Hydrogen-palladium bonds olefin carbonylation

In neutral medium A16-, A17(20)-, and A20-olefins are hydrogenated over palladium in preference to the double bonds of A4-3-ketones.67 The double bonds of A4-3-ketones and A16-20-ketones are reduced in preference to A5-,93 A7-48 155 and A9(I -olefins.2 169 The double bond of a A14-16-ketone is saturated before a 5-ene.70,163 In basic medium the carbonyl conjugated double bond is preferentially saturated in all cases92 presumably because of the strong adsorption of the enolate anion (see section II-C). Debromination (9a-bromo 11-ketone) occurs before saturation of the A4-3-keto double bond14 over Raney nickel but hydrogenation of benzyl ethers takes place concurrently with the hydrogenation of this double bond over palladium in neutral medium.96... 

In the metallic palladium-catalyzed carbonylation of olefins, some hydrogen sources are essential hydrogen halide and molecular hydrogen were found to be the most eflFective. The following sequence of reactions was proposed for the reaction mechanism of the ester and aldehyde formation catalyzed by palladium (23). The first step of the metallic palladium-catalyzed carbonylation seems to be the formation of a palladium-hydrogen bond by the oxidative addition of hydrogen chloride... 

Palladium(ii) complexes of trimethylsilyl enol ethers derived from ketones can be carbonylated (50 atm. CO) in the presence of an alcohol to give /S-keto-esters only three examples are quoted in this preliminary report. a, -Unsatur-ated esters can be converted into -keto-esters in ca. 70% yields using Na2PdCl4 in aqueous acetic acid containing t-butyl hydroperoxide or hydrogen peroxide. This method may be inappropriate if the starting ester contains other olefinic (and presumably acetylenic) bonds as these will probably also be attacked. 

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