Multiple Transformations of 2‑Alkynyl-1,8-bis(dimethylamino)naphthalenes into Benzo[<i>g</i>]indoles. Pd/Cu-Dependent Switching of the Electrophilic and Nucleophilic Sites in Acetylenic Bond and a Puzzle of Porcelain Catalysis

By means of Sonogashira reaction, a series of 2-alkynyl- and 2,7-dialkynyl derivatives of 1,8-bis­(dimethyl­amino)­naphthalene (“proton sponge”) have been obtained from the corresponding iodides. It was disclosed that changing the reaction conditions and isolation protocol or conducting the model experiments with the authentic acetylenes results in several types of palladium- and copper-assisted heterocyclizations with the participation of the CC bond and 1-NMe₂ group. These include: (<i>i</i>) a cyclization into isomeric 1<i>H</i>-benzo­[<i>g</i>]­indoles with [1,3] migration of the <i>N</i>-methyl group into the newly formed pyrrole ring; (<i>ii</i>) a similar cyclization with a loss of the methyl group; (<i>iii</i>) a tandem process of cyclization into benzo­[<i>g</i>]­indoles and their subsequent 3,3′-dimerization; and (<i>iv</i>) a copper-catalyzed oxidative transformation into 3-aroyl­benzo­[<i>g</i>]­indoles. In most cases, the reactions occur in parallel, but under certain conditions, one of the above products becomes predominant or even the only one. Remarkably, in Pd-catalyzed cyclizations <i>i</i>–<i>iii</i>, the acetylenic bond behaves as an electrophile being attacked at the β-position by the amine nitrogen atom. In contrast, in transformation <i>iv</i>, the CC bond attacks by its C_α atom on the aminomethyl radical functionality N­(Me)–CH₂· presumably arising at copper oxidation/deprotonation of the 1-NMe₂ group. Studying rearrangement <i>i</i>, some evidence for the porcelain catalysis was obtained

Multiple Transformations of 2‑Alkynyl-1,8-bis(dimethylamino)naphthalenes into Benzo[<i>g</i>]indoles. Pd/Cu-Dependent Switching of the Electrophilic and Nucleophilic Sites in Acetylenic Bond and a Puzzle of Porcelain Catalysis

By means of Sonogashira reaction, a series of 2-alkynyl- and 2,7-dialkynyl derivatives of 1,8-bis­(dimethyl­amino)­naphthalene (“proton sponge”) have been obtained from the corresponding iodides. It was disclosed that changing the reaction conditions and isolation protocol or conducting the model experiments with the authentic acetylenes results in several types of palladium- and copper-assisted heterocyclizations with the participation of the CC bond and 1-NMe₂ group. These include: (<i>i</i>) a cyclization into isomeric 1<i>H</i>-benzo­[<i>g</i>]­indoles with [1,3] migration of the <i>N</i>-methyl group into the newly formed pyrrole ring; (<i>ii</i>) a similar cyclization with a loss of the methyl group; (<i>iii</i>) a tandem process of cyclization into benzo­[<i>g</i>]­indoles and their subsequent 3,3′-dimerization; and (<i>iv</i>) a copper-catalyzed oxidative transformation into 3-aroyl­benzo­[<i>g</i>]­indoles. In most cases, the reactions occur in parallel, but under certain conditions, one of the above products becomes predominant or even the only one. Remarkably, in Pd-catalyzed cyclizations <i>i</i>–<i>iii</i>, the acetylenic bond behaves as an electrophile being attacked at the β-position by the amine nitrogen atom. In contrast, in transformation <i>iv</i>, the CC bond attacks by its C_α atom on the aminomethyl radical functionality N­(Me)–CH₂· presumably arising at copper oxidation/deprotonation of the 1-NMe₂ group. Studying rearrangement <i>i</i>, some evidence for the porcelain catalysis was obtained

Heterocyclization of Enediynes Promoted by Sodium Azide: A Case of Ambiguity of X‑ray Data and Structure Revision

It has been shown that contrary to the literature data the tandem cyclization of (<i>Z</i>)-1-aryl-3-hexen-1,5-diynes promoted by sodium azide results in the formation of the corresponding [1,2,3]­triazolo­[1,5-<i>a</i>]­pyridines, not 1<i>H</i>-benzo­triazole derivatives. Apparently, incorrect structure elucidation made by previous investigators originates from misinterpretation of X-ray data. A number of new transformations of this type as well as X-ray and NMR experiments are discussed