Oxidation by silver oxide

Dimethylcarbodihydrazide (280) reacts with aldehydes to afford 1,5-dimethyltetrahydro-l,2,4,5-tetrazin-6-ones (281), which can be oxidized by silver oxide, potassium ferricyanide or lead dioxide to yield radicals (282) related to the verdazyls these can be transformed into tetrahydro-l,2,4,5-tetrazines (283) by hydrogenation over palladium (80AG766). 

As mentioned before structure of 2-2 was proposed by spectral analyses, the position of methylenedioxyl group in isoquinoline of 2-2 is in position C-5—C-6, but it did not exclude its possibility in position C-7—C-8. A total synthesis was accomplished in order to confirm the structure and to derive more samples for pharmacological tests. Piperonal 2-4 was used as starting material. It was oxidized by silver oxide in basic condition to get 2-5, then amidized with dimethyl amine to 2-6 and directed ortho-lithiation with n-butyl-lithium in THF (tetrahydrofuran) to get homogeneous yellow solution, which upon treatment with methyl iodide afforded toluamide 2-7, the yield was 85%. The model synthesis study showed that lithiated toluamide 2-7 could condense with compound 2-14 to achieve the final product 2-2 through several steps (see below). The intermediate compound 2-14 could be synthesized starting from the same piperonal 2-4. It was reacted with cyclohexylamine to get Shiff base 2-8, the latter was reacted with 1.13 equiv. of n-butyllithium at -78°C, the metalated intermediate was carbethoxylated in situ by addition of excess ethyl chloroformate and the aldehyde 2-9 was obtained by extraction with dilute acid. Combination of 2-9 with equimolar of propane-1,3-dithiol a compound 2-10 was obtained, then 2-10 was reduced by lithium aluminum hydride and benzylated with benzyl bromide to 2-12. After treatment with bis(trifluoroacetoxy) iodobenzene, the obtained compound 2-13 was reacted with benzylamine to get the key compound 2-14. 

Since the achievements of these pioneers, the oxidation of aldehydes has been the subject of a lot of work using either thermal, photochemical, or catalytic autooxidation or else catalytic oxidation by silver oxide. 

Aldohexoses, fructose, arabinose, erythritol, glyceraldehyde, glucaric acid, and galactonic lactone are oxidized by silver oxide at 50°C. (in water or N KOH) to carbon dioxide, oxalic acid, formic acid, and glycolic acid... 

The oxidation, by silver oxide or bromine, of the hemiacetal formed on exposure of glutardialdehyde to one equivalent of Grignard reagent provides a general route to <5-lactones. 

Thiazol-2-yl radicals have also been generated by silver oxide oxidation of thiazol-2-ylhydrazine in various aromatic solvents (Scheme 69). The... 

C. HIO is prepared by oxidation of iodine with perchloric acid, nitric acid, or hydrogen peroxide or oxidation of iodine in aqueous suspension to iodic acid by silver nitrate. Iodic acid is also formed by anodic oxidation at a platinum electrode of iodine dissolved in hydrochloric acid (113,114). 

Silver carbonate, alone or on CeHte, has been used as a catalyst for the oxidation of methyl esters of D-fmctose (63), ethylene (64), propylene (65), trioses (66), and a-diols (67). The mechanism of the catalysis of alcohol oxidation by silver carbonate on CeHte has been studied (68). 

The selective oxidation is catalyzed by silver, which is the only good catalyst. Other olefins are not converted selectively to the epoxides in the presence of silver. However, propylene epoxidation is appHed commercially the catalysts are either molybdenum complexes in solution or soHd Ti02—Si02 (see... 

Cevadine contains neither a methoxyl nor a methylimino group it yields crystalline benzoyl and o-nitrobenzoyl derivatives, m.p. 255° and 236° respectively, and a methiodide, which decomposes at 210-2°, and is converted by silver oxide into eevadinemethylhydroxide.i When warmed with alcoholic soda, cevadine undergoes hydrolysis into eevine and angelic and tiglic acids. When hydrogen chloride is passed into cevadine in alcohol, ethyl tiglate and eevine are formed. ... 

We have described above the main observed phenomena for capillary effects by silver nitrates, however other chemical compounds display a different behaviours as it is described in the next section for lead oxides. 

