Abstract
Abstract[4,4′‐Bipyridine]‐3,3′‐diamine (1) reacts with HNO2 in H2SO4 to form 2,7,9,10‐tetraazaphenanthrene (2) and 9H‐pyrrolo[2,3‐c:5,4‐c′]dipyridine (3) instead of expected bipyridinediol 4 or furodipyridine 5. On the other hand, diazotization of 1 in hydrohalogenic acids leads to novel 3‐halogeno‐2,7,9,10‐tetraazaphenanthrenes 10 or 11 and this reaction represents a new type of regioselective nucleophilic substitution of hydrogen atom in heteroaromatic species. The proposed pathway of reactions was supported by an experiment with the hypothetic intermediate, i.e. 2,7,9,10‐tetraazaphenanthrene‐9‐imine (8), which was obtained on independent route.
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