An unexpected participation of oxygen in a novel synthesis of [2,2′-bi-1H-indene]-3,3′-dialkyl-3,3′-dihydroxy-1,1′-diones

This paper describes, for the first time, a short synthetic procedure for [2,2′-bi-1H-indene]-3,3′-dialkyl-3,3′-dihydroxy-1,1′-diones (1a–f). The key feature of this synthetic method lies in the participation of oxygen when the intermediate arises from the nucleophilic addition of alkylmagnesium bromide to 2,2′-biindanylidene-1,1′,3,3′-tetraone. The background leading to the development of this synthesis is discussed, together with the proposal of a novel reaction mechanism. The structures of all the new compounds have been determined by X-ray crystallography.