BBr 3 -mediated dearomative spirocyclization of biaryl ynones: facile access to spiro[5.5]dienones.

This report covers boron tribromide (BBr 3 ) mediated dearomative spirocyclization of biaryl ynones. The direct synthesis of spiro[5.5]dienones with a tri-substituted double bond is described for the first time in this paper. The scope of the reaction is broad and the spirocyclic products were obtained in moderate to good yields.