7
36
A. R. Pourali
þ
ꢁ
4
secondary thioamides and thioureas were reacted with n-Bu N IO at room tem-
4
perature to afford the corresponding amides or ureas at mild and aprotic reaction
conditions in good yields.
In conclusion, our procedure provides a selective and efficient method for
desulfurization of thioamides and thioureas under aprotic conditions using tetra-
butylammonium periodate as a cheap and commercially available reagent. Mild
reaction conditions, simple setup and workup, and solubility of the reagent in most
organic solvents are other advantages of the method.
Experimental
Chemicals were obtained from Merck and Fluka chemical companies. FT-IR spectra were recorded on
a Perkin Elmer RXI spectrometer. NMR spectra were recorded on a Brucker Avance DPX 250 MHz
instrument. The products were purified by column chromatography and the purity determination of the
products was accomplished by GLC on a Shimadzu model GC 10-A instrument or by thin layer
chromatography on silica gel polygram on SIL G=UV 254 plates.
Typical Procedure for the Conversion of Thiobenzamide to Benzamide
3
þ
To a solution of thiobenzamide (0.274 g, 2 mmol) in 10cm of methylene chloride was added n-Bu N
4
ꢁ
IO4 (0.433g, 1 mmol) at room temperature and the resulting mixture was stirred for 5 min. The
mixture becomes purple upon completion of the reaction. Then the mixture was washed with 10%
3
3
sodium thiosulfate solution (2ꢂ10cm ) and distilled water (2ꢂ10cm ). The organic phase was dried
with sodium sulfate and then filtered through a short column containing silica gel. Removal of the
ꢃ
solvent under reduced pressure afforded benzamide; yield 0.225 g (93%); mp 133–135 C (Ref. [33]
ꢃ
1
32–133 C).
Acknowledgements
The author gratefully acknowledges partial support to this work by the Damghan University Research
Council.
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[
[
[
[
[
[
[
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