Reactions of acceptor-substituted aryl iodides and bromides with potassium thiocarboxylates under white light irradiation allow for the preparation of S-aryl thioesters including synthetically versatile S-aryl thioacetates. This transition-metal and external photocatalyst-free method features extremely mild reaction conditions compared with those used in transition-metal-catalyzed protocols. Reactions proceed via the initial formation of an electron donor–acceptor (EDA) complex in the ground state, which was supported by UV–vis spectra. Electron paramagnetic resonance (EPR) spin-trapping experiments using phenyl-N-tert-butylnitrone (PBN) have revealed the radical nature of the reaction.

Published data of the last 10 years concerning the development of new and upgrading of known approaches to indole synthesis are integrated and analyzed. Modern versions of the classical syntheses such as the Fischer synthesis, Nenitzescu synthesis, Ullmann reaction, Leimgruber – Batcho synthesis, Reissert synthesis, Bartoli reaction, Madelung synthesis and Cadogan – Sundberg reaction are considered. The presented new approaches include transformations of heterocycles, synthesis from o-alkynylanilines, reductive cyclization of nitrobenzene derivatives, synthesis with the use of arynes and catalysis by N-heterocyclic carbenes. The final Section summarizes original methods for the synthesis of indoles other than those listed above; they are classified in terms of the nature of the forming bond (C–C, C–N). Rarely used methods based on benzene ring construction in pyrrole derivatives are discussed separately. The bibliography includes 246 references

Employing DABCO as a substrate, aryl(mesityl)iodonium triflates are introduced as arylating agents for a tertiary sp 3 -nitrogen. Mild conditions and exceptional selectivity of the aryl group transfer allow unprecedented N-aryl-DABCO salts to be obtained, bearing substituents of different electronic natures. This metal-free methodology has no analogy among known transition-metal-based reactions. The utility of isolated N-aryl-DABCO salts is demonstrated for the preparation of flibanserin.

The N-(2-pyridyl)-N'-ethylpiperazines are important structural motifs in several medicinally relevant compounds. Known synthetic methods toward these structures are multistep and generally based on the SAr-chemistry; their applicability is significantly limited to substrates containing electron-withdrawing groups. Here, we describe a new methodology for a rapid and modular access to this privileged scaffold. Importantly, the developed protocol proved to be very general and efficient for the substrates containing substituents of different electronic nature. An operationally simple, metal-free, one-pot synthetic procedure involves the initial reaction of activated heterocyclic N-oxides with DABCO, followed by in situ treatment of the resultant quaternary N-(2-pyridyl)-DABCO salts with nucleophiles, resulting in ring-opening. The method features mild reaction conditions, high positional selectivity, and excellent functional-group tolerance. The utility of our approach is demonstrated by the late-stage site-selective functionalizations of complex molecules; a rapid modular assembly of MC2050, a potent PARP-1 inhibitor; and gram-scale preparations.

The visible‐light‐induced arylation of tertiary phosphines with aryl(mesityl)iodonium triflates to produce the quaternary phosphonium salts occurs under mild, metal, and catalyst‐free conditions. Photo‐excited EDA complexes between diaryliodonium salts and phosphines supposedly enable this transformation, which is difficult to achieve through the traditional ground‐state reactions. Demonstrating high functional group tolerance, broad scope, and complete selectivity of the aryl group transfer, the method is particularly compatible with sterically congested phosphines, which are challenging under metal‐based catalytic methods.