Silver oxide compounds

Purdie t Methody also chiefly for hydroxy compounds. The substance is mixed with a small excess of dry silver oxide, and then shaken (or, if necessary, heated) with methyl iodide, a smooth methylation usually occurring. 

Treatment of O-silyl enols with silver oxide leads to radical coupling via silver enolates. If the carbon atom bears no substituents, two such r -synthons recombine to symmetrical 1,4-dicarbonyl compounds in good vield (Y. Ito, 1975). 

The structure of compound A was established in part by converting it to known compounds Treat ment of A with excess methyl iodide in the presence of silver oxide followed by hydrolysis with dilute hydrochlonc acid gave a tnmethyl ether of D galactose Companng this trimethyl ether with known trimethyl ethers of D galactose allowed the structure of compound A to be deduced... 

Synthesis by oxidation remains the first choice for commercial and laboratory preparation of quinones the starting material (1) provided the generic name quinone. This simple, descriptive nomenclature has been abandoned by Chemicaly hstracts, but remains widely used (2). The systematic name for (2) is 2,5-cyclohexadiene-l,4-dione. Several examples of quinone synonyms are given in Table 1. Common names are used in this article. 1,2-Benzoquinone (3,5-cydohexadiene-l,2-dione) (3) is also prepared by oxidation, often with freshly prepared silver oxide (3). Compounds related to (3) must be prepared using mild conditions because of their great sensitivity to both electrophiles and nucleophiles (4,5). 

Oxidation States. The common oxidation state of silver is +1, ie,, as found in AgCl, which is used with Mg in sea- or freshwater-activated batteries (qv) AgNO, the initial material for photographic materials, medical compounds, catalysts, etc and silver oxide, Ag20, an electrode in batteries (see Silver compounds). Few compounds are known. The aqua ion [Ag(H2 O), which has one unpaired electron, is obtained... 

Silver(II) Compounds. Sdver(II) is stabilized by coordination with nitrogen heterocychc bases, such as pyridine and dipyridyl. These cationic complexes are prepared by the peroxysulfate oxidation of silver(I) solutions in the presence of an excess of the ligand. An extensive review of the higher oxidation states of silver has beenpubhshed (21). 

Triphenylbismuth oxide [7173-99-1/, C gH BiO, has been prepared from triphenylbismuth dicyanide [41083-16-3], C2QH25B1N2, and mercuric oxide (151), and from triphenylbismuth dichloride and moist silver oxide (152). The ir and Raman spectra of this compound suggest that it is polymeric and has Bi—O—Bi bonds (153). Triphenylbismuth dihydroxide, and triarylbismuth hydroxide haUdes, eg, triphenylbismuth hydroxide chloride... 

Analogous to the oxidation of hydrazones to azo compounds, A-unsubstituted pyrazolidines are oxidized to A -pyrazolines. For example, the blcyclic pyrazolidine (415) when treated with silver oxide yields the pyrazoline (416) (65JA3023). Pyrazolidine (417) is transformed into the perchlorate of the pyrazolium salt (411) by reaction with mercury(II) acetate in ethanol followed by addition of sodium perchlorate (69JOU1480). 

Campaigne et al. have used 3-thenyl bromide obtained by benzoyl peroxide-catalyzed, side-chain bromination of 3-methylthiophene with A -bromosuccinimide, as a starting material for 3-substituted thiophenes. - 22 3-Methylthiophene is now prepared commercially from itaconic acid. The reactive halogen in 3-thenyl bromide could be directly reacted with a variety of nucleophiles, such as cyanide, or malonate, to give more complex 3-substituted compounds. 3-Thenyl bromide was converted by the Sommelet reaction to 3-thio-phenealdehyde which, with silver oxide, was oxidized to 3-thio-... 

Silber-oxydul, n. silver suboxide, -ojydver bindung,/. compound of silver oxide specif., argentate. -papier, n. silver paper, silvered paper. 

