Ketones ionic

The highly ionic thaHic nitrate, which is soluble in alcohols, ethers, and carboxyhc acids, is also a very useful synthetic reagent. Oxidation of olefins, a,P-unsaturated carbonyl compounds, P-carbonyl sulfides, and a-nitrato ketones can aH be conveniently carried out in good yields (31,34—36). 

Procedure has been proposed for the P(V) and As(V) determination based on the selective extraction of ionic associate of Crystal Violet with reduced molybdophosphate with mixture of inert (toluene) and active (methyl isobutyl ketone) solvents. Extraction of reagent is negligible. After concentration determination lower than 10 mol/1 of P(V) and As(V) is possible. 

At reflux, tetrahydrafuran slowly adds to terminal perfluoroalkylethylenes, perfluoroalkylacetylenes, and ethyl perfluoroalkylpropynoates [25] (equation 18) By contrast, the ionic addition of enamines to hexaJluoro-2-butyne is exothermic and gives dieneamines that, on acidic hydrolysis, yield fluoroalkenyl ketones [26] (equation 19)... 

Reactions in chloroaluminate(III) salts and other related binary salts often proceed smoothly to give products. However, it should be noted that these salts are water-sensitive and must be handled under dry conditions. They react with water to give hydrated aluminium(III) ionic species and HCl. When a reactant or product contains a heteroatomic functional group, such as a ketone, a strong ketone/alumini-um(III) chloride adduct is formed. In these cases, this adduct can be difficult to separate from the ionic liquid at the end of a reaction. The isolation of the product often... 

In the reaction between isoprene (IP) and methyl vinyl ketone (MVK), the selectivities between the two isomers produced in this reaction can be improved from 4 1 to 20 1 by the addition of a mild Eewis acid such as 2inc(II) iodide (5 mol %) to the ionic liquid [BMIM][PE(3] (Scheme 5.1-18). One of the key benefits of this is that the... 

Friedel-Crafts acylation reactions usually involve the interaction of an aromatic compound with an acyl halide or anhydride in the presence of a catalyst, to form a carbon-carbon bond [74, 75]. As the product of an acylation reaction is less reactive than its starting material, monoacylation usually occurs. The catalyst in the reaction is not a true catalyst, as it is often (but not always) required in stoichiometric quantities. For Friedel-Crafts acylation reactions in chloroaluminate(III) ionic liquids or molten salts, the ketone product of an acylation reaction forms a strong complex with the ionic liquid, and separation of the product from the ionic liquid can be extremely difficult. The products are usually isolated by quenching the ionic liquid in water. Current research is moving towards finding genuine catalysts for this reaction, some of which are described in this section. 

The Friedel-Crafts acylation reaction has also been performed in iron(III) chloride ionic liquids, by Seddon and co-workers [96]. An example is the acetylation of benzene (Scheme 5.1-66). Ionic liquids of the type [EMIM]Cl/FeCl3 (0.50 < X(FeCl3) < 0.62) are good acylation catalysts, with the added benefit that the ketone product of the reaction can be separated from the ionic liquid by solvent extraction, provided that X(FeCl3) is in the range 0.51-0.55. 

Rebeiro and Khadilkar have investigated the reactions between trichloroalkanes and aromatic compounds. For example, the benzoylation of aromatic compounds in ionic liquids was performed with benzotrichloride, giving ketones on aqueous workup [98]. 

Flowever, ionic liquids acting as transition metal catalysts are not necessarily based on classical Lewis acids. Dyson et al. recently reported the ionic liquid [BMIM][Co(CO)4] [38]. The system was obtained as an intense blue-green colored liquid by metathesis between [BMIM]C1 and Na[Co(CO)4]. The liquid was used as a catalyst in the debromination of 2-bromoketones to their corresponding ketones. 

So far only two groups have reported details of the use of ionic liquids with wholecell systems (Entries 3 and 4) [31, 32]. In both cases, [BMIM][PF(3] was used in a two-phase system as substrate reservoir and/or for in situ removal of the product formed, thereby increasing the catalyst productivity. Scheme 8.3-1 shows the reduction of ketones with bakers yeast in the [BMIM][PF(3]/water system. 

In order to broaden the field of biocatalysis in ionic liquids, other enzyme classes have also been screened. Of special interest are oxidoreductases for the enan-tioselective reduction of prochiral ketones [40]. Formate dehydrogenase from Candida boidinii was found to be stable and active in mixtures of [MMIM][MeS04] with buffer (Entry 12) [41]. So far, however, we have not been able to find an alcohol dehydrogenase that is active in the presence of ionic liquids in order to make use of another advantage of ionic liquids that they increase the solubility of hydrophobic compounds in aqueous systems. On addition of 40 % v/v of [MMIM][MeS04] to water, for example, the solubility of acetophenone is increased from 20 mmol to 200 mmol L ... 

The conformationally locked racemic enamine, 4-(4-rOT-butyl-1-cyclohexenyl)morpholine, reacts with (l-nitroethenyl)benzene to give a mixture of diastereomeric 1,2-oxazine 2-oxides 1 and 2 (ratio 1/2 75 25). Whether these arise via an ionic or a cycloaddition mechanism is unclear. Hydrolysis of 1 and 2 with dilute acid gave a 80 20 mixture of trans- and cis-ketones, 3 and 414. 

