Telomerization

Telomerization is a process that was developed by DuPont [12, 13], and describes a polmerization reaction between a telogen and a taxogen to produce a telomer  

Commercial telomerization usually involves the reaction of pentafluoroethyl iodide (telogen) with tetrafluoroethylene oligomers (taxogen) in the presence of a catalyst, to produce a perfluoroalkyl iodide polymer (telomer)  

The resulting perfluoroalkyl iodides do not react with nucleophiles, such as OH, to be directly converted into FTOHs or PFCAs [4], As such, perfluoroalkyl iodides are reacted with ethylene to form perfluoroalkylethyl iodides  

Perfluoroalkylethyl iodides can then be readily converted to the corresponding FTOHs and PFCAs by hydrolysis [4], 

FTOH-based products have been manufactured since the 1970s [14]. Global production of FTOHs from 2000 to 2002 was estimated at 5000 to 6500 metric tonnes per year [17]. Since that time, FTOH production has increased approximately twofold, to an estimated 12000 metric tonnes per year in 2004, representing sales of approximately 700 million annually [18]. Current production levels of FTOHs are unavailable, but are assumed to be comparable to or greater than 2004 estimates. 

Telomerization was initially developed by the Du Pont Company for free-radical polymerization of ethylene [56-61] and defined as a process of reacting a molecule, called telogen, with two or more ethylenically unsaturated molecules, called taxogens  

Haszeldine [62,63] allowed trifluoromethyl iodide to react with ethylene and obtained oligomers of the type CF3[CH2CH2] I (n = 1, 2, and 3). The reaction of trifluoromethyl iodide with tetrafluoroethylene, catalyzed by ultraviolet (UV) irradiation, yielded short-chain polymers of the general formula CF3[CF2CF2] I, where n = 1-10. Some of the members of the telomeric series were isolated. 

The photochemically catalyzed reaction of trifluoromethyl iodide with tetrafluoroethylene involves a radical chain [64]  

The polymerization mechanisms have been extended from the original free-radical reaction to anionic, cationic, and transition-metal-catalyzed telomerization. 

Pentafluoroethyl iodide (1-iodopentafluoroethane) reacts with tetrafluoroethylene under conditions similar to those for iodotrifluoromethane and yields perfluoroalkyl iodides, CF3CF2[CF2CF2] I, with an even number of carbon atoms. 

A significant inlluence of COj was observed in some telomerization reactions, that is, in dimerization with the additional incorporation of a nucleophilic mole cule. The interaction of butadiene and water in the presence of the Pd(acac) -iri phenyl phosphine system under argon leads to the formation of ociatricne as the main product. In the presence of carbon dioxide, however, the octadienols are the main reaction products, whereas the yield of octatriene is insignitlcant. It is worth noting that catalytically-smaU amounts of carbon dioxide are sufficient for tlus reaction [301,302]. 

Similar results are obtained in the telomerizaticm of isoprene with water, alcohols, ammonia and amines, which yield terpene alct ols, ethers and amines [303]. 

Dall Asta, of Moiitccaiini Edison, investigated the metathesis of cycloalkenes in the presence of a catalyst consisting of tungsten hexachloride, aluminium trichloride and carbon dioxide as the catalyst promoter. The products, the polyalkenamcrs, were vulcanized to give an elastic rubber useful for lires (304, 

Massie, of UOP, found an influence of C02 on hydroformylation. In the presence of carbon dioxide and a common Co complex catalyst, a decreased alkane formation and an increased alcohol formation were observed [306]. 

Ziegler-Natta-type catalysts, which are active in polymerization and oligomerization of alkenes. are also influenced by adding CO2 to the reaction mixture. The addition of CO2 changes the molecular we t and crystallinity of the products or the activity and selectivity of the catalyst, both in polyethylene [307,308] and in polypropylene production [309-312]. 

In particular, the concepts of biphasic catalysis were used in telomerization (Section 6.9), oligomerization (Section 6.12), hydrogenation (Section 6.2), and hydro-formylation (Section 6.1) reactions. Therefore these reactions will be considered in the following sections in some more detail and thus complement the appropriate Chapters as far as technical concepts are concerned. 

Recently, a nice example has been studied in which biphasic catalysis was not only used for catalyst recycling but also to increase the selectivity of the catalytic reaction. In the telomerization of butadiene with the bifunctional nucleophile ethylene glycol both monotelomers and ditelomers can be formed [113, 114]. When the reaction is carried out in a single liquid phase, for instance in tetrahydrofurane with a catalyst formed from palladiumbis-acetylacetonate and triphenylphosphine, the monotelomers are formed in a maximum yield of 60% with more than 20% of ditelomers as byproducts. When palladiumcarbene-complexes were used, the mono/ di-ratio switched to 1 3, thus increasing the formation of the ditelomer. However, if the monotelomers are the favored products, for instance for the production of detergents, no sufficient reaction control by choice of the ligand was possible so far. 

