Copper-catalyzed tandem intramolecular cyclization/coupling reaction: solvent effect on reaction pathway

DMSO/SOCl2-Enabled Synthesis of 3-Chloroindoles via Desulfonylative Chlorocyclization of N,N-Disubstituted 2-Alkynylanilines

The application of the DMSO/SOCl2 system enabled the intramolecular cyclization/chlorination of N,N-disubstituted 2-alkynylanilines, leading to the synthesis of a series of 3-chloroindoles with moderate to good yields. Differing from the previously reported interrupted Pummerer reaction featuring the introduction of SMe moiety, the current approach adopted an alternative pathway that realized the incorporation of chlorine atom to the indole skeleton via a desulfonylative chlorocyclization process.

Synthesis of 3-Haloindoles via Cascade Oxidative Cyclization/Halogenation of 2-Alkenylanilines Mediated by PIDA and LiBr/KI

The treatment of 2-alkenylanilines with phenyliodine(III) diacetate (PIDA) and LiBr or KI in HFIP was found to afford the corresponding 3-haloindoles via cascade oxidative cyclization/halogenation encompassing oxidative C-N/C-X (X = Br, I) bond formations. A plausible mechanism involving the in situ formation of the reactive AcO-X (X = Br, I) from the reaction of PIDA and LiBr/KI was postulated.

Copper-Catalyzed Preparation of Benzo[3,4]indolo[1,2-b]isoquinoline-8-ones and Photoluminescence Exploration

A facile synthesis of benzo[3,4]indolo[1,2-b]isoquinolin-8-ones is described. Under copper catalysis, the reaction proceeds with a high efficiency and a broad reaction scope. A deuteration experiment shows that the KIE value is 2.85. From the results on mechanism studies, copper-catalyzed C-H activation, intramolecular cis-addition of alkynes, and reductive elimination are involved. Moreover, this skeleton is indeed a new fluorophore, and its photophysical properties are also investigated.

Recent advances in the synthesis of indoles from alkynes and nitrogen sources

This review highlights ten years of success in the synthesis of indoles using alkynes and nitrogen sources as substrates.

Copper-Mediated Domino Cyclization/Trifluoromethylation/Deprotection with TMSCF3: Synthesis of 4-(Trifluoromethyl)pyrazoles

A copper-mediated synthesis of 4-(trifluoromethyl)pyrazoles is described. In one step from readily accessible α,β-alkynic tosylhydrazones, a remarkable domino sequence of cyclization, trifluoromethylation, and detosylation takes place to furnish the 4-CF₃ N-H pyrazole cores with good functional group compatibility. The reaction conditions are mild and convenient, at room temperature in air, using the commercially available trifluoromethyltrimethylsilane (TMSCF₃) as the CF₃ source. The method can be applied to the synthesis of a 4-CF₃ analogue of the anti-inflammatory drug celecoxib.