<i>Z</i>-Selective Synthesis of Trisubstituted Alkenes by the HWE Reaction Using Modified Still–Gennari Type Reagents

Application of new reagents in the <i>Z</i>-selective synthesis of trisubstituted alkenes via modified Horner-Wadsworth-Emmons carbonyl olefination is presented. The reagents tested are ethyl bis(1,1,1,3,3,3-hexafluoroisopropyl)phosphonoalkanoates, structurally similar to Still-Gennari type reagents. A set of various trisubstituted <i>Z</i>-alkenes was obtained in very high or quantitative yields with excellent <i>Z</i>-selectivity. Remarkably, the procedure was very successful for the synthesis of <i>Z</i>-2-aryl-substituted cinnamic acid esters, maintaining exclusive <i>Z</i>-selectivity even at an increased temperature.