Lewis acid-promoted deoxygenative di[β,β-bis(ethylthio)]vinylation of aldehydes with trimethylsilylketene bis(ethylthio)acetal

Article abstract of DOI:10.1021/jo010007e

Silylketene dithioacetal 1 reacted with aldehydes 2a-o, 14, or cinnamaldehyde (11) in the presence of Lewis acid to give deoxygenative divinylation products, 3-substituted 1,4-pentadienes 3a-o, 15, or 5-phenyl-1,3,6-heptatriene 13b, in good to moderate yields. Similar reaction with 2-aminobenzaldehyde (16) or salicylaldehyde (17) produced quinoline 19 or chroman 20 in 40-58% yield. Treatment of 1 with α-diketones 22a-c or α-ketoester 24 led to tetrasubstituted furans 23a-c or allylic alcohol 25, respectively, in rather low yields. The formation mechanisms of these products are discussed.

Full text of DOI:10.1021/jo010007e

3924
J . Org. Chem. 2001, 66, 3924-3929
Lew is Acid -P r om oted Deoxygen a tive
Di[â,â-bis(eth ylth io)]vin yla tion of Ald eh yd es w ith
Tr im eth ylsilylk eten e Bis(eth ylth io)a ceta l
Tatsuo Okauchi, Tatsuyoshi Tanaka, and Toru Minami*
Department of Applied Chemistry, Kyushu Institute of Technology, Sensui-cho, Tobata,
Kitakyushu 804-8550, J apan
minami@che.kyutech.ac.jp
Received J anuary 2, 2001
Silylketene dithioacetal 1 reacted with aldehydes 2a -o, 14, or cinnamaldehyde (11) in the presence
of Lewis acid to give deoxygenative divinylation products, 3-substituted 1,4-pentadienes 3a -o, 15,
or 5-phenyl-1,3,6-heptatriene 13b, in good to moderate yields. Similar reaction with 2-aminobenz-
aldehyde (16) or salicylaldehyde (17) produced quinoline 19 or chroman 20 in 40-58% yield.
Treatment of 1 with R-diketones 22a -c or R-ketoester 24 led to tetrasubstituted furans 23a -c or
allylic alcohol 25, respectively, in rather low yields. The formation mechanisms of these products
are discussed.
The reactions of allylsilanes and vinylsilanes with
of silylketene dithioacetals as high reactive vinylsilanes,
their chemistry has been scarcely studied.6,7 Accordingly,
we have begun to investigate the reactivity of silylketene
dithioacetal toward carbonyl compounds. We found an
unprecedented addition of silylketene dithioacetal 1 to
aldehydes in the presence of Lewis acid. We report here
a novel di[â,â-bis(ethylthio)]vinylation of aldehydes with
1 giving tetrakis(ethylthio)-1,4-pentadiene, and also new
synthesis of heterocyclic compounds from 1 and o-NH2
or OH-substituted benzaldehydes or R-diketones.
electrophiles have been extensively studied due to their
synthetic usefulness.1 In the presence of Lewis acid or
fluoride anion, allylsilanes reacted with electrophiles
such as ketones and aldehydes to afford homoallyl
alcohols.2 On the other hand, the reaction of vinylsilanes
with aldehydes or ketones is currently hampered by
limited substrate generality, where the use of special
vinylsilanes or reactive carbonyl compounds is indis-
pensable.1e,i We have recently reported the first synthesis
of R-silyl- and R-stannyl-â-heteroatom-substituted vinyl-
phosphonates and their functional group transformations
at the R-position.3 In connection with our exploration of
new synthetic routes for introduction of a functionalized
vinyl group, we became interested in the synthesis and
synthetic utilization of silylketene dithioacetals, which
are a new class of vinylsilanes and are expected to show
various reactivities attributable to vinylsilanes,1 ketene
dithioacetals,4 heteroatom-substituted olefins,5 etc.
Despite a hopeful prospect of developing synthetic utility
Resu lts a n d Discu ssion
Deoxygen a tive Divin yla tion of Ald eh yd es w ith
Silylk eten e Dith ioa ceta l. To compare the reactivities
of silylketene dithioacetal 18 toward carbonyl compounds
with that of vinylsilane, the reaction of 1 (1 equiv) with
benzaldehyde (2a ) (1 equiv) was carried out in CH2Cl2
in the presence of BF3‚OEt2 (1 equiv) at -78 °C for 1 h.
No allylic alcohol 4 was obtained, and unprecedented
deoxygenative addition9 of 1 to 2a proceeded to give
1,1,5,5-tetrakis(ethylthio)-3-phenyl-1,4-pentadiene (3a ) in
71% yield (entry 1 in Table 1) (Scheme 1). Hosomi and
co-workers reported that the reaction of a silylketene
dithioacetal with aromatic aldehydes in the presence of
BF3‚OEt2 or TiCl4 gave allylic alcohols 4,6 whereas we
could not obtain the corresponding allylic alcohols at all.
* To whom correspondence should be addressed. Tel: +81-(0)93-
884-3304. Fax: +81-(0)93-884-3300.
