Stannic chloride-induced unsymmetrical C-se bond cleavage of bis(N,N-dimethylcarbamoylseleno)methanes: Novel generation of selenoaldehydes

Article abstract of DOI:10.1002/hc.20190

Treatment of bis(N,N-dimethylcarbamoylseleno)methanes with SnCl₄ afforded β-1,3,5-triselenanes in moderate to high yields, and the key intermediates of the reactions, i.e., acylselonium ions and selenoaldehydes, were successfully trapped by usi

Full text of DOI:10.1002/hc.20190

Heteroatom Chemistry
Volume 17, Number 2, 2006
Stannic Chloride-Induced Unsymmetrical
C Se Bond Cleavage of
Bis(N,N-dimethylcarbamoylseleno)methanes:
Novel Generation of Selenoaldehydes
Yaling Gong, Kazuaki Shimada, Hidenori Nakamura, Masamichi
Fujiyama, Akihiro Kodama, Miyuki Otsuki, Rei Matsumoto,
Shigenobu Aoyagi, and Yuji Takikawa
Department of Chemical Engineering, Faculty of Engineering, Iwate University,
Morioka, Iwate 020-8551, Japan
Received 5 September 2005; revised 31 October 2005
reactive intermediates for the organic reactions, and
ABSTRACT: Treatment of bis(N,N-dimethylcar-
the increasing interests in the biological activities [1–
bamoylseleno)methanes with SnCl4 afforded β-1,3,5-
3] for some selenoaldehydes. The synthetic method-
triselenanes in moderate to high yields, and the key
ologies for selenoaldehydes 3 are roughly classified
intermediates of the reactions, i.e., acylselonium
to the five categories, i.e., (i) oxygen–selenium ex-
ions and selenoaldehydes, were successfully trapped
changing reactions of aldehydes [4–13], (ii) direct
by using allyltrimethylsilane or 2,3-dimethyl-1,3-
selenation of intermediary carbenes or carbenoids
butadiene to obtain the allylation products or the
using elemental selenium [14–16], (iii) sigmatropic
ꢀ
C
cycloadducts, respectively.
2006 Wiley Periodicals,
rearrangement of substituted alkenyl selenides [17],
(iv) elimination of selenides bearing a suitable leav-
ing group adjacent to the selenium atom [18–21], and
(v) alkylation of stable selenoformate esters [22–25].
Most methods required multistep processes to pre-
pare the suitable precursors for selenoaldehydes 3,
and these problems just prompted us to the new-type
generation of selenoaldehydes 3 through fragmen-
tation of easily preparable symmetrical diselenoac-
etals. However, to date, conversion of symmetrical
diseleno- or ditelluroacetals into the corresponding
chalcogenoaldehydes or chalcogenoketones was not
studied at all due to the lack of preparative method
of such precursors bearing a suitable chalcogen-
protecting group on each chalcogen atoms in spite of
their potent synthetic convenience. In the course of
our studies on the novel generation of highly reactive
species related to higher row chalcogenocarbonyl
compounds, we previously reported a convenient
Inc. Heteroatom Chem 17:125–135, 2006; Published on-
line in Wiley InterScience (www.interscience.wiley.com).
DOI 10.1002/hc.20190
INTRODUCTION
Recently, various methodologies for the generation
of selenoaldehydes 3 have been reported in the light
of their structural interests, their potentiality as new
Correspondence to: Kazuaki Shimada; e-mail: shimada@iwate-
u.ac.jp.
Contract grant sponsor: Ministry of Education, Science, Sports,
and Culture.
Contract grant number: 12650843.
Contract grant sponsor: Foundation for Japanese Chemical
Research.
Contract grant number: 333 (R).
c
ꢀ
2006 Wiley Periodicals, Inc.
125

126 Gong et al.
preparation of stable ditelluroacetal derivatives 2
using the reaction of N,N-dimethyltellurocarbamate
ions with gem-dihaloalkanes [17,26]. These results
urged us to the preparation of symmetrical dise-
lenoacetals 1 and the further reactions of 1 with
a Lewis acid on the basis of the coordinating in-
teraction between the selenocarbamate moiety and
a soft Lewis acid [27]. Actually, diselenoacetals 1,
bearing a removable N,N-dimethylcarbamoyl group
on each selenium atoms, are just expected to un-
dergo Lewis acid induced unsymmetrical C Se bond
cleavage to generate selenoaldehydes 3 via acylselo-
nium ions A through a push–pull type elimina-
tion of N,N-dimethylselenocarbamate ion and N,N-
dimethylcarbamoyl cation [28]. According to our ex-
pectation as mentioned above, we started our explo-
ration on the reaction of diselenoacetals 1 with a soft
Lewis acid, i.e., SnCl4, in the presence or absence of
trapping agents, and we just found a new and con-
venient method for generation of selenoaldehydes 3
through the reaction of 1 with SnCl4 under mild con-
ditions as well as a novel stepwise fragmentation of 1
involving the in situ formation of key intermediates
A as the actual precursors of 3 [29]. In this paper, we
describe a full account on the new and convenient
method for generation of selenoaldehydes 3 starting
from symmetrical diselenoacetals 1.
dimethylcarbamoylseleno)methanes
1a–f
[26],
which are regarded as a new class of symmetrical
diselenoacetals bearing a N,N-dimethylcarbamoyl
group on each selenium atoms. On the other hand,
stepwise treatment of 4 with NaBH4 with 5a in a
mixed solvent of C2H5OH–DMF (1:1) only gave 1a
in 20% yield along with the formation of dibenzyl
diselenide as a major product [31], and the use of
diisobutylaluminum hydride (DIBAH), in place of
NaH, also gave discourageous results. All the results
are shown in Table 1.
