Halogenation palladium acetate

Ketones from halohydrins. Palladium acetate complexed with a triarylphos-phine, particularly tri-o-tolylphosphine, converts halohydrins into ketones in the presence of K2C03. Yields are about 70-85% for substrates in which the halogen is secondary or tertiary, but less than 50% when the halogen is primary because of epoxide formation. The reaction is useful for conversion of alkenes to ketones in those instances in which halohydrins are formed regioselectively. 

Another interesting application of microwave irradiation is found in the selective dehalogenation of the iodinated indole alkaloid Plakohypaphorine F, described by E. Fattorusso et al. [117,118] (Scheme 32). The bis-halogenated compound was treated with potassium formate and palladium acetate under controlled microwave irradiation, resulting in selective deiodination. The choice of the solvent, in this case DMSO, was found to be crucial. 

The use of palladium and ruthenium as halogen-free carbonylation catalysts has been studied intensively by Shell. The catalysts were principally designed for the carbonylation of olefins in the presence of alcohols in order to yield carboxylic esters [26], but work also well for the synthesis of carboxylic acids or anhydrides. The latter are formed when the reaction is conducted in an acid as a solvent [27]. The palladium systems typically consist of palladium acetate, tertiary phosphines, and strong acids such as mineral acids or acids with weak or noncoordinating anions such as p-toluenesulfonic acid. Remarkable activities are achieved when aromatic phosphines that carry pyridines as substituents are... 

In addition to the examples described previously, a tremendous variety of compounds have been prepared using palladium-catalyzed cross-coupling reactions due to the broad functional group tolerance. The combination of copper and palladium complexes have been used to promote the formation of borane-protected arylphosphines [298]. Palladium acetate catalyzed the coupling of halogenated benzoic acid derivatives leading to the formation of water-soluble phosphine ligands [299]. Aryl triflates have also been used in the phosphination reaction [300]. Functionalized tyrosine derivatives were converted... 

The palladium-catalyzed cross-coupling of arenediazonium tetrafluoroborates and secondary phosphine oxides generates arylphosphine oxides in moderate to excellent yields (Scheme 4.196) [292]. Palladium acetate was the most effective palladium precursor, and no additional ligand was needed for solubilization and stabilization of the palladium center. The chemistry was successful with arenes bearing esters, ethers, and halogens. 

Displacement of aromatic halogen in 2,4-diiodo-estradiol with tritiated Raney nickel yields 2,4-ditritiated estradiol. Aromatic halogen can also be replaced by heating the substrate with zinc in acetic acid-OD or by deuteration with palladium-on-charcoal in a mixture of dioxane-deuterium oxide-triethylamine, but examples are lacking for the application of these reactions in the steroid field. Deuteration of the bridge-head position in norbornane is readily accomplished in high isotopic purity by treatment of the... 

Halogenated nitro compoands may suffer replacement of halogen during some reductions thus 9-bromo-lO-nitrophenanthrene reduced with zinc and acid, with stannous chloride, with ammonium sulfide, or with hydrazine in the presence of palladium gave 9-aminophenanthrene (87.5% yield). Reduction to 9-bromo-lO-aminophenanthrene was accomplished with iron in dilute acetic acid (yield 35%) [278]. 

Various procedures have been developed for the production of oximes from nitroparaffins. Direct reduction with zinc dust and acetic acid has been proposed, but the yields are poor because of the simultaneous formation of amines. A synthesis for cyclohexanone oxime has been demonstrated which involves the formation and selective hydrogenation of 1-chloro-l-nitrocyclohexane. The halogenated intermediate is prepared in quantitative yield by chlorination of the sodium salt of acz -nitrocyclo-hexane, and subsequent hydrogenation is performed in an 80% yield over palladium-on-charcoal, ... 

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