The 5-isobutoxymethyl monothioacetal is stable io2N hydrochloric acid and to 50% acetic acid some decomposition occurs in 2 A sodium hydroxide. The monothioacetal is also stable to 12 A hydrochloric acid in acetone (used to remove an A -triphenylmethyl group) and to hydrazine hydrate in refluxing ethanol (used to cleave an A-phthaloyl group). It is cleaved by boron trifluoride etherate in acetic acid, by silver nitrate in ethanol, and by trifluoroacetic acid. The monothioacetal is oxidized to a disulfide by thiocyanogen, (SCN)2. ... 

Thus, Experiment 7 involved the same oxidation-reduction reaction but the electron transfer must have occurred locally between individual copper atoms (in the metal) and individual silver ions (in the solution near the metal surface). This local transfer replaces the wire middleman in the cell, which carries electrons from one beaker (where they are released by copper) to the other (where they are accepted by silver ions). 

For example, consider the net ionic equation for the oxidation of copper metal to copper(II) ions by silver ions (Fig. K.6) ... 

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... 

The rate expression for the oxidation of water by silver(II) perchlorate, [Ag(II)] [C104-] ... 

According to experiment the induced air oxidation can be suppressed by silver(l) or copper(rr) if added in sufficient quantity . 

The effect of silver chlorite on iodomethane in the absence of any solvent gives rise to an immediate explosion. During another attempt it was observed that the presence of a solvent delays but does not prevent the explosion from happening. This accident can be intapreted in two different ways instability of the methyl chlorite formed, or violent oxidation of the iodised compound by silver chlorite, which is a strong oxidant. 

Therefore, the use of several specific techniques while implementing the method of semiconductor sensors makes it feasible to detect and analyze emission of oxygen atoms at initial stage of metal oxidation although in case of silver it should be noted that there are no phase of silver oxide formed due to its instability at such conditions [57]. Rather, the absorption of oxygen by silver would be related to dissolution and internal oxidation. 

The ligand group can be introduced either on the meso or on the /5-pyrrole position of the porphyrin ring, but the synthesis of the meso-functionalized derivatives is easier and has been more widely exploited. Balch (50-53) reported that the insertion of trivalent ions such as Fe(III) (32) and Mn(III) (33) into octaethyl porphyrins functionalized at one meso position with a hydroxy group (oxophlorins) leads to the formation of a dimeric head-to-tail complex in solution (Fig. 11a) (50,51). An X-ray crystal structure was obtained for the analogous In(III) complex (34), and this confirmed the head-to-tail geometry that the authors inferred for the other dimers in solution (53) (Fig. lib). The dimers are stable in chloroform but open on addition of protic acids or pyridine (52). The Fe(III) octaethyloxophlorin dimer (52) is easily oxidized by silver salts. The one-electron oxidation is more favorable than for the corresponding monomer or p-oxo dimer, presumably because of the close interaction of the 7r-systems in the self-assembled dimer. 

Oxidative cross-coupling reactions of alkylated derivatives of activated CH compounds, such as malonic esters, acetylacetone, cyanoacetates, and certain ketones, with nitroalkanes promoted by silver nitrate or iodine lead to the formation of the nitroalkylated products.67 This is an alternative way of performing SRN1 reactions using a-halo-nitroalkanes. 

The exchange current density of Pt-metals is relatively small, but they have high stability. Very high cost does not permit to use them in the batteries of wide application. Noticeably higher activity, very good stability and lower costs are demonstrated by silver. The most inexpensive catalyst is activated carbon that has very high surface area. This type of catalyst is used in some batteries. Activity of carbon electrode can be improved by additive of oxide (e.g. Mn02) or pyropolymers. 

The isomerization of D-mannosaccharodilactone which proceeds under the influence of alkaline reagents can also be brought about by diazomethane and by silver oxide and methyl iodide. In both cases isomerization is accompanied by methylation and there results 2,5-dimethyI-A4-D-mannosaccharo-3,6-lactone methyl ester (Cl).84... 

Halcon (2) A process for oxidizing ethylene to ethylene oxide, using atmospheric oxygen, and catalyzed by silver. Developed by Halcon International in the late 1940s and early 1950s and first commercialized at Lavera, France. See Halcon (1). 

Alkyl-3-hydroxy-4-pyridinones can be converted into analogues containing, e.g., anilino-, phenylthio-, or 2-hydroxyethylthio-substitu-ents by silver(I) oxidation (Ag20 in ethanol) followed by Michael addition (71). In aminomethylation of 3-hydroxy-4- and -2-pyridinones under Mannich conditions the position of substitution can be tailored, by reaction conditions to position C4 or C6, or by converting the OH into OMe, which directs substitution to C5 (72). 

---