Reactions of 4-(Diethylamino)selenet-2(2H)-imine with nucleophiles - Synthesis of 2-methylen-3-oxobutane selenoamides

Article abstract of DOI:10.2174/157017810791130685

3-Acetyl-N-(4-bromophenyl)-4-(diethylamino)selenet-2(2H)-imine (5a), which is conveniently obtained from the formal [2+2] cycloaddition of 4-bromophenyl isoselenocyanate and 4-(diethylamino)-3-butyn-2-one, reacts with amines, alcohols, water, and thiophen

Full text of DOI:10.2174/157017810791130685

Letters in Organic Chemistry, 2010, 7, 291-297
291
Reactions of 4-(Diethylamino)selenet-2(2H)-imine with Nucleophiles –
Synthesis of 2-Methylen-3-oxobutane Selenoamides
Plamen K. Atanassov#, Anthony Linden and Heinz Heimgartner*
Institute of Organic Chemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
Received January 21, 2010: Revised February 13, 2010: Accepted February 17, 2010
Abstract: 3-Acetyl-N-(4-bromophenyl)-4-(diethylamino)selenet-2(2H)-imine (5a), which is conveniently obtained from
the formal [2+2] cycloaddition of 4-bromophenyl isoselenocyanate and 4-(diethylamino)-3-butyn-2-one, reacts with
amines, alcohols, water, and thiophenol to give the corresponding 2-methylen-3-oxobutane selenoamides 7 in good yields
via ring opening to the ketenimine 6 and subsequent addition of the nucleophile.
Keywords: Ketenimines, ring opening, selenet-2(2H)-imines, selenium heterocycles, selenoamides, X-ray crystallography.
INTRODUCTION
Four-membered selenaheterocycles have been described
only scarcely. Whereas several examples of the saturated
selenetanes [14] and selenazetidines [15] are known, only a
single report on unsaturated 2H-selenetes was known [16]
when we prepared compounds 5 [13]. The reaction of
selenobenzaldehyde complexes 6 with bis(tert-butylthio)
ethyne (7) at low temperature gave the 2H-selenete
complexes 8, which were transformed into 9 by treatment
with tetraethylammonium bromide (Scheme 1). Electrocyclic
ring opening to the corresponding ꢀ,ꢁ-unsaturated
thioselenocarboxylic esters have been observed for 8 and 9.
Selenium is an important element for higher organisms
[1]. It is now well known that the selenoenzyme glutathione
peroxidase (GPx) acts as an antioxidant, which catalyzes the
reduction of harmful peroxides and protects the lipid
membranes and other cellular components against oxidative
damage [2]. Furthermore, it has been shown that some
simple organoselenium compounds are able to mimic the
GPx activity in vitro. Among them the most promising drug
was Ebselen (1), a heterocyclic compound that functions as
an antioxidant [3], and which is still of high interest because
of its biological activities [4, 5] (for recent reviews see [6]).
After the discovery of this compound, several other GPx
mimics have been reported, e.g., Ebselen analogues [7],
benzoselenazolinones [8], cyclic selenamides of type 2 [9],
diaryl diselenides [10], and the semisynthetic enzyme
selenolsubtilisin [11].
In the present paper, we report on the ring opening
reaction of 3-acetyl-N-(4-bromophenyl)-3-(diethylamino)
selenet-2(2H)-imine (5a, Ar = 4-BrC6H4) [13] with amines,
alcohols, water, and thiophenol.
