A new method for synthesis of alkylidene sulfones via direct alkylidenating reaction of ketones with Gem-dibromomethyl sulfones promoted by the Sm/SmI2 system in the presence of a catalytic amount of CrCl3

Article abstract of DOI:10.1081/SCC-100000178

Alkylidene sulfones were prepared in moderate to good yields via direct alkylidenating reaction of ketones with geminal dibromomethyl sulfones promoted by Sm/SmI₂ system in the presence of a catalytic amount of CrCl₃ under mild conditions.

Full text of DOI:10.1081/SCC-100000178

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A NEW METHOD FOR SYNTHESIS OF ALKYLIDENE
SULFONES VIA DIRECT ALKYLIDENATING REACTION
OF KETONES WITH GEM-DIBROMOMETHYL SULFONES
PROMOTED BY THE Sm/SmI2 SYSTEM IN THE
PRESENCE OF A CATALYTIC AMOUNT OF CrCl3
Yunkui Liu a , Huayue Wu b & Yongmin Zhang c
a Department of Chemistry , Zhejiang University , Xixi Campus, Hangzhou, 310028, P.R.
China
b Department of Chemistry , Wenzhou Normal College , Wenzhou, 325000
c Department of Chemistry , Zhejiang University , Xixi Campus, Hangzhou, 310028, P.R.
China
Published online: 09 Nov 2006.
To cite this article: Yunkui Liu , Huayue Wu & Yongmin Zhang (2001) A NEW METHOD FOR SYNTHESIS OF ALKYLIDENE
SULFONES VIA DIRECT ALKYLIDENATING REACTION OF KETONES WITH GEM-DIBROMOMETHYL SULFONES PROMOTED BY
THE Sm/SmI2 SYSTEM IN THE PRESENCE OF A CATALYTIC AMOUNT OF CrCl3 , Synthetic Communications: An International
Journal for Rapid Communication of Synthetic Organic Chemistry, 31:1, 47-52, DOI: 10.1081/SCC-100000178
To link to this article: http://dx.doi.org/10.1081/SCC-100000178
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SYNTHETIC COMMUNICATIONS, 31(1), 47–52 (2001)
A NEW METHOD FOR SYNTHESIS OF
ALKYLIDENE SULFONES VIA DIRECT
ALKYLIDENATING REACTION OF
KETONES WITH GEM-DIBROMOMETHYL
SULFONES PROMOTED BY THE Sm/SmI2
SYSTEM IN THE PRESENCE OF A
CATALYTIC AMOUNT OF CrCl3
Yunkui Liu,1 Huayue Wu,2 and Yongmin Zhang1,∗
1Department of Chemistry, Zhejiang University, Xixi
Campus, Hangzhou, 310028, P.R. China
2Department of Chemistry, Wenzhou Normal College,
Wenzhou, 325000
ABSTRACT
Alkylidenesulfoneswerepreparedinmoderatetogoodyields
via direct alkylidenating reaction of ketones with geminal dibro-
momethyl sulfones promoted by Sm/SmI2 system in the presence
of a catalytic amount of CrCl3 under mild conditions.
Vinyl sulfones have attracted special attention as important intermediates
in various synthetic transformations (1–7). They are normally prepared by the
Wittig-Horner reaction (8–11). However, this reaction has so far been limited to
preparation of arylidene sulfones. Besides, the preparation of the starting materials
∗ To whom correspondence should be addressed.
47
Copyright ꢀ 2001 by Marcel Dekker, Inc.
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C