(1) See, for examples: (a) Fleming, I.; Barbero, A.; Walter, D. Chem.
Rev. 1997, 97, 2063. (b) Langkopf, E.; Schinzer, D. Chem. Rev. 1995,
95, 1375. (c) Masse, C. E.; Panek, J . S. Chem. Rev. 1995, 95, 1293. (d)
Hosomi, A. Acc. Chem. Res. 1988, 21, 200. (e) Overman, L. E.;
Blumenkopf, T. A. Chem. Rev. 1986, 86, 857. (f) Sakurai, H. Pure Appl.
Chem. 1982, 54, 1. (g) Chan, T. H.; Fleming, I. Synthesis 1979, 761.
(h) Panek, J . S. Comprehensive Organic Synthesis; Trost, B. M., Ed.;
Pergamon Press: Oxford, 1991; Vol. 1, Chapter 2.5. (i) Fleming, I.
Organic Reactions; Kende, A. S., Ed.; J ohn Wiley & Sons: New York,
1989; Vol. 37, 57. (j) Colvin, E. W. Silicon in Organic Synthesis;
Butterworth: London, 1981; Chapter 7, 9.
(6) Tominaga, Y.; Matuoka, Y.; Kamio, C.; Hosomi, A. Chem. Pharm.
Bull. 1989, 37, 3168.
(7) For the synthesis of R-substituted silylketene dithioacetals,
see: (a) Chamberlin, A. R.; Nguyen, H. J . Org. Chem. 1986, 51, 940.
(b) Yamamoto, M.; Takemori, T.; Iwasa, S.; Kohmoto, S.; Yamada, K.
J . Org. Chem. 1989, 54, 1757.
(2) (a) Hosomi, A.; Sakurai, H. Tetrahedron Lett. 1976, 17, 1295.
(b) Hosomi, A.; Shirahata, A.; Sakurai, H. Tetrahedron Lett. 1978, 19,
3043.
(3) Kouno, R.; Okauchi, T.; Nakamura, M.; Ichikawa, J .; Minami,
T. J . Org. Chem. 1998, 63, 6239.
(4) For reviews of ketene dithioacetal, see: (a) Kolb, M. Synthesis
1990, 171. (b) J unjappa, H.; Ila, H.; Asokan, C. V. Tetrahedron 1990,
46, 5423.
(5) (a) Knight, D. W. Comprehensive Organic Synthesis; Trost, B.
M., Ed.; Pergamon Press: Oxford, 1991; Vol. 3, Chapter 1.6. (b) Braun,
M. Angew. Chem., Int. Ed. Engl. 1998, 37, 430. (c) Kauffmann, T.
Angew. Chem., Int. Ed. Engl. 1982, 21, 410.
(8) The synthetic method of silylketene dithioacetal is described in
the Supporting Information. A similar synthesis of a silylketene
dithioacetal was previously reported, see: ref 6.
(9) For example, deoxygenative addition of indoles with carbonyl
compounds is known to produce bisindolylmethanes; see: Babu, G.;
Sridhar, N.; Perumal, P. T. Synth. Commun. 2000, 30, 1609 and
references therein. For deoxygenation of carbonyl compounds by metal
reagents, see: Xi, Z.; Li, P. Angew. Chem., Int. Ed. Engl. 2000, 39,
2950 and references there-in.
10.1021/jo010007e CCC: $20.00 © 2001 American Chemical Society
Published on Web 05/03/2001

Deoxygenative Di[â,â-bis(ethylthio)]vinylation of Aldehydes
J . Org. Chem., Vol. 66, No. 11, 2001 3925
Ta ble 1. Lew is Acid -P r om oted Rea ction of Silylk eten e
Dith ioa ceta l 1 w ith Ald eh yd es 2a
Sch em e 2
productb
entry ECHO (equiv) Lewis acid (equiv) time, h
(yield, %)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
2a (1.0)
2a (0.5)
2a (0.5)
2a (1.0)
2a (0.5)
2a (0.5)
2a (1.0)
2a (0.5)
2a (0.5)
2b (0.5)
2c (0.5)
2d (0.5)
2e (0.5)
2f (1.0)
2g (1.0)
2h (0.5)
2i (1.0)
2j (0.5)
2k (0.5)
2l (0.25)
2m (1.0)
2n (1.0)
2o (1.0)
BF3‚OEt2 (1.0)
BF3‚OEt2 (0.5)
BF3‚OEt2 (0.1)
TiCl4 (1.0)
TiCl4 (0.5)
TiCl4 (0.1)
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
2.0
1.0
1.0
1.0
1.0
1.0
1.0
1.5
1.5
1.0
2.0
1.0
1.0
3a (71)
3a (71)
3a (70)
3a (63)
3a (56)
3a (60)
3a (58)
3a (58)
3a (58)
3b (70)
3c (52)
3d (60)
3e (78)
3f (88)
3g (87)
3h (60-70)
3i (60)
TMSOTf (1.0)
TMSOTf (0.5)
TMSOTf (0.1)
BF3‚OEt2 (0.5)
BF3‚OEt2 (0.5)
BF3‚OEt2 (0.5)
BF3‚OEt2 (0.5)
BF3‚OEt2 (1.0)
BF3‚OEt2 (1.0)
BF3‚OEt2 (0.5)
BF3‚OEt2 (1.0)
BF3‚OEt2 (0.5)
BF3‚OEt2 (0.5)
BF3‚OEt2 (0.5)
EtAlCl2 (1.0)
EtAlCl2 (1.0)
EtAlCl2 (1.0)
group10 and two R-ethylthio groups,11 followed by elimi-
nation of the TMS cation resulting in allyloxonium cation
6, C-O bond cleavage producing allylic cation 7.12 The
subsequent reaction with another 1 led to the product
3a with generation of the TMS cation (Scheme 2).
