Transannular Addition of Phenols to 1,1′‐Dialkynylferrocenes: Unanticipated Formation of Phenoxy[4]ferrocenophanedienes

Abstract

The reaction of some 1,1'-dialkynylferrocenes with a variety of phenols in the presence as well as in the absence of [Mo(CO)(6)] yields good to high yields of phenoxy[4]ferrocenophanedienes. Similar reactivity was observed with a thiophenol and with acetic acid. Reaction under basic reaction conditions led to the formation of the [4]ferrocenophanone 17. The phenoxy[4]ferrocenophanedienes obtained show dynamic behavior as a result of a torsional twist of the carbon bridge as indicated by the (1)H and (13)C NMR spectra. The reaction mechanism is discussed in view of recent related results of Sato et al. as well as of Pudelski et al. A vinyl cation intermediate is postulated in this context, whose relative stability is evident from the mass spectra of the compounds prepared.