Reactions with Alkanes, Alkenes, and Dienes

Activated alkanes, such as cyclohexanone, acetone, and aliphatic nitro compounds, can react with carbon dioxide even without metal catalysis. A typical example is the phenolate-catalyzed reaction of acetophenone with C02 to the corresponding carbon add. A catalytic conversion of the non-activated methane with C02 to give acetic acid was reported by Fujiwara and co-workers [72], The reaction was carried out in the presence of palladium and copper acetate and also stoichiometric amounts of the oxidant K2S208. 

Homs and co-workers described the linkage of ethene and C02 on a supported platinum/tin complex yielding 3-hydroxypropionic acid [73], Another approach to utilizing C02 was pursued by Tominaga and Sasaki, namely hydroformylation with C02 [74]. 1-Hexene, for instance, reads with a mixture of C02 and H2 in the presence of ruthenium dusters giving heptanals, heptanols, and, in small amounts, the undesired hexane as a result of simple hydrogenation. Mechanistically it is assumed that a retro water gas shift reaction occurs, in which CO and H20 are formed from C02 and H2. This carbon monoxide undergoes ordinary hydroformylation with the alkene and H2. 

3-Dienes can also read with the Cj building block C02. In the 1970s, the catalyzed telomerization of C02 with 1,3-butadiene was reported by Inoue and co-workers, which yields, in the presence of catalytic amounts of palladium and phosphine ligands, a 6-ladone with up to 90% seledivity (Equation 3.5) [75], Behr s group scaled up this reaction from the laboratory to the miniplant scale and it could be carried out in a full-scale plant in the near future [76-80]. 

Among the hydrogenation, hydroamination, hydroformylation, and oxidation of 6-lactones, hydrogenation is of particular interest owing to its facile approach to a 

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