RESULTS AND DISCUSSION
O
When
a
solution of 3-acetyl-N-(4-bromophenyl)-4-
(5a) and excess
OH
(diethylamino)selenet-2-(2H)-imine
N
Ph
Se
N
benzylamine or butylamine in THF was heated to reflux
temperature, the 2-(diaminomethylene)-3-oxobutane seleno-
amide 11a or 11b, respectively, was obtained as yellow
crystals in fair yield (Scheme 2, Table 1). The structures of
these products were assigned in analogy to those of the
previously reported ones [13]. It is worth mentioning that no
‘C=O band’ could be detected in the IR spectra (KBr) and
the 13C NMR absorptions (CDCl3) for the carbonyl C-atom
and the thioamide group appear at 181–179 ppm, indicating
Se
Ac
1
2
In recent years, isoselenocyanates have been shown to be
useful building blocks for the synthesis of Se-containing
heterocycles [12]. For example, the reaction of aryl
isoselenocyanates 3 with 4-diethylamino-3-butyn-2-one (4)
in boiling THF yielded 3-acetyl-N-aryl-4-(diethylamino)
selenet-2(2H)-imines 5 in a formal [2+2] cycloaddition [13]
(Scheme 1). In preliminary experiments it has been shown
that these four-membered selenaheterocycles react in boiling
THF with morpholine and cyclohexylamine to give the
corresponding 2-(diaminomethylene)-N,N-diethyl-3-oxobut-
ane selenoamides.
1
that no ‘acetyl group’ is present. In the H NMR spectra, the
singlet at 14.4–14.5 ppm indicates a strong intramolecular
hydrogen bond. This fact can be explained by the preferred
structures of type 11’ or the analogous enolized structure
11’’.
In the case of the reactions of 5a with alcohols (propan-
2-ol, ethanol, butan-1-ol), the respective alcohol was used as
the solvent. The products 11c–11e were isolated in 76–54%
yield as yellow crystals. Again, there was no indication of an
acetyl C=O group in the IR spectra. In the 1H NMR spectra,
the signal for the NH, which is involved in the
intramolecular hydrogen bond, appeared at 12.6–12.3 ppm
*Address correspondence to this author at the Institute of Organic
Chemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich,
Switzerland; Tel: +41 44 6354282; Fax: +41 44 6356812;
E-mail: heimgart@oci.uzh.ch
#Postdoctoral stay at the University of Zürich (4. – 12. 2004).
1570-1786/10 $55.00+.00
© 2010 Bentham Science Publishers Ltd.

292 Letters in Organic Chemistry, 2010, Vol. 7, No. 4
Atanassov et al.
O
NEt2
O
Ar
THF
reflux
[13]
N
C
Se
NEt2
+
Se
N
3
4
5
Ar
tBuS
StBu
tBuS
StBu
[16]
Se W(CO)5
CH2Cl2
Et4NBr
CH2Cl2
+
tBuS
Ar
StBu
Se
low temp.
Se
H
Ar
W(CO)5
Ar
6
7
8
9
Scheme 1.
O
O
NEt2
Se
O
NEt2
Se
NEt2
NEt2
O
H
THF
RXH
C
Se
Se
reflux
N
HN
XR
N
N
XR
Ar
Ar
Ar
Ar
5a (Ar = 4-BrC6H4)
10
11
11'
NEt2
Se
11a XR = NHBn 11b XR = NHBu 11c XR = OiPr 11d XR = OEt
11e XR = OBu 11f XR = OH 11g XR = SPh
O
H
N
XR
Ar
11"
Scheme 2.
Table 1. Preparation of 2-Methylene-3-oxobutane Selenoamides 11 from Selenet-2(2H)-imine 5a
Selenoamides 11
M.p. (°C)
Yield (%)
11a
173.9–175.4
63.2
Br
Se HN
N
N
H
O
11b
81.4–82.1
45.7
Br
Se HN
N
N
H
O

2-Methylen-3-oxobutane Selenoamides
Letters in Organic Chemistry, 2010, Vol. 7, No. 4
(Table 1). Contd…..
