**6. Conclusion**

Close nature of BD and light olefins is manifested in similar reaction properties, so that liquid-phase oxidation reactions of BD and olefins have similar mechanisms in many features. The oxidation of olefins and BD in liquid medium enables realization of several routes and obtaining a wide range of products, which are more diverse if compared with gas-phase oxidation. We have considered here the radical chain oxidative conversion of BD realized through the stable polyperoxide intermediate, the formation of which is, to a certain extent, inherent to many olefins. Palladium is able to catalyze homolytic (radical) and heterolytic (Wacker-type) oxidation of olefins. Very close to olefins, the properties of BD are manifested in reactions assisted by homogeneous and more often heterogeneous Pd-containing catalysts. (Note that the tendency to heterogenization of soluble catalysts is observed in liquidphase reactions.) We observe an interesting phenomenon when the mechanism and products of the Pd-catalyzed oxidation are controlled by promoters. In dependence on other components, the catalytic action of Pd is switched from radical oxidation to nonradical oxygenation directed to one carbon atom or 1,4-position of BD when Pd is promoted with Te or related metals. The effect of Te as an oxidation promoter of palladium and a radical inhibitor allows PdTe catalysts to show substantial efficiency in the well-known industrial synthesis of 1,4-diacetoxybutene in acetic acid and also in other oxidations of BD such as formation of crotonaldehyde and methyl ethyl ketone in aqueous media. The reaction medium and concentration of reagents are also important factors to vary the mechanism of oxidation. Low concentration of BD in the reaction mixture reduces the development of the chain process and makes it possible to realize the oxidation by the heterolytic mechanism. Polar organics are conventional solvents for various oxidations, but acetic acid and methanol exhibit special properties creating conditions for preferable formation of esters of 1,4-butanediol. The identity in mechanisms is also observed in epoxidation of olefins and BD with hydrogen peroxide, where the same catalytically active Ti silicates and polyoxometalates are successfully used to attain highly selective conversion of hydrocarbon and H2 O2 . All this shows that liquid-phase oxidation have a great potential in converting the BD into valuable oxygenates. To develop this area, extremely productive can be appeal to analogy in chemistry of BD and olefins. A large body of information relating to the oxidation of olefins can be productively applied to understand the mechanisms in oxidation of BD and to develop a strategy for synthesis of purposed oxidation products.
