Ketones hydroxyimino

For oximes, the word oxime is placed after the name of the aldehyde or ketone. If the carbonyl group is not the principal group, use the prefix hydroxyimino-. Compounds with the group Z = N—OR are named by a prefix alkyloxyimino- as oxime O-ethers or as O-substituted oximes. Compounds with the group r C=N(0)R are named by adding A-oxide after the name of the alkylideneaminc compound. For amine oxides, add the word oxide after the name of the base, with locants. For example, C5H5N—O is named pyridine A-oxide or pyridine 1-oxide. 

Note. Such derivatives of quinoxaline ketones are not encountered as often as those of quinoxalinecarbaldehydes, but a few examples can be given here. 6-Acetyl-2-phenylquinoxaline gave its oxime, 6-[l-(hydroxyimino)ethyl]-2-phe-nylquinoxaline (209) (H2NOH HCl, NaOH, EtOH, H2O, reflux, 2 h 75%). ... 

For oximes, the word oxime is placed after the name of the aldehyde or ketone. If the carbonyl group is not the principal group, use the prefix hydroxyimino-. Compounds with the group —OR... 

I.3.4.2.5. Carbonyl and Thiocarbonyl Compounds a-(Hydroxyimino)phenyl-acetonitrile oxide (generated in situ at room temperature from PhC( NOH)C ( NOH)Cl in the presence of NaHC03 or Et3N) reacts with simple aldehydes and ketones R1R2CO to give 1,4,2-dioxazoles 180 (347). Related dioxazoles, formed by cycloaddition of benzonitrile oxide to aromatic aldehydes, upon treatment with I-BuOK, undergo cyclo-reversion, allowing direct conversion to substituted benzoic acids or their esters (348). 

It is proposed that o -hydroxyimino ketones are derived from a reaction pathway initiated from the hydrogen abstraction by the im triplet-excited nitro group of the keto form, while a-di ketones are formed from the nitro-nitrite photorearrangement of the enol forms133. 

Synthesis of quinolines by nucleophilic substitution of nitrogen atom in oxime derivatives was described by Narasaka and coworkers. /3-Aryl ketone oximes 297 in the presence of trifluoroacetic anhydride and 4-chloranil afforded quinolines 298 in 72-82% yield (equation 128). However, interaction of oxime 299 with 48% HBr at 105 °C proceeded with elimination of hydroxyimino group and gave 2,3-dimethoxynaphtho[l,2-fc]quinolizinium bromide (300) in 45% yield (equation 129). ... 

The more accessible a-hydroxyimino ketones 79 (Scheme 18) undergo an acid-catalyzed condensation with diarylimines to yield the iV-oxides 80 (30-80%). ... 

Hydrogenation of hydroxyimino ketones or esters maybe accompanied by the formation of cyclic products, especially at elevated temperatures, as a result of inter- or intramolecular condensation in the course of hydrogenation. 

Hydrogenation of a-hydroxyimino ketones and esters, and also of 1,2-dioximes, may lead to the formation of pyrazines. Tetraphenylpyrazine became the predominant product in the hydrogenation of benzil monoxime and dioxime over nickel catalyst in ether or alcohol at around 100°C. Thepyrazine was formed even in the hydrogenation... 

Scheme 8.7 The formation of pyrroles from hydrogenation of an a-hydroxyimino ketone in the presence of a ketone with an active methylene group (X acyl, alkoxycarbonyl, or cyano).

Condensation of hydroxyimino ketones, e.g. hydroxyimino acetone, hydroxyimino acetophenone, with benzene-1,2-diamine derivatives affords the corresponding quinoxalines together with 1,2-dioximes or a-hydroxyimino nitriles. ... 

TABLE II.2 PYRAZINES PREPARED BY REDUCTION OF a-HYDROXYIMINO KETONES... 

Gastaldi (286) first described this synthesis, in which an a-hydroxyimino ketone was treated with aqueous sodium bisulfite saturated with sulfur dioxide, and the bisulfite compound treated with potassium cyanide followed by hydrolysis with hydrochloric acid. By this procedure, Gastaldi prepared 2,5-dicyano-3,6-dimethyl-pyrazine from hydroxyiminoacetone, and 2,5-dicyano-3,6-diphenylpyrazine and some 3-cyano-2,5-diphenylpyrazine from hydroxyiminoacetophenone. He proposed a reaction mechanism involving the intermediate compounds (21) and (22). Sharp and Spring (287) used the same procedure to prepare 2,5-dicyano-3,6-diethyl-pyrazine from ethyl hydroxyiminomethyl ketone. 

Aminomethyl phenyl ketone oximes, such as ethyl 6-amino-5-nitro-4- [2-(hydroxyimino)-2-phenylethyl]amino pyridine-2-carbamate, bearing various substituents in the phenyl group are converted into the corresponding ketones 12, and then cyclized by hydrogenating the nitro function to yield 5-amino-3-aryl-1,2-dihydropyrido[3,4-5]pyrazine-7-carbamates 13.104 1°9... 

V-Alkyl-substituted guanidin-2-amines condense with 1,2-dicarbonyl compounds to give A -alkyl-l,2,4-triazin-3-amines 7 and 8.115 6-Substituted 1,2,4-triazin-3-amines 7 can also be prepared by reaction of 2-(hydroxyimino)-l-phenylethan-l-onen5 or dibromo ketones with guanidin-2-amine.141 24 2... 

The synthesis of oxazoles from a-hydroxyimino ketones was originally described by Diels and Riley,143 and the method was later extended by Dilthey and Friedrichsen,144 and Selwitz and Kosak.145 The method involved condensation of a-hydroxyimino ketones with aromatic aldehydes in the presence of dry hydrogen chloride to form oxazole iV-oxides (67) which could easily be reduced with zinc in acetic acid to the free base (68). Catalytic reduction (Ni/H2) is also effective for the final stage.146... 

Alicyclic oximino ketones are found to react similarly. 1,2,3-Cyclo-hexanetrione-1,3-dioxime has thus been transformed into 2-phenyl-7-hydroxyimino-4,5,6,7-tetrahydrobenzoxazole-3-oxide.146... 

The synthesis of oxazole A-oxidcs from a-hydroxyimino ketones and aldehydes, and their reductive conversion into oxazoles has already been described (Section II, K). Attempted A-oxidation of 2,5-diphenyloxazole with hydrogen peroxide in acetic acid failed it led to ring-opening.418 Oxazole A-oxides show a strong absorption band around 1240 cm-1 in their infrared spectra, indicative of an aromatic A-oxide group.419 Recently, NMR data for several oxazole A-oxides have been reported.148... 

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