Alcohols telomerization with butadiene

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. 

These telomerization reactions of butadiene with nucleophiles are also catalyzed by nickel complexes. For example, amines (18-23), active methylene compounds (23, 24), alcohols (25, 26), and phenol (27) react with butadiene. However, the selectivity and catalytic activity of nickel catalysts are lower than those of palladium catalysts. In addition, a mixture of monomeric and dimeric telomers is usually formed with nickel catalysts ... 

The most characteristic reaction of butadiene catalyzed by palladium catalysts is the dimerization with incorporation of various nucleophiles [Eq. (11)]. The main product of this telomerization reaction is the 8-substituted 1,6-octadiene, 17. Also, 3-substituted 1,7-octadiene, 18, is formed as a minor product. So far, the following nucleophiles are known to react with butadiene to form corresponding telomers water, carboxylic acids, primary and secondary alcohols, phenols, ammonia, primary and secondary amines, enamines, active methylene compounds activated by two electron-attracting groups, and nitroalkanes. Some of these nucleophiles are known to react oxidatively with simple olefins in the presence of Pd2+ salts. Carbon monoxide and hydrosilanes also take part in the telomerization. The telomerization reactions are surveyed based on the classification by the nucleophiles. 

Formation of 2,7-octadienyl alcohol (32) by the reaction of water has attracted much attention as a novel practical synthetic method for n-octanol, which is of considerable industrial importance. However, the reaction of water under usual conditions of the butadiene telomerization is very sluggish. Atkins, Walker, and Manyik found that the presence of a considerable amount of carbon dioxide showed a very favorable effect on the telomerization of water (40). Reaction of water (2.0 moles) with butadiene (1.0 moles) using Pd(acac)2 and PPh3 as the catalyst was carried out in the presence of carbon dioxide (0.5 mole) at 80-90°C. tert-Butyl alcohol, acetone, and acetonitrile were used as solvents. The products that were obtained are shown in Eq. (21) and Table I. 

Telomerization of various primary and secondary alcohols has been carried out (45). The results obtained by using Pd(acac)2 and PPh3 at 60°C for 6 hours are shown in Table III. It can be said that primary alcohols react most easily with butadiene, but the higher the alcohol, the lower the reactivity to give the telomers. The reactivity of the secondary al-... 

Catalysis experiments were performed to investigate the telomerization of butadiene with ethylene glycol in selected TMS systems (e.g. si toluene DMF 1 5 4 or sl 2-octanol DMSO 1.35 3 5.2). With Pd/TPPTS as the catalyst a maximum yield of only 10% of the desired products could be achieved. With Pd/TPPMS the yield increased up to 43% in the TMS system si toluene isopropyl alcohol, but additional water had to be added to obtain a phase split after the reaction. The catalyst leaching is very high and 29% of the palladium used is lost to the product phase. 

Abstract The telomerization of butadiene with alcohols is an elegant way to synthesize ethers with minimal environmental impact since this reaction is 100% atom efficient. Besides telomerization of butadiene with methanol and water that is industrially developed, the modification of polyols is still under development. Recently, a series of new substrates has been involved in this reaction, including diols, pure or crude glycerol, protected or unprotected monosaccharides, as well as polysaccharides. This opens up the formation of new products having specific physicochemical properties. We will describe recent advances in this field, focusing on the reaction of renewable products and more specifically on saccharides. The efficient catalytic systems as well as the optimized reaction conditions will be described and some physicochemical properties of the products will be reported. 

It was shown from data summarized previously that telomerization of butadiene can occur with a large range of alcohols including reduced saccharides as well as mono- and disaccharides. It is of interest to extend such a reaction to much more complicated substrates such as polysaccharides (21) (Fig. 14). In that case, a low degree of substitution (average number of ether chains per glucose unit) is sufficient to modify deeply the physical properties of the organic polymer [51]. 

Alkyl ethers of sucrose have been prepared by reaction with long-chain alkyl halides to provide mixtures of regioisomers and products of different degree of substitution.82,83 A similar reaction with chloromethyl ethers of fatty alcohols provides formaldehyde acetals.84,85 Alkenyl ethers of various carbohydrates, and notably of sucrose, can also be obtained by palladium-catalyzed telomerization of butadiene (Scheme 6).86 88 Despite a low-selectivity control, this simple and clean alternative to other reactions can be carried out in aqueous medium when sulfonated phosphines are used as water-soluble ligands. 

