Polyols telomerization

Palladium-Catalyzed Telomerization of Butadiene with Polyols From Mono to Polysaccharides... 

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. 

This reaction is environmental friendly since it produces no salt, provides a 100% atom efficiency, and can be performed in water to fulfill some green chemistry principles. In this review, we wish to focus on the telomerization of mono and polysaccharides. As an introduction, recent results achieved with several polyols will be summarized. 

Selective modification of polyols such as ethylene glycol, 1,3-propylene glycol, or glycerol with butadiene (1) has been studied [7-10]. The monosubstituted compounds are preferred due to their potential applications as surfactants, PVC plasticizers, or even in cosmetics. The telomerization of 1 with ethylene glycol yields a complex mixture including linear and branched mono- and ditelomers, as well as 1,3,7-octatriene and vinyl cyclohexene (Fig. 2) [11]. 

Recently, the Pd/TOMPP catalytic system was used in the telomerization of butadiene with a series of polyols and TON up to 10,000 was achieved with ethylene glycol or 1,3-propanediol [14],... 

To circumvent the formation of ditelomers and to attempt recycling of the catalysts, the telomerization of polyols was studied in the presence of water using water soluble catalysts such as Pd/TPPTS (TPPTS = tris(m-sulfonato-phenyl) phosphine trisodium salt) [9, 12, 16, 17]. Behr et al. studied the telomerization of ethylene glycol under biphasic conditions. Under such reaction conditions, 80% of mono-telomer are formed and only traces of ditelomer and butadiene dimers are detected (Fig. 4). This is attributed to the solubility of the monomer in the catalyst phase. However, the catalyst is unstable and decomposes rapidly, leading to almost inactive catalyst after three runs. This is due to TPPTS oxidation during the work-up of the reaction and can be avoided by addition of 2.5 equiv. ligand in the solution prior to each run. 

While the telomerization reaction of butadiene has been known for 40 years, its application to polyols issued from the biomass is recent and continues to be under investigation. Most polyols are much less active than MeOH or H2O that have found industrial developments. Higher catalytic loading are required, but recent studies disclosed very active catalytic systems which are promising. 

The telomerization of butadiene by means of water in ILs was described by Dullius et Rottger et al. report a process for the telomerization of acyclic olefins having at least two conjugated double bonds, or their mixtures, using a palladium-carbene complex as catalyst in an IL solvent. The nucleophiles included water, alcohols, phenols, polyols, carboxylic acids, ammonia and primary and secondary amines. The acycylic olefins could be either 1,3-butadiene or isoprene. 

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... 

Telomerization of Sugar-Derived Polyols Sugar Alcohols and Dianhydrohexitols... 

Hausoul et al. [60] also reported on telomerization with aldopentoses (D-xylose, L-arabinose), aldohexoses (D-glucose, D-mannose, D-galactose), ketohexoses (d-fructose, L-sorbose) and the disaccharides D-sucrose and cellobiose, using Pd/ TOMPP as catalyst without the addition of base in /V,/V-di methyl acetamide as the solvent (Fig. 15). The Pd/TOMPP combination had previously been shown to be highly active in the telomerization of various polyols (vide supra). Good conversion... 

The previous section illustrates that the polysaccharide components of lignocellu-losic biomass provide ample opportunities for the telomerization reaction to convert (hemi-)cellulose-derived renewable building blocks such as saccharides, sugar alcohols and polyols into valuable bulk chemicals. The third key component of... 

Bouquillon S, Muzart J, Pinel C, Rataboul F (2010) Palladium-catalyzed telomerization of butadiene with polyols from mono to polysaccharides. Top Curr Chem 295 93-119... 

The etherification of polyols/carbohydrates by means of the telomerization reaction has been widely used. This can be largely explained by the efficiency of the catalysts employed as well as by their water compatibility and tolerance to the presence of several other functionalities. This section is aimed at showing the diversity of carbohydrates that have been converted by means of the telomerization in a chronological order. ° ... 

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