An indium-TMSCl promoted reaction of diphenyl diselenide and diorganyl disulfides with aldehydes: novel routes to selenoacetals, thioacetals and alkyl phenyl selenides

Article abstract of DOI:10.1016/j.tet.2008.12.079

The reactions of diphenyl diselenide and dialkyl disulfides with aldehydes in the presence of In-TMSCl have been investigated. Aliphatic aldehydes provide the corresponding selenoacetals and aromatic aldehydes lead predominantly to benzyl phenyl selenides

Full text of DOI:10.1016/j.tet.2008.12.079

Tetrahedron 65 (2009) 2072–2078
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An indium–TMSCl promoted reaction of diphenyl diselenide and diorganyl
disulfides with aldehydes: novel routes to selenoacetals, thioacetals and alkyl
phenyl selenides
*
Brindaban C. Ranu , Amit Saha, Tanmay Mandal
Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The reactions of diphenyl diselenide and dialkyl disulfides with aldehydes in the presence of In–TMSCl
have been investigated. Aliphatic aldehydes provide the corresponding selenoacetals and aromatic al-
dehydes lead predominantly to benzyl phenyl selenides on reaction with diphenyl diselenide. However,
the reaction of dimethyl disulfide and diphenyl disulfide with both aromatic and aliphatic aldehydes
produce dithioacetals. This provides a novel route to the synthesis of selenoacetals, thioacetals and
selenides from aldehydes.
Received 15 September 2008
Received in revised form 26 November 2008
Accepted 27 December 2008
Available online 8 January 2009
Keywords:
Selenoacetal
Thioacetal
Ó 2009 Elsevier Ltd. All rights reserved.
Selenides
Indium
Trimethylsilyl chloride
Aldehydes
1. Introduction
2. Results and discussion
Indium metal and its derivatives have been found to have great
potential for organic transformations and have generated new in-
teresting chemistry.1 As a part of our continued activities to develop
novel synthetic procedures using indium and indium derivatives,1e,2
recently we have communicated an interesting reaction of diphenyl
diselenide with aldehydes promoted by In–TMSCl.2r Aliphatic al-
dehydes provided the corresponding selenoacetals, whereas aro-
matic aldehydes produced predominantly benzyl phenyl selenides
under the same reaction conditions. This prompted us to investigate
the scope of this reaction in more detail and we considered to study
the reaction of dialkyldisulfides and aldehydes in the presence ofIn–
TMSCl. In contrast to the results with diphenyl diselenide we ob-
served uniform formation of dithioacetals from both aliphatic and
aromatic aldehydes using dimethyl disulfide and diphenyl disulfide.
We report here the detail of our earlier communication2r with in-
clusion of a few more aldehydes and the recent results of reaction
with disulfides (Scheme 1).
The experimental procedure is very simple. A mixture of
diphenyl diselenide/dialkyl disulfide, an aldehyde and trime-
thylsilyl chloride in acetonitrile was heated under reflux in the
presence of indium metal for a period of time (Tables 1 and 2).
Standard work-up and extraction with ether provided the product.
A wide range of structurally diverse aliphatic and aromatic alde-
hydes underwent reactions with diphenyl diselenide by this pro-
cedure to produce the corresponding products. The results are
summarized in Table 1. All the aliphatic aldehydes produced the
corresponding selenoacetals (entries 1–7, Table 1) whereas the
aromatic aldehydes furnished exclusively (entries 8–15, Table 1) or
predominantly (entries 16–18, Table 1) the corresponding benzyl
phenyl selenides. In sharp contrast, 4-fluorobenzaldehyde pro-
duced more selenoacetal than selenide (entry 19, Table 1). Al-
though, in general halo-substituted benzaldehydes led to mixtures
R = alkyl
PhSeSePh
In, TMSCl
CH3CN
reflux
R1SSR1
RCH(SePh)2
In, TMSCl
RCH(SR1)2
RCHO
RCH(SePh)2
+
RCH2SePh
CH3CN, reflux
R1 = Me, Ph
R = aryl
R = alkyl, aryl
* Corresponding author. Tel.: þ91 33 24734971; fax: þ91 33 24732805.
E-mail address: ocbcr@iacs.res.in (B.C. Ranu).
Scheme 1. Reaction of aldehydes with diselenides/disulphides in presence of In–
TMSCl.
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.12.079

B.C. Ranu et al. / Tetrahedron 65 (2009) 2072–2078
2073
Ref.
Table 1
Indium–TMSCl promoted reaction of aldehydes with diphenyl diselenide
Entry
1
Aldehyde
Time (h)
2.0
Product
Yielda (%)
70
( )
( )
2 CH(SePh)2
2 CHO
( )
6CH(SePh)2
( )
2
3
4
5
6
7
2.5
2.5
2.5
4.5
2.0
2.0
78
72
76
75
71
80
6 CHO
( )
8 CH(SePh)2
( )
8 CHO
( )
12CH(SePh)2
( 1)2CHO
( )2
( )
Ph
CH(SePh)2
Ph 2 CHO
CH(SePh)2
CHO
CHO
CH(SePh)2
8
7.0
75
2j
CHO
CH2SePh
CH2SePh
CHO
9
5.5
3.5
76
72
MeS
MeS
CHO
CH2SePh
10
AllylO
AllylO
OMe
OMe
CHO
CH2SePh
11
2.5
65
Me2N
AcO
Me2N
AcO
CH2SePh
CH2SePh
CHO
12
13
2.5
3.0
75
73
CHO
OMe
OMe
CHO
CH2SePh
14
15
3.5
3.5
72
74
OMe
OMe
CH2SePh
CHO
MeO
O
MeO
CH2SePh
CH(SePh)2
CHO
CHO
+
16
17
18
4.0
7.0
6.5
80
70
75
2j
O
O
O
O
O
(86:14)
CH2SePh
CH(SePh)2
CH(SePh)2
+
Br
Br
Br
(88:12)
CH2SePh
CHO
CHO
+
2j
Cl
F
Cl
(85:15)
CH2SePh
Cl
F
CH(SePh)2
+
19
20
6.0
65
F
(25:75)
Cl
Cl
CH2SePh
CHO
Cl
6.0
5.5
63
72
14
Cl
CH2SePh
CHO
21
TsO
TsO
a
Yields refer to those of pure and isolated products characterized by IR, 1H and 13C NMR spectroscopic data.