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LIU, WU, AND ZHANG
is both inconvenient and time-consuming. Posner and Brunelle (12) reported a
modified procedure of the Wittig-Horner reaction, which could afford alkylidene
sulfones as well as arylidene sulfones. However, the use of BuLi in low temperature
is somewhat disadvantageous. It was reported that vinyl sulfones could also be
prepared by Knoevenagel condensation of aldehyde with sulfonylacetic acid esters,
followed by decarboxylation using lithium iodide in DMP (13), but this method
is failure for the preparation of alkylidene sulfones. Another method for synthesis
of vinyl sulfones is addition of selenosulfonates to olefins followed by oxidation-
elimination of β-phenylseleno group (14), but the use of toxic benzeneseleninic
acid is unfavorable.
In past decades, the reaction of carbonyl groups with gem-dimetallic species
has played a compensatory role in olefin synthesis (15–18). It was reported that
aldehyde-selective olefination could be performed by gem-dichromium reagents
(19) and ester-carbonyl olefination was realized by the use of Ti-Zn system (20–
22). However, to the best of our knowledge, there were few reports on dimetallic
reagents using lanthanoids as the key element. Most recently, Matsubara et al. (23)
developed a convenient route to synthesize alkenylsilanes and alkenylstannanes via
direct alkylidenating reaction of ketones with dibromomethyltrimethylsilane and
dibromomethyltrimethylstannane promoted by the Sm/SmI2/CrCl3(cat.) system.
According to the facts mentioned above, we tried to apply this system directly
to alkylidenate ketones with dibromomethyl sulfones. Fortunately, the reaction
gave alkylidene sulfones in moderate to good yields (Scheme 1). The results are
summarized in Table 1.
For efficient alkylidention, both low-valent samarium and a chromium (III)
saltwereindispensable. WhenonlySmI2 wasused, thereactiongaveβ-arylsulfonyl
alcohols, while alkylidene sulfones were not detected (Entry 1). The table shows
that combination of SmI2 and Sm worked more effectively than the use of SmI2
alone (by comparing Entry 2 with 1; Entry 4 with 3). A treatment of gem-
dibromomethyl sulfones with SmI2 and Sm in the presence of CrCl3 gave the
best yield. Interestingly, treatment of ketones with gem-dichloromethyl arysul-
fones under the same reaction conditions gave only β-arylsulfonyl alcohols, and
no alkylidene sulfones were detected (Scheme 2).
In conclusion, it has been found that alkylidene sulfones, which are not avail-
able through most methods for preparation of vinyl sulfones, can be conveniently
prepared via direct alkylidenation of ketones with gem-dibromo methyl sulfones
promoted by the Sm/SmI2/CrCl3(cat.) system. The remarkable advantages of
Scheme 1.

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49
Table 1. Synthesis of Alkylidene Sulfones
Reagent (mmol)
Entry
Ar
R1
R2
SmI2 Sm CrCl3 Ratio (E:Z)a
Yield (%)b
1
2
3
4
5
6
7
8
9
10
11
12
13
p-MeC6H4
p-MeC6H4
p-MeC6H4
p-MeC6H4
p-MeC6H4
p-MeC6H4 Me Et
p-MeC6H4 Me n-Pr
p-MeC6H4 Me n-Bu
Ph
Ph
Ph
Ph
Ph
-(CH2)4-
4
2
4
2
2
2
2
2
2
2
2
2
2
0
2
0
2
2
2
2
2
2
2
2
2
2
0
0
not detectedc
20
-(CH2)4-
-(CH2)4-
-(CH2)4-
-(CH2)5-
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
31
65 (3a)
67 (3b)
78 (3c)
73 (3d)
71 (3e)
80 (3f)
72 (3g)
73 (3h)
70 (3i)
66 (3j)
60/40
62/38
65/35
65/35
67/33
70/30
70/30
Me Et
Me n-Pr
Me n-Bu
Me n-C5H11
-(CH2)4-
aRatio determined by 1H NMR (300 MHZ).
bIsolated yields.
cl-(Bromo-p-Tolysulfonyl) methyl cyclopentanol was isolated in 50% yield.
this procedure are its mild, neutral reaction conditions, easy availability of starting
materials, simple operation, and moderate to good yields.
EXPERIMENTAL
Melting points are uncorrected. IR spectra were recorded on a PE-683
spectrometer, 1H NMR spectra were obtain with a Bruker AC 80 MHz spectrome-
ter in CCl4 solution using TMS as internal standard. The E/Z ratio was determined
with a Bruker Avance 300 MHz spectrometer. Mass spectra were obtained on a HP
5989 mass spectrometer. Elemental analyses were performed on a Carlo Erba 1106
Scheme 2.

