Rhodium-catalysed cyclisation by addition of unsaturated 1,4-dicarbonyl compounds to oleic acid methyl ester

The Rh-catalysis allows the one-step synthesis of Diels-Alder-like cycloadducts from mono-unsaturated fatty acid and 1,4-dicarbonyl components. In this article we report on the addition of maleic acid-, fumaric acid- and acetylene dicarboxylic acid dimethyl ester to oleic acid methyl ester. In previous studies, Rh(OAc)2 showed the highest selectivity of the investigated catalysts towards the 3,6-disubstituted-1,2,3,6-tetrahydro-phthalic acid derivatives (THPA) for the addition of maleic anhydride to oleic acid. Thus, it was also used in this study. The relative configurations of the final products were identified by comparison with the Diels-Alder products, resulting from conjugated linoleic acid methylester (CLAMe) and the mentioned 1,4-dicarbonyl compounds.