Compounds 1 are expected to undergo unprece-
dented push–pull type stepwise fragmentation in-
volving elimination of selenocarbamate ion and acyl
cation through the coordinating interaction with a
soft Lewis acid.
Formation of β-1,3,5-Triselenanes 6 by Treating
Diselenoacetals 1 with SnCl4
Treating a dichloromethane, a chloroform, or a ben-
zene solution of 1a–f with TsOH or a hard Lewis acid,
such as BF3·OEt2 and TiCl4, resulted in quantitative
recovery of 1 in all cases. On the other hand, as ex-
pected, treatment of 1a–d with SnCl4 (2.0 mol amt.)
at RT under an Ar atmosphere afforded ꢀ-1,3,5-
triselenanes 6a–d [6,10,33–35], the trimers of se-
lenoaldehydes 3a–d, as the major products along
with 4 and the recovery of 1. The yields of 6a–d
were efficiently improved by the use of 3.0–5.0 mo-
lar amount of SnCl4, and in such cases neither the
stereoisomers of 6a–d nor any other bypoducts, ex-
cept for trace amounts of 4 and aldehydes 7, were
found in the crude products. In contrast, 1e and
1f were not reactive toward SnCl4 under the simi-
lar mild reaction condition. Interestingly, a similar
treatment of 1a with SnCl4 under an aerobic condi-
tion just gave benzaldehyde 7a as a main product
besides 4. All the results are shown in Table 2.
Interestingly, treatment of a chloroform solution
of 1a with SnCl4 at refluxing temperature afforded
an epimeric mixture of 1,2,4-triselenolanes 8a (10%,
approximately 1:1 mixture) [36–39] along with the
formation of selenocarbamate 9a (25%), diselenide
4 (14%), and a trace amount of 6a. A similar reac-
tion of a chloroform solution of 1e with SnCl4 at
RESULTS AND DISCUSSION
Stepwise Preparation of Bis(N,N-dimethylcar-
bamoylseleno)methanes 1 Starting from Bis-
(N,N-Dimethylcarbamoyl) Diselenide 4
Bis(N,N-dimethylcarbamoyl) diselenide
4
[30]
was at first prepared by treating dry N,N-
dimethylformamide (DMF), sodium metal, and
elemental selenium at 100–110◦C followed by
aerobic exposure at RT according to the previ-
ous reports [31]. Subsequently, stepwise treat-
ment of a DMF solution of diselenide 4 with
NaH [31,32] and a gem-dihaloalkane 5 (benzal
bromide 5a, m-chlorobenzal bromide 5b, p-
chlorobenzal bromide 5c, 1,1-dibromoethane 5d,
dibromomethane 5e, and ethyl dichloroacetate 5f,
respectively) efficiently afforded air-stable bis(N,N-

Stannic Chloride-Induced Unsymmetrical C Se Bond Cleavage of Bis(N,N-dimethylcarbamoylseleno)methanes 127
TABLE 1 Preparation of Bis(N,N-dimethylcarbamoylseleno)methanes 1
gem-Dihaloalkane 5
Hydride
Solvent
R
Y
Temperature ( ◦C)
Time (h)
Yield (%) 1
NaBH4
NaH
NaH
NaH
NaH
NaH
NaH
EtOH–DMF (1:1)a
DMFc
C H5
Br
Br
Br
Br
Br
Br
Cl
RT
RT
RT
RT
RT
RT
80
6
11
9
15
14
2
20 (1a)b
62 (1a)
51 (1b)
35 (1c)
59 (1d)
65 (1e)
46 (1f)
C6H5
DMFc
m6-ClC6H4
p-ClC6H4
CH3
DMFc
DMFc
DMFc
H
DMFc
CO2C2H5
72
aCondition: −50◦C to 0◦C for 30 min.
bDibenzyl diselenide was formed in 65% yield.
cCondition: 0◦C for 2 h.
TABLE 2 SnCl4-Induced Conversion of Bis(N,N-dimethylcarbamoylseleno)methanes 1 into β-1,3,5-Triselenanes 6
Substrate1
Yield (%)
R
Lewis Acid (mol amt.)
Solvent
Time (h)
6
7
4
Recovery
C H5 (1a)
BF3·OEt2 (2.0)
SnCl4 (3.0)
SnCl4 (5.0)
SnCl4 (5.0)
SnCl4 (5.0)
SnCl4 (5.0)
SnCl4 (5.0)
CH2Cl2
CH2Cl2
1
1
6
6
24
6
0
0
0
16
Trace
Trace
4
0
0
Quant.
Trace
Trace
Trace
0
C6H5 (1a)
58 (6a)a
91 (6b)
83 (6c)
46 (6d)
0
Trace (7a)
m6-ClC6H4 (1b)
p-ClC6H4 (1c)
CH3 (1d)
H (1e)
CO2C2H5 (1f)
Benzene
Benzene
CH2Cl2
Benzene
Benzene
Trace (7b)
Trace (7c)
0b
0
Quant.
Quant.
6
0
0
aReferences [6,10,33–35].
bAcetaldehyde 7d was not found or detected at all in the crude mixture may be due to evaporation during the workup procedure.
refluxing temperature just gave a small amount of
solvent-insoluble polymeric compound, characteri-
zable to be polymethylene selenide (10e, approxi-
mately 20%) [40–47] by using IR spectrum, along
with an unstable compound characterized by novel
1,2,4,5-tetraselenane (11e, approximately 4%). The
similar reaction of 1f at refluxing temperature just
gave a complex mixture.
