Synthesis of 2,7-Diazabicyclo[2.2.1]heptenes by N–O Bond Cleavage of Arylnitroso Diels–Alder 1,2-Dihydropyridine Cycloadducts

Abstract

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.

Key words

copper - Diels–Alder reaction - pyridines - rearrangement - pyrroles

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