3j (58)
3k (75)
3l (64)
3m (38)
3n (42)
3o (44)
To confirm the above-mentioned mechanism, 1,1-bis-
(ethylthio)-3-phenyl-3-trimethylsiloxy-1-propene (8), pre-
pared independently from the corresponding allylic
alcohol13 and chlorotrimethylsilane, was allowed to react
with 1 in the presence of a catalytic amount of BF3‚OEt2
(0.2 equiv) to give the expected 3a in 55% yield (eq 1).
This experimental result evidently supports the mecha-
nism shown in Scheme 2.
a
b
All reactions were carried out in CH2Cl2 at -78 °C. Isolated
yield. Yields were based on silylketene dithioacetal 1.
Sch em e 1
Furthermore, the role of the alkylthio group in this
deoxygenative divinylation was investigated. Treatment
of benzaldehyde (2a ) with methyl 2-(trimethylsilyl)vinyl
sulfide (9)14 instead of 1 under the same conditions led
to only an uncharacterizable mixture (eq 2). This result
clearly indicates that two cation-stabilizing alkylthio
So we next examined the influence of the molar ratio
of 1 to 2a and BF3‚OEt2 upon the product and the product
yield. The silylketene dithioacetal 1 was treated with a
0.5 molar amount of 2a and BF3‚OEt2 to produce only
3a in the same yield (71%) (entry 2). Even when a
catalytic amount of BF3‚OEt2 was used, 3a was obtained
in a similar yield (70%) (entry 3). These results have
indicated that the reaction of 1 with 2a led to the
formation of only the deoxygenative divinylation product
3a regardless of the molar amount of BF3‚OEt2 used. The
use of TiCl4 or trimethylsilyl trifluoromethanesulfonate
(TMSOTf), instead of BF3‚OEt2, showed a similar trend
in the yield of 3a , although the yield slightly decreased
(58-63% yield) (entries 4-9). No reaction between 1 and
2a proceeded without Lewis acid. On the basis of these
results, the formation of 3a is rationalized as follows:
Lewis acid-activated benzaldehyde underwent the addi-
tion of the electron rich silylketene dithioacetal 1 to give
the cation 5 stabilized by both a â-trimethylsilyl (TMS)
(10) For stabilization of â-cation by silyl group, see, for example:
(a) Lambert, J . B. Tetrahedron 1990, 46, 2677. (b) J arview, A. W. P.
Organomet. Chem. Rev., Sect. A 1970, 6, 153. (c) Colvin, E. W. Silicon
in Organic Synthesis; Butterworth: London, 1981; Chapter 3.
(11) For stabilization of R-cation by thio group, see, for example:
Price, C. C.; Oae, S. Sulfur Bonding; The Ronald Press Co.: New York,
1962; Chapter 2.
(12) Related allylic cation species, 2-substituted-1,3-dithiolan-2-
ylium or 2-substituted-1,3-dithiane-2-ylium salts have been isolated
and these salts were reacted with nucleophiles such as silyl enol ethers,
stannyl enol ethers and allylstannaes in CH2Cl2 to afford corresponding
oxoketene dithioacetals and alkenylketene dithioacetals, see: (a)
Hashimoto, Y.; Mukaiyama, T. Chem. Lett. 1986, 755. (b) Hashimoto,
Y.; Mukaiyama, T. Chem. Lett. 1986, 1623. (c) Hashimoto, Y.; Sugumi,
H.; Okauchi, T.; Mukaiyama, T. Chem. Lett. 1987, 1691. (d) Hashimoto,
Y.; Sugumi, H.; Okauchi, T.; Mukaiyama, T. Chem. Lett. 1987, 1695.
(13) The allylic alcohol was synthesized in 92% yield by reduction
of R-oxoketenedithioacetal with DIBALH (1.5 equiv) in CH2Cl2 at -45
°C for 3 h. For the synthesis of R-oxoketenedithioacetal, see: Dieter,
R. K. Tetrahedron 1986, 42, 3029.
(14) The compound 9 was synthesized in 60% yield from hydroalu-
mination of 2-methylthio-1-trimethylsilylethyne with LiAlH4 in trig-
lyme at 40 °C for 1 day. For an alternative synthesis of 9, see:
Voronkov, M. G.; Rakhlin, V. I.; Mirskov, R. G.; Khangazheev, S. Kh.;
Yarosh, O. G.; Tsetlina, E. O. J . Gen. Chem. USSR 1979, 103.

