Telomers

Pd-cataly2ed reactions of butadiene are different from those catalyzed by other transition metal complexes. Unlike Ni(0) catalysts, neither the well known cyclodimerization nor cyclotrimerization to form COD or CDT[1,2] takes place with Pd(0) catalysts. Pd(0) complexes catalyze two important reactions of conjugated dienes[3,4]. The first type is linear dimerization. The most characteristic and useful reaction of butadiene catalyzed by Pd(0) is dimerization with incorporation of nucleophiles. The bis-rr-allylpalladium complex 3 is believed to be an intermediate of 1,3,7-octatriene (7j and telomers 5 and 6[5,6]. The complex 3 is the resonance form of 2,5-divinylpalladacyclopentane (1) and pallada-3,7-cyclononadiene (2) formed by the oxidative cyclization of butadiene. The second reaction characteristic of Pd is the co-cyclization of butadiene with C = 0 bonds of aldehydes[7-9] and CO jlO] and C = N bonds of Schiff bases[ll] and isocyanate[12] to form the six-membered heterocyclic compounds 9 with two vinyl groups. The cyclization is explained by the insertion of these unsaturated bonds into the complex 1 to generate 8 and its reductive elimination to give 9. 

An active catalytic species in the dimerization reaction is Pd(0) complex, which forms the bis-7r-allylpalladium complex 3, The formation of 1,3,7-octa-triene (7) is understood by the elimination of/5-hydrogen from the intermediate complex 1 to give 4 and its reductive elimination. In telomer formation, a nucleophile reacts with butadiene to form the dimeric telomers in which the nucleophile is introduced mainly at the terminal position to form the 1-substituted 2,7-octadiene 5. As a minor product, the isomeric 3-substituted 1,7-octadiene 6 is formed[13,14]. The dimerization carried out in MeOD produces l-methoxy-6-deuterio-2,7-octadiene (10) as a main product 15]. This result suggests that the telomers are formed by the 1,6- and 3,6-additions of MeO and D to the intermediate complexes I and 2. 

Asymmetric dimerization with cyclopentanone-2-carboxylate using BPPM as a chiral ligand gave the telomer in 41% eefSS]. 

The reaction of hydrosilanes with butadiene is different from other reactions. Different products are obtained depending on the structurelof the hydrosilanes and the reaction conditions. Trimethylsiiane and other trialkylsilanes react to give the I 2 adduct, namely the l-trialkylsilyl-2,6-octadiene 74, in high yields[67-69]. Unlike other telomers which have the 2,7-octadienyl chain, the 2,6-octadienyl chain is formed by hydrosilylation. On the other hand, the 1 I adduct 75 (l-trichlorosilyl-2-butene)is formed selectively with trichlorosilane, which is more reactive than trialkylsilanes[69]. The Reaction gives the Z form stereoselectively[70]. A mixture of the I 1 and I 2 adducts (83.5 and 5.2%) is... 

Various butadiene telomers obtained by Pd-calalyzed reactions have one functional group at one end and a terminal and an internal double bond, and they... 

The telomer 40 is converted into lipoic acid (136) by modification of three functional groups, as shown[l 16]. 

The telomer 137, obtained by the reaction of butadiene with malonate, is a suitable compound for the syntheses of naturally occurring dodecanoic acid derivatives, such as queen substance (I38)[l 7], one of the royal jelly acids (139)[I18], and pellitorine fl40)[ll9]. 

The telomer obtained from the nitromethane 65 is a good building block for civetonedicarboxylic acid. The nitro group was converted into a ketone, and the terminal alkenes into carboxylic acids. The acyloin condensation of protected dimethyl dvetonedicarboxylate (141) afforded the 17-membered acyloin 142, which was modified to introduce a triple bond 143. Finally, the triple bond was reduced to give civetone (144)[120). 

The telomer 145 of nitroethane was used for the synthesis of recifeiolide (148)[121], The nitro group was converted into a hydroxy group via the ketone and the terminal double bond was converted into iodide to give 146. The ester 147 of phenythioacetic acid was prepared and its intramolecular alkylation afforded the 12-membered lactone, which was converted into recifeiolide (148),... 

The reactions with IF are more amenable to control giving good yields of identifiable products and lower losses from oxidative fragmentation. The reaction of IF and iodine with tetrafluoroethylene produces the telomer perfluoroethyl iodide [354-64-3] ia yields that exceed 98% based on... 

Iodine pentafluoride is an easily storable Hquid source of fluorine having Httie of the hazards associated with other fluorine sources. It is used as a selective fluorinating agent for organic compounds. For example, it adds iodine and fluorine to tetrafluoroethylene in a commercial process to produce a usefiil telomer (124). 

Often used as mixtures, the telomers are subsequently converted to commercial surfactants and stain-resistant fiber finishes through functionalizing steps using standard chemical reactions of the C—1 bond. 

