Silver carbonate secondary alcohols

Koenigs-Knorr reaction is carried out using simple, liquid aglycons (methanol or ethanol, for example), the alcohol also serves as the solvent for the halide, and is frequently present in large excess. In such cases, the halide is rapidly converted into glycoside, and the water formed in the secondary reaction between the liberated hydrogen halide and silver carbonate is seldom cause for concern. 

A modification of the Oppenauer oxidation which uses trichloroacetaldehyde on alumina provides a good, general oxidation of alcohols, and in particular will oxidize a secondary akdiol in the presence of a primary one, as shown by the examples given in Scheme 16. This method is claimed to be superiw to silver carbonate on Celite and much cheaper. Other advantages of this method are that it is neutral, nonaqueous, and halide, ester and lactone functionalities survive the reaction conditions. ... 

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. 

Although silver carbonate although is not a very powerful oxidizing agent, it is extremely useful for the oxidation of alcohols to carbonyl compounds. The silver carbonate condensed on Celite is known as Fetizon s reagent which oxidizes primary alcohols to aldehydes (e.g. 7.5 is converted into 7.6) and secondary alcohols to ketones. 

Oxides of copper and silver are used to oxidize secondary alcohols in the vapor phase at 250-300 °C [349] or in the liquid phase at room temperature [380], respectively. A similar effect is achieved with lead tetraacetate in pyridine at room temperature. Benzhydrol is thus converted into benzophenone in 80% yield [442], The oxidation of codeine with silver carbonate requires 1 h of refluxing in benzene to give a 75% yield of codeinone [376],... 

Oxidation of the primary alcoholic group to a carboxyl group in diols with primary and secondary hydroxyls is accomplished by silver carbonate [377]. Unfortunately, an extremely large excess of the reagent is needed. Similar results are obtained with a rather exotic oxidant, 4-methoxy-2,2,6,6-tetramethyl-l-oxopiperidinium chloride, which is prepared by treatment with chlorine of a stable radical, 4-methoxy-2,2,6,6-tetramethylpiperidin-1-oxyl. The compound oxidizes 1,4-butanediol to y-butyrolactone in 100% yield (isolated yield 81%) and 1,5-pentanediol to 8-valerolactone in 61% yield (isolated yield 40%) [995] (equation 292). 

A variety of methods has been devised for the confirmation of heptachlor residues (Table II). The presence in the heptachlor molecule (Figure 1) of a reactive allylic chlorine atom has been the basis of three confirmatory tests based on its ease of replacement. Reaction with a silver acetate-glacial acetic acid mixture produced 1-acetoxychlordene which, with the GLC conditions used, had a retention time close to heptachlor epoxide 44). Of the common organochlorine pesticides, only heptachlor reacted quantitatively. Endrin reacts to a small extent with the glacial acetic acid to give a secondary endrin ketone peak. When the reaction of heptachlor with silver salts was extended to silver carbonate in aqueous alcohol, 1-hydroxychlordene was obtained which can easily be converted to the more volatile and GG-responsive silyl ether. Unfortunately, this silyl ether has a Rt identical to aldrin. With silver carbonate, hepta-... 

The same allylic alcohols (142) undergo regiospecific oxidative cleavage with pyridinium chloro-chromate at the ethylenic bond to give, after saponification, a-hydroxyacids (145). Extension of this reaction to a -unsaturated ketones (146), obtained by oxidation of secondary alcohols with silver carbonate on celite, affords a-ketoacids (147) <88TL626l>. 

It is possible to run a controlled over-oxidation reaction with silver carbonate. Fetizon discovered that 1,3-and 1,4-diols are smoothly oxidized to butyrolactone and valerolactone derivatives in good yield. Oxidation of a diol can be accomplished in the presence of a variety of functional groups, even another alcohol. A primary alcohol, for example, will be oxidized faster than a secondary alcohol, as illustrated by the conversion of 113 to 114.173... 

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. 

Allylic and benzylic primary and secondary alcohols are more easily oxidized, and a number of reagents selective for these are in use, including freshly precipitated manganese dioxide, silver carbonate, dichlorodicyanoquinone, and potassium ferrate. 4-(Dimethylamino) pyridinium chlorochromate is mild and selective as demonstrated in Equation 6.26 [44]. 

The boiling point of isopropyl nitrate is 101-102°C. It can only be obtained indirectly from isopropyl iodide and silver nitrate. Direct nitration of isopropyl alcohol is difficult due to oxidation at the carbon atom carrying the secondary hydroxyl group. 

We have seen (Sec. 14.24) that an alkyl halide is conveniently detected by the precipitation of insoluble silver halide when it is warmed with alcoholic silver nitrate. The reaction occurs nearly instantaneously with tertiary, allyl, and benzyl bromides, and within five minutes or so with primary and secondary bromides. Compounds containing halogen joined directly to an aromatic ring or to a doubly-bonded carbon, however, do not yield silver halide under these conditions. Bromo-benzene or vinyl bromide can be heated with alcoholic AgN03 for days without the slightest trace of AgBr being detected. In a similar way, attempts to convert aryl... 

Palladium-catalyzed coupling of a vinyl halide with a secondary allylic alcohol in the presence of silver acetate or carbonate results in a conjugated dienol with retention of configuration of the vinyl halide. 

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