Novel acylation of a vinyl group by the reaction of an aldehyde and a vinylselenonium ylide

Article abstract of DOI:10.1039/b100660f

Vinylselenonium ylide, which was generated from (Z)-vinylselenonium salt with a base such as sodium or potassium hydride, reacted with aromatic aldehydes to produce the α,β-unsaturated ketones, which were obtained in better yields from the aldehydes with an electronwithdrawing group than from those with an electrondonating group.

Full text of DOI:10.1039/b100660f

Novel acylation of a vinyl group by the reaction of an aldehyde and a
vinylselenonium ylide
Shin-ichi Watanabe, Tomokazu Kusumoto, Chikayo Yoshida and Tadashi Kataoka*
Gifu Pharmaceutical University, 6-1 Mitahora-higashi 5-chome, Gifu 502-8585, Japan.
E-mail: kataoka@gifu-pu.ac.jp; Fax: +81-58-237-5979; Tel: +81-58-237-3931
Received (in Cambridge, UK) 17th January 2001, Accepted 23rd March 2001
First published as an Advance Article on the web 11th April 2001
Vinylselenonium ylide, which was generated from (Z)-
vinylselenonium salt with a base such as sodium or
potassium hydride, reacted with aromatic aldehydes to
produce the a,b-unsaturated ketones, which were obtained
in better yields from the aldehydes with an electron-
withdrawing group than from those with an electron-
donating group.
Scheme 2
Generally, vinylonium salts, for example vinylphosphonium,1
sulfonium,2 and selenonium3 salts, are utilized as Michael
acceptors against nucleophiles to produce saturated alkyl ylides,
which are among the most important synthons of the C–C bond
forming reaction. If the a-hydrogen of a vinylonium salt is
abstracted by a base, a vinyl onium ylide is formed. There have
been few reports about the reactivity of vinylphosphonium
ylide, which reacts with carbonyl compounds to afford allene
reaction of vinylselenonium salts 2 with sodium hydride. The
reaction of vinylselenonium salt 2a (1 equiv.) with p-
nitrobenzaldehyde (1 equiv.) in the presence of 1.3 equiv. of
sodium hydride at 0 °C for 3 h in THF gave p-nitrophenyl styryl
ketone 3a in 65% yield but did not proceed at 278 °C. Since p-
chlorobenzaldehyde gave p-chlorophenyl styryl ketone 3b
(
11%) with recovery of the aldehyde (30%), 2 equiv. of sodium
hydride were used and the yield of 3b was improved up to 58%.
However, the reactions with benzaldehyde or p-tolualdehyde
gave complex mixtures including unreacted aldehyde, and a,b-
unsaturated ketones were not isolated. To confirm the formation
of the vinylselenonium ylide, vinylselenonium salt 2b was
stirred with 1 equiv. of sodium hydride in THF at 0 °C for 3 h
4
derivatives through the Wittig olefination. However, reports on
the reaction of other vinylonium ylides with carbonyl com-
pounds have been lacking.
5
In the course of our studies on alkenylselenonium salts, we
have focused on the reactivity of vinylselenonium ylides with