The biogenetic scheme for endiandric acids also predicts the plausible existence in nature of endiandric acids E (5), F (6), and G (7). Even though they are still undiscovered, their synthesis has been achieved (Scheme 6). For endiandric acids E and F, key intermediate 24 is converted, by conventional means, to aldehyde 35 via intermediate 34. Oxidation of 35 with silver oxide in the presence of sodium hydroxide results in the formation of endiandric acid E (5) in 90 % yield, whereas elaboration of the exo side chain by standard olefination (85 % yield) and alkaline hydrolysis (90 % yield) furnishes endiandric acid F (6). The construction of the remaining compound, endiandric acid G (7), commences with the methyl ester of endiandric acid D (36) and proceeds by partial reduction to the corresponding aldehyde, followed by olefination and hydrolysis with aqueous base as shown in Scheme 6. 

The fact that pentacarbonyl carbene complexes react with enynes in a chemo-selective and regiospecific way at the alkyne functionality was successfully applied in the total synthesis of vitamins of the Kj and K2 series [58]. Oxidation of the intermediate tricarbonyl(dihydrovitamin K) chromium complexes with silver oxide afforded the desired naphthoquinone-based vitamin K compounds 65. Compared to customary strategies, the benzannulation reaction proved to be superior as it avoids conditions favouring (E)/(Z)-isomerisation within the allylic side chain. The basic representative vitamin K3 (menadione) 66 was synthesised in a straightforward manner from pentacarbonyl carbene complex 1 and propyne (Scheme 38). 

In the Koenigs-Knorr method and in the Helferich or Zemplen modifications thereof, a glycosyl halide (bromide or chloride iodides can be produced in situ by the addition of tetraalkylammonium iodide) is allowed to react with a hydrox-ylic compound in the presence of a heavy-metal promoter such as silver oxide, carbonate, perchlorate, or mercuric bromide and/or oxide,19-21 or by silver triflu-oromethanesulfonate22 (AgOTf). Related to this is the use of glycosyl fluoride donors,23 which normally are prepared from thioglycosides.24... 

Alkyl halides can be hydrolyzed to alcohols. Hydroxide ion is usually required, except that especially active substrates such as allylic or benzylic types can be hydrolyzed by water. Ordinary halides can also be hydrolyzed by water, if the solvent is HMPA or A-methyl-2-pyrrolidinone." In contrast to most nucleophilic substitutions at saturated carbons, this reaction can be performed on tertiary substrates without significant interference from elimination side reactions. Tertiary alkyl a-halocarbonyl compounds can be converted to the corresponding alcohol with silver oxide in aqueous acetonitrile." The reaction is not frequently used for synthetic purposes, because alkyl halides are usually obtained from alcohols. 

Ammoniacal silver oxide is as dangerous as the previous similar compounds. Thus, the clear solution, which is obtained after centrifuging ammoniacal silver oxide leaves a very explosive compound as a residue to which was attributed the AgaN4 formula. It seems that the decomposition of this nitride is inhibited by ammonium salts. A similar situation was created after treating this ammoniacal oxide with silver nitrate until a solid started to precipitate, and this detonated 10 to 14 days after being prepared. It was assumed that this solid was AggNH. 

Tri-O-acetyl-a-D-xylopyranosyl bromide106 (138) and N-tosyl-L-serine methyl ester107 (139) were condensed in the presence of Drierite and silver oxide, and then the O-acetyl and methyl ester groups were removed by treatment with sodium hydroxide, and the N-tosyl group by means of sodium in liquid ammonia, to give 140. Synthesis of this compound has also been described by other workers108-110 and the a-D an-omer by Brendel and Davidson.108... 

Oxidation of the complexes [Ag(Py)4][MoF6] and [Ag(Py)2][UF6] in acetonitrile by MoF6 and UF6, respectively, leads to the silver(III) compounds [Ag(Py)4(NCMe)][MoF6]3 and [Ag(Py)2(NC-Me)3][UF6]3, which are strong oxidizing agents.167 Other pyridine silver(III) complexes have been obtained by oxidation of silver nitrate and ammonia with ammonium peroxydisulfate in aqueous... 

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