Synthesis of 2‐Aminofurans by Sequential [2+2] Cycloaddition–Nucleophilic Addition of 2‐Propyn‐1‐ols with Tetracyanoethylene and Amine‐Induced Transformation into 6‐Aminopentafulvenes

Synthesis of 2-aminofuran derivatives with an azulene or N,N-dimethylanilino substituent was established by the formal [2+2] cycloaddition-retroelectrocyclization of 3-(1-azulenyl or N,N-dimethylanilino)-2-propyn-1-ols with tetracyanoethylene, followed by intramolecular nucleophilic addition to the initially formed tetracyanobutadiene moiety of the internal hydroxyl group that come from 2-propyn-1-ol. The reaction proceeds under mild conditions with short reaction period. The products of the reaction are readily available through a simple purification procedure. 2-Aminofuran derivatives obtained by this reaction could be converted into 6-aminofulvene derivatives upon reaction with various amines. The structures of 2-aminofuran and 6-aminopentafulvene with a N,N-dimethylanilino substituent were confirmed by single-crystal X-ray structural analysis.