It was assumed that novel cyclic polyselenides,
8 and 11, and polymethylene selenide 10e were
formed through an aerobic oxidation of 6 in the pres-
ence of Lewis acid. However, the formation path-
way of these products remained unclear at this time
(Scheme 1).
NMR Monitoring of the Reaction of Bis(N,N-
dimethylcarbamoylseleno)phenylmethane 1a
with SnCl4
When a CDCl3 solution of 1a was treated with
SnCl4 (0.5 mol amt.) in an NMR tube at 25◦C,
1
the signals of the H NMR spectrum of the reac-
tion mixture revealed a slight downfield shift with
the complete retaining of their original symmetri-
cal spectral pattern involving a pair of singlets as-
signed to the N,N-dimethylcarbamoyl groups. Fur-
ther addition of 1.0 molar amount of SnCl4 to the
mixture also resulted in larger downfield shift of
these signals (δ = 3.12 ppm (ꢀδ = +0.29 ppm) and

128 Gong et al.
SCHEME 1 Reaction of bis(N,N-dimethylcarbamoyl seleno)methane 1a (R = C6H5) or 1e (R = H) with SnCl4 at a higher
temperature.
δ = 3.44 ppm (ꢀδ = +0.48 ppm) assigned to the N,N-
dimethylcarbamoyl group, and δ = 7.00 ppm (broad-
ening, ꢀδ = +0.89 ppm) assigned to the methine pro-
ton) with retaining the symmetrical spectral pattern
of 1a. These results excluded out the formation of
a tight 1a-SnCl4 complex in the reaction mixture,
and a weak coordinating interaction between 1a and
SnCl4 involving an association–dissociation equili-
bration was suggested [31]. Further standing of the
mixture at 25◦C for 24 h resulted in formation of
ꢀ-1,3,5-triselenane 6a (δ = 5.59 ppm) as the main
component besides diselenide 4 (δ = 3.06 and 3.17
ppm) and a trace amount of benzaldehyde 7a along
with the formation of CDCl3-insoluble products. The
On the other hand, little information was obtained
from the 13C NMR or 77Se NMR monitoring of the
reaction due to the broadening and complication of
the signals. It is noteworthy that no signal assigned
to the intermediates, such as acylselonium ion A or
selenobenzaldehyde 3a, was observed at all through-
out the NMR monitoring experiments.
Generation and Trapping of Intermediary Sele-
noaldehydes 3 and Acylselonium Ions A by
using 2,3-Dimethyl-1,3-butadiene or
Allyltrimethylsilane
Selenoaldehydes are well recognized to behave
as 2ꢁ dienophilies in Diels–Alder reactions with
1,3-butadienes to afford the corresponding [4 + 2]
1
results of H NMR monitoring of the reaction of 1a
with SnCl4 (1.5 mol amt.) at 25◦C are shown in Fig. 1.
FIGURE 1 1H NMR monitoring experiment of the reaction of bis(N,N-dimethylcarbamoylseleno)methane 1a (R = C6H5) with
SnCl4.

Stannic Chloride-Induced Unsymmetrical C Se Bond Cleavage of Bis(N,N-dimethylcarbamoylseleno)methanes 129
cycloadducts, and these reactions are generally ap-
tained in 60% yield besides diselenide 4 (5%) and
the recovery of 1a (15%). The yield of 13a was low-
ered to 10% through the similar reaction carried
out at 0◦C, and an inseparable mixture of diselenide
14a and monoselenide 15a (14a:15a = 10:1, approxi-
mately), N,N-dimethyl-3-butenamide (16 [48], 40%),
allylation product of N,N-dimethylcarbamoyl cation
(C), and 4 (11%) were obtained besides the recovery
of 1a (11%). All the results of the trapping experi-
ments using allyltrimethylsilane are given in Table 3.
We already reported a one-step conversion
of alkyl or alkenyl N,N-dimethylselenocarbamates
or N,N-dimethyltellurocarbamates into the corre-
sponding symmetrical dialkyl or dialkenyl dichalco-
genides by treating with SnCl4 [31]. However, it is
noteworthy that the independent reaction of seleno-
carbamate 13a with SnCl4 in the presence of al-
lyltrimethylsilane at 0◦C only gave the recovery of
13a besides a trace amount of complex mixture, and
the treatment of ꢀ-1,3,5-triselenane 6a with SnCl4
in the presence of allyltrimethylsilane under a simi-
lar condition just gave a mixture of 14a and 15a in
approximately 20% yield with a similar 14a:15a ra-
tio to that obtained through the reaction of 1 with
SnCl4 as shown in Scheme 3. Both 13a and 16
were regarded as the allylation products of acylselo-
nium ion A [49–58], generated through SnCl4-
induced removal of N,N-dimethylselenocarbamate
ion from 1 and N,N-dimethylcarbamoyl cation (C),
respectively, and the formation of 14a and 15a
could also be explained by Lewis acid induced
allylation of selenoaldehydes 3 generated through
SnCl4-catalyzed retro-[2 + 2 + 2]-type fragmentation
of ꢀ-1,3,5-triselenanes 6 [6].
plied to the successful trapping of in situ gener-
ated selenoaldehydes. Actually, when a benzene so-
lution of 1a–d was treated with SnCl4 at RT in the
presence of an excess amount of 2,3-dimethyl-1,3-
butadiene, the corresponding [4 + 2] cycloadducts
12a–c were obtained in moderate yields (i.e., 12a:
51%, 12b: 33%, 12c: 51%). The reaction of 1d with
SnCl4 in the presence of 2,3-dimethyl-1,3-butadiene
also formed relatively unstable cycloadduct 12d in
approximately 42% yield along with the contamina-
tion of a small amount of inseparable impurity. All
the results are shown in Scheme 2. In contrast to the
cases starting from 1a–d, treatment of 1e and 1f with
SnCl4 under a similar reaction condition only gave
the recovery of substrates, as was expected from the
results of the reactions carried out in the absence of
trapping agents.
