1.1]Ferrocenophanes in solution?Anti orsyn isomers?

Abstract

Carbon-bridged [1.1]ferrocenophanes have generally been assumed to have syn structures, since anti isomers have been considered to be too strained. The recent discovery that such compounds may crystallize as anti isomers raises the question of whether the compounds prefer anti or syn conformations in solution. The synthesis of β-acetyl-[1.1]ferrocenophane (1) and its investigation by 1H,1H-NOESY are reported. Compound 1 was found to be a rapidly equilibrating mixture of syn isomers in CDCl3 at 22 °C.