Synthesis of 2,7-diazabicyclo[2.2.1]heptenes by N-O bond cleavage of arylnitroso diels-alder 1,2-dihydropyridine cycloadducts

The cleavage of the N-O bond of nitrosoarene-derived cycloadducts with 1,2-dihydropyridines gives different products depending on the protecting group of the starting dihydropyridine and reaction conditions. The use of catalytic amounts of CuCl in non-nucleophilic solvents in combination with a N-phenoxycarbonyl-protected nitrosophenyl-derived cycloadduct allowed the unprecedented formation of the 2,7-diazabicycle[2.2.1]heptene scaffold. It was also demonstrated that this novel bicyclic gem-diamine derivative is an isolable intermediate en route to pyrrole derivatives. On the other hand, the corresponding nitrosopyridine-derived cycloadduct showed to be unreactive with copper salts, but the application of different reductive conditions can deliver the corresponding bicyclic gem-diamine derivative or 3-aminotetrahydropyridine also in enantioenriched form. © Georg Thieme Verlag Stuttgart.