114 J. CHEM. RESEARCH (S), 1997
J. Chem. Research (S),
1997, 114†
Reductive Desulfonylation of b-Ketosulfones by TiCl4–Zn†
Hongyun Guo, Suming Ye, Junquan Wang and Yongmin Zhang*
Department of Chemistry, Hangzhou University, Hangzhou, 310028, P.R. China
b-Ketosulfones are readily reduced by TiCl4–Zn to give the corresponding ketones in good yields under mild
conditions.
b-Ketosulfones, which are important synthetic intermediates,
can be easily prepared by the phase-transfer-catalysed reac-
tion of the corresponding halides with sodium arylsulfin-
ates.1,2 a-Alkyl-b-ketosulfones can be obtained by the alkyla-
tion of b-ketosulfones.3 A useful transformation is the
reductive desulfonylation of b-ketosulfones to the corre-
sponding ketones.
obtained by the reductive cleavage of b-ketosulfones with
aluminum amalgam.5 The yield of this reaction was lower
because the ketones produced can be consumed by further
bimolecular reduction to pinacol. Two other widely exploited
desulfonylation methods involve zinc metal6 and chromous
ion.7 These procedures employ acidic media for prolonged
periods, often at elevated temperatures. Another two
methods use sodium dithionite8 and sodium hydrogen
telluride9 in basic media to provide the corresponding
ketones in moderate yields. Smith10 has reported that the
reductive cleavage of b-ketosulfones with trialkyl- or tri-
phenylstannanes can be achieved under essentially neutral
conditions. In order to obtain good to excellent yields, the
desulfonylation must be heated at reflux in toluene. It is
worth noting that (C5H5)2TiCl2-Zn is not more effective for
the reductive desulfonylation. In our experiments, we
observed that the yield was lower and the separation of crude
product by preparative TLC became more difficult. In con-
trast, the reductive cleavage of b-ketosulfones with TiCl4–Zn
circumvents most of these problems. The present method
offers some distinct advantages, such as mild and neutral
conditions, high yields, rapid reaction and easy operation.
Recently, low-valent titanium reagents4 have been of great
interest in organic synthesis. Herein we report the reductive
desulfonylation of b-ketosulfones with TiCl4–Zn to afford
corresponding ketones under mild conditions (Scheme 1,
Table 1).
O
O
TiCl4–Zn, THF
2 h, r.t.
Ph
SO2
Ph
Ph
R
R
Scheme 1
Table 1 Reductive desulfonylation of b-ketosulfones with
TiCl4–Zn
Substrate
Product
Yield mp/°C (Lit.)
(%)a
O
O
Experimental
oil11
Ph
Ph
SO2Ph
SO2Ph
Ph
83
74
Typical Procedure.sUnder an inert atmosphere of nitrogen,
TiCl4 (1.14 g, 6 mmol) was added by syringe to a stirred slurry of
zinc powder (0.2 g, 3 mmol) in THF (20 ml) in a 50 ml three-neck
flask. The mixture was stirred magnetically for 0.5 h at room tem-
perature. A light blue suspension was obtained. A solution of
substrate (1 mmol) in THF (2 ml) was then added to this stirred
suspension. The mixture was stirred for 2 h at room temperature.
The reaction was monitored by TLC. A dilute solution of HCL
(5%, 10 ml) and ether (20 ml) were added. The organic layer
was separated and the aqueous layer was extracted with either (20
mlÅ2). The combined organic solution was washed with a satu-
rated solution of NaCl (20 ml) and dried over anhydrous Na2SO4.
After evaporating the solvent under reduced pressure, the crude
product was purified by preparative TLC on silic gel using cyclo-
hexane–ethyl acetate as eluent. The product had identical spectral
data (1H NMR, IR) to that obtained from an authentic sample.
O
O
oil12
Ph
O
O
O
Ph
Ph
SO2Ph
SO2Ph
Ph
87
92
oil13
O
67–68 (68.5–699)
Ph
Ph
Ph
O
O
Ph
SO2Ph
Ph
82
55–57 (56.5–589)
Cl
Cl
This work was supported by the National Natural Science
Foundation of China.
O
O
SO2
75
48–50 (5114
)
Br
Br
Me
Received, 17th September 1996; Accepted, 19th November 1996
Paper E/6/06405A
O
O
O
O
oil12
Ph
Ph
Ph
Ph
SO2Me
SO2Me
75
76
References
oil13
1 G. E. Veermstra, Synthesis, 1975, 519.
2 J. Wildeman, Synthesis, 1979, 733.
O
O
3 B. Samuelsson and B. Lamm, Acta. Chem. Scand., 1969, 23,
2203.
82
66–68 (68.5–699)
Ph
SO2Me
Ph
Ph
Ph
4 J. E. McMurry, Chem. Rev., 1989, 89, 1513.
5 M. C. Mussatto, D. Savoia, C. Trombini and A. U. Ronchi, J. Org.
Chem., 1980, 45, 4002.
6 H. O. House and J. L. Larson, J. Org. Chem., 1968, 33, 61.
7 L. Pavlickova, B. Koutek, J. Velek and M. Soucek, Collect. Czech.
Chem. Commun., 1974, 39, 1216.
8 A. R. Harris, T. J. Mason and G. R. Hannah, J. Chem. Res. (S),
1990, 218.
aYields of isolated product.
It was discovered that the corresponding ketones are not
obtained from a-disubstituted b-ketosulfones by refluxing in
THF for 8 h.
The same reductive desulfonylation can be effected by
many existing procedures, for example, ketones can be
9 X. Huang and J. Pi, Synth. Commun., 1990, 20, 2297.
10 A. B. Smith, K. J. Hale and J. P. McCauley, Tetrahedron Lett.,
1989, 30, 5579.
*To receive any correspondence.
11 Beilstein, VII, 1923, p. 271.
†This is a Short Paper as defined in the Instructions for Authors,
Section 5.0 [see J. Chem. Research (S), 1997, Issue 1]; there is there-
fore no corresponding material in J. Chem. Research (M).
12 Beilstein, VII, 1923, p. 313.
13 Beilstein, VII, 1923, p. 373.
14 Beilstein, VII, 1923, p. 283.
Guo, Hongyun
