Palladium and iodide catalyze the one–pot sonogashira–hydrogenation–isomerization reaction to give stereodefined alkenes

Stereodefined ( Z – or E –) alkenes are essential organic functionalities in organic chemistry, either as intermediate or final products, and their synthesis heavily relies in the stereoselective hydrogenation of internal alkynes. Here we show that the one–pot internal alkyne formation (via Sonogashira reaction) / selective semi–hydrogenation reaction with H 2 to give the Z alkene / isomerization reaction to give the E alkene is catalyzed by Pd and iodide (eventually added as PdI 2 and an additional iodide source) without the need of any ligand, copper co–catalyst, organic hydride source or solid support. This simple procedure is based on the concomitant action of catalytic Pd and I atoms during the different events of the reaction sequence, leveraging the iodide atoms produced as a by–product during the first Sonogashira reaction for a selective semi-hydrogenation reaction and allowing an isomerization after the simple addition of an iodide source. In this way, the desired Z – or E –alkenes are obtained at wish by simple denying or not the evolution of the last isomerization reaction step. Machine–learning workflows and a technoeconomic analysis confirm the removal of all the unnecessary reagents as a natural evolution of this cascade reaction, to be simply catalyzed by a Pd salt.