Synthesis of polycyclic scaffolds via a gold-catalysed dearomative cyclisation cascade

Cascade hydroarylation/Diels-Alder cycloaddition of alkynylindoles with electron-deficient alkynes and alkenes

Herein, a novel cascade gold(I)-catalyzed hydroarylation of alkynylindoles and subsequent Diels-Alder cycloaddition with electron-deficient alkynes and alkenes is described. A variety of azepino-fused hydrocarbazoles and carbazoles were obtained in moderate to excellent yields. Key features of this methodology are low catalyst loadings, high regioselectivity, broad functional group tolerances, access to important heterocycles, and 100% atom economy.

Access to Azepino-Annulated Benzo[c]carbazoles Enabled by Gold-Catalyzed Hydroarylation of Alkynylindoles and Subsequent Oxidative Cyclization

Herein, we report a facile and efficient synthetic method to construct azepino[1,2-a]indoles through a novel gold(I)-catalyzed intramolecular hydroarylation of alkynylindoles. A wide range of functional groups can be well tolerated in this transformation, and the corresponding highly functionalized azepino[1,2-a]indole skeletons were obtained in moderate to excellent yields. Subsequent oxidation of the products gave the interesting and valuable polycyclic carbazoles, which were widely used as the key building blocks in materials science.

Metal-Free C-C/C-N/C-C Bond Formation Cascade for the Synthesis of (Trifluoromethyl)sulfonylated Cyclopenta[b]indolines

A bis(triflyl)ethylation [triflyl = (trifluoromethyl)sulfonyl] inserted into a sequential cyclization cascade resulted in the direct formation of gem-bis(triflyl)ated cyclopenta[b]indolines from anilide-derived allenols and alkenols. This catalyst- and irradiation-free sequence facilitated the efficient preparation of functionalized tricyclic indoline cores bearing two contiguous stereocenters. The formed cyclopenta[b]indolines can be easily transformed into a wide variety of triflylated indolines, including the tetracycle ring system found in polyveoline.