2074
B.C. Ranu et al. / Tetrahedron 65 (2009) 2072–2078
Table 2
OSiMe3
XR1
2 TMSCl
In
X = S; R1 = Ph, Me
R1XSiMe3
1
R1XXR1
TMSCl
Indium–TMSCl promoted protection of aldehydes as dithioacetals
RCH
RCHO
X = Se; R1 = Ph
2
SR1
R = alkyl, aryl
In / TMSCl
CH3CN
reflux
+ R1SSR1
R
RCHO
R1XSiMe3
SR1
Yielda (%)
.
XR1
XR1
Entry
1
Aldehyde
Disulfide
Time (h)
2
Ref.
15
In
In
RCHXR1
RCHXR1
RCH
3
( X = Se, R1 = Ph, R = aryl )
5
4
CHO
CHO
CHO
H3O
MeSSMe
PhSSPh
76
70
73
72
67
68
65
RCH2XR1
2
3
4
5
6
7
3
16
15
15
6
Scheme 2. Probable mechanism.
MeSSMe
MeSSMe
MeSSMe
MeSSMe
MeSSMe
2
MeO
Cl
CHO
CHO
CHO
producing the corresponding dimethylthioacetals, which are diffi-
cult to achieve using gaseous methanethiol by conventional
procedures.
2
1.5
2
In general, the reactions were clean and reasonably fast. The
products were obtained in high purities. Although a few aromatic
aldehydes (entries 16–19, Table 1) led to mixtures of selenides and
selenoacetals these could be separated by careful column chro-
matography. All the compounds were characterized by their spec-
troscopic data. The reaction did not proceed at all either in absence
of TMSCl or indium metal. The combination of In and TMSCl is thus
essential for this reaction. The replacement of TMSCl by BF3$Et2O
also did not produce any result. Acetonitrile was found to provide
the best results in terms of yields and reaction time compared to
other solvents like THF and dioxane.
It is suggested that indium cleaves the diselenide/disulfide bond
to form a transient indium–selenoate/thiolate complex, which on
reaction with TMSCl produces alkylseleno/thiotrimethylsilane 1
(R1XSiMe3),3 which then interacts with the aldehyde to give the
intermediate 2, ultimately leading to diseleno/thioacetal 3, as
outlined in Scheme 2. The formation of R1XSiMe3 was indicated by
the presence of the corresponding molecular ion peak (183.0368
for MþH) in HRMS of a sample from the reaction mixture of PhSSPh
and In–TMSCl in dry CH3CN. Possibly, TMSCl acts as Lewis acid
during the formation of the intermediate 2 activating aldehydes
towards nucleophilic attack by R1XSiMe3. As indium metal is well
known one-electron reducing agent it is more likely that selenoa-
cetal 3 undergoes homolytic cleavage followed by anion formation
to lead to selenides 6 in reactions of aromatic aldehydes. The in-
termediacy of a free radical species gains support when we found
that a radical quencher considerably affects the course of the re-
action of aromatic aldehydes. Thus, when the reaction of
2-methoxybenzaldehyde (entry 13, Table 1) was carried out in
presence of a quencher, 4-hydroxy TEMPO under reflux for 5 h, the
formation of the corresponding selenide was considerably di-
minished; a 1:1 mixture of selenoacetal and selenide being
obtained whereas in the normal reaction the selenide was obtained
as the only isolable product after 3 h. In contrast, the quencher had
no effect on the conversion of an aliphatic aldehyde (decanal, entry
3, Table 1) to the selenoacetal.
AcO
TsO
CHO
2.5
17
CHO
8
9
MeSSMe
MeSSMe
3
4
78
73
F
Cl
CHO
Cl
(
(
(
(
)
10
11
12
13
MeSSMe
PhSSPh
PhSSPh
PhSSPh
2
3
2
2
70
69
72
75
18
19
20
21
8CHO
)
6CHO
)
4CHO
)
2CHO
14
PhSSPh
2
73
19
CHO
a
The yields refer to those of pure isolated products characterized by IR, 1H NMR
and 13C NMR spectroscopic data.
of selenoacetals and selenides, 2,6-dichlorobenzaldehyde provided
the corresponding selenide as the only isolable product (entry 20,
Table 1), probably due to steric inhibition by two adjacent Cl
groups. It was found that an isolated pure selenoacetal of 3-bro-
mobenzaldehyde was converted to the corresponding selenide
under the same reaction conditions after 6 h. Thus, in the reactions
of aromatic aldehydes where a mixture of benzyl phenyl selenides
and selenoacetals was produced, the proportion of selenides was
increased at the cost of selenoacetals after longer periods although
100% conversion was not achieved. When the reactions of aliphatic
aldehydes were allowed to proceed for longer periods, no alkyl
selenides were obtained. Thus, it is likely that the reactions of ali-
phatic aldehydes stopped at the selenoacetal stage whereas re-
actions of aromatic aldehydes proceeded further to produce
selenides. Based on these observations we propose a mechanism as
outlined in Scheme 2.
Several aromatic and aliphatic aldehydes underwent reactions
with dialkyl and diaryl disulfide by this procedure to provide the
corresponding dithioacetals. The results are summarized in Table 2.
The reaction was uniform with aromatic as well aliphatic alde-
hydes. Several functionalities present in the aromatic ring such as
OMe, OTs, OAc, Cl, F are compatible with the reaction conditions.
