Studies in the Cycloproparene Series: Oxygen Transfer to 1-Diphenylmethylidene- 1 H-cyclopropabenzene

Abstract

Oxygen transfer from dimethyldioxiran to 1-diphenylmethylidene-1 H-cyclopropabenzene (8b) proceeds to give the corresponding epoxy derivative (7b), the simplest and most stable oxaspiropentene yet recorded. The compound has been characterized spectroscopically prior to ring expansion and rearrangement to the cyclobutenone (9b) above 20°C; this is the sole product isolated when the reaction is performed at or above room temperature. If the oxygenation reaction is performed under conditions other than strictly anhydrous, the rearrangement (7b) → (9b) competes with protonation of the oxygen atom and sequential opening of the three-membered ring to provide the hydroxyethanone (11b) via the diol (10b).