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In this paper, we describe an efficient and atom‐economical synthesis of highly functionalized pyrroles, pentafulvenes, and pyrrolopyridines by [2+2] cycloaddition–retroelectrocyclization of N‐substituted propargylamines with tetracyanoethylene, followed by the treatment of the resulting tetracyanobutadiene derivatives with silica gel. In this reaction, silica gel plays an important role to promote the intramolecular cyclization to afford the heterocyclic products from the tetracyanobutadiene intermediates. The products were obtained selectively depending on the substituent on the nitrogen atom of the starting propargylamines. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: The crystal structures of 1,3-bis(4-bromophenyl)- and 1,3-di(2-thienyl)azulenes ( 5 and 6 ) were elucidated by X-ray analysis. Two aryl groups connect to the azulenyl core with dihedral angles of 34.9–41.6° and the two aryl planes of the groups slant against the azulene ring toward different ways in their crystal structures. It was also found that the azulene rings of 5 and 6 showed a slight out-of-plane deformation in the way that the hydrogen atoms at the 4- and 8-positions are apart from the neighboring aryl ortho-hydrogen atoms to fill in the vacant space made by the slanting aryl planes. [Copyright &y& Elsevier]

Abstract: The dipyrrins (IV) obtained show a clear color change from red to blue when exposed to Broensted acids. [ABSTRACT FROM AUTHOR]