Revisiting Hafner’s Azapentalenes: Some Old and New Chemistry of 1,3-Bis(dimethylamino)-2-azapentalene

Stable azaheterocyclic derivatives of pentalene have been reported by the group of Hafner in the 1970s, however, these structures remained of low interest until recently. Herein, we revisit the synthesis of stable azapentalene derivative 1,3-bis(dimethylamino)-2-azapentalene and further explore its properties both computationally and experimentally. Beyond the reproduction and optimiza-tion of some previously reported transformations, such as formylation and amine substitution, the available scope of reactions was expanded with azo-coupling, selective halogenations, and cross-coupling reactions.