Isomerism aliphatic oximes

If the chlorination of aliphatic oximes is conducted in diethyl ether at — 60 C, aliphatic nitroso compounds III are obtained, which are in equilibrium with their dimeric form IV. The nitroso compounds on standing gradually isomerize to the hydroxamoyl chlorides II ( ). 

The most widely used route to l-benzazepin-2-ones involves the Beckmann or Schmidt reaction of the easily accessible 1-tetralones. Many biologically active compounds described in this review have been prepared on the basis of these reactions they have been fully reviewed [2], In the Beckmann reaction of 1-tetralone oximes, polyphosphoric acid is used as a catalyst-solvent in most instances. Aryl migration generally takes precedence over alkyl migration under these reaction conditions, and various 1-tetralone oximes substituted on the aromatic and/or aliphatic rings can be converted to the appropriate 2,3,4,5-tetrahydro-l//-l-benzazepin-2-ones (51) [5, 20-23, 36, 59, 65, 80, 107-112]. Both courses of the rearrangement occur in some instances, yielding l-benzazepin-2-ones (51) and the isomeric 2-benzazepine-l-ones, probably due to electronic effects of the substituents [90, 113, 114]. 

A more recent kinetic study has indicated that under acidic conditions a-ketonitrosoalkanes may rearrange rapidly to the oxime [33]. Amines also bring about the isomerization of nitrosocyclohexane [34], These observations along with the older observations mentioned in Touster s review [2] imply that the whole question of the nitrosation of aliphatic carbon atoms should be reexamined with modern techniques to establish the reaction conditions under which the true aliphatic nitroso compounds (or their dimers) can be isolated. 

Isomerism of Ketoximes.—In the case of aromatic aldehydes they all yield these stereo-isomeric oximes. With the aromatic ketones the condition is different and some yield stereo-isomers and some do not. With symmetrical aromatic ketones in which the two radicals are alike such as di-phenyl ketone, CgHb—CO—C6H,5 no different space relation of the hydroxyl group is possible as the two forms will be identical. When, however, the ketone is unsymmetrical, i.e.j the two radicals are unlike, as in mixed aromatic-aliphatic ketones such as phenyl methyl ketone, CeHs—CO—CH3, or in unsymmetrical di-aryl ketones such as phenyl tolyl ketone, CeHs—CO—C6H4—CHz then the two stereo forms are possible though both forms are not known in all cases. 

Nitrogen Compounds. The aqueous Oxone-acetone combination has been developed for the transformation of certain anilines to the corresponding nitrobenzene derivatives, as exemplified in eq 15. This process involves sequential oxidation steps proceeding by way of an intermediate nitroso compound. In the case of primary aliphatic amines, other reactions of the nitrosoalkane species compete with the second oxidation step (for example, dimerization and tautomerization to the isomeric oxime), thereby limiting the synthetic generality of these oxidations. An overwhelming excess of aqueous Oxone has been used to convert cyclohexylamine to nitrocyclohexane (eq 16)P... 

At temperatures below — 42°c, gaseous oxygen difluoride (OFj) converts primary aliphatic amines either to their nitroso or to the isomeric oxime derivatives (equation 91) ° . Although oxygen di-... 

Since the 1960s, numerous investigations have been carried out on the nature of the CN and NN double bond photoisomerization and the competitive nature of the ,Z-isomerization with other processes, such as photocychzation, photoreduction and photorearrangement. The variety of substrates studied included oxime, oxime ethers, aliphatic and aromatic azo compounds, azoxy compounds, hydra-zones, and Schiff bases. The accumulated results were the subjects of several comprehensive and thorough review articles by Wettermark, Padwa, Pratt, Griffiths, Engel, Diirr, and Taylor. ... 

---