Celite silver carbonate support

Silver carbonate supported on Celite (Fetizon s reagent) has found wide application in organic chemistry (Fieser and Fieser, 1977). It has been used mainly for the oxidation of alcohols and lactones for the oxidative... 

Optimum yields of (3-vinyl-y-butyrolactols from the Pd(II) promoted reaction of vinyl triflates with Z-but-2-en-l,4-diol (Scheme 6.33) are attained when tetra-n-butylammonium chloride is added (47]. The lactol is conveniently oxidized to the lactone with celite-supported silver carbonate. The corresponding arylbutyrolactols are obtained in high yield (70-80%) from an analogous reaction of iodoarenes with the enediol. The yields of 2-alkenyl-2,5-dihydrofurans, resulting from the Pd(0) catalysed reaction of cyclic alkynylcarbonates with acrylic esters via tandem C-C and C-0 bond forming reactions, are enhanced by the presence of tetra-n-butyl-ammonium fluoride (e.g. Scheme 6.33) (48]. 

The reagents which have been used here to illustrate these interesting reactions are periodic acid for the oxidation of 2,6-di-t-butylphenol,56 and a Celite-supported silver carbonate reagent for the oxidation of 2,6-dimethyl phenol, and 2,4,6-trimethylphenol57 (Expt 6.129). 

Methods of oxidation of hydrazo to azo compounds and hydroxylamino to nitroso compounds have been reviewed. Reagents which oxidize aromatic primary amines to azo compounds are also suitable for the oxidation of aromatic hydrazo compounds, since the hydrazo compounds are intermediates in the oxidation of the amines. Thus, manganese dioxide, mercury(II) oxide and lead tetraacetate are all suitable oxidants. Silver carbonate on Celite rapidly oxidizes both diarylhydrazines and acylhydrazines to the corresponding azo compounds in good yield. Another supported oxidant which can convert hy-drazobenzene into azobenzene in high yield is sodium periodate on silica gel. ... 

Historically, the first supported oxidizing reagent, reported by Fdtizon and Golfier, was silver carbonate on celite (another diatomaceous earth). This was obtained by precipitation of the reagent onto its support. Ag2C03 on celite smoothly oxidizes primary and secondary alcohols, a,(o-diols, hydroquinones and amines. The main practical asset of the reagent is that it avoids the need to filter off finely divided silver salts after reaction. 

Several references have appeared on the use of solid-phase oxidants. Solid potassium permanganate-copper sulphate mixtures oxidize secondary alcohols to ketones in high yield, and pyridinium chromate or chromic acid on silica gel are described as convenient off-the-shelf reagents for oxidation of both primary and secondary alcohols. Anhydrous chromium trioxide-celite effects similar transformations only when ether is present as co-solvent. An excellent review, with over 400 references, on supported oxidants covers the use of silver carbonate-celite, chromium trioxide-pyridine-celite, ozone-silica, chromyl chloride-silica, chromium trioxide-graphite, manganese dioxide-carbon, and potassium permanganate-molecular sieve. 

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