3926 J . Org. Chem., Vol. 66, No. 11, 2001
Okauchi et al.
groups11 at the â-position of vinylsilane are required in
Sch em e 3
this deoxygenative divinylation.
To explore the scope and limitations of this Lewis acid-
catalyzed deoxygenative divinylation of aldehydes, the
reactions of various aromatic aldehydes 2a -l with 1
under similar conditions were studied. The results are
summarized in Table 1. The reaction of p-tolualdehyde
(2b) and 4-methoxybenzaldehyde (2d ) (benzaldehydes
with electron-donating group),or sterically hindered aro-
matic aldehydes15 such as o-tolualdehyde (2c), 1-naphth-
aldehyde (2h ), and 2-phenylbenzaldehyde (2i) provided
the corresponding divinylation products 3b-d ,h ,i in
lower yields (52-70%) than that of 3a (entries 10-12,
16, 17). In addition, the reaction of electron-withdrawing
group substituted benzaldehydes such as 4-chlorobenz-
aldehyde (2e), 4-nitrobenzaldehyde (2f), and 4-cyanobenz-
aldehyde (2g) gave the corresponding divinylation prod-
uct 3e-g in 78-88% yields (entries 13-15). Not only
these simple aromatic aldehydes but also heteroaromatic
aldehydes such as 2-furaldehyde (2j), 2-thiophenecar-
boxyaldehyde (2k ), and terephthalaldehyde (2l) readily
reacted with 1 to give the corresponding deoxygenative
divinylation products 3j-l in moderate to good yields
(Scheme 1 and eq 3) (entries 18-20). These results
indicated that this deoxygenative divinylation proceeded
regardless of the substituent on the benzaldehyde.
has been found to yield deoxygenative 1,1- or 1,3-
divinylation products.
Syn th esis of Heter ocyclic Com p ou n d s via Rea c-
t ion of o-H et er oa t om -F u n ct ion a lized Ben za ld e-
h yd es w ith Silylk eten e Dith ioa ceta l. To extend the
synthetic utility of the allylic cation intermediate that is
stabilized by the two thio groups, we tried to trap the
intermediate with an intramolecular nucleophile such as
an NH2 or OH group. When a mixture of 2-aminobenz-
aldehyde (16) and BF3‚OEt2 was treated with 1, 2-ethyl-
thioquinoline (19) was obtained interestingly in 40%
yield.16 The formation of 19 can be reasonably explained
by sequence of trapping the allylic cation intermediate
18 with the 2-amino group, deprotonation, and subse-
quent elimination of ethanethiol (Scheme 4).
On the other hand, treatment of salicylaldehyde (17)
with 1 under the same conditions produced 4-[2,2-bis-
(ethylthio)vinyl]-2,2-bis(ethylthio)chroman (20) in 58%
yield. When 20 was subjected to hydrolysis in the
presence of CuCl2-CuO in refluxing acetone containing
water, 4-[â,â-bis(ethylthio)vinyl]-3,4-dihydrocoumarin (21)
was obtained in 85% yield (Scheme 5).
Thus, it is found that the intramolecular cyclization
readily takes place to give heterocyclic compounds, when
a nucleophilic heteroatom substituent is present at the
o-position of benzaldehyde.
R ea ct ion of Ket on es w it h Silylk et en e Dit h io-
a ceta l. Unlike aldehydes, ketones such as benzophenone,
acetophenone, and fluorenone could not be applied to this
deoxygenative reaction with 1, and only unreacted
ketones were recovered. To develop applicability of 1 to
the reaction with ketones, more reactive R-diketones or
R-ketoester was employed. The reaction of benzil (22a )
In contrast to aromatic aldehydes, aliphatic aldehydes
2m -o did not react to give the expected divinylation
products 3m -o under the above conditions. Instead, the
use of EtAlCl2 as Lewis acid produced 3m -o even though
their yields are much lower (33-44%) (entries 21-23).
The low yields are due to side reactions competing with
the formation of the divinylation products.
We furthermore examined the reactivity of 1 toward
R,â-unsaturated aldehydes. Cinnamaldehyde (11) was
treated with 1 (0.5 equiv) in the presence of BF3‚OEt2
(0.5 equiv) to afford unexpected deoxygenative 1,3-
divinylation product 13b in moderate yield (51%) (Scheme
3). The formation of 13b shows that not the allylic cation
12a but also the conjugated allylic cation 12b was
trapped with 1. On the contrary, the reaction of related
propargyl aldehyde 14 with 1 under similar conditions
afforded deoxgenative geminal divinylation product 15
albeit in modest yield (42%) (eq 4). Thus, the Lewis acid-
promoted reaction of R,â-unsaturated aldehydes with 1
(15) When sterically hindered aromatic aldehydes such as 2c and
2i were used, 3-aryl-1,1,3-tris(ethylthio)-1-propene, ArCH(SEt)CHd
C(SEt)2, were isolated in trace amounts.
(16) For alternative synthesis of 2-ethylthioquinoline, see: Beugel-
mans, R.; Bois-Choussy, M.; Boudet, B. Tetrahedron 1983, 39. 4153.

