1746
G. Sabitha et al.
LETTER
In conclusion the present procedure is a better alternative
to the existing ones for the cleavage of sulfonates and sul-
fonamides due to its simplicity, comparable yields, short-
er times and solvent free conditions.
Scheme 2
Acknowledgement
SA and BVS thank CSIR, New Delhi for the award of a fellowship.
References and Notes
†
IICT Communication No. 4320.
(1) a) Caddick, S.; Tetrahedron, 1995, 51, 10403.
b) Mingos, D.M.P; Chem. Ind. 1994, 596 and references cited
therein.
(2) Bram, G.; Loupy, A.; Villemin, D.; in Solid supports and
catalysts in organic synthesis; K. Smith, Ed.; Ellis Horwood
and Prentice Hall Chichester 1992, Chap 12.
(3) Loewenthal, H.J.E.; Tetrahedron, 1959, 6, 269.
(4) a) Greene T.W. and Wuts, P.G.M. Protective Groups in
organic synthesis, 2nd Ed. 1991 John Wiley and Sons, New
York.
b) Kocienski, P.J. Protecting Groups. 1994 Thieme, New
York.
(5) a) Denney, D.B.; Goldstein, B.; J. Org. Chem. 1956, 21, 479.
b) Kovacs, J.; Ghatak, U.R.; J. Org. Chem. 1996, 31,119.
(6) a) Closson, W.D.; Wriede, P.; Bank J. Am. Chem. Soc. 1966,
88, 1581.
b) Gostler, S.J.L.B.; Waring, A.; Bame, S.; Closson W.D.;
Wriede, P.; J. Am. Chem. Soc. 1967, 89, 5311.
(7) a) Sridhar, M.; Ashok Kumar, B.; Narender, R.; Tetrahedron
Lett. 1998, 39, 2847.
b) Nyare, B.; Grehn, L.; Ragnasson, U.; J. Chem. Soc. Chem.
Comm. 1997, 1017.
(8) Kenner, G.W.; Murray, M.A.; J. Chem. Soc. 1949, 5178.
(9) a) Typical procedure for the cleavage of sulfonates:
Piperonyl- toluenesulfonate(1a, 2.92g, 10mmol) and 37% KF
on Al2O310 (3 weight equivalents of sulfonate) were admixed
in a pyrex test tube and subjected to microwave irradiation for
3min. After cooling down to room temperature, the solid mass
was extracted with ethyl acetate and concentrated in vacuo.
The crude product was subsequently purified by column
chromatography on silica gel (100-200 mesh, ethyl acetate-
hexane 2:8) to afford sesmol (2a, 1.22g, 88% yield) as white
solid.
b) Typical procedure for the cleavage of sulfonamides: Indole
sulfonamide (3a, 2.71g, 10mmol) and 37% KF on Al2O3 (3
weight equivalents of sulfonate) were admixed in a pyrex test
tube and subjected to microwave irradiation for 5min. The
solid mass was allowed to cool to room temperature, and was
extracted with ethyl acetate (2 x 15ml). The organic layer was
concentrated in vacuo and was purified by column
chromatography on silica gel (100-200 mesh, ethyl acetate-
hexane 2:8) to afford indole (4a, 1.03g, 88% yield) as a white
solid.
mides was not successful either with non supported KF or
basic Al2O3 alone. A strong microwave effect on the rate
of the reaction was observed as the yield fell to 40-50%
under conventional conditions instead of 80-90% under
microwave irradiations.
(10) Schmitting, E.A.; Sawyer, J.S.; Tetrahedron. Lett. 1991, 7207.
Article Identifier:
1437-2096,E;1999,0,11,1745,1746,ftx,en;L08299ST.pdf
Synlett 1999, No. 11, 1745–1746 ISSN 0936-5214 © Thieme Stuttgart · New York