Scheme 13 The four generic formulas for linear polyols relevant to telomerization with 1,3-butadiene 1,2-diols (i), linear diols (ii), sugar alcohols (iii) and (poly)saccharides (iv)...

Ethylene glycol (EG) may be obtained from cellulose by many ways, for instance, by the catalytic conversion over carbide catalysts [71], It is the simplest linear polyol available and often serves as a model for more complex substrates. Many reports are therefore available on the telomerization of EG. The possible telomer products are shown in Scheme 14, the linear mono-telomer typically being the desired compound. The mono-telomer can be used, after saturation of the double bonds, as a plasticizer alcohol in polyvinylchloride production, whereas application in cosmetics and surfactants has also been indicated [72]. Early examples include the work of Dzhemilev et al., who first reported on the telomerization of butadiene with EG in 1980, yielding a mixture of the mono- and di-telomers and butadiene dimers using a palladium catalyst activated by AlEt3 [73]. Kaneda also reported the use of EG in... 

One method to overcome selectivity issues during telomerization is to chemically protect all but one alcohol functionality. The first example of telomerization with a protected sugar was performed by Zakharkin et al., who successfully telo-merized 1,3-butadiene with the primary alcohol of 1,2,3,4-di-O-isopropylidene-ot-D-galactopyranose [93]. 

Camargo M, Dani P, Dupont J, de Souza RF, Pfeffer M, Tkatchenko I (1996) Cationic cyclopalladated complexes new catalyst precursors for the telomerization of butadiene with alcohols. J Mol Catal A Chem 109 127-131... 

Dzhemilev UM, Kunakova RV, Baibulatova NZ, Tolstikov GA, Panasenko AA (1980) Telomerization of polyatomic alcohols with butadiene, catalyzed by low-valent palladium complexes. Zh Org Khim 16 1157-1161... 

The preparation of different (NHC) - Pd°(dvds) complexes allowed the authors to make a systematic comparison of structure/activity for the telomerization reaction [228]. This study showed that electron-withdrawing substituents on the carbene backbone destabilizes the catalyst and therefore enhance its reactivity. These catalysts are applicable to primary and secondary alcohol as well as phenols and represent the first industrially viable catalyst system for palladium-catalyzed telomerization of butadiene with alcohol. 

Finally, an original method to obtain telechelic polydienes is also possible — it can be associated to the telomerization of allylic alcohol with butadiene. 

Tsuji has completed three syntheses of zearalenone (119), all by quite similar routes. The first, shown in Scheme 1.28, began with acetate 59b, the minor product from the telomerization of butadiene in acetic acid. Cleavage to the alcohol and gas-phase dehydrogenation led to enone 141. Chain extension to 142 was accomplished in 70% yield by way of Michael addition of diethyl malonate to enone 141. Decarboalkoxylation and protection of the ketone then gave 143 (63%). Conversion of the ester to the primary tosylate 144 was achieved by conventional methods in 62% yield. A Wacker oxidation of the terminal olefin followed by reduction and exchange of the tosylate for an iodide then provided the aliphatic segment 145 in 64% yield. 

Although the telomerization of dienes in a two-phase system has been intensively investigated with compounds containing active hydrogen such as alcohols, amines, phenols, acids, etc., the selective and productive telomerization of butadiene continues to be a challenge. It is only recently that primary octadi-enylamines have been obtained with selectivity up to 88% in the telomerization of butadiene with ammonia using a two-phase toluene/water system and Pd(OAc)2/tppts as the catalyst [Eq. (23)] [125]. 

Palladium(I) intermediates have been proposed for the telomerization of butadiene with acetic acid yielding acetoxyoctadienes, and in a recent review the involvement of Pd(I) has been snggested for processes in which Pd(II) had been formerly suggested. These processes include alkene isomerization, methoxycarbonylation of alkynes to acrylic esters, and the aryloxycarbonylation of allyl alcohol. 

The mechanism of the telomerization reaction of alcohols with butadiene was first proposed by Jolly and has been then extensively studied. Most of the catalytic intermediates have been identified (Scheme 7). ... 

In what follows, the telomerization of butadiene with acetic acid, alcohols, phenol, C—H-acidic compounds and nitroalkanes will be considered. Also some examples of carboxytelomerization and the telomerization of substituted dienes will be given. In all reactions trifunctional compounds are formed which contain two double bonds and one functional group. 

