1- Octene, reaction with ruthenium

Selectivity of the type found with ruthenium was not possible when palladium catalysts were used. For instance, hydrogenation of a mixture of 1- and 2-octene was completely nonselective over palladium catalysts. This lack of selectivity resulted from the high isomerization activity of palladium when the reaction was stopped at only one-tenth of completion, all 1-octene had disappeared by migration of the terminal double bond inward. 

Other transition-metals have also been used. For example, Trost183 reported that heating a 1 1 mixture of 1-octene and 1-octyne in DMF-water (3 1) at 100°C with a ruthenium complex for 2 h generated a 1 1 mixture of two products corresponding to the addition of the alkene to the acetylene (Eq. 3.47). The presence of a normally reactive enolate does not interfere with the reaction. 

The preparation of the catalyst starts with the synthesis of 1-mes-ityl-3-(7-octene)-imidazole bromide. This compound is prepared by condensing mesityl imidazole with 8-bromooctene. The resulting salt is deprotonated with (TMS)2NK, where TMS is the tetrameth-ylsilyl radical. This step is performed in tetrahydrofuran at -30°C for 30 min. To this product a solution of the ruthenium complex (PCy3)2Cl2Ru=CHPh is added at 0°C. Bringing the solution slowly to room temperature, after 1 h the ligand displacement was determined to be complete. Afterwards, the reaction mixture is then diluted with n-pentane and heated to reflux for 2 h to induce intramolecular cyclization. 

Olefins such as 1-octene and cyclohexene demonstrated unusually low turnover rates compared to adamantane and cis-decalin (Table 1, entry 7), although in competitive oxidations 1-octene was twice as reactive as adamantane (Table 1, entry 8). Apparently, the catalyst is inhibited in the presence of olefins. Interestingly, upon a stoichiometric reaction of Ru VtPFPP)(0)2 with cyclohexene in methylene chloride, rapid transformation of the ruthenium porphyrin into Ru (TPFPP)(CO) was observed (Fig. 6). 

Regarding the direct oxidative cleavage of terminal unsaturated fatty acids, the reaction was first studied systematically with 1-octene. The ruthenium-catalysed oxidative cleavage with peracetic acid produces oenanthic (heptanoic) acid and formic acid. 

With methyl oleate, 53% yield of the terminal alcohol was observed. With unmodified internal olefins (2-decene, 2-tridecene, 4-octene), even higher regioselectivities in favor of the terminal alcohol could be achieved l/b up to 12 1). Proof was given that both rhodium and ruthenium complexes catalyze the isomerization-hydroformylation-hydrogenation reaction in a cooperative manner. 

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