The nature of substitution at the aromatic ring did not make much
difference in reactivity and yields. Dimethyl disulfide reacted with
several aromatic and aliphatic aldehydes (entries 1, 3–10, Table 2)
In diphenyl diselenide reactions (X¼Se, Scheme 2) the stability
of the benzylic radical 4 determines the further progress of the
reaction. Thus, the reaction of aromatic aldehydes (R¼Ph) in gen-
eral ended in the formation of selenides. The aliphatic aldehydes
being unable to provide this stability stopped at the selenoacetal
stage. In reactions with dialkyl disulfides (X¼S, Scheme 2) the ho-
molytic cleavage of 3 is not as facile as in selenide reactions,
probably because of the higher polarity of C–S bond compared to
C–Se bond4 and the lower stability of the thio-carbanion 5 (X¼S)
compared to seleno-carbanion. The seleno-carbanion also acquires
more stability having appreciable contribution from the resonance
structures A and B.4 On the other hand, sulfur being considerably

B.C. Ranu et al. / Tetrahedron 65 (2009) 2072–2078
2075
more electronegative this type of resonance stabilization is un-
likely. Thus, reaction of dialkyl disulfides did not go further and
ended with the formation of thioacetal.
access to benzyl phenyl selenides from aromatic aldehydes and an
alternative thiol-free process for dithioacetalization of aldehydes
providing a practical alternative to the preparation of dimethylth-
ioacetal, difficult to achieve by conventional methods using meth-
anethiol. Moreover, it demonstrates further potential of In–TMSCl
reagent for organic transformations.
Se
R
Se
CH
R
CH
A
B
Selenoacetals are versatile intermediates in organic synthesis
and have played a crucial role in the development of organo-
selenium chemistry.5 They are stable in basic and mildly acidic
conditions, inert to Grignard reagents and thus have similar prop-
erties to their oxygen and sulfur analogues. They can also be useful
for carbonyl protection.5 Usually, selenoacetals are prepared from
the corresponding carbonyl compounds by reaction with selenols
or [B(SeMe)3] under the catalysis of protic or Lewis acids.6 Alter-
natively, they can be prepared by exchange reactions between O-
acetals and tris(phenylseleno)borane.7 However, all these
reagentsdselenols and tris(alkylseleno)boranedare usually pre-
pared from dialkyl diselenides.6 Thus, the present procedure in-
volving diphenyl diselenide would be more convenient and
practical.
Organic selenides are of considerable interest in academia as
well as in industry because of their wide involvement in organic
synthesis8a and their biological actitivies.8b Although a number of
procedures for the synthesis of dialkyl/alkyl aryl selenides have
been reported9 most of them use alkyl halides as starting materials.
To the best of our knowledge no method is available starting from
aldehydes. Thus the present protocol (Scheme 1) provides new
routes for the synthesis of selenoacetals and benzyl phenyl
selenides.
Among various carbonyl protecting groups dithioacetals are
preferred because of their inherent stability under both acidic and
basic conditions.10 In addition, dithioacetals are also used as pre-
cursors for acyl anions and as intermediates in the conversion of
a carbonyl group into a hydrocarbon derivative.11 A number of
procedures using thiols and a variety of protic and Lewis acids,
metal salts as catalysts have been developed for thioacetalization of
carbonyl compounds. The catalysts employed are perchloric acid
supported on silica,12a Amberlyst-15,12b RuCl3,12c p-TsOH on silica
gel,12d Pr(OTf)3,12e Sc(OTf)3,12f MoO2(acac)2,12g NiCl2,12h NBS,12i
InCl3,12j tungstophosphoric acid,12k InBr3,12l LiOTf,12m tetrabutyl-
ammonium bromide,12n among others. Many of these procedures
were associated with drawbacks such as low yields and long re-
action time. Moreover, a couple of practical disadvantages re-
garding handling of thiols are their inherent foul odour and gaseous
state for methanethiol. Thus, thiol-free alternative methods using
stable (solid/liquid) dialkyl disulfides having relatively less odour
are appreciated and procedures using dialkyl disulfide and tribu-
tylphosphine,13a methylthiotrimethylsilane3 have been introduced.
However, use of tributylphosphine entails a waste of tribu-
tylphosphine oxide and purification of products from tribu-
tylphosphine oxide is also very tedious. The other reagent,
methylthiotrimethylsilane is very expensive. On the other hand,
this is highly moisture sensitive and very difficult to prepare.3 Thus,
our procedure of thioacetal formation from aldehydes using dialkyl
disulfide provides a better alternative.
4. Experimental
4.1. General
Indium metal (SRL, India), cut into small pieces was used for all
reactions. Trimethylchlorosilane was freshly distilled before use. IR
spectra were taken as thin films for liquid compounds and as KBr
pellets for solids. 1H NMR and C NMR spectra were recorded in
13
CDCl3 solutions at 300 and 75 MHz, respectively. Elemental analysis
was done using a Perkin–Elmer autoanalyzer at IACS.
4.1.1. General experimental procedure for the synthesis of
selenoacetals and aryl phenyl selenides. Representative procedure
for 1,1-diphenylselenooctane (entry 2, Table 1)
To a stirred solution of diphenyl diselenide (1 mmol, 312 mg)
and trimethylsilyl chloride (2 mmol, 218 mg) in dry acetonitrile
(3 mL) was added octanal (1 mmol, 128 mg) and the mixture was
stirred for 2 min at room temperature. The reaction mixture was
then heated under reflux with indium metal (1 mmol, 115 mg, cut
into small pieces) for 2.5 h (TLC). After completion of the reaction
acetonitrile was evaporated off in vacuo and the residue was
extracted with ether (10ꢀ3 mL). The combined ether extract was
then washed with brine, dried (Na2SO4) and evaporated to leave the
crude product, which was purified by column chromatography over
silica gel (hexane–ether 98:2) to furnish the pure 1,1-diphenylse-
lenooctane as a yellow liquid (331 mg, 78%). IR (neat): 1436, 1475,
1578 cmꢁ1
;
1H NMR (300 MHz, CDCl3):
d: 0.78 (t, J¼6.6 Hz, 3H),
1.13–1.18 (m, 7H), 1.46–1.49 (m, 3H), 1.80–1.89 (m, 2H), 4.40 (t,
J¼6.5 Hz,1H), 7.16–7.22 (m, 6H), 7.48–7.51 (m, 4H); 13C NMR (CDCl3,
75 MHz): d: 13.9, 22.5, 28.2, 28.7, 28.9, 31.6, 36.9, 44.0, 127.8 (2C),
128.9 (4C), 130.3 (2C), 134.5 (4C). Anal. Calcd for C20H26Se2: C,
56.61; H, 6.18. Found: C, 56.37; H, 6.03.
