1192
SHIRINI et al.
was converted into 4-methylacetophenone whereas
the acetophenone semicarbazone was recovered
unchanged.
chromatography on silica gel in an yield indicated in
the table. We gratefully acknowledge the Research
Council of Guilan University for partial support of
this study.
It should be noted that these deoximation reactions
did not proceed at the use either of ammonium di-
chromate, ZrCl4, or wet SiO2 alone.
REFERENCES
In conclusion we can state that a mild, efficient,
and chemoselective deoximation method has been
developed. The deoximation occurs at room tempera-
ture under solvent-free conditions.
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EXPERIMENTAL
Oximes deoximation (general procedure). To a
mixture of ZrCl4 (0.69 g, 3 mmol) and 0.4 g of wet
SiO2 (SiO2 to H2O 4:1 by weight) and ammonium
dichromate (0.252 g, 1 mmol) was added an appropri-
ate oxime (1 mmol). The resulting mixture was stir-
red at room temperature for a time specified in the
table (TLC or GLC monitoring). After completion of
the reaction CH2Cl2 (5 ml) was added to the mixture,
and 15 min later the solution obtained was filtered
and dried on anhydrous MgSO4. The solution was
filtered off, the solvent was evaporated, and the
carbonyl compound formed was isolated by column
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 8 2003