Telomerization of 1,3-butadiene

Telomerization combined with the additional incorporation of carbon monoxide is called carboxy-telomerization. The fundamental reaction which yields products containing a C9-chain is shown in Equation 21. 

For instance, with aliphatic alcohols the alkyl nona-3,8-dienoates are formed [25, 26], This nonadienoate can be used for the synthesis of another royal jelly acid, the 2-decenedioic acid (Equation 22). Carbonyla-tion of the nonadienoate in alcohol using Co2(CO)g/pyridine as the catalyst yields a linear diester which can be transformed into the royal jelly acid by hydrolysis and concomitant double bond migration [27]. 

Another s)mthesis of muscone (compare Section 1.1) also starts with the nonadienoate (Equation 23). Wacker/Hoechst-oxidation of the terminal double bond and hydrogenation of the internal one yields a ketocarboxylic acid, which reacts in a Kolbe electrolysis to 2,15-hexadecanedione, the precursor of muscone [28]. 

A stereospecific synthesis of cnrfo-brevicomin (24), a bark beetle pheromone, was published by Grigg [29]. By reduction, epoxidation and hydrolysis of the nonadienoate the l-nonene-6,7-diol is formed, which can be cyclised directly to en /o-brevicomin using palladium chloride/ copper(n)chloride as catalyst. 

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. 

In the absence of carbon dioxide, only 1,3,7-octatriene (16) was formed. The effect of carbon dioxide is not clear. One explanation is via the 

Phenol reacts with butadiene very smoothly to give octadienyl phenyl ether (23) in high yields. A branched ether (35) is a minor product. 

Primary alcohols react easily to form ethers. Reaction of methanol was carried out at 70°C using Pd(PPh3)2 (maleic anhydride) as a catalyst to give 8-methoxy-1,6-octadiene (36) (85%) accompanied by 3-methoxy-1,7-octadiene (37) (5%) and 1,3,7-octatriene (3%) (42). 

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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. 

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... 

In an analoguous case, two-phase telomerization of butadiene with ammonia to give octadienylamine has been reported where higher selectivity is realized in a two-phase system of water-toluene. Here, octadienylamine is more reactive than ammonia and consecutive reaction leads to sec and ten amines. By adopting a two-phase strategy, a primary amine selectivity as high as 91 % has been realized (Drieben-Hoscher and Keim, 1998). 

Bayer (1997) has claimed that in a water-CH2Cl2 system, using water soluble Pd(OAc)2 -triphenylphosphine trisulphonic acid catalyst, octa-2,7-dienyl-l-amine and octa 1,7-dienyl -3-amine can be obtained by telomerization of butadiene with ammonia. 

Linear oligomerization and telomerization of butadiene take place with nickel complexes in the presence of a proton source (7). In addition, cooligomerization of butadiene with functionalized olefins such as methacrylate is catalyzed by nickel complexes [Eq. (4)] (12, 13) ... 

Amines with higher basicity showed higher reactivity. For example, the yields of the 1 1 adducts of morpholine (pK = 9.61), aniline (9.42), n-butylamine (3.39), and piperidine (2.80) were 79, 67, 19, and 29%, respectively. Telomerization of butadiene with diethylamine catalyzed by... 

There appeared several reports treating the activating effect of carbon dioxide on the dimerization or telomerization of butadiene, as described before. But in none of these reactions did carbon dioxide behave as a reactant. Sasaki, Inoue, and Hashimoto found that carbon dioxide was incorporated to a small extent into the dimer of butadiene (103). 

APPLICATION OF THE TELOMERIZATION OF BUTADIENE TO NATURAL PRODUCT SYNTHESIS... 

The d-lactone (Scheme 38.11) can be efficiently obtained by the telomerization of butadiene and C02. Its biphasic hydrogenation with an in-situ-prepared Rh/ mtppts catalyst yields 2-ethylidene-6-heptenoic acid (and its isomers) [136]. Note, that the catalyst is selective for the hydrogenolysis of the lactone in the presence of two olefmic double bonds this is probably due to the relatively large [P] [Rh] ratio (10 1) which is known to inhibit C = C hydrogenations with [RhCl(wtppms)3]. The mixture of heptenoic acids can further be hydrogenated on Pd/C and Mo/Rh catalysts to 2-ethylheptanol which finds several applications in lubricants, solvents, and plasticizers. This is one of the rare examples of using C02 as a Cl building block in a transition metal-catalyzed synthetic process. 

The new recycling concept was apphed to several C - C bond-forming reactions, for example, to the telomerization of butadiene with ethylene glycol or carbon dioxide, to the isomerizing hydroformylation of frans-4-octene and to the hydroamino-methylation of 1-octene with morpholine. 

The telomerization of butadiene with ethylene glycol was chosen as an example for a reaction of a polar and a non-polar substrate to a semipolar product (Scheme 1). 

Scheme 1 Telomerization of butadiene with ethylene glycol...

One difficulty in the determination of an appropriate solvent system for the telomerization of butadiene with ethylene glycol is the change of polarity in the reaction mixture during the reaction. 

The catalyst system Pd(acac)2/TPPTS (TPPTS = trisulfonated triphenylphos-phine) was used in the experiments in which the telomerization of butadiene with ethylene glycol in TMS systems was investigated. However, the catalyst precipitates from many solvent mixtures as a yellow oil or solid, as soon as a homogenous phase is obtained. For this reason the solubihty of the catalyst was determined in various solvent systems. A solution of the catalyst in the mixture of ethylene glycol and water (si) and toluene (s2) was used in a weight ratio of 1 3. The various mediators s3 were added until a clear solution was formed or the catalyst precipitated. Only with DMF or DMSO can a clear solution be obtained. The addition of the catalyst to the polar phase causes an increase in the amount of s3 required to achieve a homogeneous system in the solvent system si toluene DMF the ratio increases from 1 5 4 to 1 5 4.4. 

Telomerization of Butadiene with Ethylene Glycol in TMS Systems... 

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. 

Table 1 Telomerization of butadiene with ethylene glycol in TMS systems. Reaction conditions 0.06 mol % Pd(acac)2 based on ethylene glycol, Pd/P =1 3 butadiene/ethylene glycol = 2.5 1, si = ethylene glycol water 2 1, 80 °C 4 h 1200 rpm...

The telomerization of butadiene with carbon dioxide to form a 5-lactone is an interesting example for a C - C bond-forming reaction with CO2 (Scheme 2). The product can be hydrogenated to 2-ethylheptanoic acid, which can be used in lubricants, as a stabilizer for PVC or as an intermediate for the production of solvents and softeners [7,15-19]. 

Scheme 2 Telomerization of butadiene with carbon dioxide...

The strong acidity of the proton at the C2 position of a [AMIM] ion has been well recognized 183). This cation can react with palladium complexes to form inactive l,3-dialkylimidazol-2-ylidene palladium complexes 200), as confirmed in a study of the conventional Pd(OAc)2/PPh3/base catalyst in ionic liquids for the telomerization of butadiene with methanol at 85°C 201). 

As compared to the esterification of sucrose, cataly tic etherification of sucrose provides another family of non-ionic surfactants that are much more robust than sucrose esters in the presence of water. Synthesis of sucroethers can be achieved according to two processes (1) the ring opening of epoxide in the presence of a basic catalyst and (2) the telomerization of butadiene with sucrose using a palladium-phosphine catalyst. 

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. 

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