Selenium dioxide oxidations

Owing to its characteristic behavior under oxidizing conditions, selenium dioxide 

Selenium dioxide reacts with semicarbazones to give selenadiazoles, the thermo- 

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Ninhydrin (also named 1 2 3-triketoindane or 1 2 3-triketohydrindene hydrate) is prepared most simply from the inexpensive phthahc anhydride (I). The latter is condensed with acetic anhydride In the presence of potassium acetate to give phthalylacetlc acid (II) reaction of the latter with sodium methoxide in methanol yields 1 3-indanedionecarboxyhc acid, which is decomposed upon warming with dilute hydrochloric or sulphuric acid to indane-1 3-dione (or 1 3-diketohydrindene) (HI). Selenium dioxide oxidation of (III) afibrds indane-1 2 3-trione hydrate (ninhydrin) (IV). 

Selenium dioxide oxidation of methyl derivatives (Scheme 30). 

Furalazine, Acetylfuratrizine, Panfuran-S. Heating nitrovin in butanol or dimethylformamide at 100—130°C affords furalazine, 6-[2-(5-nitro-2-furanyl)ethenyl]-l,2,4-triazine-3-amine (34). An improved synthesis originates with 5-nitro-2-furancarboxaldehyde and acetone, proceeds through 4-(5-nitro-2-furanyl)-3-buten-2-one followed by a selenium dioxide oxidation to the pymvaldehyde hydrate, and subsequent reaction with aininoguariidine (35). Furalazine, acetylfuratrizine (36), and the A[-A/-bis(hydroxymethyl) derivative, Panfuran-S, formed from the parent compound and formaldehyde (37), are systemic antibacterial agents. 

Selenium dioxide oxidation of 7,8-dihydro-5(6//)-quinolinone semicarbazone gave, in addition to the expected 4,5-dihydro selenadiazoloquinoline 95 (analogous to sulfur derivative 76), the oxidized l,2,3-selenadiazolo[4,5-/]quinoline 96, which, when heated to 210°C for 30 min, gave the dimeric [l,4]diselenino [2,3-/ 5,6-/ ]diquinoline (95JHC177). 

Phenylsulfonyl)indole 330 was converted to a ketone by a set of standard reactions followed by the selenium dioxide oxidation of the resulting acetyl goup to the ketoaldehyde 332 (Scheme 101). Methylthiosemicarbazide hydroiodide reacted with 332 to the triazine 333 in 83% yield. As Diels-Alder reactions with 1 -pyrrolidinocyclohexene failed, 333 was first oxidized... 

Dimethylquinoxaline reacts with pyridine and iodine to form quinoxaline-2,3-bis(methylenepyridinium iodide) (55). Condensation of (55) with p-nitrosodimethylaniline in the presence of potassium carbonate yields the bis-(p-dimethylaminonitrone) (56) and this on acid hydrolysis gives quinoxaline 2,3-dialdehyde (57) in high over-all yield. The dialdehyde is also obtained by selenium dioxide oxidation of 2,3-dimethylquinoxaline. ... 

Oxidation reactions were used in the synthesis of porphyrin d, the metal-free ligand system of naturally occurring heme d,. In a total synthesis of porphyrin d,12d oxo functions were introduced into isobacteriochlorin 3 by selenium dioxide oxidation to yield 4. The selenium dioxide selectively attacks the 3- and 8-positions of the partially reduced pyrrole rings of the chromophore. In another synthesis23a c of porphyrin d, an isobacteriochlorin 5, derived by... 

The first synthesis of a 2-azatropone, eg. 13 (R = f-Bu) has been described by Takami and co-workers. Although the yield was poor, the product itself has some novelty. It resulted (Scheme 4) from selenium dioxide oxidation of the 3//-azepine 12 (R = t-Bu) <00JOC6093>. 

Some other derivatives of thiophene were studied and described, e.g. 2-thenylmercaptane (10) and 5-nitro 2-thiophene aldehyde were synthesized by means of a selenium dioxide oxidation of 5-nitro-2-thenylbromide (23). On the other hand the same aldehyde could be obtained by nitration of 2-thenaldehydediacetate (66). This diacetate was cleaved (76% yield) by steam distillation from dilute hydrochloric acid. 

