Cascade trifluoromethylthiolation and cyclization of N-[(3-aryl)propioloyl]indoles

A General and Highly Versatile Heterogeneous Pd-Catalyzed Oxidative Aminocarbonylation of Alkynes with Aromatic and Aliphatic Amines

An efficient heterogeneous catalytic system for the oxidative aminocarbonylation of alkynes and amines in the presence of CO/O2 to afford substituted propiolamides has been developed. The active nanocatalyst, [Pd/Mg3Al-LDH]-300(D), is composed by Pd nanoaggregates (2-3 nm average particle size) stabilized over a partially dehydrated [Mg3Al-LDH] matrix. The methodology has resulted widely applicable, being the first catalytic system, either homogeneous or heterogeneous, able to activate not only aliphatic amines but also poorly-nucleophilic aromatic amines. In fact, >60 substituted propiolamides have been synthesized in good to excellent isolated yields through this methodology, being 27 novel compounds. An important characterization effort (XRD, 27Al MAS NMR, TGA, TPD-CO2, BET area, XPS, HAADF-HRSTEM and HRTEM) and optimization of the synthesis conditions of the optimal catalyst has been performed. This study, together with a series of kinetic and mechanistic essays, indicates that the optimal catalyst is composed by Pd(0) species stabilized in a partially dehydrated/dehydroxylated LDH material with a Mg/Al molar ratio of 3 and a small crystallite size. All the experimental data indicates that the in situ formation of [PdI2] active species in the material surface together with the presence of a matrix with the optimal acid/base properties are key aspects of this process.

Cascade Oxidative Trifluoromethylthiolation and Cyclization of 3-Alkyl-1-(2-(alkynyl)phenyl)indoles

Persulfate-promoted radical cascade trifluoromethylthiolation and cyclization of 3-alkyl-1-(2-(alkynyl)phenyl)indoles with AgSCF₃ were investigated. This protocol provides a novel route to CF₃S-substituted indolo[1,2-a]quinoline-7-carbaldehydes and CF₃S-substituted indolo[1,2-a]quinoline-7-methanone derivatives via the formation of the C-SCF₃ bond and C-C bond and benzylic carbon oxidation in a single step. This reaction can accommodate a broad range of functional groups. The single-crystal X-ray diffraction data confirm the chemical structure of the product. A scale-up experiment and radical inhibition experiments were operated in the reaction system. Photophysical properties of some selected 5-((trifluoromethyl)thio)indolo[1,2-a]quinoline-7-carbaldehydes were studied by UV-visible and fluorescence spectroscopy.

Copper- and Visible-Light-Catalyzed Cascade Radical Cyclization of N-Propargylindoles with Cyclic Ethers

An efficient visible-light-assisted, copper-catalyzed tandem radical cyclization of N-propargylindoles with cyclic ethers is established. A series of 2-oxoalkyl-9H-pyrrolo[1,2-a]indol-9-ones with potential biological activities were synthesized in moderate yields by using a dual catalytic system with copper acetate as a transition metal catalyst and eosin Y as a visible light catalyst. The investigation of reaction mechanism shows that it goes through a cascade oxoalkyl radical addition, cyclization, and oxidation process.

Aerobic copper-mediated domino process for the synthesis of 3-(trifluoromethylseleno)indoles

An aerobic copper-mediated domino reaction for the synthesis of 3-(trifluoromethylseleno)indoles from trifluoromethylselenolation of N-Ts 2-alkynylaniline with [(bpy)CuSeCF3]2 is reported. This reaction proceeds through a sequential oxidation, alkyne coordination, and deprotonation...

Recent advances in the synthesis of pyrrolo[1,2-a]indoles and their derivatives

The pyrrolo[1,2-a]indole unit is a privileged heterocycle found in numerous natural products and has been shown to exhibit diverse pharmacological properties. Thus, recent years have witnessed immense interest from the synthesis community on the synthesis of this scaffold. In light of the ever-increasing demand for pyrrolo[1,2-a]indoles in drug discovery, this review provides an overview of recent synthesis methods for the preparation of pyrrolo[1,2-a]indoles and their derivatives. The mechanistic pathway and stereo-electronic factors affecting the yield and selectivity of the product are briefly explained. Furthermore, we have attempted to demonstrate the utility of the developed methods in the synthesis of bioactive molecules and natural products, wherever offered.