Oxidation by mercuric oxide

A stock solution of potassium hydroxide in ethanol was prepared and stored under nitrogen. Old stocks are brown and contain a dark sediment, but they are apparently just as effective as the freshly prepared reagent. Methanolic potassium hydroxide has also been used by the submitters this remains clear and colorless for long periods but offers no other advantage over the ethanolic solution. In absence of the basic solution, the acetone hydrazone is not oxidized by mercuric oxide. 

Preparation. The reagent can be prepared in 70-90% yield by oxidation of acetone hydrazone with yellow mercuric oxide (British Drug Houses) catalyzed by potassium hydroxide. In the absence of base the hydrazone is not oxidized by mercuric oxide.1 Unstable solutions are obtained by use of silver oxide in place of mercuric oxide.2... 

Both methylene groups in 1,2 3,5-di-0-methylene-a-D-xylose are resistant to oxidation by mercuric oxide, selenium dioxide, potassium periodate, or chromium trioxide. With potassium permanganate in 85% phosphoric acid, however, the 1,2-0-methylene ring is removed preferentially, to give 3,5-0-methylene-D-xylose 1,2-carbonate. The general applicability of this reaction has not been studied. 

The second piece of evidence against Robinson s strychnine formula arises from the bromine oxidation of Wieland s Ci7-acid. If the double bond of Wieland s acid (XXVIII) is oxidized with bromine-hydrobromic acid reagent (106, 111), the keto aldehyde, XLV, is formd. It may be further oxidized by mercuric oxide to the corresponding acid (XLVI). Reduction of one of the ketonic groups of XLVI to an alcohol and dehydra-... 

Hyalobiouronic acid, 3-0-( -D-glucopyranosyl uronic acid)-2-amino-2-deoxy-D-glucose, can be obtained by the acid hydrolysis of hyaluronic add in a yield of about 60%. This result indicates that the disaccharide is a repeating unit of the polysaccharide . The structure of the disaccharide (I) was established as follows. The methyl ester of the disaccharide (II) was oxidized by mercuric oxide to the 2-amino-2-deoxy-gluconic acid derivative... 

A-Nor-B-homo steroids with different substitution patterns than those described above may be prepared by acid catalyzed cyclization of 3)3-hydroxy-5(10)-seco-cholest-tra/w-l(l0)-en-5-one acetate (134a) formed in 30-40% yield by mercuric oxide-iodine sensitized irradiation of cholestane-3j3,5a-diol... 

The oxidation of amines by mercuric acetate is an old reaction (54) which up until recent years was employed primarily to modify alkaloid structures (55). A systemic study of the oxidizing action of mercuric acetate by Leonard and co-workers led to the development of a general method for the synthesis of enamines from cyclic tertiary amines. An observation made after a large number of compounds were oxidized, but which is worth noting at the onset, is that a tertiary hydrogen alpha to the nitrogen atom is removed preferentially to a secondary a-hydrogen. 

The preceding section described the preparation of enamines by mercuric acetate oxidation of tertiary amines. The initial product in these oxidations is the ternary iminium salt, which is converted to the enamine or mixture of enamines by reaetion with base. Thus iminium salts synthesized by methods other than the oxidation of tertiary amines or the protonation of enamines are potential enamine sources. 

Enamines derived from 1-azabicycloalkanes, readily accessible by mercuric acetate oxidation of saturated bases (112), have been extensively studied recently (113-115). Since an immonium salt is formed during dehydrogenation, the composition of the liberated enamine mixture shows the relative stability of the various possible isomers. The study of infrared and NMR spectra has shown that the position of the enamine double bond is determined by factors similar to those determining the relative stability of simple olefins. 

The dimer of 1-methyl- -pyrroline (39) was obtained by reduction of N-methylpyrrole with zinc and hydrochloric acid (132) and, together with the trimer, by mercuric acetate dehydrogenation of N-methylpyrrolidine (131). J -Pyrroline-N-oxides form dimers in a similar manner (302). Treatment of 1,2-dimethyl-zl -piperideine with formaldehyde, producing l-methyl-3-acetylpiperidine (603), serves as an example of a mixed aldol reaction (Scheme 18). 

