Synthesis of E- and Z-substituted methylene-3,4-dihydro-2H-1-benzopyrans by regio- and stereocontrolled palladium-catalyzed intramolecular cyclization

A stereocontrolled synthetic approach to E- and Z-substituted methylene-3,4-dihydro-2H-1-benzopyrans 5 is described from acyclic derivatives using as a key step the palladium-catalyzed intramolecular cyclic carbopalladation of iodoalkynes 4 followed by a carbonylation or a hydride ion capture process.