144 J. CHEM. RESEARCH (S), 1999
J. Chem. Research (S),
1999, 144±145$
Synthesis of a-Phenylthioacylmethylene
Triphenylarsoranes and their Wittig-type Reactions$
Gui-Sheng Deng, Zhi-Zhen Huang, Xiao-Chun Yu and Xian Huang*
Department of Chemistry, Zhejain University Xixi Campus, Hangzhou, 310028, P.R. China
ꢀ-Phenylthio acylmethylene triphenylarsoranes, the first stable ꢀ-thiyl arsonium ylides, are prepared by
phenylsulfenylation±transylidation reaction of the corresponding acylmethylene triphenylarsoranes with phenylsulfenyl
chloride; Wittig reactions are carried out under mild reaction conditions on the arsonium ylides to provide ꢀ-phenylthio-
ꢀ,ꢁ-unsaturated ketones.
Wittig reagents with a heteroatom such as aryl or alkylthio
on the a-position can play a special role in synthesis. These
Wittig reagents behave as an equivalent of the acyl anion,
and are very useful intermediates in organic synthesis.
Scheme 2
Thus, it is of interest to introduce a thiyl group into ylides.
Although a-arylthio acylmethylene phosphonium ylides have
Chloroform was found to be superior to toluene as
reaction solvent. The ratio of Z to E isomers was easily
been synthesized by Saikachi and Nakamura,1 they were
rather unreactive and only reacted with very reactive
estimated by 1H NMR spectroscopy, as the b-vinyl proton
occurs at much lower ®eld in the Z-isomer than in the
aromatic aldehydes.2 We synthesized the phosphonium
ylides according to ref. 1 and found they reacted with di-
culty with aromatic aldehydes, e.g. benzaldehyde. Therefore,
1
E-isomer. H NMR data of 6a, 6b, 6e and 6f were in agree-
ment with those of refs. 3, 4, 5 and 6, respectively. The
stereochemistry of this reaction and the location of the
b-vinyl proton of the product are analogous to those
their application in the synthesis of a-arylthio-a,b-
unsaturated ketones is limited. Considering that arsonium
ylides are relatively easy to prepare, and it being of particu-
lar interest that they are more reactive than analogous
phosphonium or sulfonium ylides in Wittig reactions,
observed in the Wittig-type reaction of a-selenoarsonium
ylides.7 The results show that Z-isomers are the dominant
products.
we therefore synthesized a-phenylthioacylmethylene tri-
phenylarsoranes and studied their Wittig-type reactions.
Experimental
a-Phenylthio-a,b-unsaturated ketones are, as expected, pro-
duced upon Wittig reaction.
Proton nuclear magnetic resonance (1H NMR) spectra were
determined using a Varian PMX60SI (60 MHz) or a AZ-300 MHz
spectrometer using tetramethylsilane (TMS) or hexamethyldisilane
(HMDS) as the internal standard. Infrared (IR) spectra were
obtained as neat capillary cells (liquid products) or KBr disks (solid
products) on a PE 683 instrument. Mass spectra data were obtained
by electron ionization (EI) on a HP5989A mass spectrometer.
All reactions were carried out under nitrogen. All solvents were
dried and redistilled before use. Melting points were uncorrected.
Acetylmethylene triphenylarsorane, benzoylmethylene triphenyl-
arsorane, and phenylsulfenyl chloride were prepared according to
refs. 8, 9 and 10, respectively.
a-Phenylthioacylmethylene triphenylarsoranes
formed from acylmethylene triphenylarsoranes
3
1
were
and
benzenesulfenyl chloride
transylidation reaction. Two equivalents of acylmethylene
triphenylarsorane were treated with equivalent of
2
by
a
phenylsulfenylation±
1
1
benzenesulfenyl chloride 2 in dry benzene at room tem-
perature to produce white crystalline a-phenylthio acyl-
methylene triphenylarsoranes 3a and 3b (Scheme 1) in near
quantitative yield and the arsonium salts 4a and 4b were
recycled in 90 and 93% yields respectively. Compounds 3,
to our knowledge, represent the ®rst stable a-thio arsonium
ylides, showing moderate stability to heat, light and
moisture. They can be stored for more than six months in a
drying apparatus at room temperature. However, they turn
yellow when heated up to their melting points.
Typical Procedure. Synthesis of ꢀ-Phenylthio Acetylmethylene
Triphenylarsine 3a.ÐA solution of phenylsulfenyl chloride
2
(5.65 mmol) in 8 cm3 dry benzene was added dropwise to a stirred
solution of acetylmethylene triphenylarsorane 1a (11.3 mmol) in
80 cm3 dry benzene at room temperature during 40 min. The reac-
tion mixture was then stirred for two hours. After the suspension
was ®ltered o, the residue was recycled to obtain 1.85 g arsonium
salt 4a in 90% yield. The ®ltrate was evaporated under reduced
pressure to obtain 2.61 g ꢀ-phenylthio acetylmethylene triphenyl-
arsorane 3a in 98% yield as white crystals, which were recrystallized
from EtOH, mp 184±185 8C, ꢂH (60 MHz, CDCl3, TMS), 7.43±7.11
(m, 20 H) and 2.28 (s, 3 H); m/z 470 (M, 4.98%), M 1, M 2,
320, 306, 227, 152 (100) 121, 105, 77, 51, 43. IR ꢃmax/cm 1, 1590 s,
1520 vs, 1480 s, 735 vs, 685 vs (Found: C, 68.96; H, 5.03. Calc. for
C27H23AsOS: C, 68.93; H, 4.93%).
The arsonium salt 4b was recycled in 93% yield, and compound
3b was obtained as white crystals in 91% yield using the above
procedure, mp 176±177 8C, 1H NMR (60 MHz, CDCl3, TMS),
dH 7.90±7.74 (m, 2 H), 7.60±6.98 (m, 23 H); m/z 532 (M, 4.5%),
Scheme 1
1
As expected, the reaction of compounds 3 with aromatic
aldehydes 5 proceeded under mild conditions much more
easily than for the corresponding phosphonium ylides to
give the expected a-phenylthio-a,b-unsaturated ketones 6 in
good yields (Scheme 2). However, arsonium ylides 3 do not
react with aliphatic aldehydes; results are shown in Table 1.
305, 227, 152 (100), 105, 77, 51. IR ꢃmax/cm 1590 s, 1480 vs,
1440 s, 750 s, 680
32H25AsOS: C, 72.17; H, 4.73%).
Typical Procedure. Synthesis of 4-Phenyl-3-phenylthiobut-3-en-2-
s (Found: C, 72.44; H, 4.74. Calc. for
C
one (6b)4.ÐA mixture of ꢀ-phenylthio acetylmethylene triphenyl-
arsorane 3a (0.38 g, 0.8 mmol) and benzaldehyde 5b (0.06 g,
0.7 mmol) in 5 cm3 toluene was stirred at 90 8C in an oil-bath for 6
days under nitrogen atmosphere. After completion of the reaction,
the mixture was concentrated, and the product separated by ¯ash
chromatography on a preparative TLC (light petroleum±diethyl
ether, 10:1) to aord 6b in 75% yield. Oil. ꢂH (60 MHz, CCl4,
*To receive any correspondence.
$This is a Short Paper as de®ned in the Instructions for Authors,
Section 5.0 [see J. Chem. Research (S), 1999, Issue 1]; there is there-
fore no corresponding material in J. Chem. Research (M).
.
HMDS) 7.18±6.91 (m, 10 H), 7.64 (s, Z-C CH); 6.76 (s, E-C CH)
.