The formation of an enamine from an a,a-disubstituted cyclopentanone and its reaction with methyl acrylate was used in a synthesis of clovene (JOS). In a synthetic route to aspidospermine, a cyclic enamine reacted with methyl acrylate to form an imonium salt, which regenerated a new cyclic enamine and allowed a subsequent internal enamine acylation reaction (309,310). The required cyclic enamine could not be obtained in this instance by base isomerization of the allylic amine precursor, but was obtained by mercuric acetate oxidation of its reduction product. Condensation of a dihydronaphthalene carboxylic ester with an enamine has also been reported (311). 

Those epimers of 1,2,3,4-tetrahydro-j8-carbolines of general structure 139, in which the hydrogen on carbon-1 of the carboline moiety is axial, are converted into the corresponding 3,4-dihydro- -carbolinium salts (141) by mercuric acetate oxidation. Sodium dichromate... 

Recently, Kochetkov and Khomutova have reported on the mercuration of isoxazoles with mercuric acetate. The reaction occurs quite smoothly, more readily than for benzene derivatives and results in a 90-100% yield of 4-acetoxymercury derivatives (74) whose structure was proved by converting them to known 4-bromoisoxazoles (75). Under these reaction conditions isoxazole itself is oxidized by mercuric acetate, mercurous salts being thereby produced. 

Oxidation of formic acid by mercuric chloride is the subject of several early kinetic studies. Dhar showed the reaction to be first-order in oxidant and substrate and to be subject to strong retardation by added chloride ions in agreement with earlier work. The reaction is also subject to retardation by added acid and presumably involves formate ion as the principal reactant. 

The oxidation of oxalic acid by mercuric chloride to give CO2 and mercurous chloride is a classic example of an induced reaction. This reaction is extremely slow unless small quantities of chromic acid and manganous ions are added, whereon facile reduction takes place Addition of permanganate or persulphate and some reducing agents is also effective and the oxidation proceeds readily under photo- or X-irradiation (Eder s reaction). The large quantum yield points to a chain mechanism , which could also function with an inducing oxidant, viz. 

Reported also are transformations of bicyclic compounds with the P—C—O fragment. Thus, the oxidation of (33) by mercuric oxide is shown in Eq. (20) (70ZOB1673). 

The transformation of the major product 262 to ( )-corynantheidol has also been realized via complete C-3 epimerization performed by mercuric acetate oxidation and subsequent sodium borohydride reduction (753). 

Corynantheidol (255) has been prepared by Hanaoka et al. (155), who started from piperideine derivative 268 and tryptophyl bromide (197). The key cyclization step, resulting in indolo[2,3-a]quinolizine 270 as the major product besides 271, was carried out by mercuric acetate oxidation in the presence of the disodium salt of ethylenediaminetetraacetic acid (EDTA), followed by sodium borohydride reduction. Finally, lithium aluminum hydride reduction of 270 provided ( )-corynantheidol in good yield (155). 

Reduction of imino ether 540 with sodium borohydride led to 2,3-seco-2,3-dihydroyohimbine (413), which could be tecyclized by mercuric acetate oxidation, followed by acid treatment, yielding yohimbine (74) and pseudoyohimbine (88) (271-272). 

ATP and magnesium were required for the activation of acetate. Acetylations were inhibited by mercuric chloride suggesting an SH group was involved in the reaction either on the enzyme or, like lipoic acid, as a cofactor. Experiments from Lipmann s laboratory then demonstrated that a relatively heat-stable coenzyme was needed—a coenzyme for acetylation—coenzyme A (1945). The thiol-dependence appeared to be associated with the coenzyme. There was also a strong correlation between active coenzyme preparations and the presence in them of pantothenic acid—a widely distributed molecule which was a growth factor for some microorganisms and which, by 1942-1943, had been shown to be required for the oxidation of pyruvate. 

