October 2023

The pyrrolo[1,2-a]quinoxaline skeleton has significant potential for many biological and optical applications. Hence, in this study, unconjugated ynone derivatives were treated with 1,2-diaminoarenes in a gold-catalyzed cyclization to give 2-(1H-pyrrol-1-yl)anilines, which are valuable starting materials, and pyrrolo[1,2-a]quinoxalines by a one-pot and single-step approach. A reaction mechanism for the formation of the pyrrolo[1,2-a]quinoxaline skeleton featuring a key gold carbene intermediate is proposed. On the other hand, the methyl group on the C-2 position of the 2-(1H-pyrrol-1-yl)anilines was oxidized by SeO2 to give the pyrrolo[1,2-a]quinoxaline skeleton, resulting in 14 different pyrrolo[1,2-a]quinoxaline derivatives.

The development of concise and efficient methods to construct bithiophene derivatives is an appealing task in the fields of organic chemistry and organic functional materials. Herein, we summarize our recent efforts towards the development of catalytic oxidative C–H cyclization reactions of thiophenol derivatives with 1,3-diynes, which provides a straightforward and effective synthetic approach to both symmetrical and nonsymmetrical 3,3′-bibenzothiophenes. This work is expected to stimulate the application of catalytic oxidative C–H annulation of aromatics with 1,3-diynes for the exploitation of organic functional materials.

Bis(2-ethylhexyl)amine is shown to be a suitable organocatalyst to prepare racemic compounds in the reactions of α,β-unsaturated aldehydes involving an iminium ion, whereas diphenylprolinol silyl ether is a well-known chiral organocatalyst for the asymmetric versions of the same reactions. The generality and limitations of bis(2-ethylhexyl)amine are disclosed.