Deoxygenative Di[â,â-bis(ethylthio)]vinylation of Aldehydes
J . Org. Chem., Vol. 66, No. 11, 2001 3927
Sch em e 4
Sch em e 6
Sch em e 5
under acidic conditions of this reaction.18 This can be
reasonably explained by the fact that the use of excess 1
(2.2 equiv) as a proton scavenger produced 23a in higher
yield (43%) (entry 3 in Table 2).
We further attempted to apply this Lewis acid-
promoted reaction to an R-ketoester. Treatment of TiCl4-
activated ethyl pyruvate (24) with 1 produced only allylic
alcohol 25 in 54% yield, but no furan derivative was
obtained (eq 5).
Ta ble 2. Lew is Acid -P r om oted Rea ction of Silylk eten e
Dith ioa ceta l 1 w ith r-Dik eton es 22a
entry R-diketone 22 Lewis acid time, h product (yield, %)b
1
22a
22a
22a
22b
22c
BF3‚OEt2
TiCl4
TiCl4
TiCl4
TiCl4
1.0
1.0
1.0
1.5
2.0
23a (7)
2
23a (34)
23a (43)d
23b (27)
23c (23)
Con clu sion . We note the following results from this
investigation: (1) silylketene dithioacetal 1 was reacted
with aromatic, aliphatic and R,â-unsaturated aldehydes
in the presence of a catalytic or an equimolar amount of
Lewis acid to produce deoxygenative 1,1- or 1,3-divinyl-
ation products. (2) A new synthetic approach to function-
alized quinoline and chroman was developed by the
Lewis-acid-promoted reaction of o-heteroatom-substitut-
ed benzaldehydes with 1. (3) The TiCl4-promoted reaction
of R-diketones or an R-ketoester with 1 led to tetrasub-
stituted furans or an allylic alcohol.
3c
4
5
a
All reactions were carried out in CH2Cl2 at -78 °C in the
b
presence of 1.0 equiv of Lewis acid. Isolated yield based on
silylketene dithioacetal 1. c Excess of 1 (2.2 equiv) was used.
d
Isolated yield based on diketone 22a .
(1 equiv) with 1 (1 equiv) in the presence of BF3‚OEt2 (1
equiv) produced unpredicted tetrasubstituted furan 23a
albeit in miserable yield (7%) other than 22a (90%) (entry
1 in Table 2, Scheme 6). The use of TiCl4, instead of BF3‚
OEt2, fairly improved the yield of 23a up to 34% (entry
2). Accordingly, similar reaction with 1-phenyl-1,2-pro-
panedione (22b) or 2,3-butanedione (22c) using TiCl4 was
carried out to provide the corresponding tetrasubstituted
furan 23b or 23c albeit in low yields (23-27% yields)
(entries 4, 5). As outlined in Scheme 6, the formation of
23a -c would be reasonably explained by a sequence of
deoxygenative addition of 22a -c with 1 to generate the
allylic cation, subsequent cyclization to the dihydrofuryl
cation accompanying 1,2-migration of an ethylthio group,17
and elimination of a proton. The low yield of 23a -c would
be caused by decomposition of the starting substrate 1
Exp er im en ta l Section
Ma ter ia ls. Dichloromethane was distilled from P2O5. THF
and diethyl ether were distilled from sodium benzophenone
ketyl in a recycling still. Diisopropylamine (DIA), BF3‚OEt2,
and TiCl4 were distilled from CaH2. Commercial solutions of
BuLi (1.54 M in hexane) and EtAlCl2 (0.93 M in hexane) were
used. Me3SiCH2Cl was purchased from Shin-Etsu Chemical.
Gen er a l Meth od s. 1H and 13C NMR spectra were obtained
in CDCl3, operating 1H NMR at 400 or 500 MHz and 13C NMR
at 101 or 126 MHz with Me4Si as an internal standard. IR
(18) Silylketene dithioacetal 1 undergoes hydrolysis on treatment
with silica gel. For other examples of decomposition of silylketene
dithioacetal by acid, see: ref 6 and 7a.
(17) For example of the 1,2-thio migration, see: J ones, D. K.; Liotta,
D. C. Tetrahedron Lett. 1993, 34, 7209.

3928 J . Org. Chem., Vol. 66, No. 11, 2001
Okauchi et al.
spectra were recorded of thin firm on KBr plates. Mass spectra
were recorded at 70 eV. Melting points were measured in open
capillary tubes and are uncorrected.
24.2, 24.5, 26.9, 27.1, 35.6, 39.6, 94.0, 117.3, 121.7, 123.7, 127.9,
128.5, 133.0, 138.8, 152.2. Anal. Calcd for C19H28OS4: C, 56.95;
H, 7.04. Found: C, 56.84; H, 7.05.
