Oxygen-assisted hydrogen transfer

The most generally accepted mechanistic speculations center about a y3-acetoxyalkylpalladium intermediate (VI) formed by an insertion reaction of ethylene into a palladium-oxygen bond (Reaction 3). It is proposed that this intermediate would then decompose via a palladium-assisted hydride transfer to vinyl acetate (Reaction 4) (36). While Reaction 4 would appear more awkward than a simple )3-hydrogen... 

It might be speculated that this is hydrogen transfer, but that this process stops at sterically unfavourable positions. Oxygen may then be thought of as assisting the crossing of otherwise insurmountable barriers. 

Cytochrome c, a small heme protein (mol wt 12,400) is an important member of the mitochondrial respiratory chain. In this chain it assists in the transport of electrons from organic substrates to oxygen. In the course of this electron transport the iron atom of the cytochrome is alternately oxidized and reduced. Oxidation-reduction reactions are thus intimately related to the function of cytochrome c, and its electron transfer reactions have therefore been extensively studied. The reagents used to probe its redox activity range from hydrated electrons (I, 2, 3) and hydrogen atoms (4) to the complicated oxidase (5, 6, 7, 8) and reductase (9, 10, 11) systems. This chapter is concerned with the reactions of cytochrome c with transition metal complexes and metalloproteins and with the electron transfer mechanisms implicated by these studies. 

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