(diatomaceous, siliceous, or infusorial earth; filter aid; clarifying agent; adsorbent for reagents; chromatography1)

Physical Data: inorganic solid, mainly SiO2.

Solubility: insol H2O, acid, or dilute base.

Form Supplied in: Celite® is a well known trademark of Manville, Filtration and Minerals; an off-white to white solid; widely available.

General Considerations.

Celite is composed of mostly SiO2, and is known as diatomaceous earth or infusorial earth.1 Celite is used in a wide variety of applications including, but not limited to, a filter aid, heat insulating material, clarifying agent, filler, adsorbent for dynamite, chromatography, and as a mild abrasive. It is useful for removal of finely divided particulate matter like decolorizing carbon, and adsorbance of colloidal substances. Future and current uses for Celite include immobilization of enzymes, spores, or cells for chemical transformations as well as reagent support in columns for microscale chemistry. The focus of this entry is the use of Celite as a surface for reagents or reactants in heterogenous reactions including oxidation, alkylation, and dehydration of organic compounds.

Chromium Oxidations.

Oxidations employing Chromium(VI) Oxide on Celite or Pyridinium Chlorochromate on Celite have been useful for oxidation of b-hydroxynitrosamines, b-hydroxynitrosoureas,2 secondary alcohols (eq 1),3 propargyl alcohols,4 and primary alcohols to aldehydes (eq 2).5

Potassium Fluoride.

Potassium Fluoride-Celite is a heterogenous catalyst that promotes an efficient cyclization that is useful in the synthesis of prenylated flavanones (eq 3).6 Other studies include arylation reactions of 1,3-dicarbonyl compounds using fluoride ion by activation with iron,7 C-, N-, O-, and S-alkylations with alkyl halides,8 and KF/Celite alkylation reactions compared with other inorganic solid supports.9

Silver Carbonate.

Perhaps the best known reagent employing Celite is Fetizon's reagent. Silver(I) Carbonate promotes reactions with phenols, amines, hydrazines, hydroxylamines, oximes, and fragmentations. An extensive review10 describes selective oxidation of sensitive alcohols to aldehydes or ketones under neutral conditions, and includes a mechanistic discussion. Other studies include a series of papers on the oxidation of carbohydrates,11 oxidative coupling of phenols (eq 4),12 a mechanistic study,13 and oxidation of allylic alcohols (eq 5).14

Phosphorus Pentoxide.

Phosphorus(V) Oxide/Celite has been used to mediate Bischler-Napieralski reactions (eq 6),15 and has been used to dehydrate triflic acid to triflic anhydride in 70-90% yield (eq 7).16

1. The Merck Index, 11th ed.; Budavari, S. Ed.; Merck: Rahway, 1989; p 4878.
2. Saavedra, J. E.; Farnsworth, D. W.; Pei, G-K. SC 1988, 18, 313.
3. Flat, S. J.; Fleet G. W.; Taylor, B. J. S 1979, 815.
4. Wadsworth, D. H.; Geor, S. M.; Delty, M. R. JOC 1987, 52, 3662.
5. Kurth, M. J.; O'Brien, M. J.; Hope. H.; Yanuck, M. JOC 1985, 50, 2626.
6. Harwood, L. M.; Loftus, G. C.; Oxford, A.; Thomson, C. SC 1990, 20, 649.
7. Sutherland, R. G.; Abd-El-Aziz, A. S.; Piorko, A.; Lee, C. C. SC 1987, 17, 393.
8. Ando, T.; Yamawaki, J. CL 1979, 45.
9. Yamawaki, J.; Ando, T. CL 1979, 755.
10. Fetizon, M.; Golfier, M.; Mourgues, P.; Louis, J-M. In Organic Synthesis by Oxidation with Metal Compounds Mijs, W. J.; DeJonge, C. R. H. I., Eds.; Plenum: New York, 1986; 503-567.
11. Hammer, H.; Morgenlie, S. ACS 1978, 832, 343.
12. (a) Balough, V.; Fetizon, M.; Golfier, M. AG(E) 1969, 8, 444. (b) Balough, V.; Fetizon, M.; Golfier, M. JOC 1971, 36, 1339.
13. Kakis, F. J.; Fetizon, M.; Douchkine, N.; Golfier, M.; Mourgues, P.; Prange, T. JOC 1974, 39, 523.
14. Fetizon, M.; Geomez-Parra, Fl; Louis, J-M. JHC 1976, 13, 525.
15. (a) Young, S. D.; Wiggins, J. M.; Huff, J. R. JOC 1988, 53, 1115. (b) Kametani, T.; Fukumoto, K. JCS(P1) 1972, 394.
16. Stang, P. J.; Hanack, L. R.; Subramanian, L. R. S 1982, 85.

Todd M. Heidelbaugh

The Ohio State University, Columbus, OH, USA

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