Simultaneous Formation of Isomeric and Polycyclic Proton Sponges Derived from 1,8‐Diaminonaphthalenes and Xylylene Dibromides

Abstract

The interaction of 1,8‐diaminonaphthalene with o‐xylylene dibromide leads to two topologically relevant isomeric products, 1,8‐di(isoindolin‐2‐yl)naphthalene (reported previously), and its structural isomer with the bridgehead nitrogens in a bicyclic system (reported for the first time). This is the first case of isolating two heterocyclic analogs of 1,8‐bis(dimethylamino)naphthalene (proton sponge or DMAN) in one reaction. Both isomers are formed in parallel reactions and are not interconverted upon acid treatment. The first representative of heterocyclic “amide proton sponges”, which is still able to participate in intramolecular protonation due to the amide nitrogen atom, was synthesized by direct oxidation of the corresponding isoindoline derivative. Using p‐xylylene dibromide as a bridging bielectrophile, a macroheterocyclization was effectively realized to construct the first paracyclophane extended by two DMAN subunits. Mostly driven by the proximity effect, the molecular structure, unusual protonation trends and reactivity of peri‐diaminonaphthalenes N‐linked with o‐ and p‐xylylene fragments are also discussed.