Chemical modifications of Sterculia foetida L. oil to branched ester derivatives

An experimental study to modify Sterculia foetida L. oil (STO) or the corresponding methyl esters (STO FAME) to branched ester derivatives is reported. The transformations involve conversion of the cyclopropene rings in the fatty acid chains of STO through various catalytic as well as stoichiometric reactions. Full conversion of the cyclopropene rings was obtained using DielsAlder chemistry involving cyclopentadiene in water at 40 degrees C without the need for a catalyst. Olefin metathesis reactions were performed using a Grubbs 2nd generation catalyst and cyclopropene ring conversion was =99 and 54 mol% with 2,3-dimethyl-2-butene and 1-octene, respectively. Oxidation reactions were performed using established epoxidation (Sharpless) and dihydroxylation (Prilezhaev) protocols using aqueous hydrogen peroxide as the oxidant. For both reactions, full conversion of the cyclopropene rings was obtained at RT to yield the corresponding a,beta-unsaturated ketone in good selectivities. Rearrangement reactions of the cyclopropene rings to the corresponding conjugated diene were successfully performed using homogeneous and heterogeneous palladium catalysts. Excellent conversions (=99%) were obtained using homogeneous palladium catalyst in a biphasic cyclohexanewater mixture (1:1) at 90 degrees C. Relevant cold flow properties of all products were determined and compared to crude STO and STO FAME. Best results were obtained for the metathesis products of STO with 1-octene, with a cloud point (CP) and pour point (PP) of -12 degrees C.