Octadienol

The formation of 2.6-octadienol (27) by the reaction of 1,3-butadiene with water has attracted attention as a novel method for the commercial production of n-octanol, which has a considerable market. However, the reaction of water under the usual conditions is very sluggish. The addition of CO2 facilitates the telomerizdtion of water and 2,6-octadienol (27) is obtained as a major pro-duct[31]. In the absence of CO2, only 1,3,7-octatriene (7) is formed. Probably octadienyl carbonate is formed, which is easily hydrolyzed to give 27. A com-... 

Unsaturated aliphatic aldehydes were selectively reduced to unsaturated alcohols by specially controlled catalytic hydrogenation. Citral treated with hydrogen over platinum dioxide in the presence of ferrous chloride or sulfate and zinc acetate at room temperature and 3.5 atm was reduced only at the carbonyl group and gave geraniol (3,7-dimethyl-2,6-octadienol) [59], and crotonaldehyde on hydrogenation over 5% osmium on charcoal gave crotyl alcohol [763]. 

Chloroaluminate-free ionic liquids have been used for dimerization of dienes, as these ionic liquids are more stable and easier to handle than the moisture-sensitive ionic liquid chloroaluminate(III). In one example, a mixture of [BMIM]BF4/water (1 1 v/v) was used as the medium in the hydrodimerization of 1,3-butadiene catalyzed by [BMIM]2 PdCl4] (237). In addition to the dimer, 1,3,6-octatriene and 2,7-octadienol were produced. However, by using PdCl2/PPh3 as a catalyst in [BMIMJPC] (X = BF4, PFe, CF3SO3), the dimer, 1,3,6-octatriene, was obtained exclusively (238). 

Monflier showed that solvent-free telomerization of butadiene with water to form octadienols could be carried out effectively in the presence of a nonionic surfactant the conventional process is performed in the solvent sulfolane (Monfher et al., 1995). 

Some homogeneously catalyzed telomerizations, i.e., dimerizations of dienes coupled with the addition of a nucleophile [Eq. (11)], have been carried out in two-phase systems. One example has found industrial application, the synthesis of 1,7-octadienol from butadiene and water (Section VI). 

On the industrial level, aqueous two-phase systems are used more often than nonaqueous two-phase systems. The Kuraray Co. operates a pilot plant for the hydrodimerization of 1,3-butadiene in a two-phase system with a Pd/tppms catalyst (140). The reaction is carried out in sulfolane-water, from which the products, the octadienols, separate. The final products can be octanol or nonanediol made by subsequent isomerization and hydroformylation. The capacity of the Kuraray process is about 5000 tons/year. 

According to a patent [Y. Tokitoh, T. Higashi, K. Hino, M. Murosawa and N. Yoshimura, US Patent 5 057 631 (1991), to Kuraray Industries] the reaction is conducted with butadiene in sulfolane / water in the presence of Pd(OAc)2 as catalyst precursor and a soluble triarylphosphine (or its phosphonium bicarbonate, which is formed from octadienol itself and carbon dioxide) as ligand. The selectivity to 2,7-octadien-l-ol is 92-94% (TOF > 1000), while the isomeric l,7-octadien-3-ol accounts for another 3 5%. The product is extracted with hexane, while the aqueous sulfolane solution, containing the catalyst ca. 1 mmol/1) and triethylamine, is recycled. In the absence of carbon dioxide, the main product is 1,3,7-octatriene, an open-chain butadiene dimer. 

Figure 12 Schematic representation of the formation of 2,7-octadienol acid carbonate.

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]. 

Telomerization with formic acid as a telogen can produce 1,7-octadiene, which is useful as a modifier for polyolefins. This reaction proceeds with the same system that is used for the production of octadienol [14], at a temperature of 50-70°C, to yield l,7-octadiene/l,6-octadiene in a ratio of 88 12. Since these compounds phase-separate together, the product layer can be readily separated and the sulfolane layer containing the catalyst can be circulated for re-use. 

The telomerization of 1,3-butadiene to octadienol (cf. Section 2.3.5) catalyzed by palladium phosphine complexes was realized in an aqueous micellar medium [26]. The micellar effects depend strongly on the type of surfactant and on the water solubility of the palladium complexes. 

Some other C—C bond coupling reactions in micellar systems should be mentioned here. Monflier et al. [72] described, in both papers and patents, the telome-rization of 1,3-butadiene into octadienol in a micellar system by means of a palladium-phosphine catalyst. Water-soluble and amphiphilic phosphines have been used and the surfactants were widely varied. The authors have shown that the promoting effect of surfactants appeared above the CMCs of the surfactants, and they conclude that micellar aggregates were present in the reaction mixture. Cationic, anionic, and nonionic surfactants gave this micellar effect but the combination of the highly water-soluble TPPTS and the surfactant dodecyldimethylamine hydrocarbonate was found to be best. A speculation about the location of reactants shows that the reaction probably occurs in the interface between the micellar pseudophase and water. 

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