Reaktion #580699

Reaktionsgleichung

oleic acid

→

octadec-9-ene

Ausbeute 42.0%

Lösungsmittel

dichloromethane

Reaktionsbedingungen

Vorschrift

In the 1990s, it was demonstrated that homogeneous ruthenium-based catalysts were effective in catalyzing olefin metathesis; moreover, these catalysts, in contrast to the tungsten and rhenium catalysts, often tolerate functionally substituted alkenes (Grubbs, R. H., Handbook of Metathesis, Wiley-Vch, Verlag GmbH & Co. KGaA, Weinheim (2003)). Such ruthenium-based catalysts have been used to prepare α,ω-dicarboxylate esters via metathetic routes. For example, a two-step process was reported using Grubbs catalysts to prepare long-chain unsaturated α,ω-dicarboxylate methyl esters (Warwel, S., et al., Polym. Sci. Part A: Polym. Chem., 39: 1601-1609 (2001)). Cross-metathesis of monounsaturated carboxylic acid methyl esters with ethylene in the presence of the first generation catalyst 1 (FIG. 1) in solution initially gave terminally unsaturated monocarboxylate methyl esters. The resulting terminal monounsaturated esters then underwent self-metathesis in the presence of catalyst 1 to give long-chain α,ω-dicarboxylic acid methyl esters with an overall yield between 38-40% (Warwel, S., et al., Polym. Sci. Part A: Polym. Chem., 39: 1601-1609 (2001); Warwel, S., et al., Ind. Crops & Prod., 20: 301-309 (2004); Warwel, S., et al., Macromol. Chem. Phys., 202: 1114-1121 (2001); Warwel, S., et al., Macromol. Chem. Phys., 202: 849-855 (2001); Warwel, S., et al., Chemosphere, 43: 39-48 (2001)). Self-metathesis of methyl oleate in dichloromethane was reported using the second generation Grubbs catalyst 2 (FIG. 1) and gave the long chain α,ω-dicarboxylic methyl ester 5a (FIG. 2, Eq. 1) in ˜45% conversion (Dinger, M. B., and J. C. Mol, et al., Adv. Synth. Catal., 344: 671-677 (2002)). The self-metathesis of oleic acid in the presence of Cl2(PCy3)2Ru=CH—CH═CPh2 in dichloromethane solution was reported to give 1,18-octadec-9-enedioic acid (5b) and octadec-9-ene (4) in 42% yield (U.S. Pat. No. 5,728,917). However, this process gave low conversion (about 50%) of monounsaturated fatty acids and low yields of dicarboxylic acids. In addition, the reaction was performed in a solvent, dichloromethane, which is an environmental concern.

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