Reactions of Unsaturated Compounds

Homogeneous vanadium-based catalysts formed by the reaction of vanadium compounds and reducing agents such as organoaluminum compounds [10-12] are used industrially for the production of elastomers by ethylene/propene copolymerization (EP rubber) and ethylene/propene/diene terpolymerization (EPDM rubber). The dienes are usually derivatives of cyclopentadiene such as ethylidene norbomene or dicyclopentadiene. Examples of catalysts are Structures 1-4. Third components such as anisole or halocarbons are used to prevent a decrease in catalyst activity with time which is observed in the simple systems. 

The oxidation state of the active vanadium species is under discussion [13] some authors propose the trivalent V(III) state and describe the deactivation to occur by reduction to V others favor V to be the active form. Nevertheless it is generally assumed that the active site contains alkylvanadium halide entities such as VCI2R. Chain initiation is believed to arise from the sequence of reactions shown in eq. (1). 

In contrast to the heterogeneous catalysts which produce polymers with a broad molecular weight distribution MJMf) of 5-30, the compounds containing vanadium produce polymers with a narrow MJM of 2-4. 

Homogeneous catalysts for the ethylene polymerization based on bis(cyclopenta-dienyl)titanium(IV) compounds [4], tetrabenzyltitanium [14], tetraallylzirconium and hafnium are formed with diethylaluminum chloride, dimethylaluminum chloride or triethylaluminum as co-catalysts. Their activities are poor (less than 200 kg PE/mol catalyst per h), so no industrial application resulted. 

This situation changed when a new breed of homogeneous catalysts, based on metallocenes and methylalumoxane (MAO) as co-catalyst, which are 10-100 times more active than common heterogeneous ones, found great industrial and scientific interest [15,16]. The metallocene and the MAO, as well as the active complex, are soluble in hydrocarbons. Using these catalysts it became possible to tailor the microstructures of the polymers by tuning the ligands. Table 1 reviews the efficiency of the zirconocene/methylalumoxane catalysts. 

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Of greater importance is the reaction of unsaturated compounds with sulfur at 200-250°C, which normally leads to l,2-dithiole-3-thiones (trithiones) but especially with 2-aryIsubstituted 2-butenes and 1- aryl- or 2-aryl-1-butenes, thiophenes are obtained in 15-60% Thus p-methoxy-a-ethylstilbene (50) gives 2-phenyl-3-... 

Kaminsky W, Arndt M (1996) Reactions of unsaturated compounds. In Cornils B, Herrmann WA (eds) Applied homogeneous catalysis with organometallic compounds, vol 1. VCH, Weinheim, p 220... 

Reaction of Unsaturated Compounds with Dialkyl Phosphites The diesters of phosphorous acid are somewhat resistant to oxidation and used as intermediates for the reaction with olefins forming phosphonic acids. The reaction takes place in the presence of free radical initiators, such as di-/-bu-tyl peroxide [104,105]. 

Hydration, Alcoholation and the Related Reactions of Unsaturated Compounds... 

Dangyan, Y.M., Voskanyan, M.G., Zurabyan, N.Z., and Bandanyan, S.O., Reactions of unsaturated compounds. LVII. Vinylallenylphosphonates as diene fragments in the Diels-Alder reaction, Arm. Khim. Zh., 32, 460, 1979. 

Fluorinated carbocations play an important role as intermediates in electrophilic reactions of unsaturated compounds, although the highly electron-deficient double bond in fluoroalkenes is not usually susceptible to electrophilic attack. Only the most powerful electrophilic reagents... 

Hypervalent iodine oxidation reactions of unsaturated compounds such as a,/ -unsaturated compounds, alkynes, and silylenol ethers afford the important substructures of several natural products. 

Later it was found that the result of reaction of unsaturated compounds with S03 strongly depends on the structure of fluoroolefin. While HFP gives p-sultone in a high yield under the action of pure S03 [173], perfluoroallylbenzene reacts with S03 exothermally to give a mixture of /1-sultone and F-phenyl-propenyl fluorosulfate, but 3,3,3-trifluorotrichloropropene-l or 2,3-dichloro-F-butene-2 reacts with S03, forming allyl fluorosulfates 87 or 88 [175,176] ... 

The isomerization of 1-methylindene to 3-methylindene proceeds analogously. The reaction starts in the solid film at 120-130 K, and the conversion of the initial reagent is completed at 230 K. It is evident that the specific features of the reactions of unsaturated compounds in the films of their cocondensates with magnesium point to a quite unique character of these processes, which combine an unconventional nature of the active site, high performance, and mild reaction conditions. 

Thus, the courses of reactions of unsaturated compounds in the films of their co-condensates with magnesium point to a quite unique character... 

Although even saturated fatty acids may be oxidized, the rate of oxidation greatly depends on the degree of unsaturation. In the series of 18-carbon-atom fatty acids 18 0, 18 1, 18 2,18 3, the relative rate of oxidation has been reported to be in the ratio of 1 100 1200 2500. The reaction of unsaturated compounds proceeds by the abstraction of hydrogen from the a carbon, and the... 

Another non-isohypsic transformation, addition of halogens to a double bond, is probably the oldest known reaction of unsaturated compounds. It is widely used for both industrial and laboratory purposes. The products formed, 1,2-dihaloalkanes, are valuable for conversion into vinyl halides (such as vinyl chloride monomers for the production of PVC) or alkynes ... 

The cydization reaction of unsaturated compounds with CO is one of the most attractive reactions in organic synthesis. Recently, mthenium complexes were shown to have outstanding potential for catalytic activity in these reactions. 

As mentioned previously, although the benzene ring is unsaturated it is generally very stable and does not give the typical addition reactions of unsaturated compounds. Its reactions are generally substitution reactions. 

The oldest and still very common cleavage is the reaction of unsaturated compounds with ozone and the subsequent treatment of the ozonides formed (equations 95 and 96). Reduction by strong reducing agents such as complex hydrides gives alcohols [94. Cycloalkenes yield diols [82]. 

Nucleophilic substitution reactions of unsaturated compounds containing the G=G double bond are well known and are distinguished by the relative location of the double bond and leaving group. Rappoport has recently reviewed the wide and complex nature of nucleophilic vinylic substitutions. The susceptibility of simple vinyl compounds to nucleophilic attack is low and comparable to unactivated halobenzenes. As is the case with aromatic compounds, however, vinylic substrates may be activated by electron-withdrawing substituents conjugated with the reaction centre. 

R. C. Fuson, Reactions of Organic Compounds, Wiley, 1962. Ch. 17, Addition Reactions of Unsaturated Compounds. ... 

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