Mercuration diazo compound

The mechanisms of two other reactions described in Sect. 2.2 involve slow proton transfer to unsaturated carbon. The general acid catalysed cleavage of vinyl mercuric halides [42, 50] for example, allyl mercuric iodide, CH2=CHCH2HgI (XXII), gives Bronsted exponents around 0.7. Linear Bronsted plots are obtained with carboxylic acid catalysts but, as observed in other A—SE 2 reactions, general acids of different structural types (for example, hydronium ion or bisulphate ion) show substantial deviations. Bronsted catalysis of the hydrolysis of diazo compounds (N2 =CR X) has been studied by the groups of Albery and Kreevoy. With... 

Although this method has had limited application, it represents the most convenient synthesis for the important diphenylketene. This consists in converting benzil monohydrazone to the diazo compound by the action of mercuric oxide suspended in benzene. The presence of anhydrous calcium sulfate is needed to remove the water formed in the oxidation. The benzene solution is then dropped slowly into a distilling flask maintained at 100-110°, whereby the benzene distils and the diazo... 

This work was initiated in 1927, and in 1953 the last paper of the series was published. Intermittently, other related investigations were accomplished. Here, I would like to mention the reaction of aliphatic diazo compounds with mercuric chloride. The reaction of methylamine with mercuric chloride under the conditions of the diazo method was unsuccessful. Instead of the methylmercuric chloride expected, the synthesis gave negligible amounts of chloromethylmercury chloride, a compound obtained by Hellerman from mercuric dichloride and diazomethane in good yield. With diazoacetic ester, the compound (ClHg(Cl)y—C(=0)0C2H5 2Hg... 

Diazo compounds may also be prepared from hydrazines by cautious oxidation with mercuric oxide, copper sulphate or ferric chloride... 

One method for the preparation of diphenylacetylene involves oxidation of benzil dihydrazone with mercuric oxide the intermediate diazo compound loses nitrogen as formed to give the hydrocarbon ... 

Mercuric oxide, HgO (yellow modification or the less reactive red modification), resembles silver oxide in its oxidizing properties. This reagent transforms phenols and hydroquinones into quinones [383, 384] and is used especially for the conversion of hydrazones into diazo compounds [355, 386, 387, 388, 389, 390, 391, 392]. Dihydrazones of a-diketones furnish acetylenes [393, 394, 395, 396], A -Aminopiperidines are dehydrogenated to tetrazenes [397] or converted into hydrocarbons [395]. 

Mercuric trifluoroacetate, Hg(OCOCFj>2> parallels the actions of mercuric oxide. It oxidizes hydroquinones to quinones [353] and hydrazones to diazo compounds [406]. 

Ketone derivatives whose oxidations have wide applications in synthesis are hydrazones and vicinal dihydrazones. Hydrazones are transformed into diazo compounds, and vicinal dihydrazones are converted into acetylenes. By far the most widely used oxidant is yellow mercuric oxide... 

Oxidation of hydrazones. Schroeder and Katz found that oxidation of the hydrazone (1) by the usual mercuric oxide procedure gave erratic results and found silver oxide to be a much better oxidant. When (1) was shaken with silver oxide and magnesium sulfate in ether, the diaryldiazomethane was obtained in 99% yield. Mercuric oxide failed also to oxidize the hydrazone (2), but the diazo compound was... 

Corey and Achiwa3 have reported recently that mercuric iodide is an excellent catalyst not only for conversion of the cw.t/wjs-diazo compound (4) into (5) but for generation of (5) from the trans,trans-isomer of (4). Thus it is possible to synthesize sesquicarene from the commercially available famesol in 35% overall yield without separation of the trans,trans- and cis,trans-isomers. 

Regitz and Maas (1986) give in Sections 14.1 -14.2 and in the Addendum 47 references on metalla-tions of aliphatic diazo compounds, six of which were published in the period 1895-1959, 34 between 1960 and 1979, seven after 1979. The largest number of references is related to mercuration and metallo-de-mercuration, but their importance nowadays is small, due to the environmental problems related to mercury. 

Cycloaddition approaches to pyrazole derivatives were employed extensively in 1997. Thus, aldhydrazones combine with mercuric acetate to form nitrileimines which react in situ with olefins to give 1,3,5-trisubstituted 2-pyrazolines <97SC3737>. Oxidation of the latter to pyrazoles with iodobenzene diacetate was reported <97SC2683>. The most common cycloaddition pathway, however, is from the reaction of alkenes or alkynes with diazo compounds. The facial selectivity of the regiospecific reactions of diazomethane (and other... 

Mercuric oxide potassium hydroxide Diazo compounds from hydrazones s. 17, 348 19, 354... 

Mercuric oxide/potassium hydroxide Diazo compounds from hydrazones... 

The formation of organomercury compoimds by the use of halides and sodium amalgam, diazo compounds, diaizonium salts, decarboxylation reactions, mercuration of aromatic compoimds, and reactions between mercury halides (or acetates) and olefins or acetylenes has been discussed in Chapter 2 and is not further elaborated here. 

Organic compounds Organic fluorine compounds arc made by reaction of the corresponding alkane chloro-compounds with silver fluoride, mercurous fluoride, antimony trifluoride, titanium tetrafluoridc. and the arene fluoro-compounds by the diazo-reaction using hydrogen fluoride, and otherwise. The effect of the continued replacemenl of hydrogen atoms by fluorine atoms is an initial increase in reactivity, followed by a reversal of this effect, so lhal the highly substituted compounds arc relatively inert, See also Fluorocarbon. 

The observation of Schollkopf and coworkers, that the mercury method is applicable to a-diazo- 8-carbonyl compounds, but not to diazomethane, is likely to be due to the same reason as the selective sulfonation of anthraquinone in the 1-position. The mercury ion approaches the reacting CH group via a complex with the O-atom of the neighboring carbonyl group. Mercuration of a-diazo- ff-carbonyl compounds and of anthraquinone are different, however, in another aspect, namely substitution by the metal takes place at the C-atom neighboring the carbonyl group... 

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