Syn th esis of 2-Eth ylth ioqu in olin e (19). To a solution of
2-aminobenzaldehyde 1620 (27.5 mg, 0.23 mmol) and 1 (50.0
mg, 0.23 mmol) in CH2Cl2 (3 mL) was added BF3‚OEt2 (32.2
mg, 0.23 mmol) at -78 °C. The reaction mixture was stirred
for 1.5 h at this temperature. After similar workup, the residue
was chromatographed on preparative TLC (silica gel, AcOEt/
hexane ) 1:10) to afford 19 (17.0 mg, 0.09 mmol, 40%) as a
yellow oil: IR (neat) 1614, 1592, 1556, 1496, 1419, 1294, 1137,
Gen er a l P r oced u r e for th e Syn th esis of 1,1,5,5-Tetr a -
kis(eth ylth io)-1,4-pen tadien es (3a-o, 15), (E)-1,1,7,7-Tetr a-
kis(eth ylth io)-5-ph en yl-1,3,6-h eptatr ien e (13b), an d 4-[2,2-
Bis(eth ylth io)vin yl]-2,2-bis(eth ylth io)ch r om a n (20). To a
solution of aldehyde 2a -o, 11, 14, or 17 (0.23 or 0.45 mmol)
in CH2Cl2 (3 mL) was added BF3‚OEt2 (32.6 mg, 0.23 mmol)
or EtAlCl2 (0.47 mL, 0.46 mmol) at -78 °C. Then a solution of
1 (100 mg, 0.45 mmol) in CH2Cl2 (3 mL) was added dropwise
to the mixture. The reaction mixture was stirred for 1-2 h at
this temperature. The reaction was quenched by addition of
phosphate buffer (pH ) 7), and the organic layer was extracted
with CH2Cl2, washed with brine, dried over Na2SO4, and
concentrated in vacuo. The residue was chromatographed on
preparative TLC (silica gel, AcOEt/hexane ) 1:10) to afford
3a -o, 13b, 15, and 20. The reaction conditions and yields of
3a -o are summarized in Table 1. The compounds 3a ,j,l,m ,
13b, and 20 had the following properties. The properties for
compounds 3b-i,k ,n ,o and 15 are provided in the Supporting
Information.
1
1089, 815, 748 cm-1; H NMR (500 MHz) δ 1.45 (3H, t, J )
7.5 Hz), 3.35 (2H, q, J ) 7.5 Hz), 7.20 (1H, d, J ) 8.5 Hz),
7.41 (1H, ddd, J ) 8.5, 7.6, 1.3 Hz), 7.64 (1H, ddd, J ) 8.5,
7.6, 1.3 Hz), 7.70 (1H, dd, J ) 8.5, 1.3 Hz), 7.87 (1H, d, J )
8.5 Hz), 7.93 (1H, d, J ) 8.5 Hz); 13C NMR (126 MHz) δ 14.6,
24.2, 121.0, 125.1, 125.9, 127.6, 128.0, 129.5, 135.2, 148.4,
159.5. The spectral data of 19 were consistent with those of
the compound 1916 reported previously.
Hyd r olysis of 20. Hydrolysis of 20 was carried out by using
20 (50 mg, 0.125 mmol), CuCl2 (53.6 mg, 0.25 mmol), and CuO
(39.8 mg, 0.5 mmol) in acetone-H2O, according to the estab-
lished procedure.21 After similar workup, the residue was
chromatographed on preparative TLC (silica gel, AcOEt/
hexane ) 1:10) to afford 21 (29.5 mg, 0.1 mmol, 80%) as a
yellow oil: IR (neat) 1774, 1484, 1454, 1216, 1147, 919, 757
cm-1; 1H NMR (400 MHz) δ 1.26 (6H, t, J ) 7.3 Hz), 2.64 (1H,
dd, J ) 15.8, 9.6 Hz), 2.74-2.89 (5H, m), 4.63 (1H, ddd, J )
12.3, 9.2, 5.6 Hz), 5.97 (1H, d, J ) 9.2 Hz), 7.06-7.16 (3H, m),
7.26-7.29 (1H, m); 13C NMR (101 MHz) δ 14.0, 15.1, 26.9, 27.2,
35.0, 35.9, 117.1, 124.6, 125.0, 127.1, 128.6, 134.3, 134.9, 151.4,
167.5. Anal. Calcd for C15H18O2S4: C, 61.19; H, 6.16. Found:
C, 61.21; H, 6.16.
Rea ction of Keton es 22a -c or Eth yl P yr u va te (24)
w ith 1. Gen er a l P r oced u r e. To a solution of diketone (22a -
c) or ethyl pyruvate (24) (0.36 mmol) in CH2Cl2 (2 mL) was
added TiCl4 (63.8 mg, 0.36 mmol) at -78 °C. Then 1 (80 mg,
0.363 mmol) in CH2Cl2 (2 mL) was added dropwise to the
mixture. The mixture was stirred for 1-2 h at this tempera-
ture. After similar workup, the residue was chromatographed
on preparative TLC (silica gel, AcOEt/hexane ) 1:10) to afford
23a -c or 25. The reaction conditions and yields of 23a -c and
25 are summarized in Table 2 and eq 5. The compounds 23a ,
b and 25 have the following properties. The property for
compound 23c is provided in the Supporting Information.
