Isomerizing-Hydroboration of the Monounsaturated Fatty Acid Ester Methyl Oleate

Abstract

Biodiesel fuel, a mixture of fatty acid methyl esters (FAMEs) derived from plant oils, is increasingly available as a chemical feedstock. Methyl oleate (18:1), the 18-carbon monounsaturated FAME, is shown to undergo [Ir(COE)2Cl]2/dppe-catalyzed hydroboration with pinacolborane to give the product (7) in which the boronate ester group is in the terminal (C18) position. The formation of this product shows that the catalyst promotes both (1) the isomerization of the double bond from the 9,10-position of 18:1 to the terminal position and (2) the selective hydroboration of this isomer to give the product (7) in 45% yield. This tandem reaction should be capable of converting all isomers of 18:1 into the same product 7.