Bis[trinitratocerium(IV)] Chromate1

[Ce(NO3)3]2CrO4

[93250-25-0]  · Ce2CrN6O22  · Bis[trinitratocerium(IV)] Chromate  · (MW 768.26)

(mild oxidizing reagent capable of oxidizing several functional groups;2,3 releases alcohols from allyl and propargyl silyl ethers4 and carbonyl compounds from acetals4)

Alternate Name: BTNCC.

Solubility: sol DMSO, DMF; moderately sol H2O; sparingly sol EtOH, MeCN; insol PhH.

Form Supplied in: yellow-orange solid.

Preparative Method: to a solution of Potassium Dichromate (0.02 mol) in H2O (100 mL), Cerium(IV) Ammonium Nitrate (0.02 mol) in H2O (50 mL) is added, and the mixture diluted with H2O (150 mL). The resulting precipitates are filtered, triturated with acetone, separated, and dried in air (70%).

Handling, Storage, and Precautions: stable at elevated temperatures (>200 °C) and to storage at rt for months. Chromate is a cancer suspect agent. Work with this reagent should be conducted in a fume hood.

Introduction.

Reactions with this reagent (BTNCC) proceed in dry benzene and residual oxidant can be separated by simple filtration. Drawbacks of other CeIV oxidations,1,5 such as cleavage reactions, strong acidic conditions, and the necessity of employing polar solvents or cosolvents, are not encountered with this reagent.

Oxidations.

Hydroquinones, a-hydroxy ketones, and primary and secondary saturated and benzylic alcohols are converted to their quinones, a-diketones, and carbonyl compounds, respectively, in high yields (eqs 1-3).2,4 Allyl, propargyl, and deactivated benzyl alcohols remain intact.

Benzyl silyl ethers are quantitatively converted to aldehydes (eq 4).4

Smooth oxidation of thiols to disulfides (eq 5) in high yield3 occurs with this mild reagent.

Deprotection Reactions.

This reagent releases alcohols from propargyl and allyl silyl ethers without further oxidation (eq 6).4 Saturated silyl ethers remain intact.

Deprotection of acetals proceeds well to produce carbonyl compounds (eq 7).

A brief comparison between this reagent, Cerium(IV) Ammonium Nitrate (CAN),5,6 and Pyridinium Chlorochromate (PCC)3,7 is shown in Table 1.


1. (a) Ho, T. L. In Organic Synthesis by Oxidations with Metal Compounds; Mijs, W. J.; De Jonge, C. R. H. I., Eds.; Plenum: New York, 1986; Chapter 11. (b) Molander, G. A. CRV 1992, 92, 29.
2. Firouzabadi, H.; Iranpoor, N.; Parham, H.; Toofan, J. SC 1984, 14, 631.
3. Firouzabadi, H.; Iranpoor, N.; Parham, H.; Sardarian, A.; Toofan, J. SC 1984, 14, 717.
4. Firouzabadi, H.; Shiriny, F. Unpublished results.
5. Ho, T. L. S 1973, 347.
6. Trahanovsky, W. S.; Young, L. B.; Brown, G. L. JOC 1967, 32, 3865.
7. Cainelli, G.; Cardillo, G. Chromium Oxidations in Organic Chemistry; Springer: Berlin, 1984.

Habib Firouzabadi

Shiraz University, Iran



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