This process yields a purely straight-chain acid of even carbon number. Typically, the value of n varies from two to six, and distillation yields the pure components. Du Pont pioneered the development of this technology. Allied has used hexafluoroacetone to produce telomer iodides containing the... 

Other preparations of trifluoromethanesulfonic acid kiclude oxidation of methyltrifluoromethyl sulfide under a variety of conditions (10,11). Perfluorosulfonyl fluorides have also been prepared by reaction of fluoroolefkis with sulfuryl fluoride (12,13). Chinese chemists have pubflshed numerous papers on the conversion of telomer-based alkyl iodides to sulfonyl fluorides (14,15) (eqs. 8 and 9) ... 

Telomers. Bromotrifluoroethylene telomers have been prepared using chain-transfer agents such as CF SSCF (31), C2p I (32), CBr (32), or CBr F (33). For example, when the olefin is slowly added to tribromofluoromethane under light from sunlamps, a Hquid is obtained which, after saturation... 

Aqueous Formaldehyde. Water solutions of formaldehyde consist mainly of telomers of methylene glycol having <100 ppm of the formaldehyde as CH2O (5). Alcohols form hemiformals with aqueous formaldehyde according to the following, where n = 1,2,3, etc. 

When vinyl and aHyl monomers undergo chain transfer with solvents, so-caHed telomers may form, generaHy of rather low molecular weight (1). 

Telomerization. Polymerization of DAP is accelerated by telogens such as CBr, which are more effective chain-transfer agents than the monomer itself (65) gelation is delayed. The telomers are more readily cured in uv than DAP prepolymers. In telomerizations with CCl with peroxide initiator, at a DAP/CCl ratio of 20, the polymer recovered at low conversion has a DP of 12 (66). 

When lithium is used as a catalyst in conjunction with a chelating compound such as tetramethylethylenediarnine (TMEDA), telomers are generally obtained from toluene and ethylene (23), where n = 010. 

Carbon tetrachloride forms telomers with ethylene and certain other olefins (14—16). The mixture of Hquid products derived from ethylene telomerization may be represented CCl2(CH2CH2) Cl ia which nis 2l small number. Reaction of ethylene and carbon tetrachloride takes place under pressure and is induced by the presence of a peroxygen compound, eg, ben2oyl peroxide (17—19) or metal carbonyls (14,15). 

Roughly 65% of the substituents are trifluoroethoxy, and 35% are telomer alcohols prepared from tetrafluoroethylene and methanol. About 0.5 mol % of an aHyhc substituent is used as a cross-link site. The substituent pattern is beUeved to be stricdy statistical. 

Front the diazoniutn salt. Telomers are formed the reactions are carried out with twice the amount of titanium(III) salt. 

Since large tonnage production is desirable in order to minimise the cost of a polyamide and since the consumption of nylons as plastics materials remains rather small, it is important that any new materials introduced should also have a large outlet as a fibre. There are a number of polyamides in addition to those already mentioned that could well be very useful plastics materials but which would be uneconomical for all but a few applications if they were dependent on a limited outlet in the sphere of plastics. Both nylon 7 and nylon 9 are such examples but their availability as plastics is likely to occur only if they become established fibre-forming polymers. This in turn will depend on the economics of the telomerisation process and the ability to find outlets for the telomers produced other than those required for making the polyamides. 

Higher telomers are oblained at higher telrafluoroethylene loadings... 

Access to a variety of unsaturated perfluorinated telomers is provided by the homoielomenzation of perfluorinated alkenes, generally initiated and catalyzed by fluoride ton [22]... 

The first purposeful use of ATRA in polymer synthesis was in the production of telomers.26j In this early work, comparatively poor control over the polymerization was achieved and little attempt was made to explore the wider utility of the process. Some analogies may also be drawn with the work of Bamford et al, and others on transition metal/organic halide redox initiation (Sections 3.3,5.1 and 7.6.2).2M... 

Doubts against a radical mechanism were based mainly on the observation that no polymers of the alkene used for the arylation were found for a long time. It was not until the 1970s that Kopylova et al. (1971, 1972) and Ganushchak et al. (1972) obtained telomers with the general formula Ar(CH2CHZ)nCl in low yields under conditions of high vinyl monomer concentration. 

Telomers, in Meerwein reactions 248 Tetrahydropyridazines 129 Tetraphenylborates, in phase transfer catalysis of azo coupling reactions 378 f. 

Nevertheless, such a combination of polar factors actually makes this step less efficient than that is usually in the reactions with CBr4, and as a result the radical-adduct CB3CH2CHCF3 takes part in concurrent reaction of growth chain with another monomer molecule to form telomer T2 this is basically non-typical for reactions of CBr4. 

The structure of telomers Tj - T3 is confirmed by NMR spectra recorded for individual compounds. 

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