great interest. To our astonishment, the reactions of vinylsele-
nonium ylides with aromatic aldehydes did not bring about the
Wittig type reaction but caused an acylation reaction of a vinyl
group. Although there have been a few reports on the efficient
acylation of the vinyl group using aldehyde via alkoxy-
2
without the aldehyde, followed by treatment with D O to afford
a mixture of 2b and 2bA (2b+2bA = 9+16) in 40% yield. The
mixture of 2b and 2bA was treated with sodium hydride in the
presence of p-nitrobenzaldehyde under the same conditions as
for the reaction of 2a with p-nitrobenzaldehyde to give the
compound 3c, which contained no deuterium, in 49% yield
6
7
vanadium or alkoxyzirconocene intermediates, our reaction is
quite different from these reactions which use an organometallic
reagent. This transformation is a novel and original reaction,
and would attract the interest of many chemists in the
unprecedented behavior of vinyl ylides. We report herein the
first example of acylation reactions of vinylselenonium ylides
with aldehydes affording trans-chalcone derivatives efficiently
via umpolung of a carbonyl group like the Lapworth con-
densation.8
(
Scheme 3). This finding indicated that the above reactions
proceeded via a vinylselenonium ylide. On the other hand, the
reaction of vinylselenonium salt 2b and benz(aldehyde-d) with
sodium hydride in DMF at 0 °C for 4 h was conducted to trace
the hydrogen atom of an aldehyde. 3-(4-Fluorophenyl)-1-phe-
nylpropenone 3d obtained in 14% yield did not contain any
deuterium.
Firstly, vinylselenonium salts bearing an a-hydrogen were
prepared from the reactions of vinylsilanes with diphenyl
2 2
selenoxide and Lewis acid in CH Cl at rt by reference to the
9
procedure for alkynylselenonium salts (Scheme 1). † (E)-
Trimethylstyrylsilanes 1a and 1b reacted cleanly in the presence
of trifluoromethanesulfonic anhydride for 4 and 2 h to afford the
vinylselenonium triflates 2a and 2b in 87% and 59% yield,
respectively, with retention of configuration. The (Z) ster-
eochemistry of 2b was established by observation of the NOE
enhancement (10%) between the a-vinylic proton and ortho-
protons of the Z-aryl group.
Next, we investigated the reactions of vinylselenonium ylides
with aldehydes (Scheme 2). The ylides were generated by the
Scheme 3
On the basis of these results, we propose a plausible
mechanism for the reactions of vinylselenonium salts with
aldehydes (Scheme 4). Vinylselenonium ylide 4 is formed from
the reaction of vinylselenonium salt 2 with sodium hydride
followed by reaction with an aldehyde to produce betaine 5.
Deprotonation from the betaine 5 by a base gives rise to the b-
elimination to generate allenoate ion 6, which isomerizes to the
a,b-unsaturated carbonyl compound 3.
Scheme 1
DOI: 10.1039/b100660f
Chem. Commun., 2001, 839–840
This journal is © The Royal Society of Chemistry 2001
839