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LIU, WU, AND ZHANG
instrument. The reactions were performed in a Schlenk type glass apparatus un-
der a nitrogen atmosphere. THF was freshly distilled from sodium-benzophenone
ketyl prior to use.
General Procedure for the Synthesis of Alkylidene Sulfones
To a mixture of Sm powder (0.30 g, 2.00 mmol), SmI2 (0.1M in THF,
20 mL, 2.0 mmol), and anhydrous CrCl3 (0.16 g, 0.1 mmol) was added a mixture
of dibromomethyl sulfone (2.0 mmol) and ketone (1.0 mmol) in THF (4 mL) at
room temperature under an inert atmosphere of nitrogen. The mixture was stirred
for 0.5 h at the same temperature, then for 2 h at 45◦C. The resulting mixture
was treated with dilute HCl (0.1N, 5 mL) and then extracted with ether (2 × 30
mL) and dried over anhydrous NaSO4. The solvent was removed in vacuo. The
crude product was purified by preparative TLC on silica gel using cyclohexane-
ethylacetate (6:1) as eluent.
3a. Oil; 1H NMR, 7.80 (d, 2H, J = 8.0 Hz), 7.32 (d, 2H, J = 8.0 Hz), 6.16 (s,
1H), 2.40 (s, 3H), 2.32–1.50 (m, 8H) ppm; IR, 3050, 1640 cm−1; m/z, 236 (M+);
Anal. calcd. for C13H16O2S: C 66.07; H 6.82. Found: C 66.28; H 6.89.
3b. Oil; 1H NMR, 7.70 (d, 2H, J = 8.0 Hz), 7.30 (d, 2H, J = 8.0 Hz), 5.96
(s, 1H), 2.40 (s, 3H), 2.30–1.48 (m, 10H) ppm; IR, 3060, 1630 cm−1; m/z, 248
(M+); Anal. calcd. for C14H18O2S: C 67.17; H 7.25. Found: C 67.42; H 7.29.
3c. Oil; 1H NMR, 7.76 (d, 2H, J = 8.0 Hz), 7.30 (d, 2H, J = 8.0 Hz), 6.05 (s,
1H), 2.40 (s, 3H), 2.22 (q, 2H, J = 7.8 Hz), 2.02 (s, 3H), 0.97 (t, 3H, J = 7.8 Hz)
ppm; IR, 3060, 1635 cm−1; m/z, 224 (M+); Anal. calcd. for C12H16O2S: C 64.25;
H 7.19. Found: C 64.03; H 7.08.
3d. Oil; 1H NMR, 7.70 (d, 2H, J = 8.0 Hz), 7.24 (d, 2H, J = 8.0 Hz), 6.02
(s, 1H), 2.44 (s, 3H), 2.30 (t, 2H, J = 7.8 Hz), 2.01 (s, 3H), 1.68–1.12 (m, 2H),
0.88 (t, 3H, J = 7.8 Hz) ppm; IR, 3060, 1640 cm−1; m/z, 238 (M+); Anal. calcd.
for C13H18O2S: C 65.51; H 7.61. Found: C 65.20; H 7.49.
3e. Oil; 1H NMR, 7.74 (d, 2H, J = 8.0 Hz), 7.26 (d, 2H, J = 8.0 Hz), 6.02 (s,
1H), 2.40 (s, 3H), 2.18 (t, 2H, J = 7.8 Hz), 2.00 (s, 3H), 1.54–1.10 (m, 4H), 0.88
(t, 3H, J = 7.8 Hz) ppm; IR, 3060, 1640 cm−1; m/z, 252 (M+); Anal. calcd. for
C14H20O2S: C 66.63; H 7.99. Found: C 66.71; H 7.89.
3f. Oil; 1H NMR, 8.02–7.70 (m, 2H), 7.60–7.32 (m, 3H), 6.04 (s, 1H), 2.40
(s, 3H), 2.33 (q, 2H, J = 7.8 Hz), 0.90 (t, 3H, J = 7.8 Hz) ppm; IR, 3060, 1635
cm−1; m/z, 210 (M+); Anal. calcd. for C11H14O2S: C 62.83; H 6.71. Found: C
62.62; H 6.80.
3g. Oil; 1H NMR, 8.02–7.72 (m, 2H), 7.62–7.36 (m, 3H), 5.96 (s, 1H), 2.30
(t, 2H, J = 7.8 Hz), 2.02 (s, 3H), 1.62–1.30 (m, 2H), 0.88 (t, 3H, J = 7.8 Hz) ppm;
IR, 3055, 1635 cm−1; m/z, 224 (M+); Anal. calcd. for C12H16O2S: C 64.25; H
7.19. Found: C 64.48; H 7.25.

