Configuration of stilbene derivatives by 1H NMR and theoretical calculation of chemical shifts

The direct E/Z configuration assignment of tri- and tetra-substituted stilbenes (and other analogous olefins) when only one of the isomers is available is a quite challenging task. Sometimes, a chemical transformation or some other tedious method is necessary for determination of the double bond substitution pattern. In this paper, we relied on theoretical calculation of chemical shifts as a complementary tool for 1H NMR determination of the configuration of an α-phenylcinnamic acid prepared as a unique isomer by the Perkin reaction.