This procedure was followed for all the aldehydes listed in Table
1. As mentioned earlier aliphatic aldehydes produced the corre-
sponding selenoacetals (entries 1–7, Table 1) and aromatic alde-
hydes provided benzyl phenyl selenides (entries 8–15, 20, 21, Table
1) or mixtures of benzyl phenyl selenides and selenoacetals (entries
16–19, Table 1). The known compounds (entries 8, 16, 18, 20, Table
1) were identified by comparison of their spectral data with those
reported (Table 1), and the new compounds (entries 1–7, 9–15, 17,
19, 21, Table 1) were properly characterized by their IR, 1H NMR and
13C NMR spectroscopic data and elemental analysis. The data for
these compounds are presented below.
4.1.2. 1,1-Diphenylseleno butane (entry 1, Table 1)
A yellow liquid; IR (neat): 1437, 1475, 1578 cmꢁ1 1H NMR
;
(300 MHz, CDCl3)
1.94 (m, 2H), 4.49 (t, J¼6.6 Hz, 1H), 7.24–7.30 (m, 6H), 7.56–7.59 (m,
4H); 13C NMR (75 MHz, CDCl3)
: 13.2, 21.4, 43.7, 47.9, 127.8 (2C),
d
: 0.85 (t, J¼7.4 Hz, 3H), 1.51–1.64 (m, 2H), 1.87–
d
3. Conclusion
128.8 (4C), 130.2 (2C),134.5 (4C). Anal. Calcd for C16H18Se2: C, 52.19;
H, 4.93. Found: C, 51.97; H, 4.78.
In conclusion, the present procedure using the In–TMSCl pro-
vides a new route for the synthesis of selenoacetals, thioacetals and
benzyl phenyl selenides from aldehydes. The significant features of
this procedure are (a) simple one-pot operation, (b) use of stable
and readily available diselenide and disulfides as reagents, (c)
reasonably fast reaction and (d) good isolated yields of products.
Most significantly, these procedures present a novel protocol for
4.1.3. 1,1-Diphenylseleno decane (entry 3, Table 1)
A yellow liquid; IR (neat): 1436, 1475, 1578 cmꢁ1 1H NMR
;
(300 MHz, CDCl3)
1.61 (m, 3H), 1.88–1.96 (m, 2H), 4.48 (t, J¼6.5 Hz, 1H), 7.25–7.29 (m,
6H), 7.56–7.59 (m, 4H); 13C NMR (75 MHz, CDCl3)
: 14.1, 22.6, 28.3,
28.8, 29.2, 29.3, 29.4, 31.8, 37.0, 44.1, 127.9 (2C), 128.9 (4C), 130.4
d: 0.87 (t, J¼6.5 Hz, 3H), 1.21–1.29 (m, 11H), 1.52–
d

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B.C. Ranu et al. / Tetrahedron 65 (2009) 2072–2078
(2C), 134.6 (4C). Anal. Calcd for C22H30Se2: C, 58.41; H, 6.68. Found:
C, 58.25; H, 6.53.
7.16–7.25 (m, 5H), 7.41–7.45 (m, 2H); 13C NMR (75 MHz, CDCl3)
d:
20.9, 30.9, 121.3 (2C), 127.3, 128.9 (2C), 129.7 (2C), 129.9, 133.6 (2C),
136.1, 149.3, 169.3. Anal. Calcd for C15H14O2Se: C, 59.02; H, 4.62.
Found: C, 58.78; H, 4.43.
4.1.4. 1,1-Diphenylseleno tetradecane (entry 4, Table 1)
A pale yellow viscous oil; IR (neat): 1437, 1475, 1578 cmꢁ1 1H
;
NMR (300 MHz, CDCl3)
1.51–1.56 (m, 3H), 1.88–1.95 (m, 2H), 4.47 (t, J¼6.7 Hz, 1H), 7.22–
7.29 (m, 6H), 7.56–7.58 (m, 4H); 13C NMR (75 MHz, CDCl3)
: 14.0,
d
: 0.88 (t, J¼6.4 Hz, 3H), 1.06–1.35 (m, 19H),
4.1.12. (2-Methoxyphenyl)methyl phenyl selenide (entry 13,
Table 1)
d
A yellow liquid; IR (neat): 1247, 1437, 1475, 1577 cmꢁ1; 1H NMR
22.5, 28.1, 28.7, 29.2 (2C), 29.3, 29.4, 29.5 (2C), 29.54, 31.8, 36.9,
44.0, 127.8 (2C), 128.8 (4C), 130.3 (2C), 134.5 (4C). Anal. Calcd for
C26H38Se2: C, 61.41; H, 7.53. Found: C, 61.23; H, 7.42.
(300 MHz, CDCl3)
7.02–7.04 (m, 1H), 7.16–7.25 (m, 4H), 7.45–7.49 (m, 2H); 13C NMR
(75 MHz, CDCl3) : 26.7, 55.2, 110.4, 120.1, 126.9, 127.6, 128.1, 128.6
d: 3.79 (s, 3H), 4.12 (s, 2H), 6.78–6.84 (m, 2H),
d
(2C), 129.9, 131.4, 133.6 (2C), 156.9. Anal. Calcd for C14H14OSe: C,
60.66; H, 5.09. Found: C, 60.40; H, 4.88.
4.1.5. 3-Phenyl-1,1-diphenylseleno propane (entry 5, Table 1)
A pale yellow liquid; IR (neat): 1438, 1477, 1577 cmꢁ1 1H NMR
;
(300 MHz, CDCl3)
J¼6.6 Hz, 1H), 6.96–6.98 (m, 2H), 7.10–7.22 (m, 9H), 7.46–7.49 (m,
4H); 13C NMR (75 MHz, CDCl3)
: 34.8, 38.9, 43.0, 126.5, 128.4 (2C),
d
: 2.13–2.20 (m, 2H), 2.81 (t, J¼7.5 Hz, 2H), 4.34 (t,
4.1.13. (3-Methoxyphenyl)methyl phenyl selenide (entry 14,
Table 1)
d
A yellow gummy oil; IR (neat): 1263, 1436, 1475, 1583 cmꢁ1; 1H
128.9 (2C), 129.0 (2C), 129.5 (4C), 130.8, 135.2 (4C), 141.0 (2C). Anal.
Calcd for C21H20Se2: C, 58.62; H, 4.68. Found: C, 58.38; H, 4.54.
