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H. Veisi, A. Sedrpoushan, M. A. Zolfigol, F. Mohanazadeh, and S. Hemmati
Vol 50
Scheme 2
the reaction, EtOH (10 mL) was added and insoluble catalyst was
removed by filtration. The filtrate was evaporated under reduced
pressure and the resulting crude material was purified by
chromatography column (eluent: CH2Cl2) to give pure carbonyl
compounds.
dithioacetal was rapid and gave excellent yields of the
products, when catalyzed by SPSA in the presence of
wet‐SiO2 (5 min, 98%, entry 21, Table 1). As shown in
Table 1, various types of 1,3‐dithianes and 1,3‐dithiolanes
(aromatic, aliphatic, and α,β‐unsaturated) with electron‐
donating and ‐withdrawing groups were cleanly and
rapidly converted to the corresponding parent carbonyl
compounds in the solvent‐free conditions using SPSA at
room temperature.
Acknowledgments. The authors are thankful to Payame Noor
University (PNU), Bu‐Ali Sina University, and Iranian Research
Organization for Science and Technology (IROST) for financial
support.
CONCLUSION
In conclusion, in this study, the authors have introduced a
new and useful solvent‐free application of SPSA as an effi-
cient solid acid heterogeneous catalyst for the thioacetaliza-
tion of aldehydes and ketones and dethioacetalization under
mild reaction conditions at room temperature. The method
is highly chemoselective for protection of aldehydes in the
presence of ketones. Moreover, the method has advantages
in terms of high yields of products, short reaction times, op-
erational simplicity, and easy work up of products.
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General procedure for deprotection of 1,3‐dithianes and
1,3‐dithiolanes using silica phenyl sulfonic acid in solvent‐
free condition. Substrate (1 mmol), SPSA (0.5 g) and 0.5 g
wet‐SiO2 were added to a mortar and the mixture was pulverized
with a pestle. A spontaneous reaction took place [2–5 min, Table
1, monitored by TLC (9:1, hexane/acetone)]. After completion of
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet