Submitted to: American Oil Chemists' Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 20, 1998
Publication Date: N/A
Technical Abstract: We recently reported the synthesis of delta-lactone from Delta 5 unsaturated fatty acids by a mineral acid catalyzed process in the presence of a polar solvent that stabilized the transition state leading to the formation of delta-lactone. We now report the synthesis of delta-lactones from Delta 5 unsaturated triglycerides in near quantitative yield based on the amount of Delta 5 unsaturation present. Surprisingly, polar solvents are not required for high delta-lactone yields or regioselectivities (ratio of delta- vs. gamma-lactone). In addition, we found that sulfuric acid serves as a good catalyst for this cyclization with triglycerides where reaction of sulfuric acid with Delta 5 unsaturated fatty acids gave decreased yields of delta-lactone. These delta-lactones were subsequently found to be good starting materials for the synthesis of Delta 5-oxygenated fatty acids, esters and amides. We have also demonstrated a cyclization of meadowfoam fatty acids to 6-chloro-delta-lactones in a 70% yield. The 6-chloro-delta-lactone possessed considerably different reactivity toward ring opening than the unhalogenated analogs. One principal reaction of 6-chloro-delta-lactones is its conversion to 5-keto or 6-keto fatty acids in the presence of alkali.