Furthermore, when a dichloromethane solution
of 1a was treated with SnCl4 in the presence of al-
lyltrimethylsilane at −70◦C, selenocarbamate 13a,
allylation product of acylselonium ion A, was ob-
SCHEME 2 Trapping of selenoaldehydes 3 using 2,3-
dimethyl-1,3-butadiene.
TABLE 3 Reaction of Bis(N,N-dimethylcarbamoylseleno)phenylmethane 1a with SnCl4 in the Presence of Allyltrimethylsilane
Yield (%)
Temperature ( ◦C)
Time (h)
13a
14a
15a
16
4
Recovery
−70
2.5
5
60
10
0
0
0
40
5
11
15
11
0
20a
2a
aYields of diselenide14a and monoselenide 15a were estimated approximately from the integration of the 1H NMR spectrum of the mixture.

130 Gong et al.
moval of N,N-dimethylcarbamoyl cation (C) from A
at higher temperature as shown in Scheme 4. ꢀ-1,3,5-
Triselenanes 6 were assumed to be afforded through
elimination of stable N,N-dimethylcarbamoyl cation
(C) from A and the subsequent trimerization of the
resulting selenoaldehydes 3 in the final stage [4].
CONCLUSION
In conclusion, we found a new method for the gen-
eration of selenoaldehydes 3 through the reaction of
bis(N,N-dimethylcarbamoylseleno)methanes 1 with
SnCl4 as well as the evidences of stepwise frag-
mentation pathway from 1 to 3 involving the for-
mation of acylselonium ions A. Further attempts
directed toward the generation of telluroaldehy-
des through a similar route starting from bis(N,N-
dimethylcarbamoyl) ditelluride are under way in our
laboratory.
SCHEME 3 Reactions of β-1,3,5-triselenane 6a or N,N-
dimethylselenocarbamate 13a with SnCl4 in the presence of
allyltrimethylsilane.
Plausible Stepwise Pathway of SnCl4-Induced
Unsymmetrical Cleavage of
Bis(N,N-dimethylcarbamoylseleno)methanes 1
These results mentioned above just supported the
stepwise pathway of conversion of 1 into 3 involving
the formation of A at low temperature and the subse-
quent removal of N,N-dimethylcarbamoyl cation (C)
from A at higher temperature as shown in Scheme 4.
The formation of 4 could also be explained by aero-
bic oxidation of N,N-dimethylselenocarbamate ion–
SnCl4 complex B during standing and the usual
workup procedure. All results just presented us a
stepwise pathway of SnCl4-induced conversion of 1
into selenoaldehydes 3 involving the formation of
novel acylselonium ions A through weak coordinat-
ing interaction of SnCl4 with 1 and the subsequent re-
EXPERIMENTAL
Instruments
The melting points were measured in open capil-
lary tubes with a Buchi 535 micro-melting-point
apparatus and were uncorrected. H NMR spectra
were recorded on a Bruker AC-400P spectrometer
(400 MHz), and the chemical shifts of the H NMR
spectra are given in δ relative to internal tetramethyl-
silane (TMS). 13C NMR spectra were recorded on a
Bruker AC-400P spectrometer (100 MHz). 77Se NMR
spectra were recorded on a Bruker AC-400P spec-
trometer (76 MHz). Mass spectra were recorded on
1
1
SCHEME 4 Plausible stepwise pathway for the generation of selenoaldehydes 3 through the reaction of bis(N,N-
dimethylcarbamoylseleno)methanes 1 with SnCl4.

Stannic Chloride-Induced Unsymmetrical C Se Bond Cleavage of Bis(N,N-dimethylcarbamoylseleno)methanes 131
a Hitachi M-2000 mass spectrometer with electron-
7.16–7.19 (1H, m), 7.25–7.29 (2H, m), 7.53–7.55 (2H,
m); 13C NMR (CDCl3) ꢂ: 36.6 (q), 36.9 (q), 40.4 (d),
127.26 (d), 127.29 (d), 128.2 (d), 143.1 (s), 164.6 (s).
Calcd for C13H18N2O2Se2: C, 39.81; H, 4.62; N, 7.14%.
Found: C, 39.29; H, 4.59; N, 6.80%.
impact ionization at 20 or 70 eV using a direct in-
let system. IR spectra were recorded for thin film
(neat) or KBr disks on a JASCO FT/IR-7300 spec-
trometer. Elemental analyses were performed using
a Yanagimoto CHN corder MT-5.
1b (R = m-ClC6H4). Pale yellow needles, mp
93.9–95.4◦C; MS (m/z): 428 (M+; 1%, 80Se, 35Cl), 72
(CONMe2; bp); IR (KBr): 2928, 1679, 1569, 1477,
Materials
1
Column chromatography was performed using silica
gel (Merck, Cat. No. 7734 or 9385) without a
pretreatment. Dichloromethane (CH2Cl2) and chlo-
roform (CHCl3) were dried over P4O10, and were
freshly distilled before use. Hexane, benzene, and
N,N-dimethylformamide (DMF) were dried over cal-
cium hydride (CaH2) and freshly distilled before use.