Yield (%)
293
Selenoamides 11
M.p. (°C)
11c
154.6–154.7
73.5
75.8
54.3
Br
Se
O
N
N
H
O
11d
115.4–116.9
Br
Se
O
N
N
H
O
11e
127.5–128.3
Br
Se
O
N
N
H
O
11f
133.4–134.8
129.1–130.0
71.0
59.0
H
Br
Se
O
N
N
H
O
11g
Br
Se
S
N
N
H
O
and in the 13C NMR spectra, the carbonyl C-atom and the
thioamide group absorb at 200–199 ppm, i.e., at significantly
lower field than in the amine adducts 11a and 11b. For this
reason, the structure of 11c was established by X-ray
crystallography. Suitable crystals were obtained from
acetonitrile by slow evaporation of the solvent at room
temperature. The molecular structure is shown in Fig. (1).
the region around C(1)–C(2) bond is quite planar. The C(3)–
N(3) bond is also quite short, indicating delocalisation of the
C(3)=Se electron density in the thioamide moiety. The NH
group forms an intramolecular hydrogen bond with the
ketone O-atom (N(1)….O(13) 2.607(2) Å, and N(1)–
H….O(13) 141(2)°), thereby creating a six-membered loop
with a graph set motif [18] of S(6). These data show that, at
least in the crystalline state, the structure for the alcohol
adducts 11c–11e is described best with formula 11’ (Scheme
2).
In the crystal structure of 11c, the C(1)–C(2) bond
(1.382(3) Å) is somewhat longer than a formal C=C bond
(1.34 Å), while the C(1)–N(1) and C(1)–O(1) bonds are
quite short (1.349(3) and 1.344(2) Å, respectively) compared
with formal C–N and C–O bonds (1.47 and 1.43 Å,
respectively). Furthermore, the C(2)–C(13) bond is shorter
(1.446(3) Å) than a formal C–C bond (1.54 Å), whereas
C(13)–O(13) is slightly longer (1.246(2) Å) than a normal
C=O bond (1.22 Å). This indicates significant ꢀ-electron
delocalisation in this region of the molecule. Nonetheless,
The reaction of 5a with water was carried out in THF and
the mixture was heated to reflux for 58 h. After evaporation
of the solvent and treatment with methanol, 11f was obtained
in 71% yield as a yellow solid. Similarly, the reaction of 5a
with 5 equivalents of thiophenol in boiling THF yielded,
after preparative layer chromatography, the yellow
crystalline 11g in 59% yield. The spectroscopic data of these

294 Letters in Organic Chemistry, 2010, Vol. 7, No. 4
Atanassov et al.
Starting Materials
4-(Bromophenyl)isoselenocyanate was prepared acco-
rding to the protocol described in ref. [20]. 4-
(Diethylamino)-3-butyn-2-one was prepared according to the
protocol in ref. [21]. 3-Acetyl-N-(4-bromophenyl)-4-
(diethylamino)selenet-2(2H)-imine was prepared according
to the procedure described in ref. [13].
General Procedure for the Reaction of Selenet-2(2H)-
imine 5a with Amines
To a stirred solution of 5a in THF, 5 equiv. of benzyl
amine or butyl amine, respectively, were added. The mixture
was stirred for 2 h under reflux. Then, the solvent was
evaporated to dryness under reduced pressure, and the
residue was treated with Et2O (benzyl amine) or
CH2Cl2/hexane (butylamine). In the case of benzylamine,
yellow crystals formed. With butyl amine, the oily glue was
purified by preparative TLC (AcOEt/hexane 1:3), the solvent
was evaporated, the remaining oil was dissolved in
CH2Cl2/hexane, the solvent was evaporated under reduced
pressure and a yellow solid formed.
Fig. (1). ORTEP plot [17] of the molecular structure of 11c (50%
probability ellipsoids; arbitrary numbering of atoms).
two products are in good agreement with those of 11a–11e
and, therefore, we ascribe the structures 11f’ and 11g’ to the
obtained products. It is interesting to note that 11f possesses
the OH group, i.e. the enol structure, and does not exist in
the tautomeric amide form. This is indicated by a second OH
signal in the 1H NMR spectrum at 8.42 ppm.
2-{[(4-Bromophenyl)amino](benzylamino)methylene}-N,N-
diethyl-3-oxobutane Selenoamide (11a)
From 0.3 g (0.75 mmol) of 5a and 0.40 g (5 equiv.) of
benzylamine in THF (25 mL). Yield: 0.24 g (63.2%). M.p.
