Aliphatic oximes

The nitrosation of oximes can also serve to produce N-hydroxy-N-nitrosamines (Scheme 3.9). The acidified nitrite procedure can be applied to oximes derived from terpenes [132] and hydroxyguanidine [133] for the synthesis of N-hydroxy-N-nitrosamines. However, some a, 5-uri saturated oximes were converted into pyrazole-1,2-dioxides [134]. The alkyl nitrites under basic conditions have produced interesting results. Quinone dioximes yielded only monodiazeniumdiolates [135], while simple aliphatic oximes gave products resulting from addition to the imine double bond... 

Reduction of aliphatic oximes is specifically catalysed by protons, The process exhibits a single four-electron wave on polarography and Ey, is dependent on pH. Some half-wave potentials are given in Table 10.7, Around pH 6-8 this wave decreases in height and finally disappears because protons can no longer be supplied... 

G. A Brief Discussion of Aliphatic Oximes in Aqueous Solution... 

Although the major research and development effort on oxime reactivators has focused on the positively charged pyridinium ring, the poor ability of the charged oximes to cross the blood-brain barrier (BBB) has prompted several studies on noncharged aliphatic oximes in an effort to increase reactivation of OP-inhibited AChE in the central nervous system. The most smdied noncharged oximes are mono isonitrosoacetone (MINA, 44) and diacetyl monoxime (DAM, 45) " . 

The pX a (6.5-8.2) and nucleophilicity of MINA, 44, and of a series of aliphatic oximes derived from it, were found to be consistent with their ability to reactivate AChE inhibited by the nerve agents, sarin and VX. Yet, despite their ability to significantly reactivate AChE in the brains of sarin-intoxicated rats, these aliphatic oximes are not used as antidotes for treatment of OP poisoning in humans this is presumably due to their poor stability in aqueous solution and to their rapid clearance from the circulation. 

Table 6 lists the absorption characteristics of the series of UV-sensitive monomers investigated [218]. Aliphatic oxime acrylates show absorption maxima below 230 nm, while benzophenone oxime acrylate shows an absorption maximum at 252 nm. It is important to note that while benzophenone has absorption at 360 nm owing to the n-n transition, the corresponding oxime has no strong absorption above 300 nm. Pyrene-1-carboxaldehyde oxime acrylate (POA) and 9-phenanthrenecarboxaldehyde... 

Leclerc, G., Bieth, N., Schwartz, J. Synthesis and p-adrenergic blocking activity of new aliphatic oxime ethers. J. Med. ChettL 1980, 23, 620-624. 

Macchia, B., Balsamo, A., Lapucci, A., Martinelli, A., Macchia, F., Bresci, M. C., Fantoni, B., Martinotti, E. An interdisciplinary approach to the design of new structures active at the P-adrenergic receptor. Aliphatic oxime ether derivatives. J. Med, ChettL 1985, 28, 153-160. 

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 ( ). 

It was found that in the case of diphosphonylation reactions with cyclic aliphatic oximes, diethyl H-phosphonate is the better phosphorus reagent All bisphosphonates thus obtained show diagnostic triplets (/ === 140 Hz) at 57.8-63.6 ppm due to carbons bearing gem-diphosphonate groups in their C H] NMR spectra. 

Yu et al. [143] described the ortho amidation of aromatic and aliphatic oximes under C-H activation. Pd(OAc)2 as a catalyst in combination with Sequiv. of K2S20g as an oxidant was required for the amidation reaction (Scheme 13.98). 

Aromatic ketimines as well as aldimines are viable substrates for ortho amidation, carbamoylation, and sulfamidation. Not only aromatic, but also aliphatic oximes were converted into the amides regioselectively in high yields. It was suggested that the reaction proceeds by the oxidation of the amide to a nitrene species, which then inserts into the ortho-palladated arene. An alternative mechanism, which involves a Pd-nitrene or Pd(IV) species, was also considered for this reaction. 

Aliphatic oximes this particular example is LIX 63. The stars indicate chiral centers... 

Such stabilization is characteristic of pyrrole-2-carbaldehyde oximes and does not occur in other aromatic and aliphatic oximes. The stereospeciflc facile transformation of E-ZZ-isomer mixtures to pure salts of Z-isomer is the first known method for the synthesis of individual Z-isomers of aldoxime salts. 

Qninone oximes C=0 st 1680-1620 Aliphatic oximes Aromatic oximes... 

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