NMR (300 MHz, CDCl3)
3H), 7.06–7.11 (m, 1H), 7.15–7.19 (m, 3H), 7.37–7.40 (m, 2H); 13C
NMR (75 MHz, CDCl3) : 32.1, 54.9, 112.6, 113.9, 121.0, 127.2, 128.8
d: 3.66 (s, 3H), 4.00 (s, 2H), 6.64–6.74 (m,
d
4.1.6. 1-Cyclohexyl-1,1-diphenylseleno methane (entry 6, Table 1)
(2C),129.3, 130.3, 133.5 (2C),140.0, 159.4. Anal. Calcd for C14H14OSe:
C, 60.66; H, 5.09. Found: C, 60.42; H, 4.93.
A pale yellow liquid; IR (neat): 1437, 1475, 1577 cmꢁ1 1H NMR
;
(300 MHz, CDCl3)
(m, 4H), 1.88–1.92 (m, 1H), 4.44 (d, J¼3.1 Hz, 1H), 7.20–7.29 (m, 6H),
7.48–7.53 (m, 4H); 13C NMR (75 MHz, CDCl3)
: 26.1 (3C), 31.2 (2C),
43.9, 54.7, 127.7 (2C), 129.0 (4C), 131.4 (2C), 134.3 (4C). Anal. Calcd
for C19H22Se2: C, 55.89; H, 5.43. Found: C, 55.69; H, 5.31.
d: 1.15–1.26 (m, 2H), 1.31–1.42 (m, 4H), 1.62–1.78
4.1.14. (4-Methoxyphenyl)methyl phenyl selenide (entry 15,
Table 1)
d
A yellow gummy liquid; IR (neat): 1438, 1475, 1577 cmꢁ1 1H
;
NMR (300 MHz, CDCl3)
d
: 3.77 (s, 3H), 4.08 (s, 2H), 6.78 (d, J¼8.7 Hz,
2H), 7.12 (d, J¼8.7 Hz, 2H), 7.23–7.26 (m, 3H), 7.43–7.46 (m, 2H); 13C
4.1.7. 2-Methyl-1,1-diphenylseleno propane (entry 7, Table 1)
NMR (75 MHz, CDCl3) d: 31.6, 55.1, 113.7 (2C), 127.0, 128.8 (2C),
A yellow liquid; IR (neat): 1437, 1475, 1578 cmꢁ1
;
1H NMR
129.8 (2C), 130.4, 131.4, 133.3 (2C), 158.4. Anal. Calcd for C14H14OSe:
C, 60.66; H, 5.09. Found: C, 60.41; H, 4.88.
(300 MHz, CDCl3)
d
: 1.02 (d, J¼6.7 Hz, 6H), 2.09–2.15 (m, 1H), 4.48
(d, J¼2.9 Hz, 1H), 7.23–7.28 (m, 6H), 7.53–7.56 (m, 4H); 13C NMR
(75 MHz, CDCl3)
d
: 20.3 (2C), 33.6, 55.7, 127.6 (2C), 128.9 (4C), 131.1
4.1.15. 3-Bromophenyl-1-selenophenylmethane (entry 17, Table 1,
major)
(2C), 134.2 (4C). Anal. Calcd for C16H18Se2: C, 52.19; H, 4.93. Found:
C, 51.95; H, 4.76.
A yellow oil; IR (neat): 1437, 1475, 1577 cmꢁ1
;
1H NMR
(300 MHz, CDCl3)
d
: 4.00 (s, 2H), 7.06–7.08 (m, 2H), 7.23–7.30 (m,
4.1.8. (4-Thiomethylphenyl)methyl phenyl selenide (entry 9,
Table 1)
5H), 7.40–7.44 (m, 2H); 13C NMR (75 MHz, CDCl3)
d: 31.9, 122.7,
127.8, 128.1, 129.5 (2C), 130.1, 130.3 (2C), 132.2, 134.4 (2C), 141.5.
Anal. Calcd for C13H11BrSe: C, 47.88; H, 3.40. Found: C, 47.63; H,
3.25.
A yellow solid; mp 55–57 ꢂC; IR (KBr): 1438,1475,1577 cmꢁ1; 1H
NMR (300 MHz, CDCl3)
d
: 2.44 (s, 3H), 4.06 (s, 2H), 7.08–7.24 (m,
: 15.6, 31.7, 126.6
7H), 7.41–7.44 (m, 2H); 13C NMR (75 MHz, CDCl3)
d
(2C), 127.2, 128.3, 128.8 (2C), 129.2 (2C), 130.2, 133.5 (2C), 135.4.
Anal. Calcd for C14H14Se: C, 57.33; H, 4.81. Found: C, 57.05; H, 4.63.
4.1.16. 3-Bromophenyl-1,1-diselenophenylmethane (entry 17, Table
1, minor)
A yellow gummy liquid; IR (neat): 1436, 1473, 1576 cmꢁ1 1H
;
4.1.9. (4-Allyloxy-3-methoxyphenyl)methyl phenyl selenide (entry
10, Table 1)
NMR (300 MHz, CDCl3)
d: 5.39 (s, 1H), 7.00–7.06 (m, 1H), 7.14–7.33
(m, 8H), 7.35 (s, 1H), 7.40–7.43 (m, 4H); 13C NMR (75 MHz, CDCl3)
d
:
A yellow gummy liquid; IR (neat): 1263, 1436, 1475, 1510,
42.4, 121.9, 126.5, 128.2 (2C), 128.9 (4C), 129.6, 130.2, 130.3 (2C),
130.9, 134.7 (4C), 143.4. Anal. Calcd for C19H15BrSe2: C, 47.43; H,
3.14. Found: C, 47.19; H, 2.98.
1577 cmꢁ1 1H NMR (300 MHz, CDCl3)
; d: 3.76 (s, 3H), 4.06 (s, 2H),
4.54–4.58 (m, 2H), 5.25–5.42 (m, 2H), 6.01–6.07 (m, 1H), 6.66–6.76
(m, 3H), 7.19–7.25 (m, 3H), 7.42–7.46 (m, 2H); 13C NMR (75 MHz,
CDCl3)
d
: 32.5, 55.9, 69.9, 112.3, 113.2, 117.9, 120.8, 122.6, 127.3, 128.9
4.1.17. 1-(Bis(phenylselanyl)methyl)-4-fluorobenzene (entry 19,
Table 1, major)
A light-yellow liquid; IR (neat): 686, 734, 835, 1020, 1064, 1157,
1228, 1296, 1434, 1473, 1508, 1573, 1600, 1681, 2852, 2923, 2995,
(2C), 130.3, 133.3, 133.8 (2C), 146.9, 149.1. Anal. Calcd for
C17H18O2Se: C, 61.26; H, 5.44. Found: C, 61.06; H, 5.30.