study on the vinylselenonium ylides to exploit their new
reactions.
This research was partially supported by the Ministry of
Education, Science, Sports and Culture, Grant-in-Aid for
Encouragement of Young Scientists, 2000, 11771388.
Notes and references
3
†
A typical example: Trifluoromethanesulfonic anhydride (0.8 cm , 4.7
mmol) was added dropwise to a stirred solution of diphenyl selenoxide (1.1
g, 4.3 mmol) and (E)-trimethylstyrylsilane (0.84 g, 4.7 mmol) in
3
dichloromethane (30 cm ) at 0 °C. The mixture was stirred at rt for 4 h. After
Scheme 4
the solvent was evaporated under reduced pressure, the precipitate was
washed several times with ether and recrystallised from CH
afford 1.82 g (87%) of 2a as colorless prisms: mp 113–114 °C; d
2
Cl
2
–Et
7.41 (d,
H, J 16.0), 7.50 (t, 2H, J 8.0), 7.63–7.71 (m, 9H), 7.73–7.90 (m, 6H);
2
O to
Next, potassium hydride, as a stronger base than sodium
hydride, was adopted in this reaction to improve the yield of
compound 3 (Table 1).‡ The reaction of p-nitrobenzaldehyde
with 2 equiv. of vinylselenonium salt 2a in the presence of 3
equiv. of potassium hydride in THF at 0 °C for 0.5 h afforded
the chalcone derivative 3a in excellent yield (entry 1). The
reactions of p-halobenzaldehydes also gave the corresponding
a,b-unsaturated carbonyl compounds 3b and 3e in high yields
compared with the reactions using sodium hydride (entries 2
and 3). Although no chalcone derivative had been obtained from
the reaction of benzaldehyde or p-tolualdehyde using sodium
hydride, trans-chalcone 3f was given using potassium hydride
in THF–DMSO (13+1) at 230 °C in up to 60% yield (entry 5);
moreover, the reaction with p-tolualdehyde bearing the elec-
tron-donating group afforded chalcone derivative 3g in moder-
ate yield (entry 6).
H
1
+
FABMS m/z 337 [M 2 TfO]
requires C, 52.0; H, 3.5%.
3 3
; Found: C, 51.8; H, 3.5. C21H17F O SSe
‡ A typical example: Potassium hydride (12 mg, 0.3 mmol) was added to a
stirred solution of vinylselenonium salt 2a (97 mg, 0.2 mmol) and p-
3
bromobenzaldehyde (19 mg, 0.1 mmol) in THF (3 cm ) at 0 °C. The mixture
was stirred at the same temperature for 0.5 h, poured into water and
extracted with ethyl acetate. The extracts were washed with brine and dried
over MgSO
residue was separated by preparative TLC (hexane–AcOEt = 5+1) to give
e (22 mg, 76%) as colorless powder: d 7.42–7.43 (m, 3 H), 7.48 (d, 1H,
J 16.0), 7.64 (d, 4H, J 8.0), 7.82 (d, 1H, J 16.0), 7.89 (d, 2H, J 8.0); EIMS
4
. After the solvent was evaporated under reduced pressure, the
3
H
+
m/z 287 (M) ; Found: C, 62.9; H, 4.0. C15H11BrO requires C, 62.7; H,
3.9%.
1
H. J. Bestmann and R. Zimmerman, in Comprehensive Organic
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Table 1 Reactions of vinylselenonium salt 2a with aldehydes in the
a
presence of KH
Product
(%
Entry RCHO
Conditions
yield)
2
3
4
A. C. Knipe, in The Chemistry of the Sulphonium Group, Part 1, ed.
C. J. M. Stirling, Wiley, Chichester, 1981, p. 313.
1
2
3
4
5
6
a
p-O
p-ClC
p-BrC
PhCHO
2
NC
6
H
4
CHO KH, THF, O °C, 0.5 h
3a (94)
3b (77)
3e (76)
3f (43)
3f (60)
Y. Watanabe, Y. Ueno and T. Toru, Bull. Chem. Soc. Jpn., 1993, 66,
6
H
4
CHO
CHO
KH, THF, O °C, 0.5 h
KH, THF, O °C, 0.5 h
2
042.
6
H
4
H. J. Bestmann, Angew. Chem., Int. Ed. Engl., 1977, 16, 349; T. Minami,
S. Shikita, S. So, M. Nakayama and I. Yamamoto, J. Org. Chem., 1988,
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KH, THF, 210 °C, overnight
b
KH, THF–DMSO, 230 °C, 2 h
b
p-MeC
6
H
4
CHO KH, THF–DMSO, 230 °C, 3.5 h 3g (49)
2
387.
2
a: RCHO+KH = 2+1+3. b THF+DMSO = 13+1.
5
S. Watanabe, K. Yamamoto, Y. Itagaki and T. Kataoka, J. Chem. Soc.,
Perkin Trans. 1, 1999, 2053; S. Watanabe, E. Mori, H. Nagai and T.
Kataoka, Synlett, 2000, 49; S. Watanabe, E. Mori, H. Nagai, T. Iwamura,
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Yamamoto, Y. Itagaki, T. Iwamura, T. Iwama, T. Kataoka, G. Tanabe
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In conclusion, we have shown the first example of the
reactions of vinylselenonium ylides with aldehydes, which
proceed via the b-elimination of the adducts of the vinylsele-
nonium ylides and the aldehydes because the selenonio group is
a good leaving group to produce trans-chalcone derivatives.
The results described in this paper implies that the vinylselenon-
ium ylides would react with other carbonyl compounds
differently from vinylphosphonium ylides, and we continue our
6
7
8
T. Hirao, D. Misu and T. Agawa, J. Am. Chem. Soc., 1985, 107, 7179.
B. Zheng and M. Srebnik, J. Org. Chem., 1995, 60, 3278.
A. Lapworth, J. Chem. Soc., 1903, 83, 995.
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O. Muraoka, J. Org. Chem., 1998, 63, 6382.
840
Chem. Commun., 2001, 839–840