3-Ferrocenyl-1-methyl- and 1-ferrocenyl-3-methylcyclopropenes

Dehydrobromination of isomeric 3-bromo-1-ferrocenyl-2-methylcyclopropanes afforded 3-ferrocenyl-1-methyl- and 1-ferrocenyl-3-methylcyclopropenes. These undergo smooth opening of the three-membered ring to give 1- and 2-ferrocenylbuta-1,3-dienes and 1- and 2-methyl-1H-cyclopentaferrocenes; with 1,3-diphenylisobenzofuran they give the classical Diels–Alder adducts.