Ethanol was dried over anhydrous magnesium sul-
fate (MgSO4), and was freshly distilled before use.
All the substrates and reagents, including elemental
selenium, benzal bromide, m-chlorobenzal bromide,
p-chlorobenzal bromide, 1,1-dibromoethane, dibro-
momethane, ethyl dichloroacetate, 2,3-dimethyl-
1,3-butadiene, allyltrimethylsilane, boron trifluo-
ride diethyl ether complex (BF3·OEt2), stannic
chloride (SnCl4), titanium tetrachloride (TiCl4),
p-toluenesulfonic acid, sodium metal, diisobuty-
laluminum hydride (DIBAH), sodium borohy-
dride (NaBH4), anhydrous sodium sulfate powder
(Na2SO4), and molecular sieves 4A (MS-4A) were
commercially available reagent grade, and were used
without any pretreatment.
1361, 1249, 1092, 888, 669 cm−1; H NMR (CDCl3)
δ: 2.87 (6H, s), 3.00 (6H, s), 6.05 (1H, s), 7.15–7.54
(4H, m); 13C NMR (CDCl3) δ: 36.7 (q), 36.8 (q), 39.2
(d), 126.4 (d), 127.3 (d), 128.3 (d), 129.4 (d), 133.8
(s), 145.1 (s), 164.2 (s). Calcd for C13H17ClN2O2Se2:
C, 36.60; H, 4.02; N, 6.57%. Found: C, 37.27; H, 4.12;
N, 6.46%.
1c (R = p-ClC6H4). Colorless needles, mp 115.8–
117.7◦C; MS (m/z): 428 (M+; 10%, 80Se, 35Cl), 276
(M+ − SeCONMe2; 49%, 80Se, 35Cl), 224 (M+ − p-
ClC6H4CHSe; 5%, 80Se, 35Cl), 72 (CONMe2; bp); IR
(KBr): 2922, 2852, 1664, 1588, 1508, 1485, 1362,
1
1256, 1097, 835 cm−1; H NMR (CDCl3) δ: 2.87 (6H,
s), 3.00 (6H, s), 6.05 (1H, s), 7.22–7.27 (2H, m), 7.47–
7.50 (2H, m); 13C NMR (CDCl3) δ: 36.7 (q), 36.9 (q),
39.2 (d), 128.3 (d), 129.6 (d), 132.8 (s), 141.8 (s), 164.4
(s). Calcd for C13H17ClN2O2Se2: C, 36.60; H, 4.02; N,
6.57%. Found: C, 36.43; H, 4.08; N, 6.52%.
1d (R = CH3). Yellow oil; MS (m/z): 332 (M+;
1%, 80Se), 260 (M+ − CONMe2; 3%, 80Se), 224 (M+ −
CH3CHSe; 5%, 80Se), 72 (CONMe2; bp); IR (neat):
2920, 1661, 1480, 1439, 1362, 1257, 1090, 895 cm−1;
1H NMR (CDCl3) δ: 2.08 (3H, d, J = 7.2 Hz), 2.91
(6H, s), 3.03 (6H, s), 5.05 (1H, q, J = 7.2 Hz); 13C
NMR (CDCl3) δ: 26.6 (q), 33.6 (s), 36.4 (q), 36.9 (q),
165.2 (s). Calcd for C8H16N2O2Se2: C, 29.10; H, 4.88;
N, 8.49%. Found: C, 29.38; H, 4.59; N, 8.20%.
Synthesis of Bis(N,N-dimethylcarbamoylseleno)-
methanes 1
A 20 mL DMF solution of bis(N,N-dimethyl-
carbamoyl) diselenide (4, 906 mg, 3.00 mmol)
was treated with sodium hydride (158 mg, 6.60
mmol) at 0◦C to RT for 2 h and then with a gem-
dihaloalkane 5 (4.50 mmol) at RT for 6 h. The
reaction was quenched with an excess amount
of water, and the reaction mixture was extracted
with benzene. The organic layer was washed with
brine, and was dried over anhydrous Na2SO4
powder. After removing the solvent in vacuo, the
residual crude mixture was subjected to column
chromatographic separation on silica gel to afford
bis(N,N-dimethylcarbamoylseleno)methanes 1.
1e (R = H). Colorless needles, mp 102.7–
103.3◦C (dec.); MS (m/z): 318 (M+; 5%, 80Se), 72
(CONMe2; bp); IR (KBr): 2921, 1656, 1363, 1258,
1
1098, 896, 653 cm−1; H NMR (CDCl3) δ: 2.92 (6H,
br s), 3.04 (6H, br s), 4.32 (2H, s); 13C NMR (CDCl3)
δ: 18.1 (t), 36.7 (q), 37.1 (q), 165.2 (s). Calcd for
C7H14N2O2Se2: C, 26.59; H, 4.46; N, 8.86%. Found:
C, 26.66; H, 4.60; N, 8.57%.
