.4, 48.5, 35.2, 22.9; MS (EI) m/z: 77 (95), 104 (85), 169 (100),
171 (95), 518 (M+, 10%). Anal. Calcd for C23H23BrN2O2Se: C
53.30, H 4.47, N 5.40; Found: C 53.54, H 4.88, N 5.20.
=
6.71 (dd, J 8.5 and 2.4, 1H, Ar-H), 6.66 (t, J 7.6, 1H, HC C),
4.89 (s, 2H, NHCH2Ph), 3.74 (s, 3H, OCH3), 3.41 (d, J 7.6, 2H,
(2Z,5Z)-Methyl
4-(4-bromobenzylamino)-5-(4-chlorophenyl-
=
C CHCH2Ph); dC (100 MHz, CDCl3) 167.5, 164.4, 156.1, 151.5,
imino)-2-(2-methylpropylidene)-2,5-dihydroselenophene-3-carbo-
xylate (8f). 76%, yellow crystals, mp 125–126 ◦C; vmax/cm-1
3284, 1649, 1607, 1585; dH (400 MHz, CDCl3) 8.40 (brs, 1H,
NH), 7.38 (d, J 8.4, 2H, Ar-H), 7.27 (d, J 8.7, 2H, Ar-H), 7.10
(d, J 8.5, 2H, Ar-H), 6.79 (d, J 8.7, 2H, Ar-H), 6.28 (d, J 9.3, 1H,
139.4, 138.5, 133.3, 131.7, 131.3, 130.3, 129.04, 129.0, 128.6, 128.4,
126.4, 124.2, 121.2, 121.1, 118.7, 108.6, 51.6, 48.5, 40.8; MS (EI)
m/z: 44 (100), 169 (40), 171 (52), 634 (M+, 6%). Anal. Calcd for
C27H21BrCl2N2O2Se: C 51.05, H 3.33, N 4.41; Found: C 51.12, H
3.39, N 4.31.
=
HC C), 4.87 (s, 2H, CH2Ph), 3.77 (s, 3H, OCH3), 2.11–2.19 (m,
1H, CH(CH3)2), 0.97 (d, J 6.6, 6H, CH(CH3)2); dC (100 MHz,
CDCl3) 167.6, 163.4, 155.8, 150.9, 138.7, 132.5, 131.7, 130.8,
129.6, 129.1, 127.1, 121.0, 120.6, 108.3, 51.5, 48.5, 35.3, 22.9;
MS (EI) m/z: 169 (100), 171 (85), 552 (M+, 2%). Anal. Calcd for
C23H22BrClN2O2Se: C 49.98, H 4.01, N 5.07; Found: C 49.87, H
3.93, N 5.05.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China for Distinguished Young Scholars (No.
20525207), the National Natural Science Foundation of China
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(No. 20832006 and 20672013), the Ministry of Science and
Technology of China (2009ZX09501-006) and Beijing Municipal
Commission of Education.
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20 Crystal data for 6a: C30H28N2O8SSe, M = 655.56, T = 296 K, triclinic,
¯
˚
space group P1, a = 8.6334(1), b = 11.8180(2), c = 15.3160(2) A,
◦ ◦ ◦
3
˚
a = 77.339(1) , b = 88.859(1) , g = 89.677(1) , V = 1524.38(4) A ,
Z = 2, rcalcd = 1.428 g cm-3, absorption coefficient 1.352 mm-1,
reflections collected/unique 13248/7085 [R(int) = 0.0161], final R
indices [I>2sigma(I)], R1 = 0.0342, wR2 = 0.0965. Crystal data for
8j: C27H21BrCl2N2O2Se, M = 635.23, T = 113 K, triclinic, space
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¯
˚
group P1, a = 9.781(2), b = 11.518(2), c = 11.812(2) A, a =
◦
◦
◦
3
˚
88.96(3) , b = 72.07(3) , g = 80.99(3) , V = 1249.8(4) A , Z =
2, rcalcd = 1.688 g cm-3, absorption coefficient 3.343 mm-1, reflec-
tions collected/unique 9144/5860 [R(int) = 0.0355], final R indices
[I>2sigma(I)], R1 = 0.0367, wR2 = 0.0921. CCDC 721793 (compound
6a) and 721794 (compound 8j).
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3270 | Org. Biomol. Chem., 2009, 7, 3264–3270
This journal is
The Royal Society of Chemistry 2009
©