Carboxylic acids with selenium dioxide

Benzo[ ]perimidinone carbaldehyde and carboxylic acid derivatives have also been prepared by alkyl oxidation. Thus, treatment of the 2-methyl derivative 588 with selenium dioxide at reflux in dioxane gave the aldehyde 589, which then gave carboxylic acid 590 on reaction with sodium chlorite <2001JME2004>. 

Treatment of 2-methyl-l,5-naphthyridine (103 R = Me) with selenium dioxide gave the carboxylic acid (103 R = C02H) whereas the analogous oxidation of the N,N - dioxide of... 

Methyl-2-oxo-l,2-dihydro-l,6-naphthyridine-3-carbonitrile (43, R = Me) with selenium dioxide gave 2-oxo-l,2-dihydro-l,6-naphthyridine-3-carbonitrile (43, R = H), presumably by decarboxylation of an intermediate 5-carboxylic acid (43, R = CO2H) (reactants, AcOH, reflux, 20 h 55%).1166... 

Chromic acid oxidation of 1- or 2-methylphenazine affords the corresponding carboxylic acids and oxidation with selenium dioxide gives the corresponding aldehydes.Alkoxyphenazi-nes are readily dealkylated using hydrobromic acid in acetic acid, or with aluminum tri-halides. Alkoxyphenazine A -oxides can be also dealkylated with aluminum trichloride in ethereal solution or aluminum tribromide in benzene. " ... 

Alkylpyrazines with other substituents have been oxidized to carboxylic acids as follows 2-acetamido-6-methylpyrazine was oxidized in aqueous magnesium sulfate with potassium permanganate to 2-acetamido-6aqueous potassium permanganate at room temperature to 2-carboxy-3-chloropyrazine, which was also obtained by oxidation of 2-chloro-3-methylpyrazine with selenium dioxide in boiling aqueous pyridine (947). Oxidations of 2-methoxy-3-methyl-... 

In most situations, carbon substituents can be oxidised with survival of the ring, thus alkyl-pyridines can be converted into pyridine carboxylic acids with a variety of reagents. Some selectivity can be achieved only a- and y-groups are attacked by selenium dioxide the oxidation can be halted at the aldehyde oxidation level. ... 

II) (10). The same ketone may also be obtained by oxidation with potassium permanganate in acid solution, with selenium dioxide (11), or by photooxidation (12). It exhibits halochromism (13), and may be oxidized further to 6,7-dimethoxyisoquinoline-l-carboxylic acid (III), which was at first misinterpreted as a dimethoxycinchoninic acid. Among the evidence... 

Oxidation of a methyl side chain is not an attractive route to chromone-2-carboxylic acids because of the ease with which the pyrone ring is attacked by oxidising agents to form salicyclic acid or its derivatives [112]. When 2,3-dimethylchromone is oxidised [113] with selenium dioxide, the main product (57 per cent yield) is the 2-aldehyde (25) a small amount of the 2-carboxylic acid (26) is formed simultaneously. The aldehyde (25) may be oxidised to the carboxylic acid by chromium trioxide in cold acetic acid. 

An alternative practical synthesis of triquinacene-2-carboxylic acid (as the dextrorotatory enantiomer) has l n described by Deslongchamps and Soucy Their protocol begins with hydroxy ketone 467 and passes via the 2-methyl derivative (Scheme XXXVIII). Selenium dioxide oxidation of the hydrocarbon provided the aldehyde which was further oxidized and then hydrolyzed to arrive at the add. 

The pyrazine ring is stable toward permanganate oxidation, and this explains a variety of pyrazinecarboxylic acids that have been prepared from quinoxalines or benzo-fused quinoxalines. In contrast, alkyl side chains on pyrazines are effectively oxidized by permanganate, selenious acid, selenium dioxide, or dichromate to afford the corresponding carboxylic acids (Section 8.03.7.1). Oxidation of pyrazines with hydrogen peroxide or percarboxylic acids gives pyrazine A -oxides and/or A, A -dioxides (Section 8.03.5.2). 

Methylbenzoselenazole (28a) and chloral affords the alcohol (44). Hydrolysis of the latter yields j8-(2-benzoselenazolyl)acrylic acid (45) which can be oxidized to ben-zoselenazole-2-carbaldehyde (46) along with benzoselenazole-2-carboxylic acid (47 Scheme 16) (52JCS3197). Aldehyde (46) was obtained by selenium dioxide oxidation of (28a) (53CB888). 

Dialkyl ketones have been little studied as precursors in this reactioiL Selenium dioxide with hydrogen peroxide and r-butyl alcohol effects a similar reaction with these substrates to give 35-40% yield of the conesponding carboxylic acid. In methyl alkyl ketones, the regioselectivity is of the order of 5 1 in favor of meAyl migration. ... 

SAFETY PROFILE Poison by ingestion and inhalation. A corrosive irritant to skin, eyes (at 2 ppm), and mucous membranes. Potentially explosive reaction with chlorobenzene + sodium, dimethyl sulfoxide, molten sodium, chromyl chloride, nitric acid, sodium peroxide, oxygen (above 100°C), tetravinyl lead. Reacts with carboxylic acids (e.g., acetic acid) to form violently unstable products. Violent reaction or ignition with Al, chromium pentafluoride, diallyl phosphite + allyl alcohol, F2, hexafluoroisopropylideneaminolithium, hydroxylamine, iodine chloride, PbOa, HNO2, organic matter, potassium, selenium dioxide, sulfur acids (e.g., sulfuric acid. 

Aldehydes are transformed into carboxylic acids by hydrogen peroxide and its derivatives. In the presence of selenium dioxide as a catalyst, acrolein is oxidized to acrylic acid in 90% yield on treatment with a 12% solution of hydrogen peroxide in tert-amyl alcohol at 40 C for 3 h [725]. Methacrolein is converted into methacrylic acid by 90% hydrogen peroxide in the presence of selenium dioxide at 60 °C [725] or by peroxysulfuric acid 200 (equation 346). 

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