1f (R = CO2C2H5). Yellow oil; MS (m/z): 390
(M+; 15%, 80Se), 222 (M+ − CHSeCO2C2H5; 82%,
80Se), 72 (CONMe2; bp); IR (neat): 2980, 1728, 1661,
1365, 1273, 1258, 1096, 890, 673 cm−1; 1H NMR
(CDCl3) δ: 1.23 (3H, t, J = 7.0 Hz), 2.88 (6H, br s), 2.99
(6H, br s), 4.78 (2H, q, J = 7.0 Hz), 5.52 (1H, s); 13C
NMR (CDCl3) δ: 13.9 (q), 36.4 (d), 36.8 (q), 36.9 (q),
1a (R = C6H5). Pale yellow needles, mp 184.2–
185.6◦C (dec.); MS (m/z): 394 (M+; 3%, 80Se), 250
(C6H5CHSe2; 6%, 80Se), 242 (M+ − C3H6NOSe; bp,
80Se), 170 (C6H5CHSe; 35%, 80Se); IR (KBr): 2925,
1659, 1357, 1251, 1089, 890, 698 cm−1; 1H NMR
(CDCl3) δ: 2.87 (6H, br s), 2.99 (6H, br s), 6.12 (1H, s),

132 Gong et al.
62.4 (t), 163.7 (s), 170.2 (s). Calcd for C10H18N2O4Se2:
C, 30.93; H, 4.64; N, 7.22%. Found: C, 31.08; H, 4.51;
N, 7.06%.
Calcd for C6H12Se3: C, 22.45; H, 3.77%. Found: C,
22.51, H, 3.76%.
Reaction of Bis(N,N-dimethylcarbamoylseleno)-
phenylmethane 1a with SnCl4 under an Aerobic
Condition
Reaction of Bis(N,N-dimethylcarbamoylseleno)-
methanes 1 with SnCl4
A dry dichloromethane or benzene solution of 1
(1.00 mmol) was treated with SnCl4 (1.305 g, 5.00
mmol) at RT under an Ar atmosphere for a few hours.
The reaction was quenched with an excess amount of
aqueous NaHCO3 solution, and the reaction mixture
was extracted with chloroform. The organic layer
was washed with water, and was dried over anhy-
drous Na2SO4 powder. After removing the solvent in
vacuo, the residual crude mixture was subjected to
chromatographic separation on silica gel to afford
ꢀ-1,3,5-triselenanes 6.
A
dichloromethane solution of 1a (392 mg,
1.00 mmol) was treated with SnCl4 (1.305 g,
5.00 mmol) at RT under an aerobic condition for 4 h.
The reaction was quenched with an excess amount of
aqueous NaHCO3solution, and the reaction mixture
was extracted with chloroform. The organic layer
was washed with water, and was dried over anhy-
drous Na2SO4 powder. After removing the solvent in
vacuo, the residual crude mixture was subjected to
chromatographic separation on silica gel to obtain
benzaldehyde 7a and 4.
6a (R = C6H5). (Known compound); colorless
needles, mp 197.7–198.5◦C (lit. [6, 35], 195.0–
208.0◦C); MS (m/z): 170 (M+/3; bp, 80Se); IR (KBr):
2927, 1491, 1475, 1450, 777, 697, 479 cm−1; 1H NMR
(CDCl3) δ: 5.59 (3H, s), 7.27–7.36 (15H, m); 13C NMR
(CDCl3) δ: 45.8 (d), 127.8 (d), 128.5 (d), 129.1 (d),
139.2 (s). Calcd for C21H18Se3: C, 49.72; H, 3.58%.
Found: C, 49.57; H, 3.54%.
Reaction of Bis(N,N-dimethylcarbamoylseleno)-
methane 1a with SnCl4 at a Higher Temperature
A 10 mL chloroform solution 1a (392 mg, 1.00 mmol)
was treated with SnCl4 (783 mg, 3.00 mmol) at reflux-
ing temperature for 16 h in the presence of MS-4A.
The reaction was quenched with an excess amount
of aqueous NaHCO3 solution, and the mixture was
extracted with chloroform. The organic layer was
washed with water, and was dried over anhydrous
Na2SO4 powder. After removing the solvent in vacuo,
the crude mixture was subjected to column chro-
matographic separation on silica gel to afford a cis–
trans mixture of 1,2,4-triselenolane 8a (about 1:1,
6b (R = m-ClC6H4). Colorless needles, mp
180.7–183.3◦C; MS (m/z): 204 (M+/3; bp, 80Se, 35Cl),
169 (m-ClC6H4CSeH–Cl; 31%, 80Se, 35Cl), 155 (bp);
IR (KBr): 3067, 1590, 1471, 1422, 1130, 1076, 874,
790, 711 cm−1; 1H NMR (CDCl3) δ: 5.50 (3H, s),
7.25–7.45 (12H, m); 13C NMR (CDCl3) δ: 44.8 (d),
125.9 (d), 127.9 (d), 128.9 (d), 130.5 (d), 134.9 (s),
140.5 (s). Calcd for C21H15Cl3Se3: C, 41.31; H, 2.48%.
Found: C, 41.47; H, 2.45%.
1
estimated by the integration of H NMR spectra of
the mixture), selenocarbamate 9a, and diselenide
4. The mixture of 8a was subjected to repeated
column chromatography on silica gel to obtain a
small amount of one isomer of 8a (isomer 1).
6c (R = p-ClC6H4). (Known compound); color-
less needles, mp 183.1–186.1◦C (lit. [10], 184.0–
185.0◦C); MS (m/z): 276 (bp), 274 (5%), 224 (42%),
206 (M+/3; 3%, 80Se, 37Cl), 204 (M+/3; 18%, 80Se, 35Cl),
203 (M+/3-1; 27%, 80Se, 35Cl); IR (KBr): 2930, 1487,
8a (R = C6H5, Isomer-1). Orange crystals, mp
99.4–100.6◦C (dec.); MS (m/z): 420 (M+; 2%, 80Se),
250 (PhCHSe2; 2%, 80Se), 170 (PhCHSe; bp, 80Se);
IR (KBr): 3025, 2925, 1491, 1449, 775, 695, 668,
632 cm−1; 1H NMR (CDCl3) δ: 6.91 (2H, s), 7.21–7.36
(6H, m), 7.65–7.68 (4H, m); 13C NMR (CDCl3) δ: 55.8
(d), 127.7 (d), 128.5 (d), 128.8 (d), 139.0 (s); 77Se NMR
(CDCl3) δ: 660.7, 701.0.
