Rhenium-Catalyzed Formation of Indene Frameworks via C−H Bond Activation: [3+2] Annulation of Aromatic Aldimines and Acetylenes

A rhenium complex, [ReBr(CO)3(thf)]2, catalyzes the reaction of an aromatic aldimine with an acetylene to give an indene derivative in a quantitative yield. The reaction proceeds via C−H bond activation, insertion of the acetylene, intramolecular nucleophilic cyclization, and reductive elimination. In contrast to ruthenium and rhodium catalysts, which are usually employed in this type of reaction, the rhenium catalyst promotes the intramolecular nucleophilic cyclization of the alkenylmetal species generated by insertion of the acetylene

Rhenium-Catalyzed Insertion of Terminal Acetylenes into a C−H Bond of Active Methylene Compounds

A rhenium complex, [ReBr(CO)3(thf)]2, catalyzed the intermolecular reactions of 1,3-dicarbonyl compounds with terminal acetylenes and gave the corresponding alkenyl derivatives in excellent yields. These reactions could apply to an intramolecular version and gave the corresponding cyclic compounds quantitatively

Efficient Catalytic Insertion of Acetylenes into a Carbon−Carbon Single Bond of Nonstrained Cyclic Compounds under Mild Conditions

A rhenium complex, [ReBr(CO)3(thf)]2, catalyzes the reaction of a 1,3-dicarbonyl cyclic compound with an acetylene to give a medium-sized cyclic compound in excellent yield. By using isocyanide as an additive, the catalytic activity of the rhenium complex changes dramatically, and the insertion of acetylenes into a carbon−carbon single bond occurs under mild conditions. A plausible mechanism is that the reaction proceeds via the formation of a rhenacyclopentene intermediate, ring opening by a retro-aldol reaction, isomerization, and reductive elimination

Rhenium-Catalyzed Formation of Indene Frameworks via C−H Bond Activation: [3+2] Annulation of Aromatic Aldimines and Acetylenes

A rhenium complex, [ReBr(CO)3(thf)]2, catalyzes the reaction of an aromatic aldimine with an acetylene to give an indene derivative in a quantitative yield. The reaction proceeds via C−H bond activation, insertion of the acetylene, intramolecular nucleophilic cyclization, and reductive elimination. In contrast to ruthenium and rhodium catalysts, which are usually employed in this type of reaction, the rhenium catalyst promotes the intramolecular nucleophilic cyclization of the alkenylmetal species generated by insertion of the acetylene

Efficient Catalytic Insertion of Acetylenes into a Carbon−Carbon Single Bond of Nonstrained Cyclic Compounds under Mild Conditions

A rhenium complex, [ReBr(CO)3(thf)]2, catalyzes the reaction of a 1,3-dicarbonyl cyclic compound with an acetylene to give a medium-sized cyclic compound in excellent yield. By using isocyanide as an additive, the catalytic activity of the rhenium complex changes dramatically, and the insertion of acetylenes into a carbon−carbon single bond occurs under mild conditions. A plausible mechanism is that the reaction proceeds via the formation of a rhenacyclopentene intermediate, ring opening by a retro-aldol reaction, isomerization, and reductive elimination

Rearrangement of Indene Skeletons under Mild Conditions

Isomerization between two isomers of 1,2-disubstituted 3-aminoindenes occurs via the rearrangement of indene frameworks. In contrast to previous rearrangements of indene derivatives, which occur under high-temperature conditions or the irradiation of light, this rearrangement proceeds at room temperature without UV light irradiation. An amino group at the 3-position plays an important role to accelerate the rearrangement under mild conditions

Insertion of Polar and Nonpolar Unsaturated Molecules into Carbon−Rhenium Bonds Generated by C−H Bond Activation: Synthesis of Phthalimidine and Indene Derivatives

A rhenium complex, [ReBr(CO)3(thf)]2, catalyzes the reaction of an aromatic aldimine with an isocyanate and an acetylene to give a phthalimidine and an indene derivative in a quantitative yield, respectively. The reactions proceed via C−H bond activation, insertion of the isocyanate or the acetylene, intramolecular nucleophilic cyclization to the aldimine of the generated amido− or alkenyl−rhenium species, and reductive elimination. In contrast to ruthenium and rhodium catalysts, which are usually employed in this type of reaction, the rhenium catalyst promotes the insertion of a polar unsaturated molecule. This occurs more easily than the insertion of a nonpolar unsaturated molecule

Rhenium-Catalyzed Synthesis of Multisubstituted Aromatic Compounds via C−C Single-Bond Cleavage

A reaction between a β-keto ester and an acetylene in the presence of a rhenium complex, [ReBr(CO)3(thf)]2, as a catalyst, provided a 2-pyranone derivative in excellent yield via retro-aldol reaction (C−C single bond cleavage). By adding an acetylene-bearing ester group(s) after the formation of 2-pyranones, an aromatization reaction proceeded and multisubstituted aromatic compounds were obtained in good to excellent yields

Rhenium-Catalyzed Formation of Bicyclo[3.3.1]nonene Frameworks by a Reaction of Cyclic β-Keto Esters with Terminal Alkynes

Treatment of cyclic β-keto esters with terminal alkynes in the presence of a catalytic amount of a rhenium complex, [ReBr(CO)3(thf)]2, gave bicyclo[3.3.1]nonene derivatives. The reaction conditions and yields of the bicyclo[3.3.1]nonenes were improved by the sequential use of tetrabutylammonium fluoride (TBAF) after the rhenium-catalyzed reactions

Rhenium-Catalyzed Formation of Bicyclo[3.3.1]nonene Frameworks by a Reaction of Cyclic β-Keto Esters with Terminal Alkynes

Treatment of cyclic β-keto esters with terminal alkynes in the presence of a catalytic amount of a rhenium complex, [ReBr(CO)3(thf)]2, gave bicyclo[3.3.1]nonene derivatives. The reaction conditions and yields of the bicyclo[3.3.1]nonenes were improved by the sequential use of tetrabutylammonium fluoride (TBAF) after the rhenium-catalyzed reactions