Chelates ketoxime

Bis(alkylideniminoxy)ethanes (124,128,131,135,140) are of potential value, particularly as chelating ligands for metal cations. A special investigation has been undertaken in order to increase their yields in the reaction of ketoximes with dichloroethane (88ZOR2538). As a result, special conditions have been found which allow l,2-bis(organylideniminoxy)ethanes to be synthesized from oximes of dialkyl or alkyl aryl (hetaryl) ketoximes and 1,2-dichloroethane and an alkali metal hydroxide suspension in DMSO in yields up to 78%. 

The copper-specific extractants used to extract copper from other base metals in acidic sulfate liquors are known as hydroxyoximes, and the interaction is known as chelation. The basic structures of modem oxime extractants are shown in Figure 5.4, where A = H for aldoximes and A = CHj for ketoximes. The R-chain is usually C9H19 (occasionally C12H25). The complexation of copper by these extractants is shown schematically in Equation (5.1). Extraction of each copper ion releases two protons, thereby providing a useful source of acid for further leaching (see Figure 5.2). pH is an important parameter controlling the equilibrium position of this reaction. 

A rhodium-catalyzed one-pot synthesis of substituted pyridine derivatives from a,(3-unsaturated ketoximes and alkynes was developed in 2008 by Cheng and coworkers [99], Good yields of the desired pyri-dines can be obtained (Scheme 3.48). The reaction was proposed to proceed via rhodium-catalyzed chelation-assisted activation of the (3—C—H bond of a,(3-unsaturated ketoximes and subsequent reaction with alkynes followed by reductive elimination, intramolecular electro-cyclization, and aromatization to give highly substituted pyridine derivatives finally [100]. Later on, in their further studies, substituted isoquinolines and tetrahydroquinoline derivatives can be prepared by this catalyst system as well [101]. Their reaction mechanism was supported by isolation of the ort/jo-alkenylation products. Here, only asymmetric internal alkynes can be applied. 

Ketoximes have been reacted with aliphatic aldehydes and diphenylborinic acid. " a-Hydroxyalkylation at the oxime oxygen is favoured by a bulky substituent in the aldehyde (leading subsequently to a BOCON diphenylboron chelate), while formaldehyde reacts by A-alkylation (giving a COBON chelate). 

Like the pyridine aldoximes, the ketoximes give metal chelate complexes . The a f-pyridyl oxime of 2-benzoylpyridine gives such complexes whilst the n-pyridyl oxime does not. The stereochemical assignments are based on the Beckmann rearrangement of the oximes , and the behaviour of the two oximes with metal ions is that to be expected from the structures of chelates in this series . The Beckmann rearrangement has been used several times in the pyridine series 8- , The oximes prepared from 2-phenacyl-and 2,6-diphenacyl-pyridine give pyridine-2-acetic acid anilide and pyri-dine-2,6-diacetic acid dianilide, respectively, and must be the n-pyridyl compounds ". ... 

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