4.1.10. (4-N,N-Dimethylphenyl)methyl phenyl selenide (entry 11,
Table 1)
3055 cmꢁ1; 1H NMR (300 MHz, CDCl3)
d
: 5.50 (s, 1H), 6.87–6.92 (m,
2H), 7.21–7.30 (m, 8H), 7.43–7.46 (m, 4H); 13C NMR (75 MHz, CDCl3)
: 42.6, 115.2 (d, JC–F¼21.6 Hz, 2C),128.4 (2C),129.1 (4C), 129.8 (d, JC–
A yellow solid; mp 62–65 ꢂC; IR (KBr): 1438, 1485, 1500,
d
1577 cmꢁ1
;
1H NMR (300 MHz, CDCl3)
d
: 2.91 (s, 6H), 4.09 (s, 2H),
6.60–6.65 (m, 2H), 7.10–7.13 (m, 2H), 7.22–7.25 (m, 3H), 7.45–7.48
(m, 2H); 13C NMR (75 MHz, CDCl3)
: 31.9, 40.5 (2C), 112.5 (2C),
¼8.3 Hz, 2C), 130.8 (2C), 134.8 (4C), 137.2, 161.9 (d, JC–F¼245.1 Hz).
F
Anal. Calcd for C19H15FSe2: C, 54.30; H, 3.60. Found: C, 54.24; H,
3.57.
d
125.8, 126.8, 128.7 (2C), 129.5 (2C), 131.1, 132.9 (2C), 149.4. Anal.
Calcd for C15H17NSe: C, 62.07; H, 5.90. Found: C, 61.85; H, 5.73.
4.1.18. (4-Fluorobenzyl)(phenyl)selane (entry 19, Table 1, minor)
A light-yellow liquid; IR (neat): 690, 736, 835, 1157, 1226, 1506,
4.1.11. (4-Acetylphenyl)methyl phenyl selenide (entry 12, Table 1)
1579, 1600, 2929, 2999, 3053 cmꢁ1 1H NMR (300 MHz, CDCl3)
; d:
A pale yellow oil; IR (neat): 1436,1475,1577,1762 cmꢁ1; 1H NMR
3.99 (s, 2H), 6.81–6.87 (m, 2H), 7.04–7.08 (m, 2H), 7.16–7.18 (m, 3H),
(300 MHz, CDCl3)
d
: 2.27 (s, 3H), 4.08 (s, 2H), 6.95 (d, J¼8.4 Hz, 2H),
7.34–7.37 (m, 2H); 13C NMR (75 MHz, CDCl3)
d:
31.4, 115.3

B.C. Ranu et al. / Tetrahedron 65 (2009) 2072–2078
2077
(d, JC–F¼21.5 Hz, 2C), 127.5, 129.1 (2C), 130.4 (d, JC–F¼8.0 Hz, 2C),
4.1.24. 2-(Bis(methylthio)methyl)-1,3-dichlorobenzene (entry 9,
Table 2)
A light-yellow liquid; IR (neat): 696, 777, 1087, 1175, 1435, 1456,
1558, 1577, 2914, 2976, 3065 cmꢁ1 1H NMR (300 MHz, CDCl3)
2.14 (s, 6H), 5.41 (s, 1H), 7.00–7.02 (m, 1H), 7.17–7.21 (m, 2H); 13C
NMR (75 MHz, CDCl3) : 17.8 (2C), 54.0, 127.9, 128.9, 130.6, 133.6,
130.6, 133.9 (2C), 134.5, 161.8 (d, JC–F¼244.0 Hz). Anal. Calcd for
C13H11FSe: C, 58.88; H, 4.18. Found: C, 58.90; H, 4.15.
;
d:
4.1.19. 4-(Phenylselanylmethyl)phenyl 4-methyl benzenesulfonate
(entry 21, Table 1)
d
A yellowish solid; mp 108–110 ꢂC; IR (KBr): 553, 657, 688, 711,
732, 813, 866, 1151, 1176, 1199, 1377, 1500, 1595, 1703, 2916,
135.9, 136.0. Anal. Calcd for C9H10Cl2S2: C, 42.69; H, 3.98. Found: C,
42.67; H, 3.99.
3043 cmꢁ1 1H NMR (300 MHz, CDCl3)
; d: 2.37 (s, 3H), 3.94 (s, 2H),
6.76 (d, J¼8.5 Hz, 2H), 6.99 (d, J¼8.5 Hz, 2H), 7.14–7.23 (m, 5H), 7.31
Acknowledgements
(d, J¼7.8 Hz, 2H), 7.60 (d, J¼8.3 Hz, 2H); 13C NMR (75 MHz, CDCl3)
d:
21.8, 31.4, 122.3 (2C), 127.7 (2C), 128.6 (2C), 129.0 (2C), 129.6, 129.8
(2C), 130.0 (2C), 132.4, 134.0, 137.9, 145.4, 148.4. Anal. Calcd for
C20H18O3SSe: C, 57.55; H, 4.35. Found: C, 57.51; H, 4.33.
We are pleased to acknowledge financial support from CSIR,
New Delhi [Grant No. 01(1936)/04] for this investigation. A.S. also
thanks CSIR for his fellowship.
