Thermal Cyclization of Phenylallenes That Contain<i>ortho</i>-1,3-Dioxolan-2-yl Groups: New Cascade Reactions Initiated by 1,5-Hydride Shifts of Acetalic H Atoms
shift of the acetalic H atom onto the central cumulene carbon atom; 2) a subsequent 6π‐electrocyclic ring‐closure of the resulting reactive ortho‐xylylenes; and 3) a final aromatization step with concomitant ring‐opening of the 1,3‐dioxolane fragment. If the 1,3‐dioxolane ring of the starting allenes was replaced by a dimethoxymethyl group, the reactions led to mixtures of two disubstituted naphthalenes