1
1404, 1102, 1011, 835, 756, 729, 647 cm−1; H NMR
(CDCl3) δ: 5.51 (3H, s), 7.32–7.38 (12H, m); 13C NMR
(CDCl3) δ: 44.8 (d), 129.1 (d), 129.5 (d), 134.5 (s),
137.2 (s). Calcd for C21H15Cl3Se3·CHCl3: C, 36.13; H,
2.20%. Found: C, 36.48; H, 2.37%.
6d (R = CH3). (Known compound); yellow nee-
dles, mp 139.1–140.3◦C (lit. [34], 144◦C); MS (m/z):
324 (M+; 21%, 80Se), 108 (M+/3; 94%, 80Se), 55 (bp);
IR (KBr): 2948, 1436, 1370, 1153, 1027, 960 cm−1; 1H
NMR (CDCl3) δ: 1.82 (9H, d, J = 7.0 Hz), 4.35 (3H,
q, J = 7.0 Hz); 13C NMR (CDCl3) δ: 21.8 (q), 34.1 (d).
8a (R = C6H5, Isomer-2). Orange crystals, mp
102.5–104.0◦C (dec.); MS (m/z): 420 (M+; 3%, 80Se),
250 (PhCHSe2; 5%, 80Se), 170 (PhCHSe; bp, 80Se);
IR (KBr): 3025, 2936, 1490, 776, 771, 694, 643 cm−1;
1H NMR (CDCl3) δ: 6.48 (2H, s), 7.32–7.36 (6H, m),
7.74–7.77 (4H, m).

Stannic Chloride-Induced Unsymmetrical C Se Bond Cleavage of Bis(N,N-dimethylcarbamoylseleno)methanes 133
9a (R = C6H5). Yellow oil; MS (m/z): 413 (M+;
the residual crude mixture was subjected to column
chromatographic separation on silica gel to afford
the corresponding [4 + 2] cycloadducts 12.
2%, 80Se), 322 (M+ − CH2Ph; 10%, 80Se), 261
(M+ − SeCONMe2; bp, 80Se); IR (neat): 3026, 2928,
1668, 1493, 1361, 1094, 893, 760, 696 cm−1; 1H NMR
(CDCl3) δ: 2.88 (3H, s), 2.98 (3H, s), 3.85 (2H, dd,
J = 5.1 Hz), 5.66 (1H, s), 7.17–7.44 (10H, m); 13C
NMR (CDCl3) δ: 31.9 (t), 36.7 (q), 36.9 (q), 39.1 (d),
126.8 (d), 127.5 (d), 128.0 (d), 128.5 (d), 128.6 (d),
129.0 (d), 138.2 (s), 142.2 (s), 164.9 (s). Calcd for
C17H19NOSe2: C, 49.65; H, 4.66; N, 3.41%. Found: C,
49.73; H, 4.63; N, 3.15%.
12a (R = C6H5). (Known compound) [12, 15].
12b (R = m-ClC6H4). Pale yellow oil; MS (m/z):
286 (M+; 55%, 80Se, 35Cl), 206 (M+ − Se; 45%, 80Se,
35Cl), 204 (M+ − H2Se; bp, 35Cl); IR (neat): 2919,
1598, 1569, 1474, 1428, 1381, 1079, 882, 785, 739,
694 cm−1; 1H NMR (CDCl3) δ: 1.74 (3H, s), 1.83 (3H,
s), 2.51 (1H, dd, J = 16.7, 2.6 Hz), 2.67 (1H, dd,
J = 16.4, 10.0 Hz), 3.11 (1H, d, J = 14.9 Hz), 3.39
(1H, d, J = 14.9 Hz), 4.15 (1H, dd, J = 10.1, 4.1 Hz),
7.17–7.33 (4H, m); 13C NMR (CDCl3) δ: 19.8 (q), 20.7
(q), 24.1 (dd), 38.0 (d), 40.5 (dd), 125.0 (s), 125.7 (d),
127.0 (d), 127.6 (d), 129.7 (s), 134.2 (s), 145.7 (s).
Calcd for C13H15ClSe: C, 54.66; H, 5.29%. Found: C,
55.04; H, 5.21%.
Reaction of Bis(N,N-dimethylcarbamoylseleno)-
methane 1e with SnCl4 at a Higher Temperature
A 10 mL chloroform solution 1e (316 mg, 1.00 mmol)
was treated with SnCl4 (783 mg, 3.00 mmol) at reflux-
ing temperature for 16 h in the presence of MS-4A.
The reaction was quenched with an excess amount
of aqueous NaHCO3 solution, and the mixture was
extracted with chloroform. The organic layer was
washed with water, and was dried over anhydrous
Na2SO4 powder. After removing the solvent in vacuo,
the crude mixture was subjected to column chro-
matographic separation on silica gel to afford insolu-
ble compound 10e, characterized to polymethylene
selenide, and 1,2,4,5-tetraselenane 11e, along with
diselenide 4 and trace amounts of uncharacterized
products.