The technical realization of telomerizations is not very well investigated. In a recent paper the telomerization of isoprene with methanol was studied in detail and different concepts of realization were proposed both for single phase operation as well as for biphasic catalysis [115]. One possible alternative proved to be the bipha-sic telomerization with an aqueous methanolic solution as catalyst phase, followed by distillation of unreacted isoprene and methanol, then finally extracting the telomers from the aqueous layer with isoprene. The second alternative for the product separation is without any extraction step and uses only phase separation and distillation steps. 

Further work was done in the telomerization of butadiene with carbon dioxide yielding a a-lactone in good yields [116-118]. For the catalyst recycle the successive extraction of the product with 1,2,4-butanetriol was proposed and investigated in detail. Mortreux et al. studied the telomerization of butadiene with sucrose which could also be carried out efficiently in water-organic medium in the presence of Pd salt and TPPTS [119]. Mono- and dioctadienylether were selectively obtained using aqueous sodium hydroxide/isopropanol mixtures. 

A typical case in which a 1 1 adduct is formed quantitatively is that of allylic derivatives109) (allyl alcohol or allyl acetate)  

Chlorotrifluoroethylene macromonomers 112) have been obtained as follows the monomer is reacted in acetonitrile with carbon tetrachloride in the presence of the Fe+ + + /benzoin redox system whereby oligomers with polymerization degrees ranging from 1 to 20 are obtained  

Species of type (I) can be used as a telogen with allyl acetate or allyl alcohol whereby monoadducts are formed  

To fit these to-hydroxy telomers with terminal double bonds they were esterified with acrylic acid in the presence of p-toluenesulfonic acid. Subsequent azeotropic distillation of the formed water yields macromonomers exhibiting the following structure 

These macromonomers were successfully copolymerized with methyl methylacrylate and vinyl acetate  

Polymerization of D3 and D4 has also been used in preparation of various telechelics mostly with —OH, —OR, —OCOR, or —Cl end-groups. 

Sommer et al. ) have prepared linear PDMS with acetoxy end-groups by telomerization of D4 with diacetoxydisiloxanes in the presence of H2S04  

The preparation of oligomers with other end-groups have also been described. The content of cyclic products in these products usually has not been determined but it may be lower than in the equilibrated mixture containing high polymer, because of the contribution of the end-groups to the thermodynamic potential. 

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Ziegler process) and telomerization of alkenes to medium chain derivatives for detergents and fats. Both processes operate by insertion of an alkene into AIR bonds. 

CH2 CH C CH. Colourless gas with a sweet odour b.p. 5°C. Manufactured by the controlled low-temperature telomerization of ethyne in the presence of an aqueous solution of CuCI and NH Cl. Reduced by hydrogen to butadiene and, finally, butane. Reacts with water in the presence of HgSO to give methyl vinyl ketone. Forms salts. Forms 2-chloro-butadiene (chloroprene) with hydrochloric acid and certain metallic chlorides. 

Dimerization and Telomerization of Conjugated Dienes and Related Reactions... 

The dimerization of isoprene is possible, but the reaction of isoprene is slower than that of butadiene. Dimerization or telomerization of isoprene, if carried out regioselectively to give a tail-to-liead dimer 18 or a head-to-tail... 

Although acetonitrile is one of the more stable nitriles, it undergoes typical nitrile reactions and is used to produce many types of nitrogen-containing compounds, eg, amides (15), amines (16,17) higher molecular weight mono- and dinitriles (18,19) halogenated nitriles (20) ketones (21) isocyanates (22) heterocycles, eg, pyridines (23), and imidazolines (24). It can be trimerized to. f-trimethyltriazine (25) and has been telomerized with ethylene (26) and copolymerized with a-epoxides (27). 

The higher molecular weight petfluoroalkyl iodides ate prepared by telomerization of tetrafluoroethylene with lower molecular weight perfluoroalkyl iodides (46,48). 

Prepa.ra.tlon There are five methods for the preparation of long-chain perfluorinated carboxyUc acids and derivatives electrochemical fluorination, direct fluorination, telomerization of tetrafluoroethylene, oligomerization of hexafluoropropylene oxide, and photooxidation of tetrafluoroethylene and hexafluoropropylene. 

Fluorinated carboxyflc acids are also prepared by telomerization of tetrafluoroethylene, followed by oxidation (19—21). 

The lower molecular weight oils, waxes, and greases of PCTFE can be prepared direcdy by telomerization of the monomer or by pyrolysis of the higher molecular weight polymer (45—54). 

Other common radical-initiated polymer processes include curing of resins, eg, unsaturated polyester—styrene blends curing of mbber grafting of vinyl monomers onto polymer backbones and telomerizations. 

A telomerization reaction of isoprene can be carried out by treatment with 2-chloro-3-pentene, prepared by the addition of dry HCl to 1,3-pentadiene (67). An equimolar amount of isoprene in dichi oromethane reacts with the 2-chloro-3-pentene at 10°C with stannic chloride as catalyst. l-Chloro-3,5-dimethyl-2,6-octadiene is obtained in 80% yield by 1,4-addition. 

