Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 30, 2003
Publication Date: October 1, 2003
Citation: KENAR, J.A. PREPARATION OF LONG-CHAIN BETA-ENAMINONES AND BETA-DIKETONES FROM LONG CHAIN, 3,5-DISUBSTITUTED ISOXAZOLE COMPOUNDS.. JOURNAL OF THE AMERICAN OIL CHEMISTS' SOCIETY. v.80. pp.1027-1032. 2003. Interpretive Summary: Currently, about 18 billion pounds of soybean oil are produced annually in the United States. Soybean oil is used primarily for food and feed purposes. Only a small amount (approximately 300 million pounds) is used industrially. The current social climate regarding environmental issues and pollution related to the use and waste disposal of non-renewable resources (petroleum based products) in industrial applications has clearly underscored the importance of utilizing renewable resources for industrial applications. The development of new approaches to utilize soybean oil to derive novel oleochemicals with unique chemical and physical properties is integral to extend the variety of compounds and uses obtainable from soybean oil. Recently, we reported the successful preparation of fatty heterocyclic compounds (ring systems composed of nitrogen and oxygen atoms) derived from soybean oil fatty esters. Here we report their use as starting materials to prepare new types of multi-functionalized fatty compounds. These newly functionalized fatty compounds may have interesting pharmacological properties and this methodology can be used to prepare compounds similar to those found in various plant waxes. Finding new methods to effectively modify fatty acids and vegetable oils obtained from renewable resources and obtain bio-based products not only benefits farmers, but also the environment. It will help to decrease our dependence on the ever-tightening supply of non-renewable resources.
Technical Abstract: A series of long-chain fatty compounds containing the beta-enaminone functionality were prepared in yields ranging from 71-87% from their corresponding fatty 3,5-disubstituted isoxazole precursors utilizing a Raney nickel catalyzed reductive ring opening procedure. These newly prepared multi-functional fatty compounds were subsequently hydrolyzed under mild acidic conditions (pH 4-5) to give their corresponding fatty beta-diketones in yields ranging from 79-98%. Both the fatty beta-enaminone and beta-diketone functionalized compounds were characterized by nuclear magnetic resonance, infrared spectroscopy, gas chromatography-mass spectrometry, and melting point. The mass spectra for these two classes of compounds, derived utilizing electron impact ionization, gave distinctive McLafferty rearrangement fragmentation ions that clearly established the newly introduced functionality to be at the C-2 and C-4 positions of the lipid's alkyl chain. 1H NMR spectra of the pure beta-diketone compounds were complex owing to the keto enol tautomerism displayed by the beta-diketone moiety. In solution the fatty beta-diketone compounds were shown to exist mainly in the enolic tautomeric form. Long-chain beta-diketone compounds are known to be relatively common constituents of some plant waxes, and the overall procedure starting from soybean methyl esters provides a complementary approach to prepare these types of compounds.