Light-Promoted Low-Valent-Tungsten-Catalyzed Ambient Temperature Amination of Boronic Acids with Nitroaromatics

Deoxygenative Reduction of 1°, 2° and 3° Amides via In Situ Generated Tungsten Cluster Acting as H-Bonding Donor

A protocol of amide-to-amine transformation that is convenient, mild, and easy to perform is a long-sought goal from the viewpoint of catalysis. Herein, we have utilized easily accessible W(CO)4(NCMe)2 as a precatalyst for the deoxygenative reduction of 1°, 2° and 3° amides under mild conditions. Mechanism studies unraveled that the in situ generated W4-cluster is potentially a vital species in activating C═O of amides by providing the H-bonding network during the catalytic cycle. Significantly, this tactic offers a complementary pattern to conventional metal-catalyzed amide deoxygenative reactions with activation of the C═O bond via direct coordination with amide.

Low-valent-tungsten catalysis enables hydroboration of esters and nitriles

In the research presented herein, low-valent-tungsten-catalyzed hydroboration of esters and nitriles was investigated. Aromatic and aliphatic substrates were smoothly reduced to corresponding alcohol derivatives and N,N-diborylamines in the presence of W(CO)4(NCMe)2. Valuable derivatives were conveniently accessed by introducing a further functionalization process to crude hydroboration mixtures in one pot.

Palladium-Catalyzed Dual C-H Carbonylation of Diarylamines Leading to Diversified Acridones under CO-Free Conditions

A Pd-catalyzed dual C-H carbonylation of commercially available diarylamines using Co2(CO)8 as a safe CO source has been developed. This methodology provides a facile approach for the synthesis of diversified acridones in moderate to good yields. The protocol features good functional group compatibility, operational safety, easy scale-up, and versatile transformations.

Reductive coupling of nitro compounds with boronic acid derivatives: an overview

The purpose of this review is to summarize the current literature on reductive C-N coupling of nitro compounds and boronic acids, with special emphasis on the mechanistic features of the reactions. The metal-catalyzed reactions are discussed first. This is followed by electro-synthesis and organophosphorus-catalyzed reactions. Finally, the available examples of catalyst-free reactions will be covered at the end of this review.

Reductive Arylation of Nitroarenes with Chloroarenes: Reducing Conditions Enable New Reactivity from Palladium Catalysts

Palladium-catalyzed C-N bond forming reactions are a key tool in modern synthetic organic chemistry. Despite advances in catalyst design enabling the use of a variety of aryl (pseudo)halides, the necessary aniline coupling partner is often synthesized in a discrete reduction step from a nitroarene. An ideal synthetic sequence would avoid the necessity of this step while maintaining the reliable reactivity of palladium catalysis. Herein, we describe how reducing conditions enable new chemical steps and reactivity from well-studied palladium catalysts, resulting in a new, useful transformation: the reductive arylation of nitroarenes with chloroarenes to form diarylamines. Mechanistic experiments suggest that under reducing conditions, BrettPhos-palladium complexes catalyze the dual N-arylation of typically inert azoarenes─generated via the in situ reduction of nitroarenes─via two distinct mechanisms. Initial N-arylation proceeds via a novel association-reductive palladation sequence followed by reductive elimination to yield an intermediate 1,1,2-triarylhydrazine. Arylation of this intermediate by the same catalyst via a traditional amine arylation sequence forms a transient tetraarylhydrazine, unlocking reductive N-N bond cleavage to liberate the desired product. The resulting reaction allows for the synthesis of diarylamines bearing a variety of synthetically valuable functionalities and heteroaryl cores in high yield.

Low-Valent Tungsten-Catalyzed Controllable Oxidative Dehydrogenative Coupling of Anilines

Herein, we have developed an efficient tungsten-catalyzed homogeneous system for oxidative dehydrogenative coupling of anilines to selectively produce various azoaromatics and azoxyaromatics as well as 2-substituted indolone N-oxides by simply regulating the reaction solvent with peroxide as a terminal oxidant under additive-free conditions. These findings provide an experimental framework for exploring tungsten catalysis in organic synthesis and offer an efficient and convenient tactic for the selective oxidation of anilines.