Synthesis and properties of highly branched Jatropha curcas L. oil derivatives

The synthesis and properties of a number of novel branched Jatropha curcas L. oil (JO) derivatives containing vicinal di-ester units in the fatty acid chains are reported. Both the length (acetyl vs. hexanoyl) and the stereochemistry of the vicinal di-ester units (cis vs. trans) were varied. The compounds were prepared by two different synthetic approaches using catalytic chemistry. The first approach involves epoxidation of JO using a Sharpless epoxidation with methyltrioxorhenium as the catalyst to give epoxidized JO (1), followed by an esterification reaction with the corresponding anhydrides using ammonium-12-molybdophosphate (AMP) as catalyst to give trans-di-esters of JO (4a, 4b). The second approach is based on the dihydroxylation of JO using either the Prilezhaev method, resulting in trans-diols of JO (2), or the Upjohn method using osmium tetroxide as catalyst to give cis-diols of JO (3). In subsequent steps, the diols were esterified with acetic- or hexanoic anhydride using dimethylaminopyridine as catalyst to produce the corresponding cis- and trans-di-esters of JO (5a, 5b, 6). The best cold flow properties (lowest pour- and cloud point, crystallization and melting temperature) were obtained for JO with hexanoyl branches in a trans orientation (5b, pour point of -14°C, melting point of -5°C, and crystallization temperature of -25°C) and these values are considerably better than for the JO source.