Transition-metal trifluoromethane-sulphonates - recyclable catalysts for the synthesis of branched fatty derivatives by Diels-Alder reactions at unsaturated fatty esters

Diels-Alder reactions of conjugated linoleic acid ethyl ester (1) with diff erent quinones and with a variety of alpha/beta-unsaturated aldehydes and k etones are described in this paper. Using Sc(OTf)(3) or Cu(OTf)(2) as catal ysts the reactions can be carried out at 25-40 degrees C with good yields. For the first time in oleochemistry it is possible to prepare Diels-Alder c ycloadditions with catalyst concentrations of 10 mol-% instead of stoichiom etric amounts of Lewis acids. Furthermore, the reaction time was partly sho rtened drastically. The catalyst Sc(OTf)(3) can be removed by a simple extr action of the organic layer with water. After evaporation of the aqueous ph ase to dryness the catalyst can be reused without loss of yield.