3- Nitroso-2-oxazolidones

One of the first reports involving vinyl diazonium ions and possible vinyl cations is the work of Newman and co-workers (107) on the alkaline decomposition of 3-nitroso-2-oxazolidones, 132. When an aqueous suspension or... 

Scheme VIII. Alkaline Decomposition of 3-Nitroso-2-oxazolidones.

More recently, such vinyl cations generated by the alkaline decomposition of 3-nitroso-2-oxazolidones have been trapped by halogens to give vinyl halides as products (108). It has been suggested that unsaturated carbenes, RjC=C , may be the intermediates in the basic decomposition of 132 (109). Indeed, when 132 (Ri=R2=CH3, R3=H) was treated with lithium ethoxide in the... 

In addition to the methods mentioned in a previous preparation,6 diphenylacetylene has been prepared by the action of potassium hydroxide on 5,5-diphenyl-3-nitroso-2-oxazolidone (100%).7 The present procedure is a modification of that of Schlenk and Bergmann.8... 

The nitroso derivatives are generally reasonably stable, except the parent compound of the series, 3-nitroso-2-oxazolidone (m.p. 50°-53°C dec.) and 5-phenyl-3-nitroso-2-oxazolidone (m.p. 76.5°-77.5°C dec., both of which are considered dangerous materials. Probably other unstable members of this class of compounds exist. 

Table IV gives the properties of a representative series of 3-nitroso-2-oxazolidones.

Arylacetylenes. Treatment of 5,5-disubstituted 3-nitroso-2-oxazolidones (1) with -bulylamine in ether at room temperature gives arylacetylenes in almost quantitative yield, when at least one of the groups of C5 is an aryl group. - The method has also been used to prepare 2-ethynylihiophene. ... 

Earlier work has shown that 5,5-disubstituted 3-nitroso-2-oxazolidones on treatment with aqueous KOH at room temperature give acetylenes when both substituents are aryl groups (e.g. Ph, Ph, 100% yield) aldehydes, when both of them are alkyl groups (e.g.. Me, Me, 80% yield), and when one is an alkyl group and the other an aryl group, a mixture of the acetylene and a ketone is obtained (e.g. Me, Ph, 74 and 16% yields, respectively) (equation 112) °. A change of reagent to -butylamine... 

Disubstituted 3-nitroso-2-oxazolidones (20) are transformed by butylamine in ether into acetylenes 2-ethynylthiophen, 3,5-di-t-butyl-phenylacetylene, and dicyclopropylacetylene have been prepared in this way. 

The formation of vinyl cations by deamination of vinyl amines in neutral media, is therefore not established and the possibility that a carbene intermediate is actually involved must be considered. Thus, the products of the alkaline decomposition of N-nitroso-oxazolidones 109 were earlier explained (Newman and Kutner, 1951 Newman and Weinberg, 1956) in terms of a mechanistic scheme involving vinyl cation intermediates (equation 19). Such a scheme has recently been... 

The reactivity of the ethenediazonium salt 9.100 towards the nucleophiles mentioned shows that it has the properties of the corresponding carbocation, since it can ethylate the nucleophile and is prone to attack at the C()ff)-atom of the original ethene-l-diazonium ion. The thermal decomposition pattern is typical of that for an oxonium salt. Reactions with amines are similar to those of ketene acetals. No product that could be explained in terms of an azo coupling reaction, e.g., with 2-naphthol, could be observed. The electrophilicity of the diazonio group is, therefore, low. N-Azo coupling products with azide ions have been postulated with good arguments, however, by Kirmse and Schnurr (1977) with certain short-lived ethene diazonium intermediates produced from nitroso oxazolidones. 

Decomposition of the 7V-nitroso-oxazolidone (163) with base in a solution of ethoxyacetylene gives the allene diethylacetal (164) the carbene intermediate in the suggested mechanism is supported by previous work. ... 

Oxadiazolinones, substituted, 391 Oxaziranes, oxidation of, 406 2-Oxazolidones, 442 Oximes, 395 oxidation of, 415, 416 reaction with C-nitroso compounds, 351 4,4 -[Oxybis(4-nitro-o-phenyleneazo)]bis-JV,N-(dimethylaniline), 294... 

Dimethylethylidenecarbene. When treated with abase 5,5-dialky 1-N-nitro-sooxazolidones decompose, probably through unsaturated carbonium ions, to give dialkylethylidenecarbenes, which can be trapped by reaction with olefins to give methylenecyclopropanes.1 Thus 5,5-dimethyl-N-nitroso-2-oxazolidone (3) is converted into dimethylethylidenecarbene through the postulated intermediates shown. Isolated yields of cyclopropanes are 18-56%. 

CARBENES, GENERATION Chloral. Dibromofluoromethane. Dimethoxy-methyl)trimethoxysilane. Dimethyl diazomethylphosphonate. S -Dimethyl-N-nitroso-2-oxazolidone. Ethylidene iodide-Diethylzinc. Ethyl trichloroacetate. Phenyl(dibromochloro methyl) mercury. Phenyl(dihalocarbomethoxymethyl)mer-cury. Phenyl(trifluoromethyl)mercury. Phenyl(trihalomethyl)mercury. Sodium chlorodiiluoroacetate. Zinc powder. 

Enecyclopropane from N-nitroso-2-oxazolidone ring via enecarbenes... 

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