2,3-Bis(eth ylth io)-4,5-d ip h en ylfu r a n (23a ): white crys-
tal; mp 54-55.5 °C; IR (KBr) 1492, 1444, 1259, 948, 767, 698
cm-1; 1H NMR (500 MHz) δ 1.04 (3H, t, J ) 7.3 Hz), 1.39 (3H,
t, J ) 7.32 Hz), 2.40 (2H, q, J ) 7.32 Hz), 3.00 (2H, q, J )
7.32 Hz), 7.18-7.44 (10H, m); 13C NMR (126 MHz) δ 14.6, 15.4,
28.9, 29.6, 122.6, 125.6, 126.0, 127.6, 127.7, 128.3, 128.6, 130.1,
130.3, 132.8, 149.0, 150.9. Anal. Calcd for C20H20OS2: C, 70.55;
H, 5.92. Found: C, 70.37; H, 5.97.
1,1,5,5-Tetr akis(eth ylth io)-3-ph en yl-1,4-pen tadien e (3a):
colorless oil; IR (neat) 1600, 1492, 1448, 1259, 755, 698 cm-1
;
1H NMR (500 MHz) δ 1.22 (6H, t, J ) 7.3 Hz), 1.22 (6H, t, J
) 7.3 Hz), 2.68-2.83 (8H, m), 5.63 (1H, t, J ) 9.5 Hz), 6.21
(2H, d, J ) 9.5 Hz), 7.17-7.30 (5H, m); 13C NMR (126 MHz) δ
14.3, 15.2, 27.0, 27.2, 47.5, 126.3, 127.4, 128.6, 131.1, 138.7,
142.8. Anal. Calcd for C19H28S4: C, 59.32; H, 7.34. Found: C,
59.14; H, 7.27.
1,1,5,5-Tetr akis(eth ylth io)-3-(2-fu r yl)-1,4-pen tadien e (3j):
yellow oil; IR (neat) 1502, 1448, 1259, 1008, 730 cm-1; 1H NMR
(500 MHz) δ 1.23 (12H, t, J ) 7.3 Hz), 2.68-2.83 (8H, m), 5.66
(1H, t, J ) 9.2 Hz), 5.99-5.99 (1H, m), 6.12 (2H, d, J ) 9.2
Hz), 6.27-6.27 (1H, m), 7.32-7.32 (1H, m); 13C NMR (126
MHz) δ 14.1, 15.1, 26.9, 27.3, 42.4, 105.0, 110.1, 132.1, 134.0,
141.6, 154.9. Anal. Calcd for C17H26OS4: C, 54.50; H, 6.99.
Found: C, 54.69; H, 7.01.
1,4-Bis[1,1,5,5-tetr a k is(eth ylth io)-1,4-p en ta d ien e-3-yl]-
ben zen e (3l): yellow oil; IR (neat) 1504, 1446, 1373, 1201, 831,
755 cm-1 1H NMR (500 MHz) δ 1.21 (12H, t, J ) 7.3 Hz),
;
1.22 (12H, t, J ) 7.3 Hz) 2.67-2.84 (16H, m), 5.59 (2H, t, J )
9.5 Hz), 6.16 (4H, d, J ) 9.5 Hz), 7.12 (4H, s); 13C NMR (126
MHz) δ 14.2, 15.1, 26.9, 27.2, 47.1, 127.5, 130.9, 138.6, 140.6.
Anal. Calcd for C32H50S8: C, 55.60; H, 7.29. Found: C, 55.98;
H, 7.34.
1,1,5,5-Tetr a k is(eth ylth io)-3-(2-p h en yleth yl)-1,4-p en ta -
d ien e (3m ): yellow oil; IR (neat) 1496, 1452, 1373, 1259, 750,
698 cm-1; 1H NMR (500 MHz) δ 1.22 (6H, t, J ) 7.3 Hz), 1.22
(6H, t, J ) 7.3 Hz), 1.71 (2H, tt, J ) 8.3, 7.6 Hz), 2.60 (2H, t,
J ) 8.3 Hz), 2.61-2.81 (8H, m) 4.34 (1H, dt, J ) 9.3 Hz, 7.6
Hz), 5.98 (2H, d, J ) 9.3 Hz), 7.15-7.28 (5H, m); 13C NMR
(126 MHz) δ 14.2, 15.1, 26.8, 27.1, 33.6, 37.8, 43.1, 125.7, 128.3,
128.3, 130.0, 140.8, 142.3. Anal. Calcd for C21H32S4: C, 61.11;
H, 7.81. Found: C, 60.83; H, 7.81.
