The trapping of 6,6-dimethylisobenzofulvene by its 1,3-dipolar precursor : a rare example of dipolar[6 4] cycloaddition

A new route to isobenzofuran and isobenzofulvene is reported that is proposed to involve the 14e electrocyclic fragmentation of a transient 1,3-dipolar intermediate formed by ring-opening of a fused aziridinocyclobutane. 6,6-Dimethylisobenzofulvene generated in this way reacts with its 1,3-dipole precursor to form a [10pi + 4pi] cycloadduct, the first of this type involving the participation of a 1,3-dipolar species.