[2+2] Cycloaddition Reactions with a Tungsten-Stabilized 2<i>H</i>-Phenol

The phenol ligand of the complex TpW(NO)(PMe3)(η2-phenol) exists in solution as its 2H tautomer. This normally inaccessible isomer of phenol undergoes a [2+2] cycloaddition with several ketenes across the C3−C4 bond of the phenol. The resulting cyclobutanone can be selectively reduced with sodium borohydride without disturbing the enone functionality, and the resulting hydroxy[4.2.0]bicyclooctenone, which contains four new stereocenters, may be removed from the metal.