A-Acyloin oximes

Although adsorbed molecules of extractants are well oriented at the interface, the interfacial reactions occur more slowly, as recalculated for the same volume, than reactions in the aqueous phase. The extraction of palladium(II) from HCl solutions with dialkyl sulfides is a classic example of a very slow process. Modifying the extractant structure by adding a hydrophilic hydroxyl group and/or a phase transfer catalyst, e.g., trialkylamine or quaternary ammonium salt, increases the rate of extraction. The addition of sulfonic and phosphoric acids to hydroxyoximes may enhance the rate of copper extraction due to the formation of reverse micelles and the development of the microscopic interface. The a-acyloin oximes that form an intermediate complex that has a five-member ring with copper(II) increase the rate of extraction of aromatic hydroxyoximes. The addition of surfactants may cause both retardation and acceleration of extraction. If the interfacial tension is decreased, surfactants cause an increase in the interfacial surface area in dispersed systems. When they adsorb at the interface, they cause an additional... 

There are, however, other binding forces that might be used to hold a, for example, nonionic substrate in a cavity. One such possibility that has been investigated is the use of hydrophobic interactions . This can be illustrated with an example. The macrocycles (34) and (55) obtainable by means of acyloin condensation, followed by conversion to the oxime, possess functionalities that are potential catalysts for the hydrolysis of activated esters. If hydrophobic interactions are important, an activated ester of a long chain fatty (i.e. hydrophobic) acid, for example, the p-nitro-phenolate ester of lauric acid, should associate in water with the hydrophobic... 

An oxidative cleavage of cycloalkanones to unsaturated aldehyde-esters has been developed. Thus, for example, cyclononanone was converted into 2,2-dithio-trimethylenecyclononanone, which was cleaved using lead(iv) acetate (66 %), and the product so obtained treated with methanol and sodium periodate to give (208 in = 5). Cyclododecanone was similarly converted into (208 n = 8). 1,2-Bis(trimethyl-silyloxy)cycloalkenes, prepared by acyloin condensations, have been converted into 2-alkyl-2-hydroxycycloalkanones by treatment with methyl-lithium and an alkyl halide, and the oximes of these a-hydroxyketones cleaved to give open-chain co-cyanoketones using mesyl chloride-pyridine. ... 

Various methods for the a-hydroxylation of carbonyl compounds have appeared. lodosobenzene shows a high degree of selectivity in the preparation of acyloins, and benzeneseleninic anhydride appears to be an excellent reagent for the hydroxylation at the tertiary centre in a-alkylcycloalkanones. Enol silyl ethers give acyloins with osmium tetroxide and V-methylmorpholine V-oxide,and a-acyloxycarbonyl compounds with silver acetate and iodine. a-Acyloxyketones may also be prepared conveniently by treatment of oximes with acid chlorides [equation (42)]. ... 

Oximes of acyloins and a-diketones polymerize with metals to yield ring-containing products. Poly[Cu(II) benzoin oxime] was postulated to possess structure [63] (63). 

---