1252
S. P. Chavan et al.
LETTER
Scheme 2
From the Table it is evident that thioacetals of aromatic
ketones (entries 4,5 and 6) are deprotected faster than nor-
mal ketones (entries 8, 9 and 10). 1,3-Oxathiolanes of ar-
omatic aldehydes are deprotected with equal ease (entries
1, 2 and 3). 1,3-Oxathiolanes of aliphatic aldehydes were
more resistant to the reagent and reaction goes only at
high temperature (entries 11 and 12). The difference in re-
activity of 1,3-oxathiolanes of aldehydes and ketones can
be used to advantage in effecting selective deprotection of
1,3-oxathiolanes derived from ketones in the presence of
aldehydes.
References and Notes
(1) (a) Greene, T. W.; “Protecting Groups In Organic Synthesis”
Wiley Interscience, New York 1981 (b) Lynch, J. E.; Eliel, E.
L. J. Am. Chem. Soc. 1984, 106, 2843 (c) Romo, J.;
Rosenkranz, G.; Djerassi, C. J. Am. Chem. Soc. 1951, 73, 4961
(d) Corey, E. J.; Erickson, B. W. J. Org. Chem. 1971, 36, 3553
(e) Fuji, K.; Idhikawa, K.; Fujita, E. Tetrahedron Lett. 1978,
356 (f) Barton, D. H. R.; Magnus, P. D. J. Chem. Soc. Perkin
Trans. 1972, 542 (g) Nishide, S. K.; Yokota, K. Tetrahedron
Lett. 1993, 34, 3425 (h) Ravindranathan, T.; Chavan, S. P.;
Varghese, J. P. J. Chem. Soc. Chem. Commun.1994, 1937.
(2) Kihlberg, J. O.; Leigh, D. A.; Bundle, D. R.; J. Org. Chem.
1990, 55, 2860.
(3) Veenman, G. H.; van Boom, J. H.; Tetrahedron Lett. 1990, 31,
275.
(4) Djerassi, C.; Shamma, M. J. Am. Chem. Soc. 1958, 80, 4723.
(5) Mandai, T.; Takeshita, M.; Kawada, M.; Otera, J. Chem. Lett.
1984, 1259.
The example in Scheme 2 illustrates the difference in the
rate of reaction for selective deprotection of the 1,3-ox-
athiolanes derived from ketones (analyzed by GC).
In conclusion the present protocol is chemoselective, effi-
cient, rapid, nonhazardous, solvent free and therefore
should find widespread utility in organic synthesis. We
are currently exploring the utility of the present protocol
for other functional group transformations.
(6) For other uses of Amberlyst 15, see (a) Perni, R. B. Synth.
Commun. 1989 2383 (b) Ballini, R.; Petrini, M. Synthesis
1990, 336.
(7) General Procedure:
A mixture of 1,3-oxathiolane (1 mmol), glyoxylic acid
(10 mmol) and Amberlyst 15 (0.125 gm) was stirred at room
temperature or added in a glass test tube and mixed thoroughly
followed by irradiation in a microwave oven. Progress of the
reaction was monitored by TLC. After the completion of the
reaction, this mixture was extracted with ether. The ether
extract was washed with 10 mL NaHCO3 (20%) solution and
dried over anhydrous Na2SO4 and filtered. Evaporation of the
solvent under reduced pressure gave pure carbonyl
compound.
Acknowledgement
One of the authors (PBS) thanks CSIR, New Delhi for financial sup-
port. Funding from CSIR, New Delhi under YSA (SPC) scheme is
gratefully acknowledged.
Article Identifier:
1437-2096,E;2001,0,08,1251,1252,ftx,en;D11401ST.pdf
Synlett 2001, No. 8, 1251–1252 ISSN 0936-5214 © Thieme Stuttgart · New York