Primary and short-chained alcohols react very easily with butadiene to form ethers. Hagihara showed that the telomerization of methanol proceeds smoothly even at low temperatures (40—100°C) and with a short reaction time (1—3 h). The primary telomer is always the main product which is accompanied by the secondary telomer and small amounts of the by-product 1,3,7-octatriene. 

The telomerization of various higher alcohols has also been carried out. The primary alcohols react most easily with butadiene, whereas secondary and tertiary alcohols yield only small amounts of telomers. Steric hindrance alone cannot be the only factor responsible for the reactivity because the voluminous 2,2-bis(trifluoromethyl)benzylalcohol reacts smoothly to produce the 2,7-octadienyl ether. 

TelomerizatiorL Conj ugated dienes combine with nucleophiles such as water, amines, alcohols, enamines and stabilized carban-ions in the presence of palladium acetate and triphenylphosphine to produce dimers with incorporation of one equivalent of the nucleophile. Telomerization of butadiene (eq 7) yields linear 1,6- and 1,7-dienes and has been used for the synthesis of a variety of naturally occurring materials. ... 

Generally, octatriene formation is favored by higher temperatures, higher phosphine and/or butadiene concentrations and, importantly, by an increase in steric bulk of either the ligand or the nucleophile. Indeed, Harkal et al. showed a selectivity switch from telomerization products to 1,3,7-octatriene formation by altering the steric demand of the /V-heterocyclic carbene ligand in the reaction of butadiene with isopropanol under further identical reaction conditions [48]. For the more basic nucleophiles, such as the alcohols, the telomer products are stable under experimental conditions, i.e. product formation is irreversible, but for more acidic substrates such as phenol, product formation is reversible and more 1,3,7-octatriene will be formed after the substrate has been depleted. 

Jackstell R, Frisch A, Beller M, Rottger D, Malaun M, Bildstein B (2002) Efficient telomerization of 1,3-butadiene with alcohols in the presence of in situ generated palladium (O)carbene complexes. J Mol Catal A Chem 185 105-112... 

Jackstell R, Harkal S, Jiao HJ, Spannenberg A, Borgmann C, Rottger D, Nierlich F, Elliot M, Niven S, Cavell KJ, Navarro O, Viciu MS, Nolan SP, Beller M (2004) An industrially viable catalyst system for palladium-catalyzed telomerizations of 1,3-butadiene with alcohols. Chem Eur J 10 3891-3900... 

Parvulescu AN, Flausoul PJC, Bruijnincx PCA, Korhonen ST, Teodorescu C, Klein Gebbink RJM, Weckhuysen BM (2011) Telomerization of 1,3-butadiene with biomass-derived alcohols over a heterogeneous Pd/TPPTS catalyst based on layered double hydroxides. ACS Catal 1 526-536... 

Flausoul PJC, Parvulescu AN, Lutz M, Spek AL, Bruijnincx PCA, Klein GRJM, Weckhuysen BM (2011) Mechanistic study of the Pd/TOMPP-catalyzed telomerization of 1,3-butadiene with biomass-based alcohols on the reversibility of phosphine alkylation. ChemCatChem 3 845-852... 

Palkovits R, Parvulescu AN, Hausoul PJC, Kruithof CA, Klein Gebbink RJM, Weckhuysen BM (2009) Telomerization of 1,3-butadiene with various alcohols by Pd/TOMPP catalysts new opportunities for catalytic biomass valorization. Green Chem 11 1155-1160... 

Telomerization reactions, the formation of short oligomers from dienes, represent a very efficient organic transformation with an overall atom economy of 100%, and they have been the subject of intensive research in both academic and industrial laboratories. Complexes of palladium are known to catalyze the reaction of dienes with a variety of nucleophiles. Mechanistically, the reactions are thought to proceed by allyl coordination of two butadiene molecules to a palladium(O) center followed by the formation of a C-C bond. The eight-carbon chain is then attacked by a nucleophile at the terminal or at the 3 position. The reaction usnally leads to a mixture of cis/trans isomers and n- and iio-prodncts. When the nncleophile is methanol, l-methoxyocta-2,7-diene 1 (n-product) is generally the major prodnct, which is a nseful precnrsor for plasticizer alcohols (octanols), solvents, corrosion inhibitors, and monomers for polymerization. ... 

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