(E)-1,1,7,7-Tet r a k is(et h ylt h io)-5-p h en yl-1,3,6-h ep t a -
tr ien e (13b): yellow oil; IR (neat) 1492, 1446, 1259, 970, 757,
698 cm-1; 1H NMR (500 MHz) δ 1.21 (3H, t, J ) 7.3 Hz), 1.22
(3H, t, J ) 7.3 Hz), 1.24 (3H, t, J ) 7.3 Hz), 1.25 (3H, t, J )
7.3 Hz), 2.71-2.82 (8H, m), 4.99 (1H, dd, J ) 7.2, 7.2 Hz), 5.89
(1H, dd, J ) 15.3, 6.7 Hz), 6.25 (1H, d, J ) 9.5 Hz), 6.61 (1H,
d, J ) 10.4 Hz), 6.78 (1H, ddd, J ) 15.3 Hz, 10.4 Hz, 1.2 Hz),
7.2-7.3 (5H, m); 13C NMR (126 MHz) δ 14.3, 14.4, 15.0, 15.3,
26.9, 27.1, 27.1, 27.8, 49.4, 126.5, 127.7, 127.9, 128.6, 130.6,
131.3, 133.8, 135.9, 139.5, 142.8. Anal. Calcd for C21H30S4: C,
61.41; H, 7.36. Found: C, 61.10; H, 7.39.
2,3-Bis(eth ylth io)-5-m eth yl-4-p h en ylfu r a n (23b): yellow
oil; IR (neat) 1498, 1444, 1259, 1008, 748, 700 cm-1; 1H NMR
(500 MHz) δ 1.01 (3H, t, J ) 7.3 Hz), 1.32 (3H, t, J ) 7.3 Hz),
2.33 (3H, s), 2.39 (2H, q, J ) 7.32 Hz), 2.89 (2H, q, J ) 7.32
Hz), 7.30-7.44 (5H, m); 13C NMR (126 MHz) δ 14.9, 14.5, 15.2,
28.8, 30.0, 121.9, 125.0, 127.1, 128.2, 129.4, 132.5, 146.9, 151.3.
Anal. Calcd for C15H18OS2: C, 64.70; H, 6.52. Found: C, 64.52;
H, 6.50.
Eth yl 4,4-bis(eth ylth io)-2-h yd r oxy-2-m eth yl-3-bu ten -
a te (25): yellow oil; IR (neat) 3496, 1731, 1571, 1448, 1373,
1
1243, 1124 cm-1; H NMR (400 MHz) δ 1.23 (3H, t, J ) 7.3
Hz), 1.25 (3H, t, J ) 7.3 Hz), 1.28 (3H, t, J ) 7.2 Hz), 1.56
(3H, s), 2.70-2.85 (4H, m), 4.17-4.27 (2H, m), 4.45 (1H, s),
4-[2,2-Bis(et h ylt h io)vin yl]-2,2-b is(et h ylt h io)ch r om a n
(19) (a) Schaumann, E.; Behr, H.; Lindstaedt, J . Chem. Ber. 1983,
116, 66. (b) Bogoradovskii, E. T.; Zavgorodnii, V. S.; Moshinskaya, A.
V.; Petrov, A. A. J . Gen. Chem. USSR 1982, 1846.
(20) 2-Aminobenzaldehyde was synthesized according to the estab-
lished procedure. Smith, L. I.; Opie, J . W. Organic Synthesis; Horning,
E. C., Ed.; J ohn Wiley & Sons: New York, 1955; Vol. 3, 56.
(21) Krief, A. Encyclopedia of Reagents for Organic Synthesis;
Paquette, L. A., Ed.; J ohn Wiley & Sons: Chichester, 1995; Vol. 2,
1331.
(20): white crystal; mp 76.0-77.0 °C; IR (KBr) 1581, 1484,
1
1448, 1220, 1004, 916, 757 cm-1; H NMR (500 MHz) δ 1.23
(3H, t, J ) 7.3 Hz), 1.28 (3H, t, J ) 7.3 Hz), 1.28 (3H, t, J )
7.16 Hz), 1.30 (3H, t, J ) 7.16 Hz), 2.30 (1H, dd, J ) 13.9,
11.2 Hz), 2.39 (1H, dd, J ) 13.9, 6.1 Hz), 2.75-2.93 (8H, m),
4.73 (1H, ddd, J ) 11.2, 9.2, 6.1 Hz), 6.02 (1H, d, J ) 9.2 Hz),
6.85-7.16 (4H, m); 13C NMR (126 MHz) δ 14.2, 14.5, 14.6, 15.2,

Deoxygenative Di[â,â-bis(ethylthio)]vinylation of Aldehydes
J . Org. Chem., Vol. 66, No. 11, 2001 3929
6.23 (1H, s); 13C NMR (101 MHz) δ 13.9, 14.0, 14.8, 27.0, 27.3,
Research Fund of KIT. We also thank the Center for
Instrumental Analysis KIT for the use of their facilities.
27.6, 61.8, 73.7, 134.5, 138.4, 174.9. Anal. Calcd for
C
11H20O3S2: C, 49.97; H, 7.62. Found: C, 49.77; H, 7.54.
Su p p or tin g In for m a tion Ava ila ble: Experimental pro-
cedures and spectral and analytical data for compounds 1, 3b-
i,k ,n ,o, 8, 9, 15, and 23c. This material is available free of
charge via the Internet at http://pubs.acs.org.
Ack n ow led gm en t. We are grateful for financial
support of this work by a Grant-in-Aid for Scientific
Research from the Ministry of Education, Science,
Sports and Culture of J apan and by the C. O. E.
J O010007E