Zn-Catalyzed Cyanation of Aryl Iodides

Copper-catalyzed C-C bond cleavage coupling with CN bond formation toward mild synthesis of lignin-based benzonitriles

N-participated lignin depolymerization is of great importance for the transformation of waste lignin into value-added chemicals. The vast majority of developed strategies employ organic amines as nitrogen source, and considerable methods rely on excessive use of strong base, which suffers severe environmental issues. Herein, benzonitrile derivatives are synthesized from oxidized lignin β-O-4 model compounds in the presence of solid nitrogen source (NH4)2CO3 under mild, base-free conditions over commercially available copper catalyst. Mechanism studies suggest the transformation undergoes a one-pot, highly coupled cascade reaction path involving oxidative C-C bond cleavage and in-situ formation of CN bond. Of which, Cu(OAc)2 catalyzes the transfer of hydrogen from Cβ (Cβ-H) to Cα, leading to the cleavage of Cα-Cβ bonds to offer benzaldehyde derivative, this intermediate then reacts in-situ with (NH4)2CO3 to afford the targeted aromatic nitrile product. Tetrabutylammonium iodide (TBAI), acting as a promoter, plays a key role in breaking the Cα-Cβ bonds to form the intermediate benzaldehyde derivative. With this protocol, the feasibility of the production of value-added syringonitrile from birchwood lignin has been demonstrated. This transformation provides a sustainable approach to benzonitrile chemicals from renewable source of lignin.

Synthesis and characterization of a green and recyclable arginine-based palladium/CoFe2O4 nanomagnetic catalyst for efficient cyanation of aryl halides

The utilization of magnetic nanoparticles in the fields of science and technology has gained considerable popularity. Among their various applications, magnetic nanoparticles have been predominantly employed in catalytic processes due to their easy accessibility, recoverability, effective surface properties, thermal stability, and low cost. In this particular study, cyanuric chloride and arginine were utilized to synthesize an arginine-based oligomeric compound (ACT), which was supported on cobalt ferrite, resulting in a green catalyst with high activity and convenient recyclability for the cyanation reaction of aryl halides. The Pd/CoFe2O4@ACT nanomagnetic catalyst demonstrated excellent performance in the cyanation of various aryl iodides and bromides, yielding favorable reaction outcomes at a temperature of 90 °C within a duration of 3 hours. The synthesized nanoparticles were successfully characterized using various techniques, including FTIR, FE-SEM, EDX/MAP, XRD, TEM, TGA, BET, and ICP-OES. Moreover, the Pd/CoFe2O4@ACT catalyst exhibited remarkable catalytic activity, maintaining an 88% performance even after five consecutive runs. Analysis of the reused catalyst through SEM and TEM imaging confirmed that there were no significant changes in the morphology or dispersion of the particles. Ultimately, it was demonstrated that the Pd/CoFe2O4@ACT nanomagnetic catalyst outperformed numerous catalysts previously reported in the literature for the cyanation of aryl halides.

Magnetically separable triazine-based Cu(ii)-vitamin B5 complex in nitromethane toward efficient heterogeneous cyanation reaction of aryl halides

In the current study, a highly efficient heterogeneous copper catalyst has been developed by supporting copper acetate on a magnetically separable triazine-vitamin B₅ system. After the successful characterization of the prepared nanoparticles by various techniques such as FT-IR, FE-SEM, EDX/MAP, XRD, TEM, TGA, VSM, and ICP-OES, the catalytic efficiency of them were evaluated in the cyanation reaction of aryl halides in the presence of nitromethane as a non-toxic and cost-effective cyanation source. The cyanation products were obtained in desirable yields. Notably, the magnetic nanocatalyst can be easily recovered and reused at least five times without a significant decrease in its performance.

Regiodivergent Cu-Promoted, AcOH-Switchable Distal Versus Proximal Direct Cyanation of 1-Aryl-1H-indazoles and 2-Aryl-2H-indazoles via Aerobic Oxidative C-H Bond Activation

A copper-promoted regiodivergent, AcOH-switchable, distal and proximal direct cyanation of N-aryl-(1H/2H)-indazoles via aerobic oxidative C(sp²)-H bond activation has been developed. The inclusion or exclusion of AcOH as an additive is the foremost cause for the positional switch in the C-CN bond formation method that results in (C-2')-cyanated 2-aryl-2H-indazoles 3a-j, (C-2')-cyanated 1-aryl-1H-indazoles 4a-j [distal], or C-3 cyanated 2-aryl-2H-indazoles 5a-i [proximal] products in good to excellent yields and showed various functional group tolerance. The cyanide (CN^-) ion surrogate was generated via the unification of dimethylformamide and ammonium iodide (NH₄I). The utilization of molecular oxygen (aerobic oxidative strategy) as a clean and safe oxidant is liable for generous value addition. The further pertinence of the developed protocol has been demonstrated by transforming the synthesized cyanated product into numerous other functional groups, which will, undoubtedly, accomplish utilization in the synthetic area of biologically important compounds and medicinal chemistry.

Pd-Catalyzed Cross-Couplings: On the Importance of the Catalyst Quantity Descriptors, mol % and ppm

This Review examines parts per million (ppm) palladium concentrations in catalytic cross-coupling reactions and their relationship with mole percentage (mol %). Most studies in catalytic cross-coupling chemistry have historically focused on the concentration ratio between (pre)catalyst and the limiting reagent (substrate), expressed as mol %. Several recent papers have outlined the use of “ppm level” palladium as an alternative means of describing catalytic cross-coupling reaction systems. This led us to delve deeper into the literature to assess whether “ppm level” palladium is a practically useful descriptor of catalyst quantities in palladium-catalyzed cross-coupling reactions. Indeed, we conjectured that many reactions could, unknowingly, have employed low “ppm levels” of palladium (pre)catalyst, and generally, what would the spread of ppm palladium look like across a selection of studies reported across the vast array of the cross-coupling chemistry literature. In a few selected examples, we have examined other metal catalyst systems for comparison with palladium.

Cu2 O-Catalyzed Conversion of Benzyl Alcohols Into Aromatic Nitriles via the Complete Cleavage of the C≡N Triple Bond in the Cyanide Anion

Nitrogen transfer from cyanide anion to an aldehyde is emerging as a promising method for the synthesis of aromatic nitriles. However, this method still suffers from a disadvantage that a use of stoichiometric Cu(II) or Cu(I) salts is required to enable the reaction. As we report herein, we overcame this drawback and developed a catalytic method for nitrogen transfer from cyanide anion to an alcohol via the complete cleavage of the C≡N triple bond using phen/Cu₂ O as the catalyst. The present condition allowed a series of benzyl alcohols to be smoothly converted into aromatic nitriles in moderate to high yields. In addition, the present method could be extended to the conversion of cinnamic alcohol to 3-phenylacrylonitrile.

Iodine Promoted Conversion of Esters to Nitriles and Ketones under Metal-Free Conditions

We report a novel strategy to prepare valuable nitriles and ketones through the conversion of esters under metal-free conditions. By using the I₂/PCl₃ system, various substrates including aliphatic and aromatic esters could react with acetonitrile and arenes to afford the desired products in good to excellent yields. This method is compatible with a number of functional groups and provides a simple and practical approach for the synthesis of nitrile compounds and aryl ketones.