Nitrosolic acids

Via pure KDNM, all other alkali (or ammonium) DNM salts can be obtained (i) by ion exchange or (ii) by release of the methyl nitrosolic acid when a water solution of KDNM is buffered with H3PO4 (pH = 6.5) followed by low-temperamre extraction with diethyl ether and a basic work-up (equations 6 and 7) ... 

Wieland was the first who studied nitrosolic acids . He was especially interested in the simplest member of this group, the methylnitrosolic acid, ON—C(H)=NOH (10), because he already thought of the dioxime of carbon dioxide, HO—N=C=N—OH, which is an intriguing isomer of methylnitrosolic acid. Wieland tried first the reaction sequence in... 

SCHEME 9. Mechanism for the synthesis of nitrosolic acids proposed by Wieland ... 

Scheme 9 to synthesize 10 which, however, did not work although successfully utilized for the generation of other nitrosolic acids. 

The easiest way to 10 goes via the synthesis of KDNM (see Section n.C). Acidification of an aqueous solution of KDNM, which should be buffered with H3PO4 (pH = 6.5), followed by low-temperature extraction with diethyl ether, gives the monomeric emerald-green nitrosolic acid 10 dissolved in the ether phase. Slow removal of the solvent yields the yellowish dimeric form of 10. The acid (10) is only poorly characterized. It is known to slowly decompose into HCN and HNO2 in basic solution (decomposition of the anion DNM), while the free acid (10) rapidly decomposes to give fuhninic acid, HCNO and hyponitrous acid, HON=NOH. It should be noted that both the free acid and its metal DNM salts are highly explosive. 

The ethyl nitrolic acid (IX) has been shown [45] to be electrolytically reducible to N-hydroxyacetamidoxime (X), which can be oxidized anodically to ethyl nitrosolic acid. In alkaline solution ethyl nitrolic acid (IX) forms an azo derivative (XI) [46] in low yield according to ... 

Potassium salt 1,2,4-Oxadiazole 4-oxides from nitrosolic acids and halides... 

Azohydroperoxides O-Carbamylhydroxylamines Carbazic acid esters Hydrazoformic acid esters N-Hydroxyureas N-Nitrimines N-Nitrosoacylamines N-Nitrosocarboxylic acid amides 20 Nitrosolic acids... 

Indazoles have been used as the biosteres of indoles in drug discovery. In the synthesis of the nonsteroidal anti-inflammatory drug (NSAID) bendazac, benzylaniline was used as its starting material. Nitrosolation was accomplished using nitrous acid. The resulting A-nitroso intermediate was reduced with sodium thiosulfate to the corresponding hydrazine, which cyclized to the indazolone. Subsequent alkylation with methyl chloroacetate was followed by hydrolysis to deliver bendazac. 

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