Benzil Monoxime

Methode 6S 11,25 g (0,05 mol) Benzil-monoxim, 5,3 g(0,05 mol) Benzaldehyd und 10 g(0,13 mol) Am-moniumacetat werden in 50 ml Eisessig 1 h unter RiickfluB gekocht. Beim Abkuhlen kristallisieren 15,5 g Rohprodukt aus. Es wird aus Essigsaure/Wasser umkristallisiert Ausbeute 13,4g (85%) Schmp. 244° (farblose Kristalle). 

In 1,2-diketones or their functional derivatives no conjugation is apparent in the dipole moment values, but these can serve for determining conformation on the central, formally single bond. In ( )- and (Z)-benzil monoximes (62) the configuration on C=N was known, and the ap conformation on N—O was assumed (and finally confirmed) from dipole... 

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... 

SYNS a-BENZIL MONOOXIME BENZIL, MONOXIME BENZIL, MONOOXIME BENZIL, 3-MONOXIME BENZIL, OXIME 1,2-DIPHENYL-ETHANEDIONE MONOXIME ETHANEDIONE, DIPHENYL-, MONOOXIME... 

Other reducing conditions have also been widely used. Thus zinc and sodium hydroxide has been utilized for the conversion of 1-hydroxyimino-l-phenylacetone to 2,5-dimethyl-3,6-diphenylpyrazine (191) dithionite for the conversion of a-benzoyl a-hydroxyiminoacetanilide to 2,5-diphenyl-3,6-bis(7V-phenylcarbamoyl)-pyrazine (192) sodium amalgam for benzil monoxime to tetraphenylpyrazine (193) aluminum amalgam for hydroxyiminoacetoacetic ester to 2,5-bisethoxy-carbonyl-3,6-dimethylpyrazine (194) and sodium and alcohol for benzil dioxime to tetraphenylpyrazine (195). 

The highly substituted 5,6-dihydro-4//-l,3,4-oxadiazine (264 R = Pr") is formed as a by-product (20%) along with benzil monoxime (40%) on subjecting the O-benzylated monoxime of benzoin (PhCH(OH)C(Ph)=NOCH2Ph) to a Mitsunobu reaction (PhjP and diisopropyl azodicarboxylate) <87JOC4978>, Substitution of the diisopropyl by the diethyl ester raises the yield of oxadiazine (264 R = Et) to 50%,... 

Cyanocarboxylic acid esters. 2-Oximinocyclohexanone dimethyl ketal, trimethyl orthoformate, and a little methanesulfonic acid added at -70° under Ng to liq. SO2, and refluxed 0.5 hr. at ca. -10° methyl 5-cyanopentanoate. Y 97%. -Similarly at 72° Benzil monoxime and triethyl orthoformate -> benzonitrile (Y 95%) and ethyl benzoate (Y 98%). M. M. Rogic et al., J. Org. Chem. 39, 3424 (1974) Beckmann fragmentation with tetrakis(triphenylphosphine)palladium cf. K. Maeda et al., Chem. Commun. 1975, 689. 

A soln. of benzil monoxime, benzaldehyde, and NH4-acetate in glacial acetic acid refluxed 1 hr. 2,4,5-triphenylimidazole 3-oxide. Y 85.5%. F. e. s. H. Lettau, Z. Chem. 10, 338 (1970) 1-subst. analogs with amines instead of NH4-acetate s. ibid. 10, 431 isolation of 2-imidazolones from formaldehyde s. ibid. 10, 462 oxazole N-oxides in the absence of NH4-acetate or amines cf. Y. Goto, M. Yama-zaki, and M. Hamana, Chem. Pharm. Bull. 19, 2050 (1971). 

---