12c (R = p-ClC6H4). (Known compound) [12];
pale yellow oil; MS (m/z): 286 (M+; bp, 80Se, 35Cl);
IR (neat): 2988, 2915, 1490, 1407, 1089, 1014, 829,
738 cm−1; 1H NMR (CDCl3) δ: 1.74 (3H, s), 1.83 (3H,
s), 2.50 (1H, dd, J = 16.7, 3.2 Hz), 2.66 (1H, dd,
J = 16.7, 10.0 Hz), 3.10 (1H, d, J = 14.9 Hz), 3.39
(1H, d, J = 14.9 Hz), 4.17 (1H, dd, J = 10.0, 4.1 Hz),
7.20–7.32 (4H, m); 13C NMR (CDCl3) δ: 19.8 (q), 20.8
(q), 24.0 (dd), 37.7 (d), 40.6 (dd), 125.0 (s), 128.3
(d), 128.6 (d), 129.1 (s), 132.4 (s), 142.2 (s). Calcd
for C13H15ClSe: C, 54.66; H, 5.29%. Found: C, 54.42;
H, 5.20%.
10e (R = H). Colorless solid, mp 170.3–172.1◦C
(lit. [47], 165◦C); IR (KBr): 3040, 1605, 1402, 1383,
1231, 1118, 700, 466 cm−1.
12d (R = CH3). Pale yellow oil; MS (m/z): 190
(M+; 47%, 80Se), 109 (M+ − Se-1; 7%), 67 (C5H7;
bp); IR (neat): 2957, 2868, 1668, 1455, 1375, 1216,
759 cm−1; 1H NMR (CDCl3) δ: 1.39 (3H, d, J = 6.8 Hz),
1.72 (3H, s), 1.78 (3H, s), 2.18 (1H, dd, J = 15.6, 9.9
Hz), 2.31 (1H, dd, J = 15.6, 2.6 Hz), 2.98 (1H, d,
J = 14.8 Hz), 3.19 (1H, dd, J = 9.6, 4.1 Hz), 3.25 (1H,
d, J = 14.7 Hz).
11e (R = H). Yellow crystals, mp 94◦C; MS
(m/z): 348 (M+; 78%, 80Se), 174 (CH2Se2; 54%, 80Se),
94 (CH2Se; 63%, 80Se); IR (KBr): 2915, 1347, 1117,
1089, 761, 739 cm−1; 1H NMR (CDCl3) δ: 4.62 (4H, s).
Calcd for C2H4Se4: C, 6.99; H, 1.17%. Found: C, 7.36;
H, 1.31%.
Reaction of Bis(N,N-dimethylcarbamoylseleno)-
methanes 1 with SnCl4 in the Presence of 2,3-Di-
methyl-1,3-butadiene
Reaction of Bis(N,N-dimethylcarbamoylseleno)-
methane 1a with SnCl4 in the Presence of Allyl-
trimethylsilane
2,3-Dimethyl-1,3-butadiene (411 mg, 5.00 mmol)
was added to
a
dry benzene solution of
1
Allyltrimethylsilane (571 mg, 5.00 mmol) was added
to a dry dichloromethane solution of 1a (392 mg,
1.00 mmol), then the reaction mixture was treated
with SnCl4 (1.305 g, 5.00 mmol) at 0◦C or −70◦C
for a few hours under an Ar atmosphere. The reac-
tion was quenched with an excess amount of aque-
ous NaHCO3 solution, and the reaction mixture was
extracted with chloroform. The organic layer was
washed with water and was dried over anhydrous
(1.00 mmol), and then the reaction mixture was
treated with SnCl4 (1.305 g, 5.00 mmol) at RT for
a few hours under an Ar atmosphere. The reac-
tion was quenched with an excess amount of aque-
ous NaHCO3 solution, and the reaction mixture was
extracted with chloroform. The organic layer was
washed with water, and was dried over anhydrous
Na2SO4 powder. After removing the solvent in vacuo,

134 Gong et al.
Na2SO4 powder. After removing the solvent in vacuo,
the residual crude mixture was subjected to chro-
matographic purification using silica gel to separate
products 13a,16, and the inseparable mixture of 14a
and 15a.
of aqueous NaHCO3 solution, and the mixture was
extracted with chloroform. The organic layer was
washed with water, and was dried over anhydrous
Na2SO4 powder. After removing the solvent in vacuo,
the crude mixture was subjected to column chro-
matographic separation on silica gel to afford the
inseparable mixture of diselenide 14a and monose-
lenide 15a as the main components.
13a (R = C6H5). Pale yellow oil; MS (m/z): 283
(M+; 2%, 80Se), 153 (SeCONMe2; 23%, 80Se), 131
(M+ − SeCONMe2; bp), 72 (CONMe2; 98%); IR (neat):
2924, 1731, 1667, 1454, 1361, 1260, 896, 699 cm−1;
1H NMR (CDCl3) δ: 2.80 (3H, s), 2.84–2.90 (2H, m),
2.93 (3H, s), 4.64 (1H, t, J = 8.6 Hz), 4.96 (1H, br d,
J = 10.0 Hz), 5.04 (1H, br d, J = 17.0 Hz), 5.70 (1H,
ddt, J = 17.0, 10.0, 6.9 Hz), 7.14–7.33 (5H, m); 13C
NMR (CDCl3) δ: 36.3 (q), 36.9 (q), 40.9 (t), 47.0 (d),
116.8 (br s), 126.8 (d), 127.7 (br s), 128.3 (d), 135.7
(d), 142.2 (s), 164.9 (s). Calcd for C13H17NSe: C, 55.32;
H, 6.07; N, 4.96%. Found: C, 55.67; H, 6.12; N, 4.83%.
ACKNOWLEDGMENTS
We thank Ms. Yoriko Fujisawa in Iwate University
for the elemental analysis measurement.
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