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ALKYLIDENE SULFONES
51
3h. Oil; 1H NMR, 7.98–7.68 (m, 2H), 7.58–7.30 (m, 3H), 5.94 (s, 1H), 2.36
(t, 2H, J = 6.0 Hz), 2.02 (s, 3H), 1.60–1.20 (m, 4H), 0.88 (t, 3H, J = 7.8 Hz) ppm;
IR, 3060, 1640 cm−1; m/z, 238 (M+); Anal. calcd. for C13H18O2S: C 65.51; H
7.61. Found: C 65.83; H 7.49.
3i. Oil; 1H NMR, 7.98–7.68 (m, 2H), 7.62–7.30 (m, 3H), 5.98 (s, 1H), 2.37
(t, 2H, J = 6.0 Hz), 2.02 (s, 3H), 1.60–1.20 (m, 6H), 0.88 (t, 3H, J = 7.8 Hz) ppm;
IR, 3065, 1640 cm−1; m/z, 252 (M+); Anal. calcd. for C14H20O2S: C 66.63; H
7.99. Found: C 66.38; H 7.88.
3j. Oil; 1H NMR, 7.88–7.58 (m, 2H), 7.52–7.28 (m, 3H), 5.92 (s, 1H), 2.40
(s, 3H), 2.24–1.50 (m, 8H) ppm; IR, 3060, 1635 cm−1; m/z, 222 (M+); Anal. calcd.
for C12H14O2S: C 64.84; H 6.35. Found: C 65.12; H 6.24.
6a (24). Colorless crystal, m.p. 80◦–81◦C (Lit. 82◦–83◦C); 1H NMR, 8.06–
7.85 (m, 2H), 7.72–7.43 (m, 3H), 4.53 (s, 1H), 3.72 (brs, 1H), 1.58 (s, 3H), 1.38
(s, 3H) ppm; IR, 3565, 3010, 1455, 1330, 1155, 1090, 760 cm−1
.
6b. Colorless crystal, m.p. 99◦–100◦C; 1H NMR, 7.74 (d, 2H, J = 8.0 Hz),
7.23 (d, 2H, J = 8.0 Hz), 4.41 (s, 1H), 3.63 (brs, 1H), 2.42 (s, 3H), 1.56 (s, 3H),
1.33 (s, 3H) ppm; IR, 3570, 3010, 1460, 1330, 1210, 1150, 1090, 760, 685 cm−1
;
m/z, 264 (M+ + 2), 262 (M+); Anal. calcd. for C11H15ClO3S: C 50.28; H 5.75.
Found: C 50.48; H 5.77.
6c. Colorless crystal, m.p. 139◦–141◦C; 1H NMR, 8.04–7.78 (m, 2H), 7.70–
7.41 (m, 3H), 4.46 (s, 1H), 3.58 (brs, 1H), 1.88–1.17 (m, 10H) ppm; IR, 3520,
2950, 2880, 1650, 1460, 1320, 1160, 1090, 960, 725, 690cm−1;m/z, 290(M+ + 2),
288 (M+); Anal. calcd. for C13H17ClO3S: C 54.07; H 5.93. Found: C 54.35; H
5.86.
ACKNOWLEDGMENTS
We thank the National Natural Science Foundation of China (Project No.
29872010 and 294938004) and the Laboratory of Organometallic Chemistry,
Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, for
financial support.
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Received February 1, 2000

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