Five-Membered 2-Methylene-2,3-dihydro Heterocycles from Ruthenium Butatrienylidene Intermediates and 2-(Dimethylamino)methyl-Substituted Furans, Thiophenes, and Selenophenes

Trapping of the primary butatrienylidene intermediate trans-[Cl(dppm) 2 Ru=C=C=C=CH 2 ] + with five-membered 2-(dimethylamino)methyl-substituted heterocycles provides an easy and efficient route to aminoallenylidene complexes with appended 2-methylene-2,3-dihydrofuran, -thiophene, or -selenophene moieties. Upon warming or acid catalysis isomerization to the aromatic 2-methylated isomers is observed.