Samarium(II) iodide, 46, 3 Sandmeyer reaction, 2, 7 Schiemann reaction, 5, 4 Schmidt reaction, 3, 8, 9 Selenium dioxide oxidation, 5, 8 24, 4 Seleno-Pummerer reaction, 40, 3 Selenoxide elimination, 44, 1 Shapiro reaction, 23, 3 39, 1 Silanes ... 

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. 

Oxidation of 6-methylphenanthridines with potassium dichromate in acetic acid results in oxidative loss of the methyl group, the product being the phenanthridone (e.g. 67 Scheme 62) (61JCS3771). If a second methyl group is present it remains unchanged. Selenium dioxide oxidizes the 6-methyl group to the aldehyde. 

Solvent-free selenium dioxide oxidation of 5,6-diaminopyrimidin-4-one was reported to give the [l,2,5]selenadia-zolo[3,4-i/ pyrimidin-7-one <2004MI289> as shown in Scheme 76. The fused selenadiozole ring may be alternatively formed by reacting the diamine in Seheme 76 with H2Se03 <1996CHEC-II(7)489>. 

A chemical correlation of the (—)-methyl derivative 109 with the ( )-methylester 111 was possible by selenium dioxide oxidation of the former and subsequent silver... 

Oxidation of the sulfur- or selenium-bridged azepines (171 X=S or Se) with mercury(II) oxide in methanol yields ultimately the 4f/-azepine (68JCS(C)23ll) with hydrogen peroxide as oxidant, the sulfur compound furnishes the sulfoxide (171 X=SO). Selenium dioxide oxidation of 7,8-dimethyl-lf/-l-benzazepin-2-one affords the 2,3-dioxo derivative (173) that displays no evidence of enol tautomers or heteroaromaticity (7ici(L)1439). 

Selenium dioxide oxidation of dimethyl 3-oxo-tjxo-tricyclo(4.2.1.02 5]nonan-fw/o,< i3V>-7,8-di-carboxylate gave dimethyl 3,4-dioxo-< vo-tricyclo[4.2.1.02 5]nonane-em/o,e rfo-7,8-dicarboxy-late.107... 

Silylation followed by selenium dioxide oxidation converted 13 into 14. Epoxidation of the derived TES ether proceeded by addition of oxygen to the more open face of the alkene, leading to 15. Ozonolysis followed by diastereoselective one-carbon homologation provided 17. This set the stage for intramolecular epoxide opening by the carboxylate, to give 2, in which all of the stereogenic centers of tetrodotoxin have been established. 

Selenium dioxide oxidation of the ketones (166 R = H, Cl) is reported115 to give the corresponding indolones (168) in moderate yield... 

Methyl groups in the 2-, 4- or 6-position of pyrimidine are also more reactive. In addition to typical reactions such as condensation with benzaldehyde, selenium dioxide oxidation and halogenation, they can be converted into oximino groups by nitrous acid, and undergo Claisen condensation with (C02Et)2. In the reaction of 2,5-dimethylpyrimidine with benzaldehyde, only the electrophilic 2-methyl group reacts preferentially to yield the 2-styryl derivative (631). In quinazolines partial double bond fixation makes a methyl group in the 4-position more reactive than that in the 2-position. 

Scheme 2 shows Rapoport s synthesis [15]. The cinnamic acid derivative 3 prepared from m-methoxy benzaldehyde [20] was ethylated by diethyl sulfate to give ethyl cinnamate derivative 4, followed by Michael addition with ethyl cyanoacetate to afford compound 5. Compound 5 was converted to lactam 6 by the reduction of the cyano group and subsequent cyclization. Selective reduction of the lactam moiety of 6 was achieved by treatment with trimethy-loxonium fluorob orate followed by sodium borohydride reduction. Amine 8 was obtained by the reductive methylation of amine 7. Amine 8 was converted to compound 9 by methylene lactam rearrangement [21], followed by selenium dioxide oxidation to provide compound 10. Allylic rearrangement of compound 10 and subsequent hydrolysis gave compound 12. The construction of the decahydroisoquinoline structure began with compound 12,... 

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