4.1.20. General experimental procedure for dithioacetalization.
Representative one for 4-chlorobenzaldehyde (entry 4, Table 2)
To a stirred mixture of 4-chlorobenzaldehyde (141 mg, 1 mmol),
dimethyl disulfide (170 mg, 1.8 mmol) and indium metal (115 mg,
1 mmol, cut into small pieces) in dry acetonitrile (2.5 mL) was
added trimethylchlorosilane (327 mg, 3 mmol) and the mixture
was stirred at room temperature for 2 min followed by heating
under reflux for 2 h (as monitored by TLC). Acetonitrile was evap-
orated under reduced pressure and the residue was extracted with
ether (3ꢀ10 mL). The ether extract was washed with water and
dried (Na2SO4). Evaporation of solvent left the crude product,
which was purified by column chromatography over silica gel using
hexane–ether (98:2) as eluant to afford a pure dimethylthioacetal
of 4-chlorobenzaldehyde as a colourless oil (157 mg, 72%). The
spectroscopic data (IR, 1H and 13C NMR) of this compound are in
good agreement with those reported.15
This procedure was followed for all the reactions listed in Table
2. Most of these compounds (entries 1–4, 7, 10–14, Table 2) are
known and were identified by comparison of their spectroscopic
data with those reported (references in Table 2). The unknown
compounds (entries 5, 6, 8, 9, Table 2) were characterized by their
spectroscopic data (IR, 1H and 13C NMR) and elemental analysis.
These data are given below.
References and notes
1. (a) Cintas, P. Synlett 1995, 1087–1096; (b) Li, C.-J. Tetrahedron 1996, 52, 5643–
5668; (c) Li, C.-J.; Chan, T. H. Tetrahedron 1999, 55, 11149–11176; (d) Chauhan, K.
K.; Frost, C. G. J. Chem. Soc., Perkin Trans. 1 2000, 3015–3019; (e) Ranu, B. C. Eur. J.
Org. Chem. 2000, 2347–2356; (f) Ghosh, R. Indian J. Chem. 2001, 40B, 550–557;
(g) Podelech, J.; Maier, T. C. Synthesis 2003, 633–655; (h) Nair, V.; Ros, S.; Jayan,
C. N.; Pillai, B. S. Tetrahedron 2004, 60, 1959–1982.
2. (a) Ranu, B. C.; Hajra, A.; Jana, U. J. Org. Chem. 2000, 65, 6270–6272; (b)
Ranu, B. C.; Hajra, A.; Jana, U. Tetrahedron Lett. 2000, 41, 531–533; (c) Ranu, B. C.;
Samanta, S.; Hajra, A. Synlett 2002, 987–989; (d) Ranu, B. C.; Das, A.; Samanta, S.
Synlett 2002, 727–730; (e) Ranu, B. C.; Dey, S. S.; Hajra, A. Tetrahedron 2002, 58,
2529–2532; (f) Ranu, B. C.; Hajra, A.; Dey, S. S.; Jana, U. Tetrahedron 2003, 59,
813–819; (g) Ranu, B. C.; Samanta, S. J. Org. Chem. 2003, 68, 7130–7132; (h)
Ranu, B. C.; Das, A.; Hajra, A. Synthesis 2003, 1012–1014; (i) Ranu, B. C.; Samanta,
S. Tetrahedron 2003, 59, 7901–7906; (j) Ranu, B. C.; Mandal, T.; Samanta, S. Org.
Lett. 2003, 5, 1439–1441; (k) Ranu, B. C.; Mandal, T. J. Org. Chem. 2004, 69, 5793–
5795; (l) Ranu, B. C.; Mandal, T. Synlett 2004, 1239–1242; (m) Ranu, B. C.; Das, A.
Tetrahedron Lett. 2004, 45, 6875–6877; (n) Ranu, B. C.; Jana, R.; Samanta, S. Adv.
Synth. Catal. 2004, 346, 446–450; (o) Ranu, B. C.; Das, A. Adv. Synth. Catal. 2005,
347, 712–714; (p) Ranu, B. C.; Chattopadhyay, K.; Banerjee, S. J. Org. Chem. 2006,
71, 423–425; (q) Ranu, B. C.; Mandal, T. Tetrahedron Lett. 2006, 47, 2859–2861;
(r) Ranu, B. C.; Mandal, T. Tetrahedron Lett. 2006, 47, 5677–5680; (s) Ranu, B. C.;
Chattopadhyay, K.; Jana, R. Tetrahedron Lett. 2007, 48, 3847–3850; (t) Ranu, B.
C.; Banerjee, S.; Adak, L. Tetrahedron Lett. 2007, 48, 7374–7379; (u) Ranu, B. C.;
Bhadra, S.; Adak, L. Tetrahedron Lett. 2008, 49, 2588–2591.
3. Evans, D. A.; Truesdale, L. K.; Grimm, K. G.; Nesbitt, S. L. J. Am. Chem. Soc. 1977,
99, 5009–5017.
4. Rogers, M. T.; Campbell, T. W. J. Am. Chem. Soc. 1947, 69, 2039–2041.
5. (a) Clive, D. L. J. Tetrahedron 1978, 34, 1049–1132; (b) Krief, A. Tetrahedron 1980,
36, 2531–2640; (c) Krief, A.; Hevesi, L. In Organic Chemistry of Selenium and
Tellurium Containing Functional Groups; Patai, S., Ed.; Wiley: New York, NY,
1985; (d) Krafft, G. A.; Meinke, P. T. J. Am. Chem. Soc. 1986, 108, 1314–1315; (e)
Reich, H. J.; Chow, F.; Shah, S. K. J. Am. Chem. Soc. 1979, 101, 6638–6648; (f)
Clarembeau, M.; Krief, A. Tetrahedron Lett. 1986, 27, 1723–1726.
6. (a) Clarembeau, M.; Cravador, A.; Dumont, W.; Hevesi, L.; Krief, A.; Lucchetti, J.;
Van Ende, D. Tetrahedron 1985, 41, 4793–4812 and references cited therein; (b)
Dumont, W.; Krief, A. Angew. Chem., Int. Ed. Engl. 1977, 16, 540–541.
7. Clive, D. L. J.; Menchen, S. M. J. Org. Chem. 1979, 44, 1883–1885.
8. (a) Krief, A.; Hevesi, L. Organoselenium Chemistry; Springer: Berlin, 1998; Vol. 1;
(b) Krief, A. In Comprehensive Organometallic Chemistry; Trost, B. M., Ed.; Per-
gamon: Oxford, 1991; pp 85–192.
