3.5.6.7- Tetrahydro-2-hydroxyimino-3

Likewise, 2-hydroxyimino-4-methylcyclohexanone (305) and the same synthon (303) gave 3-amino-6-methyl-5,6,7,8-tetrahydro-2-quinoxalinecarbonitrile 4-oxide (306) (Pr OH, 20°C, 48 h 74%). ... 

The 1,2,5-thiadiazole system was also constructed from ketoximes and S4N4-SbCl5 and by rearrangement of 4-hydroxyimino-2,3,5,6-tetrahydro-3,5-dioxo-l,2,6-thiadiazines in the presence of acid. ... 

Hydroxyimino-6,7,8,9-tetrahydro-4//-pyrido[ 1,2-a]pyrimidin-4-ones 532 were obtained when 6,7,8,9-tetrahydro-4//-pyrido[l,2-a]pyrimidin-4-ones 531 reacted with sodium nitrite in aqueous hydrochloric acid at 0°C or in aqueous sulfuric acid first at 60°C, then at 80°C (if R1 = NH2) (83JMC1494). The hydroxy group of 9-hydroxyimino-6-methyl-4-oxo-6,7,8,9-tetrahydro-4//-pyrido[ 1,2-a]pyrimidine-3-carboxylate 533 (R = Me)... 

Oxidation of Oximes A different type of N-oxidation reaction involves the direct oxidation of oximes to nitro compounds. Although a variety of oxidizing agents have been described for this reaction, the use of non-heme iron-based systems is rather limited. In this context, the oxidation of the oxime group in tetrahydro-4H-pyrido[ 1,2-a]pyrimidines was carried out at room temperature in the presence of 50 mol% of Clayfen [K10 montmorillonite-supported iron(III) nitrate] (Scheme 3.45) [147]. Under these conditions the corresponding nitro derivatives were obtained in 32-35% yield. 1SN mass studies revealed that the reaction involved the direct oxidation of the hydroxyimino group. 

Hydroxy- and 7-amino-3-aryl-2,3,6,7-tetrahydro-lH,5H-pyrido [3,2,1-z/lquinazolin-l-ones were prepared from 1,7-diones with NaBH4 in MeOH, and by treatment with NH4OAc in the presence of NaBH3CN in a 1 1 mixture of CHC13 and MeOH at 50 °C, respectively (06USA2006/ 0004028). 7-Amino derivatives were also obtained from 7-hydroxyimino derivatives by catalytic hydrogenation over Pd/C catalyst in a mixture of DMF and 2.5 N HC1 methanol solution at 50 °C for 12 h. 

Cookson condensed 3-hydroxyimino-l-methyl-4-piperidone with ethyl acetoacetate in the presence of zinc to give ethyl 4,5,6,7-tetrahydro-2,6-dimethyl-6-azaindole-3-carboxylate, which was oxidized with mercuric acetate to the 6,7-dihydro compound. 

Thiophen 3-Hydroxyimino-2-methoxycarbonyl-4-methyl-tetrahydro E6a, 379 (Oxo - Oxim)... 

Dioxo-6,7,8,9-tetrahydro-4//derivatives of (12) exhibit a solvent- and substituent-dependent oxo-enol tautomerism <85JHC1253>. 9-Amino-4-oxo-6,7-dihydro-4/f derivatives of (12) exist predominantly as the enamine tautomer and not as the 9-imino-6,7,8,9-tetrahydro tautomer. The latter tautomeric form predominates for 9-hydroxyimino-, 9-hydrazino-, and 9-aminomethylene-4-oxo-6,7,8,9-tetrahydro-4 f derivatives of (12) <83JCR(S)i6i, 83JCS(P2)165,83JCS(P2)1409,830MR(2l)687>, with a solvent-dependent E-Z geometric isomerism. 9-(Arylmethylenehydrazono)-4-oxo-6,7,8,9-tetra-... 

Nitro-4-oxo-l,6,7,8-tetrahydro- and 9,9-dinitro-4-oxo-6,7,8,9-tetrahydro-47/- derivatives of (12) and its 2,3-benzologue could be prepared from 9-hydroxyimino-4-oxo-6,7,8,9-tetrahydro- and 9-formyl-4-oxo-l,6,7,8,9-tetrahydro-47/ derivatives of (12) and its 2,3-benzologue using Clayfen <90JOC6198>. 

Hydroxyiniino-2-methyl-2-morpholino-2,3,4,5,6,7-tetrahydro-3a//-mdole 1-oxide (188) gave 5-hydroxyimino-3-methyl-5,6,7,8-tetrahydrocinnoline (189) (H2NNH2 H2O, AcOH, H2O, reflux, 15 min 85%). ... 

To a mixture of 4 mL acetic acid and 1.5 mL acetic anhydride was added 0.5 g 4-methyl-5,6,7,8-tetrahydro-5-(hydroxyimino)-2-hydroxyquinoline (3.0 mmol). The solution was saturated with anhydrous HCl gas and then held at reflux for 18 h. At the end of the reaction period, the solution had become dark, whereupon it was cooled, diluted with water, and allowed to stand for several hours. The white precipitate that formed was washed with water and crystallized from alcohol to provide 0.30 g 4-methyl-5-acetamido-2-quinolone, in a yield of 53%, m.p. 355°C. 

---