173.9–175.4°C (Et2O). IR: 3425w (br), 3245m, 3173m,
3085m, 2983m, 1606s, 1497s, 1452s, 1400s, 1373s, 1350s,
1267s, 1212m, 1184s, 1169m, 1139s, 1094m, 1067m, 1026m,
1003m. 1H NMR (CDCl3): 14.59 (s, NH); 7.76, 7.42
(AA'BB', JAB = 8.8, 4 arom. H); 7.39–7.28 (m, 5 arom. H);
6.25 (t-like, NH); 4.81 (dd, J = 14.2, 4.5, 1 H of PhCH2);
4.79 (dd, J = 14.2, 5.4, 1 H of PhCH2); 3.92–3.42 (m, 2
CH2); 1.73 (s, MeCO); 1.38, 1.32 (2t, J = 7.3, 2 Me). 13C
NMR (CDCl3): 181.1 (s, CO); 180.4 (s, CSe); 167.3, 140.3,
135.7, 118.1, 105.2 (5s, 3 arom. C, C(2), C(1’)); 131.1,
129.0, 128.5, 125.8 (4d, 9 arom. C); 49.7, 47.7 (2t, 2 CH2);
42.2 (t, PhCH2); 26.3 (q, MeCO); 13.4, 10.1 (2q, 2 Me). ESI-
MS: 510 (84), 509 (26), 508 (100, [M+1]+), 507 (18), 506
(51), 505 (17). Anal. Calcd for C22H26BrN3OSe (507.33): C,
52.08; H, 5.17; N, 8.28. Found: C, 51.95; H, 5.19; N, 8.24.
A reaction mechanism for the formation of the products
is proposed in Scheme 2. Electrocyclic ring opening of the
selenete 5a leads to the ketenimine 10. Then, nucleophilic
addition of amines, alcohols, water or thiophenol onto this
reactive intermediates gives the observed adducts 11.
Our attempts to obtain the products with tert-butanol and
tert-butylamine failed. Probably, the reason is the steric
hindrance of the addition of the sterically crowded
nucleophiles. The selenete 5a starts to decompose at
temperatures above 90°C and is sensitive to basic media. For
example, the attempt to perform the reaction between 5a and
sodium thiophenolate led to complete decomposition of the
starting selenete.
In summary, we have shown that the selenete 5a at
elevated temperature undergoes an electrocyclic ring
2-{[(4-Bromophenyl)amino](1-butylamino)methylene}-N,N-
diethyl-3-oxobutane Selenoamide (11b)
opening generating keteneimine 10 as
a
reactive
intermediate, which can be trapped with N, O, and S-
nucleophiles to give N,N-diethyl-2-methylene-3-oxobutane
selenoamides of type 11.
From 0.3 g (0.75 mmol) of 5a, 0.27 g (5 equiv.) of
butylamine in THF (25 mL). Yield: 0.16 g (45.7%), after
preparative TLC. M.p. 81.4–82.1°C (CH2Cl2/hexane). IR:
3420w (br), 3250m, 3182m, 3100m, 2958s, 2930s, 2870m,
1602s, 1504s, 1373s, 1286s, 1186s, 1152m, 1097m, 1010m.
EXPERIMENTAL
General
1H NMR (CDCl3): 14.51 (s, NH); 7.68, 7.34 (AA’,BB’, JAB
=
8.8, 4 arom. H); 5.77 (t-like, BuNH); 3.90–3.74, 3.65–3.33
(2m (1:7), 4 CH2); 1.78 (s, MeCO); 1.74–1.59 (m, CH2);
1.35, 1.23, 0.88 (3t, J = 7.3, 3 Me). 13C NMR (CDCl3): 180.4
(s,CO); 179.1 (s, CSe); 166.5, 139.5, 117.5, 104.5 (4s, 2
arom. C, C(2), C(1’)); 130.1, 124.8 (2d, 4 arom. C); 46.7,
44.5, 41.1, 30.5, 19.1 (5t, 5 CH2); 25.4, 12.8, 12.5, 9.2 (4q, 4
Me). CI-MS: 478 (13), 477 (17), 476 (78), 475 (22), 474
(100, [M+1]+), 473 (21), 472 (45), 471 (13), 470 (14), 396
(48), 394 (42), 213 (46). Anal. Calcd for C19H28BrN3OSe
See ref. [19]. TLC: silica gel 60 F254 plates (0.25 mm;
Merck). Column chromatography (CC): silica gel 60 (0.040-
0.063 mm; Merck). Melting Points: Büchi B-540 apparatus,
1
in capillaries; uncorrected. IR spectra in KBr (cm–1). H-
NMR (300 MHz) and 13C-NMR (75.5 MHz) spectra: Bruker
ARX-300 instrument in CDCl3; chemical shifts in ppm;
multiplicity of C-atoms from DEPT spectra. CI-MS:
Finnigan SSQ-700 or MAT-90 instrument; NH3 as carrier
gas; ESI-MS: Finnigan TSQ-700 instrument.