9. (a) Bieber, L. W.; de Sa, A. C. P. F.; Menezes, P. H.; Goncalves, S. M. C. Tetrahedron
Lett. 2001, 42, 4597–4599; (b) Krief, A.; Derock, M. Tetrahedron Lett. 2002, 43,
3083–3086 and references therein; (c) Nishino, T.; Okada, M.; Kuroki, T.; Wa-
tanabe, T.; Nishiyama, Y.; Sonoda, N. J. Org. Chem. 2002, 67, 8696–8698 and
references therein; (d) Grieco, P. A.; Yokoyama, Y.; Williams, E. J. Org. Chem.
1978, 43, 1283–1285.
4.1.21. 4-(Bis(methylthio)methyl)phenyl acetate (entry 5, Table 2)
A yellowish liquid; IR (neat): 651, 763, 858, 912, 1016, 1164, 1199,
1369, 1504, 1766, 2916 cmꢁ1 1H NMR (300 MHz, CDCl3)
; d: 2.12 (s,
6H), 2.31 (s, 3H), 4.80 (s, 1H), 7.08 (d, J¼8.49 Hz, 2H), 7.45 (d,
J¼8.52 Hz, 2H); 13C NMR (75 MHz, CDCl3)
d: 15.1 (2C), 21.3, 55.9,
121.6 (2C), 128.8 (2C), 137.3, 150.2, 169.4. Anal. Calcd for C11H14O2S2:
C, 54.51; H, 5.82. Found: C, 54.41; H, 5.89.
4.1.22. 4-(Bis(methylthio)methyl)phenyl 4-methyl
benzenesulfonate (entry 6, Table 2)
A yellowish liquid; IR (neat): 659, 711, 813, 837, 866, 1093, 1153,
1176, 1197, 1373, 1498, 1596, 2916, 2979 cmꢁ1 1H NMR (300 MHz,
;
CDCl3)
d
: 2.03 (s, 6H), 2.41 (s, 3H), 4.72 (s, 1H), 6.93 (d, J¼8.62 Hz,
2H), 7.28 (d, J¼8.40 Hz, 2H), 7.31 (d, J¼8.62 Hz, 2H), 7.67 (d,
10. Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis, 3rd ed.; John
Wiley: New York, NY, 1999; pp 329–347.
11. Pettit, G. R.; Van Tamelen, E. E. Org. React. 1962, 12, 356–529.
J¼8.16 Hz, 2H); 13C NMR (75 MHz, CDCl3)
d: 14.9 (2C), 21.7, 55.7,
122.4 (2C), 128.5 (2C), 128.9 (2C), 129.8 (2C), 132.3, 138.8, 145.5,
148.9. Anal. Calcd for C16H18O3S3: C, 54.21; H, 5.12. Found: C, 54.17;
H, 5.09.
12. (a) Khan, A. T.; Parvin, T.; Choudhury, L. H. Synthesis 2006, 2497–2502; (b)
Wiles, C.; Watts, P.; Haswell, S. J. Tetrahedron Lett. 2007, 48, 7362–7365; (c)
De, S. K. Adv. Synth. Catal. 2005, 347, 673–676; (d) Ali, M. H.; Gomes, M. G.
Synthesis 2005, 1326–1332; (e) De, S. K. Synthesis 2004, 2837–2840; (f)
Kamal, A.; Chouhan, G. Tetrahedron Lett. 2003, 44, 3337–3340; (g) Rana, K.
K.; Guin, C.; Jana, S.; Roy, S. C. Tetrahedron Lett. 2003, 44, 8597–8599; (h)
Khan, A. T.; Mondal, E.; Sahu, P. R.; Islam, S. Tetrahedron Lett. 2003, 44,
919–922; (i) Kamal, A.; Chouhan, G. Synlett 2002, 474–476; (j) Ranu, B. C.;
Das, A.; Samanta, S. Synlett 2002, 727–730; (k) Firouzabadi, H.; Iranpoor, N.;
Amani, K. Synthesis 2002, 59–62; (l) Ceschi, M. A.; Felix, L. de A.; Peppe, C.
Tetrahedron Lett. 2000, 41, 9695–9699; (m) Firouzabadi, H.; Karimi, B.;
Eslami, S. Tetrahedron Lett. 1999, 40, 4055–4058; (n) Ranu, B. C.; Das, A. Aust.
J. Chem. 2004, 57, 605–608.
4.1.23. 1-(Bis-methyl sulfanyl-methyl)-4-fluorobenzene (entry 8,
Table 2)
A colourless liquid; IR (neat): 843, 1157, 1223, 1506, 1601, 2916,
2979 cmꢁ1
;
1H NMR (300 MHz, CDCl3)
d
: 2.00 (s, 6H), 4.68 (s, 1H),
6.90–6.96 (m, 2H), 7.29–7.34 (m, 2H); 13C NMR (75 MHz, CDCl3)
d:
15.0 (2C), 55.8, 115.4 (d, JC–F¼21.8 Hz, 2C), 129.3 (d, JC–F¼8.2 Hz, 2C),
135.6, 162.2 (d, JC–F¼245.3 Hz). Anal. Calcd for C9H11FS2: C, 53.43; H,
5.48. Found: C, 53.46, H, 5.45.
13. (a) Tazaki, M.; Takagi, M. Chem. Lett. 1979, 767–770.
14. Patel, V. F.; Pattenden, G. Tetrahedron Lett. 1988, 29, 707–710.

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15. Drosten, G.; Mischke, P.; Voss, J. Chem. Ber. 1987, 120, 1757–1761.
16. Liu, P.; Binnun, E. D.; Schaus, J. V.; Valentino, N. M.; Panek, J. S. J. Org. Chem.
2002, 67, 1705–1707.
18. Zanno, P.; Parliament, T. H. Perfum. Flavor. 1982, 7, 48–50.
19. Kim, S.; Kim, S. S. Tetrahedron Lett. 1987, 28, 1913–1916.
20. Ong, B. S. Tetrahedron Lett. 1980, 21, 4225–4228.
17. Hojo, M.; Masuda, R.; Saeki, T.; Fujimori, K.; Tsutsumi, S. Tetrahedron Lett. 1977,
44, 3883–3886.
21. Braga, A. L.; Silveira, C. C.; Dornelles, L.; Zeni, G.; Galarza, F. A. D.; Wessjohann,
L. A. Synth. Commun. 1995, 25, 3155–3162.