A nickel-catalyzed Negishi coupling of cyclobutanone oxime esters with aryl zinc reagents has been developed, in which nickel serves both as an initiator for imine radicals and a catalyst for the coupling of aryl zinc reagents with oxime esters. The protocol can avoid the use of poisonous cyanide and has broad substrate scope as well as good functional group compatibility. Therefore, this method provides an attractive strategy for the synthesis of valuable nitriles. Preliminary mechanistic studies indicate that a radical pathway is involved in the product formation.

Transition metal complexes-catalyzed homogeneous asymmetric hydrogenation is an important method for the synthesis of chiral compounds. At present, it is mainly focused on precious transition metal catalytic systems, such as ruthenium, rhodium, iridium and palladium. However, they are suffered from the difficulties of limited resource, high cost and environmental contamination. Therefore, it is important and necessary to develop catalytic systems based on cheap, non-toxic or low toxic, environmentally friendly and earth-abundant iron, cobalt, nickel, copper transition metal, which are in accordance with the requirements and research trend of the sustainable development of modern chemistry. The recent progress of nickel-catalyzed homogeneous asymmetric hydrogenation of prochiral unsaturated compounds containing carbon oxygen double bond (C=O), carbon carbon double bond (C=C) and carbon nitrogen double bond (C=N) is reviewed, and some breakthroughs and considerable research results achieved are introduced. In addition, the advantages and disadvantages of different types of substrates in nickel catalyst system are analyzed, and the future research direction is prospected.

Nitrogen-containing organic compounds are ubiquitous in natural products, drug molecules and organic intermediates. Therefore, the introduction of nitrogenous functional groups into organic compounds is of great significance. Despite transition metal-catalyzed C—N coupling reaction provided an effcient strategy to access these ntrogen-containing compounds, extra steps are generally required to obtain the pre-functionalized starting materials. Recently, transition metal-catalyzed C—H amination has emerged as a more atom- and step-economical strategy to construct C—N bonds. Compared to the noble metals (e.g. palladium and rhodium), base metal catalysts, such as copper, cobalt and nickel, have attracted dramatic attentions, due to their earth abundance, cost effectiveness, and unique catalytic activities. Herein, the recent advances in copper-, cobalt- and nickel-catalyzed C—H amination reactions assisted by directing groups were summmarized according to the types of base metals, C—H bonds, and amination reagents with an emphasis on the discussion of various amination reagents and their application. Finally, the limitations and development trend of this research field are analyzed and prospected.

Transition metal-catalyzed cross-coupling reactions for building carbon-carbon bonds have received extensive attention due to their high efficiency and selectivity. In recent years, electrophiles which containing C(sp³)—O bonds have been used to replace organic halides in cross-coupling reactions for the construction of C(sp³)—C bonds, due to their advantages of commercial availability or facile synthesis, high reaction selectivity, and environmental friendliness. Among those reported highly efficient catalysts, nickel catalysts have been gradually applied to such reactions and achieved remarkable advances due to their earth-abundant, cheap, unique catalytic activities and selectivity. Because of the small radius of the nickel atom, C(sp³)—Ni can inhibit and/or manipulate β-H elimination reactions, which reduces the formation of by-products. Nickel has several variable valence states and can flexibly participate in redox-neutral coupling reactions and reductive cross-coupling reactions. The latest research progress in nickel-catalyzed coupling reactions employing alcohol derivatives as electrophiles is reviewed. It is separated into four sections including nickel-catalyzed cross-coupling reactions involving methanol or primary alcohol derivatives, nickel-catalyzed cross-coupling reactions involving secondary alcohol derivatives, nickel-catalyzed cross-coupling reactions involving acetal and N,O-acetal derivatives, and nickel-catalyzed cross-coupling reactions involving tertiary alcohol derivatives.

The synthesis of alkyl boronic esters has attracted much attention because of their wide applications in organic synthesis, materials and medicines. Transition-metal catalyzed hydroboration of alkenes was one of the most effective methods to construct alkyl boronic esters. Compared with rhodium, ruthenium, palladium, iridium and other precious metal catalysts, iron, cobalt and nickel catalysts were not only low cost, but also they displayed unique reactivity and selectivity. In this paper, the important advances in hydroboration of alkenes catalyzed by iron, cobalt and nickel have been summarized since 1994, including catalytic activity, selectivity and substrate scope of different catalytic systems.

The construction of skipped diene is a vital research area for organic synthesis, whose structure is found in many bioactive molecules. The synthesis of skipped diene from simple and readily available starting materials is highly desirable. Herein a nickel-catalyzed multicomponent coupling of 1,3-butadiene, aldehydes, alkynes, and Schwartz reagents for the preparation of skipped dienes is described. The reagents are common feedstock chemicals, especially 1,3-butadiene is an abundant feedstock produced from petroleum cracking. Moreover, the hydrozirconation of alkynes using Schwartz reagent was applied to in-situ prepared the alkenylzirconium reagents, which were used directly without further treatment. Various (E,E)-1,4-diene products were synthesized with excellent regio- and stereo-selectivity. The mild and straightforward reaction condition enables a broad substrate scope and good functional group tolerance. This protocol provides a useful and practical synthesis of skipped dienes.

The preparation of C-aryl glycosides via mild Ni/bipyridine-catalyzed reductive arylation of C(1)-glycosyl halides with electron-deficient aryl bromides was developed. Moderate to high α-selectivities were achieved for C-glycosides. A broad range of aryl halides including electron-rich aryl iodides were employed to yield C-aryl glycosides in 40%~5% yields. This method can be scaled up on a gram scale by lowering the loading of nickel catalyst to 2 mol%.

An efficient heterogeneous catalytic system based on NiGa layered double oxide (Ni₃Ga-LDO) for the C—N coupling between isochroman and primary arylamines has been described. Various primary arylamines were tolerated by the catalytic system, and good to excellent yields for the corresponding coupled products could be obtained. The results indicated that Ni species played the key role in the oxidative cross-coupling process, and the catalyst had good catalytical and structural stability. The protocol provides an effective alternative approach to construct C—N bond.