2-Methylen-3-oxobutane Selenoamides
Letters in Organic Chemistry, 2010, Vol. 7, No. 4
295
2-{[(4-Bromophenyl)amino](1-butoxy)methylene}-N,N-
diethyl-3-oxobutane Selenoamide (11e)
(473.31): C, 48.21; H, 5.96; N, 8.88. Found: C, 48.46; H,
5.59; N, 8.66.
A solution of 5a (0.3 g, 0.75 mmol) in 1-butanol (20 mL)
was stirred at 80°C for 5 h. The solvent was evaporated, the
oily residue treated with MeOH, the solid formed was
purified by preparative TLC (AcOEt/hexane 1:3), and the
oily product, after evaporation of the solvent, was treated
with MeOH to give yellow crystals. Yield: 0.19 g (54.3%),
after preparative TLC. Yellow crystals. M.p. 127.5–128.3
(MeOH). IR: 3442w (br), 2955m, 2920m, 2870m, 1617s,
1584s, 1556s, 1484s, 1431s, 1377s, 1266s, 1200s, 1118m,
Reactions of Selenet-2(2H)-imine 5a with Alcohols
In all of the cases, the respective alcohol was used as a
solvent.
2-{[(4-Bromophenyl)amino](isopropoxy)methylene}-N,N-
diethyl-3-oxobutane Selenoamide (11c)
A solution of 5a (0.3 g, 0.75 mmol) in 2-propanol (25
mL) was heated to reflux for 12 h. The solution was
concentrated and after cooling to room temperature, crystals
formed,which were filtered off. Yield: 0.25 g (73.5%). After
preparative TLC (silicagel, hexan/AcOEt 1:1): Yield: 61.8%.
Yellow crystals. M.p. 154.6–154.7°C (MeOH). IR: 3425w
(br), 3085w, 3063w, 3005w, 2974m, 2935m, 2871w, 1614s,
1584s, 1562s, 1488s, 1465m, 1455m, 1431s, 1393m, 1374m,
1356m, 1340m, 1297m, 1284m, 1267s, 1217s, 1178m,
1
1097m, 1059s, 1003m. H NMR (CDCl3): 12.36 (s, NH);
7.44, 7.07 (AA'B,B', JAB = 8.8, 4 arom. H); 4.42–4.08, 3.88–
3.58 (2m, 3 CH2); 2.21 (s, MeCO); 1.60–1.51 (m, CH2); 1.43
(t, J = 6.9, Me); 1.30 (m, CH2, Me); 0.84 (t, J = 7.3, Me). 13
C
NMR (CDCl3): 199.1 (s, CO); 192.1 (s, CSe); 159.0, 136.7,
117.6, 110.1 (4s, 2 arom. C, C(2), C(1')); 132.2, 123.2 (2d, 4
arom. C); 72.5, 49.8, 48.2, 31.3, 18.6 (5t, 5 CH2); 27.7, 13.6,
12.6, 10.6 (4q, 4 Me). CI-MS: 479 (14), 478 (17), 477 (77),
476 (23), 475 (100, [M+1]+), 474 (21), 473 (46), 472 (14),
471 (13), 421 (10), 419 (12), 403 (18), 401 (19), 397 (16),
395 (16). Anal. Calcd for C19H22BrN2O2Se (474.29): C,
48.11; H, 5.74; N, 5.91. Found: C, 48.81; H, 5.56; N, 5.83.
