Rhenium-Catalyzed Intramolecular Carboalkoxylation and Carboamination of Alkynes for the Synthesis of C3-Substituted Benzofurans and Indoles.

A rhenium-catalyzed carboalkoxylation and carboamination of alkyne is reported. This reaction provides an efficient route to synthesize de novo C3-substituted benzofurans and indoles under mild conditions in moderate to good yields. Mechanistic studies revealed that the rhenium played the role of a π acid catalyst to activate the alkynes, followed by a charge-accelerated [3,3]-sigmatropic rearrangement.

Dual Gold-Catalyzed Formal Tetradehydro-Diels-Alder Reactions for the Synthesis of Carbazoles and Indolines.

This work reports a dual gold-catalyzed tetradehydro-Diels-Alder reaction for the synthesis of nitrogen-containing aromatic heterocycles. Under the catalytic system (IPrAuNTf2 /DIPEA), indolines and carbazoles as well as other N-containing aromatic heterocycles were prepared in high yields with good functional group tolerance. Unlike the traditional thermal tetradehydro-Diels-Alder reactions, diluted reaction concentration and radical prohibitors are not required for this protocol. Experimental data support a mechanism involving gold vinylidene species, which undergoes a 6 π electrocyclization, followed with 1,2-hydrogen shift.

De Novo Synthesis of Phenols and Naphthols through Oxidative Cycloaromatization of Dienynes.

In this work, a rhodium-catalyzed oxidative cycloaromatization of dienynes, which provides a highly straightforward and efficient way to access polysubstituted naphthols and phenols under mild conditions, is described. Challenged electron-withdrawing groups are well tolerated in this protocol, and late-stage phenyl ring formation is demonstrated.