Decane, metathesis

After tremendous success in propane metathesis (lower alkane) reactirMi, catalyst precursor 27 was employed for metathesis of -decane (higher alkane). The n-decane metathesis reactimi carried out at 150°C produced a broad distribution of linear alkanes from methane to C30 (triacontane) with trace amoimt of branched alkanes without any olefinic or cyclic products [74], Interestingly, the formation of lower... 

Fig. 4 Product distribution of n-decane metathesis for the catalysts [(=SiO)WMe5]si.Ai-5oo...

Double sequential ene-yne ring-closing metathesis on a series of chiral 3,4-bisallyloxybut-l-ynes using both Grubbs catalysts has been used to generate chiral dioxabicyclo[4.4.0]decanes (Scheme 48) <2003JOC7889>. 

The maximal Y value for Cu-PPX catalyst is 1150 [116], It is much more than the activity of all known catalysts of this reaction. For comparison, the same reaction of C-Cl bond metathesis was investigated on the special prepared catalyst containing 1 mass% of high-dispersed metallic Cu deposited on silica. In conditions analogous to those of the reaction with the nanocomposite Cu-PPX film, Y for this catalyst was 4. Moreover, it has low selectivity in this case the formation of by-products from condensation processes takes place along with the main reaction, whereas Cu-PPX catalyst gives monochlorosubstituted decanes only [116]. 

The adsorption of chemical compounds on nanoparticles of synthesized composites not only leads to electrical sensor effects, but also can result in new catalytic processes caused by the surface properties of such nanoparticles [61]. The important catalytic properties of PPX-metal composites prepared via cry-ochemical vapor deposition synthesis were discovered while studying the isomerization of 3,4-dichlorobutene into trans- and cw-l,4-dichlorobutene catalyzed by Pd nanoparticles of Pd-PPX [64] and the reaction C-Cl bonds metathesis in the mixture of n-decane with CCI4 catalyzed by Cu nanoparticles of Cu-PPX [76]. 

Catalytic reaction of the C-Cl bonds metathesis under the influence of a Cu-PPX nanocomposite film was studied in the mixture of -decane with CCl, at molar ratio CCVn-decane = 4 1 ... 

Mo[0(CF3)2CH3]2(=CHCMe2PH)(=Naryl) to carry out alkane metathesis, a fundamentally new type of reaction for organometallic catalysis (Equation (54)). " Re207/Al203 also served as an effective co-catalyst for the metathesis portion of the reaction at 175 °C. This tandem catalytic was system was shown to convert decane solvent into a distribution of C2-C30 alkanes. These systems have the pontential for substantial development in the near future. 

Further investigation on the metathesis of 1-decene (an expected olefin during the alkane metathesis of -decane) and the hydrogenation of the products formed clearly demonstrated that the distribution resulting from alkane and olefin metathesis completely differs with the same catalyst. If there is no double-bond migration, 9-octadecene and ethylene are expected to be the major primary products. Indeed, these primary products are observed, as the temperature reaches 150°C. However, after just 15 min, Cj to C12 and C13 to C20 olefins are also observed, clearly indicating that some isomerization of double bond occurs leading to several competitive metatheses (Fig. 5). 

While in alkane metathesis mechanism (Scheme 20, b), the n-decane undergoes o-bond metathesis to generate methane and the W-bis-decyl species which, upon P-H elimination, produces the W-H with a coordinated olefin. Further, the a-hydrogen transfer from the alkyl to alkylidyne forms the hydrido W-bis-carbene [55, 76]. This upon [2-1-2] cycloaddition and cycloreversion gives an internal olefin and hydrido W-bis-carbene. Successive insertion/elimination steps (by chain walking) [77] give the terminal alkene, which reacts to a new W-alkylidene. The CH activation of the pendant W-hydride with -decane followed by p-H elimination provides 1-decene. A second metathesis between 1-decene and newly formed W-alkylidene followed by hydrogenolysis produces the alkane. 

Starting with -hexane (Cg) metathesis, dehydrogenation should give the corresponding 1-hexene, followed by its homo-metathesis to yield ethylene and decene, which upon hydrogenation, should ideally produce ethane and decane (Cj q products) as the major products (Scheme 2.18, path a). However, this tandem reaction process was not selective since -decane represented <50% of the total primary products of heavy alkanes when the reaction was catalyzed with Ir-2(H2). The authors attributed this unexpected distribution of alkanes to the isomerization of the (x-olefin prior its metathesis, as depicted in pathway b (Scheme 2.18). 

Figure 2.20 Gas chromatography (GC) chromatograms of the metathesis reactions of n-decane using (a) lr-8(H4) and ReOy/AljOj after 9days at 175°C and (b) Ir-17(C2H4)/Al203 and Re202/Al203 after 7 days at 175°C.

The method of synthesis of ten-membered rings by olefin metathesis, involving tricyclo[4.4.0.0 ]decane intermediates, is also popular, and this year is illustrated by Wender and Lechleiter s synthesis of isabelin (165) (see also Section 2). 

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