1
1169m, 1147m, 1122s, 1092s, 1071s, 1054m, 1004m. H
NMR (CDCl3): 12.54 (s, NH); 7.43, 7.05 (AA'BB', JAB = 8.7,
4 arom. H); 4.57–4.43 (m, CH2); 4.20–4.01 (m, CH); 3.74–
3.66 (m, CH2); 2.27 (s, MeCO); 1.43 (t, J = 7.1, Me); 1.33–
1.26 (m, 2 Me); 1.10 (d, J = 5.9, Me). 13C NMR (CDCl3):
199.8 (s, CO); 193.2 (s, CSe); 157.8, 137.5, 117.7, 96.2 (4s,
2 arom. C, C(2), C(1')); 132.4, 123.6 (2d, 4 arom. CH); 76.9
(d, Me2CH); 49.7, 48.2 (2t, 2 CH2); 28.4 (q, MeCO); 22.9,
22.1, 12.8, 10.7 (4q, 4 Me). ESI-MS: 486 (23), 485 (94), 484
(27), 483 (100, [M+Na]+), 482 (24), 481 (52), 480 (18), 479
(20). Anal. Calcd for C18H25BrN2O2Se (460.27): C, 46.97; H,
5.47; N, 6.09. Found: C, 47.20; H, 5.55; N, 6.05.
Reaction of Selenet-2(2H)-imine 5a with Water
To a solution of 5a (0.3 g, 0.75 mmol) in THF (25 mL),
H2O (0.5 mL) was added, and the mixture heated to reflux
for 58 h. The solvent was removed, the remaining oily glue
was treated with MeOH, and a yellow solid formed.
Suitable crystals of 8a for the X-ray crystal structure
determination were obtained from MeCN by slow
evaporation of the solvent at room temperature.
2-{[(4-Bromophenyl)amino](hydroxy)methylene}-N,N-di-
ethyl-3-oxobutane Selenoamide (11f)
Yield: 0.22 g (71%). Yellow crystals. M.p. 133.4–
134.8°C (MeOH). IR: 3442w (br), 3304m, 3109w, 3047w,
3008m, 2924s, 2853m, 1630s, 1600s, 1585s, 1529s, 1489s,
1439s, 1425s, 1396s, 1378s, 1358m, 1334s, 1302s, 1241s,
2-{[(4-Bromophenyl)amino](ethoxy)methylene}-N,N-diethyl-
3-oxobutane Selenoamide (11d)
A solution of 5a (0.3 g, 0.75 mmol) in abs. EtOH (25
mL) was heated to reflux for 8 h. Then, the solvent was
removed, the oily residue was treated with MeOH, and a
yellow solid formed, which was purified by preparative TLC
(AcOEt/hexane 1:3). The solvent was removed, the obtained
oily product was treated with MeOH, and the solid material
formed was recrystallized from Et2O/hexane, by cooling in
an ice bath. Yield: 0.25 g (75.8%). After preparative TLC,
yield 60.1%. Yellow crystals. M.p. 115.4–116.9
(Et2O/hexane). IR: 3423w (br), 3084w, 3059w, 3026w,
2980m, 2934m, 2870w, 1614s, 1582s, 1550s, 1487s, 1465m,
1454m, 1425s, 1379s, 1359s, 1344s, 1287m, 1271m, 1217s,
1
1217s, 1126s, 1094m, 1074s, 1008m. H NMR (CDCl3):
13.96 (s, NH); 8.42 (s, OH); 7.43, 7.35 (AA'BB', JAB = 8.9, 4
arom. H); 4.68–4.52, 4.00–3.75, 3.60–3.45 (3m (1:2:1), 2
CH2); 1.93 (s, MeCO); 1.42 (t, J = 7.1, Me); 1.22 (t, J = 7.2,
Me). 13C NMR (CDCl3): 197.5 (s, CO); 167.9 (s, CSe);
167.1, 136.1, 117.5, 110.8 (4s, 2 arom. C), C(2), C(1'));
132.0, 122.2 (2d, 4 arom. C); 50.7, 48.6 (2t, 2 CH2); 19.7 (q,
MeCO); 12.9, 10.7 (2q, 2 Me). CI-MS: 423 (13), 422 (14),
421 (80), 420 (19), 419 (100, [M+l]+), 418 (21), 417 (47),
416 (16), 415 (15), 405 (10), 403 (20), 401 (19), 341 (43),
339 (42), 248 (14), 222 (16). Anal. Calcd for
C15H19BrN2O2Se (418.19): C, 43.08; H, 4.58; N, 6.70.
