Non-Friedländer Route to Diversely 3-Substituted Quinolines through Au(III)-Catalyzed Annulation Involving Electron-Deficient Alkynes

Gold(III)-catalyzed annulation of electron-deficient alkynes and 2-amino-arylcarbonyls provides general modular one-step access to a broad scope of quinoline products. This highly selective reaction is a useful alternative to the classic Friedländer synthesis, which requires harsh reaction conditions. In contrast, the developed method works under relatively mild PicAuCl2-catalyzed conditions and exhibits a high functional group tolerance (40 examples; yields of ≤96%). Another feature of the developed approach is a versatility toward other electron-deficient alkynes. Alkynylsulfones, alkynylcarbonyls, alkynylphosphonates, propiolonitriles, and trifluoromethylated alkynes can be used as the starting materials for the preparation of quinolines diversely substituted at position 3. On the basis of experimental data, we proposed a reaction mechanism in which gold(III) functions as a strong electrophilic activator of the C≡C bond and the carbonyl group. The synthetic potential of the presented method is additionally illustrated by practical postmodifications of the obtained compounds, including a two-step synthesis of interpirdine, a potent drug candidate.

Facile access to 3-sulfonylquinolines via Knoevenagel condensation/aza-Wittig reaction cascade involving ortho-azidobenzaldehydes and β-ketosulfonamides and sulfones

Quinoline-based sulfonyl derivatives, and especially sulfonamides, are relevant and promising structures for drug design. We have developed a new convenient protocol for the synthesis of 3-sulfonyl-substituted quinolines (sulfonamides and sulfones). The approach is based on a Knoevenagel condensation/aza-Wittig reaction cascade involving o-azidobenzaldehydes and ketosulfonamides or ketosulfones as key building blocks. The protocol is appropriate for both ketosulfonyl reagents and α-sulfonyl-substituted alkyl acetates providing the target quinoline derivatives in good to excellent yields.

Lighting Up the Organochalcogen Synthesis: A Concise Update of Recent Photocatalyzed Approaches

This review describes the recent advances in photocatalyzed reactions to form new carbon–sulfur and carbon–selenium bonds. With a total of 136 references, of which 81 articles are presented, the authors introduce in five sections an updated picture of the state of the art in the light-promoted synthesis of organochalcogen compounds (from 2019 to present). The light-promoted synthesis of sulfides by direct sulfenylation of C–C π-bonds; synthesis of sulfones; the activation of Csp2–N bond in the formation of Csp2–S bonds; synthesis of thiol ester, thioether and thioacetal; and the synthesis of organoselenium compounds are discussed, with detailed reaction conditions and selected examples for each protocol.

3-Arylsulfonylquinolines from N-Propargylamines via Cascaded Oxidative Sulfonylation Using DABSO

We report a cascaded oxidative sulfonylation of N-propargylamine via a three-component coupling reaction using DABCO·(SO₂)₂ (DABSO). 3-Arylsulfonylquinolines were obtained by mixing diazonium tetrafluoroborate, N-propargylamine, and DABSO under argon atmosphere in dichloroethane (DCE) for 1 h. In a radical pathway, DABSO was utilized as the sulfone source and an oxidant in this radical-mediated cascaded reaction.

Metal-free regioselective cascade sulfonylation-cyclization of 3-aza-1,5-enynes with sulfur dioxide and aryldiazonium tetrafluoroborates to construct 1,2-dihydropyridines

Radical cascade cyclization of tethered alkynes has emerged as an efficient tool to construct small but complex cyclic compounds. However, it currently relies on aryl or heteroaryl-tethered alkynes to give...

Visible light organic photoredox catalytic cascade reactions

Over the past years, impressive progress has been made in the development of organic photoredox catalytic cascade reactions without the participation of expensive and toxic transition metals under visible light irradiation. These transformations highly depend on the in situ generation of various radical species in the photoredox catalytic cycles. Numerous chemically and biomedically valuable building blocks have been synthesized through this efficient and sustainable protocol. In this review, we highlight the recent progress in this blooming area by presenting a series of new catalytic cascade reactions mediated by organic photoredox catalysts and describe their mechanisms and applications which have appeared in the recent literature.

Visible-Light-Induced Multicomponent Cascade Cycloaddition of N-Propargyl Aromatic Amines, Cyclobutanone Oxime Esters, and K2S2O5: Access to Cyanoalkylsulfonylated Quinolines

A visible-light-induced cascade cyanoalkylsulfonylation/cyclization/aromatization of N-propargyl aromatic amines with K₂S₂O₅ and cyclobutanone oxime esters for the construction of cyanoalkylsulfonylated quinolines is developed. This cascade transformation features mild reaction conditions, a broad substrate scope, and excellent functional group compatibility, providing a convenient route toward cyanoalkylsulfonylated quinolines via the formation of a C-C bond and two C-S bonds in one step.

Visible Light as the Key for the Formation of Carbon–Sulfur Bonds in Sulfones, Thioethers, and Sulfonamides: An Update

This review summarizes the most relevant advancements made in the photocatalyzed synthesis of sulfones, thioethers, and sulfonamides from 2017 to the beginning of 2021. Synthetic strategies towards the construction of sulfur–carbon bonds are discussed together with the proposed reaction mechanisms. Interestingly, sulfur-based functional groups, which are of fundamental importance for the pharmaceutical field, can be assembled by photocatalysis in an easy and straightforward way under milder reaction conditions employing less toxic and expensive sulfur sources in comparison with common strategies.

1 Introduction

2 Sulfones

2.1 Sodium Sulfinates and Sulfinic Acids

2.2 Sulfonyl Halides

2.3 Sulfonyl Hydrazones

2.4 Sulfur Dioxide Surrogates

2.5 Miscellaneous

3 Thioethers

4 Sulfonamides

5 Conclusions

Synthesis and applications of sodium sulfinates (RSO2Na): a powerful building block for the synthesis of organosulfur compounds

This review highlights the preparation of sodium sulfinates (RSO2Na) and their multifaceted synthetic applications. Substantial progress has been made over the last decade in the utilization of sodium sulfinates emerging as sulfonylating, sulfenylating or sulfinylating reagents, depending on reaction conditions. Sodium sulfinates act as versatile building blocks for preparing many valuable organosulfur compounds through S-S, N-S, and C-S bond-forming reactions. Remarkable advancement has been made in synthesizing thiosulfonates, sulfonamides, sulfides, and sulfones, including vinyl sulfones, allyl sulfones, and β-keto sulfones. The significant achievement of developing sulfonyl radical-triggered ring-closing sulfonylation and multicomponent reactions is also thoroughly discussed. Of note, the most promising site-selective C-H sulfonylation, photoredox catalytic transformations and electrochemical synthesis of sodium sulfinates are also demonstrated. Holistically, this review provides a unique and comprehensive overview of sodium sulfinates, which summarizes 355 core references up to March 2020. The chemistry of sodium sulfinate salts is divided into several sections based on the classes of sulfur-containing compounds with some critical mechanistic insights that are also disclosed.

Visible-light-mediated synthesis of quinolines

Visible light promoted synthetic routes of quinolines using different strategies are hereby documented.

Recent advances and prospects in the metal-free synthesis of quinolines

Metal-free synthesis of quinolines has recently gained attention, and this review focuses on the recent advances in the metal-free synthesis of quinolines.