Palladium complexes nitro

Asymmetric synthesis of tricyclic nitro ergoline synthon (up to 70% ee) is accomplished by intramolecular cyclization of nitro compound Pd(0)-catalyzed complexes with classical C2 symmetry diphosphanes.94 Palladium complexes of 4,5-dihydrooxazoles are better chiral ligands to promote asymmetric allylic alkylation than classical catalysts. For example, allylic substitution with nitromethane gives enantioselectivity exceeding 99% ee (Eq. 5.62).95 Phosphi-noxazolines can induce very high enatioselectivity in other transition metal-catalyzed reactions.96 Diastereo- and enantioselective allylation of substituted nitroalkanes has also been reported.9513... 

Reduction of nitro aromatics to anilines with CO (Equation 16) catalysed by palladium complexes generated from tppts or 25 (Table 2)47-547-548,550b or by [Rh(CO)4] systems549-5503 in aqueous media. 

When the Pd bears chiral ligands, these reactions can be enantioselective.1448 ir-Allylmo-lybdenum compounds behave similarly.1449 Because palladium compounds are expensive, a catalytic synthesis, which uses much smaller amounts of the complex, was developed. That is, a substrate such as an allylic acetate, alcohol, amine, or nitro compound1450 is treated with the nucleophile, and a catalytic amount of a palladium salt is added. The rr-allylpal-ladium complex is generated in situ. Alkene-palladium complexes (introducing the nucleophile at a vinylic rather than an allylic carbon) can also be used.1451... 

Chiral crown ether phosphine-palladium complexes have been used to catalyse the alkylation of carbanions derived from a-nitro ketones and a-nitro esters,63 and proline rubidium salts have been used to catalyse asymmetric Michael addition of nitroalkanes to prochiral acceptors 64 80% enantioselectivity can be achieved in each case. 

Oxidation of alkenes to ketones. This palladium complex is an effective catalyst for air oxidation of 1-alkenes to methyl ketones in high yield via a nitro-nitrosyl redox couple. ... 

The carbonylation of nitro arenes can lead to amines, isocyanates, carbamates, azo compounds, or ureas.80 Iron, ruthenium, rhodium, or palladium complexes have been used as catalysts. The carbonylation to give isocyanates, for example, involves the steps... 

Feringa from The Netherlands was the first to report an abnormal Wacker oxidation in 1986.21 Dec-1 -ene was oxidized in the presence of a tertiary alcohol to a mixture of aldehyde 8 and methyl ketone 9. Surprisingly, aldehyde 8 was isolated as the major product (8/9 = 70/30). Even more strikingly, styrene was transformed exclusively to its corresponding phenylacetaldehyde under the same conditions. Feringa proposed that the aldehyde formation involved an oxygen transfer reaction via initial cycloaddition of the nitro-palladium complex, followed by p-hydrogen elimination. 

Reductions. Acenaphthoquinonediimine ligated palladium complexes and a polymer-bound palladaisoindoline have found use as catalysts for semihydrogenation of alkynes and reduction of several common unsaturated compounds (including the nitro group), respectively. 

In comparison to the nickel-catalysed aryl halide coupling reactions, the palladium-catalysed analogues are not sensitive to the steric hindrances and to the presence of nitro group. The nickel(O) complexes are more reactive than the appropriate palladiums, and thus more effective in the reactions with the least reactive aryl chlorides. However, the palladium complexes are more convenient and selective, even in the cross-coupling reaction of two electronically different aryl halides. 

Even palladium complexes can be activated by Lewis acids in the carbonylation of aromatic nitro compounds. The carbonylation at atmospheric pressure and 100-140 °C of... 

Palladium complexes with an heterocyclic N-containing ligand have been used in the carbonylation of aromatic nitro compounds with cocatalysts such as cyclopentadienyl halides or oxyhalides of transition metals belonging to group V e.g. CP2VCI) [168], a cyclopentadienyl halide or oxyhalide together with phosphorus oxytrichloride [169], or a 1,3-diketone derivative of vanadium [170], even also in the presenee of phosphorus oxychloride [171]. 

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