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). 

Isoprene (2-methyl-1,3-butadiene) can be telomerized in diethylamine with / -butyUithium as the catalyst to a mixture of A/,N-diethylneryl- and geranylamines. Oxidation of the amines with hydrogen peroxide gives the amine oxides, which, by the Meisenheimer rearrangement and subsequent pyrolysis, produce linalool in an overall yield of about 70% (127—129). 

Synthetic methods for the production of citroneUal iaclude the catalytic dehydrogenation of citroneUol (110), the telomerization of isoprene (151), and the Utbium-catalyzed reaction of myrcene with secondary alkylamines (128). 

Telomerization Reactions. Butadiene can react readily with a number of chain-transfer agents to undergo telomerization reactions. The more often studied reagents are carbon dioxide (167—178), water (179—181), ammonia (182), alcohols (183—185), amines (186), acetic acid (187), water and CO2 (188), ammonia and CO2 (189), epoxide and CO2 (190), mercaptans (191), and other systems (171). These reactions have been widely studied and used in making unsaturated lactones, alcohols, amines, ethers, esters, and many other compounds. 

Coupling of butadiene with CO2 under electrochemically reducing conditions produces decadienedioic acid, and pentenoic acid, as weU as hexenedioic acid (192). A review article on diene telomerization reactions catalyzed by transition metal catalysts has been pubUshed (193). 

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). 

Telomerization of 3,3-dimethyldiaziridine with butadiene catalyzed by Pd complexes yielded 2 1 adducts (123) and (124) (80IZV220). 

Homolytic cleavage of dlazonlum salts to produce aryl radicals is induced by titan1um(III) salt, which is also effective in reducing the a-carbonylalkyl radical adduct to olefins, telotnerization of methyl vinyl ketone, and dimerization of the adduct radicals. The reaction can be used with other electron-deficient olefins, but telomerization or dimerization are important side reactions. 

Chloro-2,2,3-trifluoropropionic acid has been prepared by permanganate oxidation of 3-chloro-2,2,3-trifluoropropanol which is one of the telomerization products of chlorotrifluoroethylene with methanol. The present procedure is a modification of one reported earlier and is undoubtedly the method of choice for making propionic acids containing 2 fluorine atoms, i.e., 2,2,3,3-tetrafluoropropionic acid, 3,3-dichloro-2,2-difluoropropionic acid, and 3-bromo-2,2,3-trifluoropropionic acid. When preparing 2,2,3,3-tetrafluoropropionic acid from tetrafluoroethylene, it is desirable to use an additional 50 ml. of acetonitrile and externally applied heat to initiate the reaction. 

Similarly, Itexafluoroprapylene undergoes fluoride ion induced homotelo-merization to give a series of dimers and trimers These telomerizations can be induced by other nucleophiles, such as amines Indeed, the selectivity of the pi oce-,s can be changed significantly by varying reagents and reaction conditions [25, 26] (equations 19 and 20)... 

ITowever, most normal somatic cells lack telomerase. Consequently, upon every cycle of cell division when the cell replicates its DNA, about 50-nucleotide portions are lost from the end of each telomere. Thus, over time, the telomeres of somatic cells in animals become shorter and shorter, eventually leading to chromosome instability and cell death. This phenomenon has led some scientists to espouse a telomere theory of aging that implicates telomere shortening as the principal factor in cell, tissue, and even organism aging. Interestingly, cancer cells appear immortal because they continue to reproduce indefinitely. A survey of 20 different tumor types by Geron Corporation of Menlo Park, California, revealed that all contained telomerase activity. 

The palladium-catalyzed hnear telomerization of 1,3-bntklienes provides a useful method for thepreparation of functionalized alkenes. A proposed catalytic cycle for the paliadinm-catalyzed... 

Temperature-dependent phase behavior was first applied to separate products from an ionic liquid/catalyst solution by de Souza and Dupont in the telomerization of butadiene and water [34]. This concept is especially attractive if one of the substrates shows limited solubility in the ionic liquid solvent. 

In addition to the applications reported in detail above, a number of other transition metal-catalyzed reactions in ionic liquids have been carried out with some success in recent years, illustrating the broad versatility of the methodology. Butadiene telomerization [34], olefin metathesis [110], carbonylation [111], allylic alkylation [112] and substitution [113], and Trost-Tsuji-coupling [114] are other examples of high value for synthetic chemists. 

When the products are partially or totally miscible in the ionic phase, separation is much more complicated (Table 5.3-2, cases c-e). One advantageous option can be to perform the reaction in one single phase, thus avoiding diffusional limitation, and to separate the products in a further step by extraction. Such technology has already been demonstrated for aqueous biphasic systems. This is the case for the palladium-catalyzed telomerization of butadiene with water, developed by Kuraray, which uses a sulfolane/water mixture as the solvent [17]. The products are soluble in water, which is also the nucleophile. The high-boiling by-products are extracted with a solvent (such as hexane) that is immiscible in the polar phase. This method... 

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