The unconventional 3-diazoindoles were prepared by oxidative conversion of hydrazones and oximes. Thus, l-methyl-3-diazo-2-oxindole (21d) was prepared by mercuric oxide oxidation of l-methylisatin-3-hydrazone 297 (X = NNH2) in benzene at room temperature (1891JPR551) (Scheme 91). It can also be prepared by decomposition of l-methylisatin-3-tosyl-hydrazone 297 (X = NNHTs) with aqueous sodium hydroxide in a two-... 

Oxidation of Hydroxylamine by Mercurous Nitrate at 20° 0.07% Carey Lea Dextrine Ag Sol Used Total Volume BOMl. 

The oxidation probably involves a mercurated complex through the electron pair on nitrogen followed by a concerted removal of a proton from the a-carbon and then cleavage of the mercury-nitrogen bond. The suggestion that a trans elimination occurs is reinforced by the evidence that yohimbine can be hydrogenated by mercuric acetate, whereas reserpine methyl reserpate, deserpine, or pseudoyohimbine does not react [122]. 

In an analogous synthesis,23 3-butyI-l-heptyne was also characterized by mercuric oxide-sulfuric acid hydration4 to the known 3-butyl-2-heptanone,5 6 which also formed the known semicar-bazone.6... 

The former is deposited in yellow crystals, mixed with sulphur when acetoxime is treated with phosphorus pentasulphide in carbon bisulphide soln. the insoluble product extracted with alcohol and the alcoholic soln. heated to boiling the compound separates from cold water in large, transparent, seemingly monoclinic prisms, melts at 146° 150° with decomposition, and is readily soluble in water, but only sparingly in alcohol, and insoluble in ether and carbon bisulphide. It decomposes carbonates, gives a colourless precipitate with lead acetate, and is decomposed by hot dilute nitric acid with separation of sulphur and formation of phosphoric acid it is also decomposed by mercuric oxide, the filtrate from the precipitated mercury sulphide giving all the reactions of phosphoric acid. 

Diaryl-3-formyl-l,6,6aselectively oxidized on carbon 2, and not on carbon 5 either by mercuric acetate or by peracetic acid (Eq. 15).39 A 3-alkoxycarbonyl substituent has the same orienting effect in this oxidation.45... 

Aryl-l,2,4-dithiazole-3-thiones react with phenylacetylene giving two compounds, namely, A-(4-aryl-l,3-dithiol-2-ylidene) thiobenz-amide (52) and 2,5-diaryl- 1,6,6a IV-trithia-3-azapentalene, which may also be considered as AT-(5-aryl-l -dithiohS-ylideneJthiobenz-amide (53). This compound is converted into the corresponding benzamide (54) by mercuric acetate oxidation, the opposite reaction being realized with phosphorus pentasulfide.79... 

The corresponding methyl-derivative (342, R = Me) leads to a furan under these conditions but deprotection by mercuric oxide and boron trifluoride produces an E/Z mixture of diketones corresponding to (343). Replacing one of the phenyl substituents in (342, R = H) with methyl leads instead to the (E)-ketone (344). Various mechanisms are possible for these reactions, but an attractive one involves methylation on sulphur and ring expansion to (345), followed by trapping by water and ring opening272 ... 

Cycleanine has been cleaved, with oxidation, by mercuric acetate in acetic acid to give the salt (27),77 and the thermolytic demethylation of the alkaloid has been shown to proceed sequentially through norcycleanine and isochondodendrine to the tetra-O-demethyl compound.78 The spatial conformation of the alkaloid has been studied by time-dependent n.m.r. spectroscopy.79... 

Ankorine (92) has been synthesized from cincholoipon ethyl ester by reaction with 2-benzyloxy-3,4-dimethoxyphenacyl bromide to give (91 X = H2), followed by reduction, oxidation to the lactam by mercuric acetate and EDTA, cyclization,... 

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