Mono- and Dinuclear α-Diimine Nickel(II) and Palladium(II) Complexes in C–S Cross-Coupling

Nucleophilic Aromatic Substitution of Heteroaryl Halides with Thiols

The nucleophilic aromatic substitution (SNAr) between heteroaryl halides (Cl, Br) and thiols proceeds smoothly in DMAc under the action of K2CO3 at rt-100 °C. For most electron-deficient heteroarenes, reaction takes place without introducing an additional electron-withdrawing group. For electron-rich heteroarenes, an additional electron-withdrawing group such as a simple ester, keto, cyano, and nitro group is required to ensure the reaction completes. The reactivity trend of heteroaryl halides is highly dependent on the electronic nature of the heteroarenes and orientation of halogens. Besides thiols, a couple of functionalized thioureas and thioamides are compatible with these conditions, providing the corresponding heteroaryl thioethers in good yields.

Regioselective Direct C-H Bond Heteroarylation of Thiazoles Enabled by an Iminopyridine-Based α-Diimine Nickel(II) Complex Evaluated by DFT Studies

Direct C-H bond arylation is a highly effective method for synthesizing arylated heteroaromatics. This method reduces the number of synthetic steps and minimizes the formation of impurities. We report an air- and moisture-stable iminopyridine-based α-diimine nickel(II) complex for direct C5-H bond arylation of thiazole derivatives. Under a low catalyst loading and performing the reactions at lower temperatures (80 °C) under aerobic conditions, we produced mono- and diarylated thiazole units. Competition experiments and density functional theory calculations revealed that the mechanism of C-H activation in 4-methylthiazole involves an electrophilic aromatic substitution.

Nickel Catalyzed Cross-Coupling of Aryl and Alkenyl Triflates with Alkyl Thiols

We report a nickel catalyzed C-S cross-coupling of aryl and alkenyl triflates with alkyl thiols. A variety of the corresponding thioethers were synthesized using an air-stable nickel precatalyst under mild reaction conditions with short reaction times. A broad substrate scope, including pharmaceutically relevant compounds, could be demonstrated.

Ni-catalyzed C-S bond construction and cleavage

Sulfur-containing compounds have attracted considerable interest due to their wide-ranging applications in pharmaceuticals, agriculture, natural products, and organic materials. The development of efficient and rapid methods for the construction and transformation of sulfur-containing compounds is of great importance. Since nickel is inexpensive and has a variety of valence states, strong nucleophilicity and low energy barriers for oxidative addition, the construction and transformation of sulfur-containing compounds by nickel-catalyzed cross-coupling have become important strategies. In addition, sulfur-containing compounds have also been playing increasingly important roles in the field of cross-coupling due to their thermodynamically stable but dynamic activity. This review will focus on nickel-catalyzed construction and transformation of various sulfide-containing compounds, such as sulfides, disulfides, and hypervalent sulfur-containing compounds.

Stepwise synthesis and catalysis in C-S cross-coupling of pyridine-functionalized N-heterocyclic carbene nickel (II) complexes by mechanochemistry

The synthesis of three N-heterocyclic carbene complexes by stepwise grinding was described in this paper. The benzimidazolium salts ([H2L]Br2 and [H2L](PF6)2 ([H2L] =1,1’-di(2-picolyl)-3,3’-methylenedibenzoimidazolium) were initially prepared. Their reactions with Ni(OAc)2·4H2O...

Ni(II) Precatalysts Enable Thioetherification of (Hetero)Aryl Halides and Tosylates and Tandem C-S/C-N Couplings

Ni‐catalyzed C−S cross‐coupling reactions have received less attention compared with other C‐heteroatom couplings. Most reported examples comprise the thioetherification of most reactive aryl iodides with aromatic thiols. The use of C−O electrophiles in this context is almost uncharted. Here, we describe that preformed Ni(II) precatalysts of the type NiCl(allyl)(PMe₂Ar’) (Ar’=terphenyl group) efficiently couple a wide range of (hetero)aryl halides, including challenging aryl chlorides, with a variety of aromatic and aliphatic thiols. Aryl and alkenyl tosylates are also well tolerated, demonstrating, for the first time, to be competent electrophilic partners in Ni‐catalyzed C−S bond formation. The chemoselective functionalization of the C−I bond in the presence of a C−Cl bond allows for designing site‐selective tandem C−S/C−N couplings. The formation of the two C‐heteroatom bonds takes place in a single operation and represents a rare example of dual electrophile/nucleophile chemoselective process.