Lewis-acid catalysed ene reaction of electrondeficient aldehydes and ketones at unsaturated fatty acid derivatives

Abstract

The SnCl4 catalysed reaction of oleic acid ethyl ester (1) with glyoxylic acid ethyl ester (2) or mesoxalic acid diethyl ester (5) proceeds with good results yielding the corresponding 1:1-adducts. Besides the ene adducts also δ-lactones are formed by the reaction of (1) with (5). The product yield shows a strong dependency on type and quantity of the Lewis-acid used. A maximum yield was obtained with a stoichiometric amount of SnCl4. In contrast to the thermal ene reaction about 75% of the yield was attained already during the first 30 min of the reaction.