Copper-Catalyzed Arylation of Nitrogen Heterocycles from Anilines under Ligand-Free Conditions

Efficient Synthesis and Iodine-Functionalization of Pyrazoles via KIO3/PhSeSePh System under Acidic Conditions

This manuscript reports a novel method for the direct iodination of the C-4 pyrazole ring generated in situ by the reaction of 1,1,3,3-tetramethoxypropane and various hydrazines. In this approach, potassium iodate (KIO3) is used as the iodinating agent and (PhSe)2 is used as catalysts under acidic conditions. This protocol provides a convenient method for the efficient synthesis of 4-iodo-1-aryl-1H-pyrazoles, valuable intermediates for several different coupling reactions.

Copper-Promoted One-Pot Sandmeyer-Type Reaction for the Synthesis of N-Aryltriazoles

Herein, we report the copper-catalyzed one-pot Sandmeyer-type reaction of aromatic amines with triazoles to afford N-aryl-1,2,3-triazoles. Diazonium salts, formed from aromatic amines and tert-butyl nitrite in the presence of fluoroboric acid, reacted with triazoles in a copper-catalyzed Sandmeyer-type reaction. The reaction proceeded under mild conditions to afford N-aryltriazoles in moderate to good yields. This method is amenable to a wide range of aromatic amines and triazoles and shows diverse functional group tolerance. Inhibition of the reaction upon the addition of free radical scavengers suggested a radical pathway, in which the aryl radical, copper, and triazole formed a complex that underwent reductive elimination to give aryltriazole compounds; this is consistent with the mechanism underlying the Sandmeyer reaction. Thus, we demonstrate a new effective strategy for the construction of C-N bonds via Sandmeyer-type reactions and a valuable alternative approach for the synthesis of aryltriazole derivatives.

Copper nanoparticle anchored biguanidine-modified Zr-UiO-66 MOFs: a competent heterogeneous and reusable nanocatalyst in Buchwald-Hartwig and Ullmann type coupling reactions

We have designed a functionalized metal-organic framework (MOF) of UiO topology as a support, with an extremely high surface area, adjustable pore sizes and stable crystalline coordination polymeric structure and implanted copper (Cu) nanoparticles thereon. The core three dimensional Zr-derived MOF (UiO-66-NH2) was modified with a biguanidine moiety following a covalent post-functionalization approach. The morphological and physicochemical features of the material were determined using analytical methods such as FT-IR, SEM, TEM, EDX, atomic mapping, XRD and ICP-OES. The SEM and XRD results justified the unaffected morphology of Zr-MOF after structural modifications. The as-synthesized UiO-66-biguanidine/Cu nanocomposite was catalytically explored in the aryl and heteroaryl Buchwald-Hartwig C-N and Ullmann type C-O cross coupling reactions with excellent yields. A library of biaryl amine and biaryl ethers was synthesized over the catalyst under mild and green conditions. Furthermore, the catalyst was isolated by centrifugation and recycled 11 times with no significant copper leaching or change in its activity.

Biosynthesis of CuO nanoparticles using aqueous extract of herbal tea (Stachys Lavandulifolia) flowers and evaluation of its catalytic activity

Plant derived biogenic synthesis of nanoparticles (NP) has been the recent trend in material science as featured sustainable catalysts. A great deal of the current nanocatalytic research has been oriented on the bio-inspired green catalysts based on their wide applicability. In this context, CuO NPs are synthesized following a green approach using an herbal tea (Stachys Lavandulifolia) flower extract. The phytochemicals contained in it were used asthe internal reductant without applying harsh chemicals or strong heat. The derived nanoparticles also got stabilized by the biomolecular capping. The as-synthesized CuO NPs was characterized over FT-IR, FE-SEM, EDS, TEM, XRD, TGA and UV–Vis spectroscopy. These NPs were exploited as a competent catalyst in the aryl and heteroaryl C–heteroatom (N, O, S) cross coupling reactions affording outstanding yields. The nanocatalyst was isolated and recycled in 8 consecutive runs with reproducible catalytic activity. Rigidity of the CuO/S. Lavandulifolia nanocomposite was further justified by leaching test and heterogeneity test.

Is Cu(iii) a necessary intermediate in Cu-mediated coupling reactions? A mechanistic point of view

The different pathways have been summarized to disclose the key intermediate in copper-mediated coupling reactions.

Access to 2-substituted-2H-indazoles via a copper-catalyzed regioselective cross-coupling reaction

A CuCl catalyzed C-N cross-coupling reaction using commercially available 1H-indazoles with diaryliodonium salts is described. The methodology features ample structural versatility, affording 2-substituted-2H-indazole in good yields and complete N(2)-regiocontrol. Furthermore, the utility of the reaction was demonstrated in the synthesis of a known estrogen receptor β agonist. Mechanistic studies using density functional theory calculations suggested that the complete regioselectivity can be attributed to the only weak base TfO^- in our system which could not deprotonate indazoles, and the catalyst oxidation process would be the rate-determining step.

Aromatic substitutions of arenediazonium salts via metal catalysis, single electron transfer, and weak base mediation

Radical aromatic substitutions of arenediazonium salts can be initiated by various methods. The recent developments of weak base-mediated protocols provide great advantages over conventional metal-mediated or photoredox reactions by their operational simplicity, price, hazard potential and scalability.

Palladium/copper-catalyzed arylation of alkenes with N′-acyl arylhydrazines

An efficient and ligand-free palladium/copper-catalyzed Heck-type coupling reaction of N′-acyl arylhydrazines with olefins for the practical synthesis of arylalkenes.

Copper(ii)-catalyzed coupling reaction: an efficient and regioselective approach to N′,N′-diaryl acylhydrazines

An efficient and regioselective copper(ii)-catalyzed coupling reaction of N′-aryl acylhydrazines for the synthesis of N′,N′-diaryl acylhydrazines has been developed.