The same kind of results were obtained using the ionic hquid [bmim] [PFg ] as the medium to carry out the reaction in the presence of TEA at 60 °C for 30 s under microwave irradiation [151,152]. Toluene can be also used as the solvent as well TEA as the acid [153]. Heating at 60 °C for a longer period also allowed the reaction of different ketones, thus increasing the potential of the reaction for the generation of molecular diversity around a tricycUc scaffold such as 236 in Scheme 87. 

The aziridine aldehyde 56 undergoes a facile Baylis-Hillman reaction with methyl or ethyl acrylate, acrylonitrile, methyl vinyl ketone, and vinyl sulfone [60]. The adducts 57 were obtained as mixtures of syn- and anfz-diastereomers. The synthetic utility of the Baylis-Hillman adducts was also investigated. With acetic anhydride in pyridine an SN2 -type substitution of the initially formed allylic acetate by an acetoxy group takes place to give product 58. Nucleophilic reactions of this product with, e. g., morpholine, thiol/Et3N, or sodium azide in DMSO resulted in an apparent displacement of the acetoxy group. Tentatively, this result may be explained by invoking the initial formation of an ionic intermediate 59, which is then followed by the reaction with the nucleophile as shown in Scheme 43. 

Cyclisation of malonates is one of the few reliable ionic reactions giving four-membered rings. Hence when the ais and trans ketones (38) were wanted for a photochemical study, acids (39) were the obvious starting materials as these could be made by cyclisation of (40). Analysis... 

Aldehydes and diethyl(triethylgermyl)phosphine give (38) while unsaturated aldehydes and ketones form 1,4-dipolar addition products (39), presumably via ionic cleavage of the germanium-phosphorus bond. Hydrolysis of these compounds produces the y-substituted phosphorus aldehydes or ketones. -... 

The ionic potentials can be experimentally determined either with the use of galvanic cells containing interfaces of the type in Scheme 7 or electroanalytically, using for instance, polarography, voltammetry, or chronopotentiometry. The values of and Aj f, obtained with the use of electrochemical methods for the water-1,2-dichloroethane, water-dichloromethane, water-acetophenone, water-methyl-isobutyl ketone, o-nitrotol-uene, and chloroform systems, and recently for 2-heptanone and 2-octanone [43] systems, have been published. These data are listed in many papers [1-10,14,37]. The most probable values for a few ions in water-nitrobenzene and water-1,2-dichloroethane systems are presented in Table 1. 

In almost all theoretical studies of AGf , it is postulated or tacitly understood that when an ion is transferred across the 0/W interface, it strips off solvated molecules completely, and hence the crystal ionic radius is usually employed for the calculation of AGfr°. Although Abraham and Liszi [17], in considering the transfer between mutually saturated solvents, were aware of the effects of hydration of ions in organic solvents in which water is quite soluble (e.g., 1-octanol, 1-pentanol, and methylisobutyl ketone), they concluded that in solvents such as NB andl,2-DCE, the solubility of water is rather small and most ions in the water-saturated solvent exist as unhydrated entities. However, even a water-immiscible organic solvent such as NB dissolves a considerable amount of water (e.g., ca. 170mM H2O in NB). In such a medium, hydrophilic ions such as Li, Na, Ca, Ba, CH, and Br are selectively solvated by water. This phenomenon has become apparent since at least 1968 by solvent extraction studies with the Karl-Fischer method [35 5]. Rais et al. [35] and Iwachido and coworkers [36-39] determined hydration numbers, i.e., the number of coextracted water molecules, for alkali and alkaline earth metal... 

Spectroscopic investigations of the lithium derivatives of cyclohexanone (V-phenylimine indicate that it exists as a dimer in toluene and that as a better donor solvent, THF, is added, equilibrium with a monomeric structure is established. The monomer is favored at high THF concentrations.110 A crystal structure determination was done on the lithiated A-phenylimine of methyl r-butyl ketone, and it was found to be a dimeric structure with the lithium cation positioned above the nitrogen and closer to the phenyl ring than to the (3-carbon of the imine anion.111 The structure, which indicates substantial ionic character, is shown in Figure 1.6. 

Thiolates, generated in situ by the action of ammonium tetra-thiomolybdate on alkyl halides, thiocyanates, and disulfides, undergo conjugate addition to a, (1-unsaturatcd esters, nitriles, and ketones in water under neutral conditions (Eq. 10. II).29 Conjugate addition of thiols was also carried out in a hydrophobic ionic liquid [bmim]PF6/water-solvent system (2 1) in the absence of any acid catalyst to afford the corresponding Michael adducts in high to quantitative yields with excellent 1,4-selectivity under mild and neutral conditions (Eq. 10.12). The use of ionic liquids helps to avoid the use of either acid or base catalysts... 

Monoketones are poor ligands. Di-2-pyridylketone ((py)2C O) accommodates this deficiency in an unusual way when it reacts with Co(OAc)2 to form clusters, including [Co4(HQ)4(0 Ac)4] II20, where the monodeprotonated hydrated gem-diol form of the ketone (HQ-) (Equation (5)) binds as an ionic ligand.423 This cluster adopts a tetranuclear cubane shape with four deprotonated O atoms of the diol occupying the alternating vertices to the Co ions. 

FIGURE 2.28 Showing proposed ionic mechanism to account for stereochemistry during hydrogenation of cyclic ketones. Surface attachments of adsorbed species are uncertain. 

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