Polyketoesters from oleic acid. Synthesis and functionalization
Abstract
In this study, we exploited the reactivity of the methyl oleate enone derivative for the conversion of this renewable raw material to ketone-containing hydroxyesters. The radical-mediated thiol–ene addition to the conjugated double bonds has been investigated and low yields were obtained due to secondary reactions. The thiol-Michael addition under acidic and basic/nucleophilic conditions was also examined. While using vanadyl triflate (VO(OTf)2), a slight excess of thiol was necessary to complete the reaction, by using both basic/nucleophilic catalysts 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), quantitative conversion was achieved under stoichiometric conditions in shorter reaction times. The obtained hydroxyester, carrying sulphide and ketone functional groups, was used to obtain polyesters by Novozyme-435 enzymatic polymerization. The coupling between the ketone group of the repeating unit and a model oxyamine has been used to demonstrate the polyketoester functionalization via oxime formation.