Found: C, 43.92, H, 4.79; N, 6.50.
1
1192m, 1169m, 1119m, 1094m, 1069m, 1052s, 1005s. H
NMR (CDCl3): 12.37 (s, NH); 7.44, 7.08 (AA'BB', J = 8.7, 4
arom. H); 4.40–4.10, 3.95–3.66 (2m, 3 CH2); 2.23 (s,
MeCO); 1.43, 1.29 (2t, J = 7.0, 2 Me); 1.19 (t, J = 7.0, Me).
13C NMR (CDCl3): 199.0 (s, CO); 193.1 (s, CSe); 158.8,
136.8, 117.6, 93.2 (4s, 2 arom. C, C(2), C(1')); 132.3, 123.1
(2d, 4 arom. CH); 68.8 (t, CH2O); 49.8, 48.2 (2t, 2 CH2);
27.7 (q, MeCO); 14.8, 12.6, 10.5 (3q, 3 Me). CI-MS: 451
(13), 450 (15), 449 (78), 448 (21), 447 (100, [M+1]+), 446
(21), 445 (46), 444 (15), 443 (14), 418 (12), 369 (16), 367
(16), 294 (20), 292 (10). Anal. Calcd for C17H23BrN2O2Se
(446.24): C, 45.76; H, 5.20; N, 6.28. Found: C, 45.60, H,
5.15, N, 6.27.
Reaction of Selenet-2(2H)-imine 5a with Thiophenol
A solution of 5a (0.3 g, 0.75 mmol) and thiophenol (0.4
g, 3.6 mmol, ca. 5 equiv.) in THF (25 mL) was heated to
reflux for 11 h. Then, the solvent was removed under
reduced pressure, the remaining oily residue was treated with
MeOH, and a yellow solid formed, which was purified by
preparative TLC (AcOEt/hexane 1:3). After evaporation of
the solvent, the oily product was again treated with MeOH to
obtain yellow crystals.

296 Letters in Organic Chemistry, 2010, Vol. 7, No. 4
Atanassov et al.
2-{[(4-Bromophenyl)amino](phenylsulfanyl)methylene}-
N,N-diethyl-3-oxobutane Selenoamide (11g)
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ACKNOWLEDGEMENTS
We thank the analytical units of our institute for spectra
and analyses. Financial support of this work by the Professor
Dr. Hans E. Schmid-Stiftung and F. Hoffmann-La Roche AG,
Basel, is gratefully acknowledged.
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2-Methylen-3-oxobutane Selenoamides
Letters in Organic Chemistry, 2010, Vol. 7, No. 4
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type: ꢃ and ꢄ; 2ꢀ
= 60°; transmission factors (min; max):
(max)
0.409; 0.572; total reflections measured: 46394; symmetry
independent reflections: 5939; reflections with I > 2ꢅ (I): 4389;
reflections used in refinement: 5939; parameters refined: 226; final
R(F) [I > 2ꢅ (I) reflections]:0.0354; wR(F2) (all data): 0.0783;
2
2
weights: w = [ꢅ 2(Fo ) + (0.0308P)2 + 1.0827P]–1 where P = (Fo
+
[15]
2Fc2)/3; goodness of fit: 1.031; final ꢆ max /ꢅ = 0.004; ꢆꢇ (max;
min) = 0.49; –0.58 [e Å–3].
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