Recent advances and prospects in the nickel- catalyzed cyanation

Palladium-Catalyzed Denitrative Synthesis of Aryl Nitriles from Nitroarenes and Organocyanides

A denitrative cyanation of nitroarenes using organocyanides and a palladium catalyst was developed. The key for this reaction was the utilization of an aminoacetonitrile as a cyano source to avoid the generation of stoichiometric metal- and halogen-containing chemical waste. A wide range of nitroarenes, including heteroarenes and pharmaceutical molecules, can be converted into aryl nitriles.

Light-Triggered, Ni-Catalyzed Cyanation of Aryl Triflates with 1,4-Dicyanobenzene as the CN Source

A light-triggered, Ni-catalyzed cyanation of aryl triflates was herein reported, which provides a benign photochemical synthesis of aryl nitriles using 1,4-dicyanobenzene as the CN source instead of HCN or a metallic CN source. This mild method uses a readily available bisphosphine ligand and a soluble organosilicon reagent as the reductant and is carried out under purple light without an external photocatalyst. This cyanation was effective for aryl triflates derived from phenols and bisphenols as well as lignin-derived phenolic compounds, demonstrating its potential utility for the synthesis of aryl nitriles from biomass.

Cyanation with isocyanides: recent advances and perspectives

Cyanation has attracted considerable attention in organic synthesis because nitriles are key structural motifs in numerous important dyes, agrochemicals, natural products and drug molecules. As the fourth generation of cyanating reagents, isocyanides occupy a prominent place in the synthesis of nitriles due to their favorable stability, easy operability and high reactivity. In recent years, three types of cyanation with isocyanides have been established: the cleavage of the C-NC bond of tertiary alkyl isocyanides (Type I), the rearrangement of aryl isocyanides with azides (Type II), and the reductive cyanation of ketones with α-acidic isocyanides (Type III). This review focuses on advances in cyanation with isocyanides with an emphasis on reaction scope, limitations and mechanisms, which could reveal their remarkable value and superiority for accessing various nitriles. In addition, the future development prospects of this specific field are also introduced. We believe that this feature article will serve as a comprehensive tool to navigate cyanation with isocyanides across the vast area of synthetic chemistry.

Air-Tolerant Nickel-Catalyzed Cyanation of (Hetero)aryl Halides Enabled by Polymethylhydrosiloxane, a Green Reductant

An air-tolerant nickel-catalyzed cyanation of aryl bromides is reported. The reaction uses a NiCl₂/Xantphos catalyst in combination with substoichiometric quantities of zinc cyanide and polymethylhydrosiloxane. This silane is a green, homogeneous alternative to the traditional, insoluble solid reductant zinc and renders the reaction tolerant to air. The reaction can be performed under an air atmosphere, obviating the need for degassing, a glovebox, or Schlenk techniques. The reaction scope is broad, proceeding in good yields with a variety of (hetero)arenes.

Photochemically Enabled, Ni-Catalyzed Cyanation of Aryl Halides

A light-promoted Ni-catalyzed cyanation of aryl halides employing 1,4-dicyanobenzene as a cyanating agent is reported. A broad array of aryl bromides, chlorides, and druglike molecules could be converted into their corresponding nitriles (65 examples). Mechanistic studies suggest that upon irradiation, the oxidative addition product Ni(II)(dtbbpy)(p-C₆H₄CN)(CN) undergoes homolytic cleavage of the Ni-aryl bond to generate an aryl radical and a Ni(I)-CN species, the latter of which initiates subsequent cyanation reactions.

Recent advances and perspectives in ruthenium-catalyzed cyanation reactions

The cyanation reaction has achieved rapid progress in recent times. The ability to exhibit multiple oxidation states increased the demand of ruthenium in the field of catalysis. These cyanation reactions have wide application in pharmacological and biological fields. This review gives an overview of the ruthenium-catalyzed cyanation reactions covering literature up to 2021.

Cyanide-Free Cyanation of sp2 and sp-Carbons by Oxazole based Masked CN Source Using Flow Microreactors

We herein report a cyanide-free continuous-flow process for cyanation of sp 2 and sp carbons to synthesize aryl, vinyl and acetylenic nitriles from (5-methyl-2-phenyloxazol-4-yl) boronic acid [OxBA] reagent as a sole source of carbon-bound masked -CN source. Non-toxic and stable OxBA reagent is generated by lithiation-borylation of bromo-oxazole, and the consecutive Suzuki-Miyaura cross-coupling with aryl, vinyl, or acetylenic halides and demasking [4 + 2]/retro-[4 + 2] sequence were successfully accomplished to give the desired cyano compounds with reasonably good yields in a four-step flow manner. A unique feature of this cyanation protocol in flow enables to cyanate a variety of sp 2 and sp carbons to produce a broad spectrum of aryl acetonitrile. It is envisaged that the OxBA based cyanation would replace existing unstable and toxic approaches as well as non-toxic cyanation using two different sources of "C" and "N" to incorporate the -CN group.

Decorated palladium nanoparticles on chitosan/δ-FeOOH microspheres: A highly active and recyclable catalyst for Suzuki coupling reaction and cyanation of aryl halides

In this study, an eco-friendly and low cost magnetic nanocomposite consisting of chitosan/δ-FeOOH microspheres (CS/δ-FeOOH) was fabricated as a stabilizer by using a simple method. Pd nanoparticles (Pd NPs) were decorated on the designed CS/δ-FeOOH, and the resulting Pd NPs@CS/δ-FeOOH microspheres were employed as a heterogeneous catalyst in the construction of biaryl and benzonitriles. Pd NPs@CS/δ-FeOOH microspheres efficiently catalyzed the conversion of aryl iodides and bromides to the desired biaryls within 3 h. Moreover, Pd NPs@CS/δ-FeOOH microspheres showed high catalytic potential against synthesis of benzonitriles by providing yields up to of 99% within 4 h. More importantly, it was proved that Pd NPs@CS/δ-FeOOH microspheres were able to be easily recycled and reused up to eight runs for both reactions. This study reveals that Pd NPs@CS/δ-FeOOH microspheres are useful and recyclable nanocatalysts, which catalyze the synthesis of biaryl and benzonitriles with good reaction yields.

The ammoxidation of alcohols over heterogeneous catalysts for the green synthesis of nitriles

This is the first review on the ammoxidation of alcohols over heterogeneous catalysts, in which issues and potential solutions are demonstrated.

Recent advances and prospects in the palladium-catalyzed cyanation of aryl halides

Aryl nitriles are compounds with wide significance. They have made their own space in various sectors including pharmaceuticals, industries, natural product chemistry, and so on. Furthermore, they are also key intermediates in various transformations in organic chemistry. Transition metal-catalyzed cyanation reactions have proved to be a better replacement for the existing traditional synthetic strategies for aryl nitriles. Palladium is one of the most studied transition metals other than copper and nickel owing to its wide functional group compatibility and catalytic efficacy. There have been drastic developments in the field of palladium-catalyzed cyanation since its discovery in the 1973. This review summarizes the recent developments in the palladium-catalyzed cyanation of aryl halides and covers literature from 2012-2020.