Octadienol from Butadiene

Although 2,7-octadien-l-ol itself has a variety of uses, its main market involves hydrogenation to -octanol, whose phthalate diester is utilized as a plasticizer with superior properties to the currently used branched octanol (2-ethyl-hexanol). 

The synthesis from butadiene and water occurs according to Equation 23. 

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. 

The process reported here uses a clever combination of the factors that promote catalyst life and efficiency. The soluble phosphine or its phosphonium salt, used in a molar excess of about 50 over palladium, stabilizes the palladium complex in aqueous solution the sulfolane-water solution ensures the solubility of the reactants, while extraction with hexane under CO2 pressure recovers the product with only small contamination by palladium, phosphorus or nitrogen. The phosphine or its phosphonium salt and the ammonium bicarbonate remain in the aqueous solution. Since the TON is good and the solution can be recycled, consumption of palladium is very low. 

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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. 

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