Chemistry Letters 2001
513
mide, crotyl bromide, benzyl chloride, 2-bromoacetophenone
and ethyl bromoacetate. When crotyl bromide was used in
place of allyl bromide, the corresponding (E)-isomer (2-buten-
yl p-tolyl sulfone, Entry 6) was obtained in 80% yield, without
the formation of any rearranged product (1-methyl-2-propenyl
p-tolyl sulfone). This was checked by employing a secondary
allylic halide viz. 3-chloro-1-butene in lieu of crotyl bromide in
the above reaction and observed the formation of corresponding
coupled product (1-methyl-2-propenyl p-tolyl sulfone, Entry
“Comprehensive Organic Synthesis,” Pergamon Press,
Oxford, (1991), Vol. 6, p. 157; P. D. Magnus, Tetrahedron,
33, 2019 (1977).
3
For reports on Pd- and Te-catalyzed coupling reaction of
sulfonyl chlorides see: S. S. Labadie, J. Org. Chem., 54,
2496 (1989); using tetra-n-butylammonium oxone see: B.
M. Trost, and R. Braslace, J. Org. Chem., 53, 532 (1988);
H. Suzuki, Y. S. I. Nishioka, S. I. Padmanabhan, and T.
Ogawa, Chem. Lett., 1988, 727; using fluorides catalyst
see: A. A. Kolomeitsev, V. N. Movchun, N. V.
Kondratenko, and Y. L. Yagupolski, Synthesis, 1990, 1151;
using Aliquat 336 see: G. Bram, A. Loupy, M. C. Roux-
Schmitt, J. Sansoulet, T. Strzalko, and J. Seyden-Penne,
Synthesis, 1987, 56; using sodium formaldehyde sulfoxy-
late see: A. R. Harris, Synth. Commun., 18, 659 (1988); for
a more recent multistep report using (phenylsulfonyl)-1,2-
propadiene see: A. Padwa and P. E. Yeske, J. Org. Chem.,
56, 6386 (1991).
E. Block, in “The Chemistry of Functional Groups,” E.
Supplement, Part l, ed. by S. Patai, Wiley, New York
(1980), chap. 13; J. Smeek and J. S. Fowler, J. Org. Chem.,
33, 3422 (1968).
Y. Yamamoto and N. Asao, Chem. Rev., 93, 2307 (1993);
C. J. Li, Chem. Rev., 93, 2023 (1993); A. Lubineau. J.
Auge, and Y. Queneau, Synthesis, 1994, 741; C. J. Li,
Tetrahedron, 52, 5643 (1996).
L. A. Paquette and T. M. Mitzel, J. Am. Chem. Soc., 118,
1931 (1996); L. A. Paquette and P. C. Lobben, J. Am.
Chem. Soc., 118, 1917 (1996); C. J. Li, D. L. Chen, Y. Q.
Lu, J. X. Haberman, and J. T. Mague, J. Am. Chem. Soc.,
118, 4216 (1996).
L. L. Frye, E. L. Sullivan, K. P. Cusack and J. M. Funaro,
J. Org. Chem., 57, 697 (1992); S. S. Labadie, J. Org.
Chem., 54, 2496 (1989).
Aluminum chloride and iron powder used were of com-
mercial grade and procured from Central Drug House (Pvi)
Ltd., New Delhi-110 002; sulfonyl chlorides used were
obtained commercially and distilled before use.
10). The present procedure was not satisfactorily applicable to
an alkane sulfonyl chloride, a similar reaction of methanesul-
fonyl chloride with allyl bromide led to allyl methyl sulfone in
50% yield (Table 1). The same reaction was also not equally
effective when alkyl halides were used in place of allyl halides
and needs 7–8 h with 35–40% conversion only (Entries 15 and
1
6). Further increasing the reaction time gave no signiflcant
improvement in yields but rather decomposition occurred.
Similar treatment of other sulfonyl chlorides gave the corre-
sponding β,γ-unsaturated sulfones in 70–90% yields and the
typical results are summerised in Table 1. Although the
detailed mechanism of this reaction is not clear at this stage, it
is likely that this procedure features in situ activation of metal
to generate allyl metal which reacted with sulfonyl chloride to
form allylic sulfones after acidic quenching. We have
employed iron and aluminum because these metals are cheap
and readily available. All the compounds obtained were char-
4
5
6
1
acterised by infrared and H NMR spectroscopy and finally by
comparison with authentic samples.
In conclusion this new aluminum chloride–iron system
constitutes a useful alternatilve to the commonly accepted pro-
cedure for the synthesis of various sulfones of potentially high
synthetic utility. The main advantages of this new method are
mild reaction conditions, tolerence to olefinic double bonds,
simple operation, no polluting solvents and excellent yields of
the products.
7
8
References and Notes
l
B. M. Trost, Bull. Chem. Soc., Jpn., 61, 107 (1988).
2
For a review of sulfone chemistry see: B. M. Trost,