Synthesis of 8-Stearolactone from Oleic Acid

8-Stearolactone was prepared from oleic acid using concentrated sulfuric acid under various conditions in the presence of polar, nonparticipating solvents. 8-Stearolactone was formed in as high as 15:1 ratios over the thermodynamic product, y-Iactone, in the presence of methylene chloride, 100% wt/vol, at room temperature with two equivalents of sulfuric acid for 24 h. This procedure is applicable to other olefinic fatty acids such as estolides and fatty acid methyl esters. Temperature plays a role in the regioselectivity of the cyclization for 8-lactone, as lower temperatures (20°C) gave higher 8/y ratios. At higher temperatures (50°C) in the presence of sulfuric acid and methylene chloride the yield of lactone was 75% but with a 8/y ratio of only 0.3:1. Cyclization of oleic acid to lactone also occurred with other acids. Oleic acid underwent reaction with perchloric acid, one equivalent, in the absence of solvent at 50°C, which yielded 8-lactone in a modest yield with a 3.1 8/y ratio. The same temperature effect was observed with perchloric acid that was observed in the case of sulfuric acid. Because 8-stearolactone is much more reactive than the corresponding fatty acid, fatty acid ester, or y-lactone, we believe that it will be a useful synthon for many new industrial products including new biodegradable detergents. Paper no. )9382 in JADeS 77, 243-248 (March 2000).