Copper-Catalyzed Thiolation of Hydrazones with Sodium Sulfinates: A Straightforward Synthesis of Benzylic Thioethers

A facile and sustainable protocol for the thiolation of hydrazones with sodium sulfinates has been developed in the presence of CuBr₂ and DBU in DMF to afford diverse benzylic thioethers. Control experiments reveal a radical pathway involving a thiyl radical as a key intermediate.

Recent Advances in Palladium-Catalyzed Oxidative Couplings in the Synthesis/Functionalization of Cyclic Scaffolds Using Molecular Oxygen as the Sole Oxidant

Over the past years, Pd(II)-catalyzed oxidative couplings have enabled the construction of molecular scaffolds with high structural diversity via C–C, C–N and C–O bond-forming reactions. In contrast to the use of stoichiometric amounts of more common oxidants, such as metal salts (Cu and Ag) and benzoquinone derivatives, the use of molecular oxygen for the direct or indirect regeneration of Pd(II) species presents itself as a more viable alternative in terms of economy and sustainability. In this review, we describe recent advances on the development of Pd-catalyzed oxidative cyclizations/functionalizations, where molecular oxygen plays a pivotal role as the sole stoichiometric oxidant.

1 Introduction

2 Oxidative C–C and C–Nu Coupling

2.1 Intramolecular Oxidative C–Nu Heterocyclization Reactions

2.1.1 C–H Activation

2.1.2 Wacker/Aza-Wacker-Type Cyclization

2.1.3 Tandem Wacker/Aza-Wacker and Cyclization/Cross-Coupling Reactions

2.2 Intermolecular Oxidative C–Nu Heterocoupling Reactions

2.3 Intramolecular Oxidative (C–C) Carbocyclization Reactions

2.4 Intermolecular Oxidative C–C Coupling Reactions

2.4.1 Cyclization Reactions

2.4.2 Cross-Coupling Reactions

2.4.3 Homo-Coupling Reactions

3 Aerobic Dehydrogenative Coupling/Functionalization

4 Oxidative C–H Functionalization

5 Summary

Transition Metal Catalyst-Free C-3 Sulfonylmethylation of Imidazo[1,2-a]pyridines with Glyoxylic Acid and Sodium Sulfinates in Water

Herein, we describe an efficient and benign protocol for direct C-3 sulfonylmethylation of imidazo[1,2-a]pyridines with glyoxylic acid and sodium sulfinates. Various sulfonylmethylated imidazo[1,2-a]pyridines were synthesized in water under transition metal catalyst-free conditions. This multicomponent reaction featured available substrates, good functional group tolerance, moderate to excellent yields, and mild reaction conditions.

Palladium-Catalysed Intermolecular Direct C–H Bond Arylation of Heteroarenes with Reagents Alternative to Aryl Halides: Current State of the Art

Abstract:

Abstract: This unprecedented review with 322 references provides a critical up-to-date picture of the Pd-catalysed intermolecular direct C–H bond arylation of heteroarenes with arylating reagents alternative to aryl halides that include aryl sulfonates (aryl triflates, tosylates, mesylates, and imidazole-1-sulfonates), diaryliodonium salts, [(diacetoxy)iodo]arenes, arenediazonium salts, 1-aryltriazenes, arylhydrazines and N’-arylhydrazides, arenesulfonyl chlorides, sodium arenesulfinates, arenesulfinic acids, and arenesulfonohydrazides. Particular attention has been paid to summarise the preparation of the various arylating reagents and to highlight the practicality, versatility, and limitations of the various developed arylation protocols, also comparing their results with those achieved in analogous Pd-catalysed arylation reactions involving the use of aryl halides as electrophiles. Mechanistic proposals have also been briefly summarised and discussed. However, data concerning Pd-catalysed direct C–H bond arylations involving the C–H bonds of aryl substituents of the examined heteroarene derivatives have not been taken into account.

A new method for C(sp2)-H sulfonylmethylation with glyoxylic acid and sodium sulfinates

We herein describe a C4 sulfonylmethylation of pyrazol-5-amines with glyoxylic acid and sodium sulfinates. The reaction only needed to add water as the solvent, and it featured mild reaction condition,...

An update on the use of sulfinate derivatives as versatile coupling partners in organic chemistry

The use of sulfinic acids and their salts continues to be extensively developed in organic chemistry. This is attributable to their dual capacity for acting as nucleophilic or electrophilic reagents, as well as their ease of preparation and stability on storage. This report highlights the research accomplished since 2015 on this topic, updating a previous review published by our team in 2014.

Copper-catalysed regioselective sulfenylation of indoles with sodium sulfinates

A copper-catalysed sulfenylation of indoles with sodium sulfinates that affords 3-sulfenylindoles in good-to-excellent yields in N,N-dimethyl formamide (DMF) is described. In the process, DMF serves not only as a solvent but also as a reductant. This transformation is easy to carry out and has mild reaction conditions and good functional group tolerance.

Halo-substituted benzenesulfonyls and benzenesulfinates: convenient sources of arenes in metal-catalyzed C–C bond formation reactions for the straightforward access to halo-substituted arenes

The use of halo-substituted ArSO₂R as an aryl source in metal-catalyzed C–C bond formation reactions presents several advantages, as the reaction often proceeds without cleavage of the C–halo bonds.