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

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 H-1 and C-13 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.