Oxidation of Alcohols under mild conditions...

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Silica Sulfuric Acid/Potassium Permanganate/Wet SiO2 as an Efficient Heterogeneous Method for the Oxidation of Alcohols under Mild Conditions
BiBi Fathemeh Mirjalili, Mohamad Ali Zolfigol, ,* Abdolhamid Bamoniri,à and Amin Zarei

Bull. Korean Chem. Soc.  Vol. 24, No. 3,400,(2003)

http://journal.kcsnet.or.kr/publi/bul/bu03n3/400.pdf

Excerp...Along this line, we have introduced potentially useful oxidants for selective oxidation and oxidative deprotection of different functional groups. Therefore, we decided to choice a new reagent or reagent systems to overcome the above limitations. In addition, for our propose both clean and easy work-up were also important. On the other hand, any reduction in the amount of sulfuric acid needed and/or any simplification in handling procedures is required for risk reduction, economic advantage and environment protection. In addition, there is current research and general interest in heterogeneous systems because of the importance such systems have in industry and in developing technologies.


Conclusion
In conclusion, the cheapness and the availability of the reagents, easy and clean work-up, and high yields make this method attractive for the large-scale operations. This procedure is very simple and contamination by over oxidation side-products is avoided. Moreover, the new element here is that the reaction is heterogeneous. This could be worthwhile for overcoming of the limitations of chromium based oxidant. We believe that the present methodology would be an important addition to existing methodologies.

References

1. Hudlicky, M. Oxidation in Organic Chemistry; ACS Monograph
186, 1990.
2. Trost, B. M. Comprehensive Organic Synthesis (Oxidation),
Pergamon: New York, 1991; Vol. 7.
3. Warnhoff, E. W.; Mortin, D. G.; Jonson, W. S. Org. Syn. 1963, 40,
162.
4. House, H. O. Modern Synthetic Reactions, 2nd ed.; Benjamin, W.
A., Ed.; Benjamin, Inc.: Menlo Park, CA, 1972; pp 257-291.
5. (a) Firouzabadi, H.; Iranpoor, N.; Zolfigol, M. A. Synth. Commun.

[demorol]

Silica Sulfuric Acid/KbrO₃/Wet SiO₂ as an Efficient Heterogenous System for the Oxidation of Alcohols Under Mild Conditions

Acta Chim. Slov. 2003, 50, 563-568

(http://acta.chem-soc.si/50/50-3-563.pdf)

Abstract: A combination of silica sulfuric acid and potassium bromate in the presence of wet SiO₂ were used as an effective oxidizing agent for the oxidation of alcohols to their corresponding aldehyde or ketone derivatives in dichloromethane, acetonitrile or toluene in good yields.

Experimental

General:

Chemicals such as alcohols, potassium bromate, dichloromethane, toluene, acetonitrile and silica gel were purchased from Fluka, Merck and Aldrich chemical companies. Silica sulfuric acid was synthesized according to our previously reported procedure.^9-11 The oxidation products were characterized by comparison of their spectral (IR, ¹H NMR), TLC and physical data with the authentic samples.

Oxidation of Hydroquinone to p-Benoquinone. A Typical Procedure:

A mixture of hydroquinone (0.275g, 2.5 mmol), potassium bromate (0.167g, 1 mmol), silica sulfuric acid (0.2g) and wet SiO₂ (60% w/w, 0.2g) in dichloromethane (5 mL) was stirred at room temperature for 30 minutes. The heterogeneous mixture was filtered and washed with Na₂S₂O₃ solution (10%, 2×20 mL). The organic phase was collected. Anhydrous Na₂SO₄ (2g) was added to the solution and filtered after 15 minutes. Dichloromethane was removed. The solid was crystallized from n-hexane. The p-benzoquinone was obtained in good yield (Table).




Preparation of Silica Sulfuric Acid

Synlett 2003, 1877-1879
DOI:

10.1055/s-2003-41469

A 500 mL suction flask was used. It was equipped with a constant-pressure dropping funnel containing chlorosulfonic acid (23.3g, 0.2 mol) and gas inlet tube for conducting HCl gas over an adsorbing solution i. e. H₂O. Into it were charged 60.0g of silica gel. Chlorosulfonic acid was added dropwise over a period of 30 min at r.t. HCl gas evolved from the reaction vessel immediately. After the addition was complete the mixture was shaken for 30 min. A white solid (silica sulfuric acid) 76.0g was obtained.