Homocoupling reactions of terminal alkynes and arylboronic compounds catalyzed by in situ formed Al(OH) 3 -supported palladium nanoparticles

Porphyrin N-Pincer Pd(II)-Complexes in Water: A Base-Free and Nature-Inspired Protocol for the Oxidative Self-Coupling of Potassium Aryltrifluoroborates in Open-Air

Metalloporphyrins (and porphyrins) are well known as pigments of life in nature, since representatives of this group include chlorophylls (Mg-porphyrins) and heme (Fe-porphyrins). Hence, the construction of chemistry based on these substances can be based on the imitation of biological systems. Inspired by nature, in this article we present the preparation of five different porphyrin, meso-tetraphenylporphyrin (TPP), meso-tetra(p-anisyl)porphyrin (TpAP), tetrasodium meso-tetra(p-sulfonatophenyl)porphyrin (TSTpSPP), meso-tetra(m-hydroxyphenyl)porphyrin (TmHPP), and meso-tetra(m-carboxyphenyl)porphyrin (TmCPP) as well as their N-pincer Pd(II)-complexes such as Pd(II)-meso-tetraphenylporphyrin (PdTPP), Pd(II)-meso-tetra(p-anisyl)porphyrin (PdTpAP), Pd(II)-tetrasodium meso-tetra(p-sulfonatophenyl)porphyrin (PdTSTpSPP), Pd(II)-meso-tetra(m-hydroxyphenyl)porphyrin (PdTmHPP), and Pd(II)-meso-tetra(m-carboxyphenyl)porphyrin (PdTmCPP). These porphyrin N-pincer Pd(II)-complexes were studied and found to be effective in the base-free self-coupling reactions of potassium aryltrifluoroborates (PATFBs) in water at ambient conditions. The catalysts and the products (symmetrical biaryls) were characterized using their spectral data. The high yields of the biaryls, the bio-mimicking conditions, good substrate feasibility, evading the use of base, easy preparation and handling of catalysts, and the application of aqueous media, all make this protocol very attractive from a sustainability and cost-effective standpoint.

Homocoupling of terminal alkynes catalyzed by CuCl under solvent-free conditions

A series of symmetrical 1,4-disubstituted buta-1,3-diynes is prepared with excellent yields (up to 95%) through homocoupling of terminal alkynes catalyzed by a copper salt under solvent-free conditions. This method provides an environmentally friendly process to prepare 1,3-diynes in short reaction times under mild conditions. Furthermore, the method is suitable for a wide substrate scope and has excellent functional group compatibility. The reaction can also be scaled up to gram level.

Recent Advances in the Application of Nanometal Catalysts for Glaser Coupling

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Synthesis of symmetrical 1,3-diynes from terminal alkynes through an oxidative process is generally called Glaser coupling. The classic Glaser coupling is catalyzed by copper salts under an atmosphere of molecular oxygen as an oxidant. Over the past years, different metal catalysts and oxidants were successfully used in this atom economical C-C coupling reaction. Moreover, several procedures for the preparation of unsymmetrical 1,3-diynes by coupling two different alkyne substrates have been developed. In this review, we will highlight the usefulness of transition metal nanoparticles as efficient catalysts in homo- and hetero-coupling of alkynes by hoping that it will be beneficial to the development of novel and extremely efficient catalytic systems for this fast-growing and important reaction.

Study of the versatility of CuBTC@IL-derived materials for heterogeneous catalysis

The versatility of CuBTC (HKUST-1) MOF materials to be functionalized to improve their catalytic activity performance was evaluated. CuBTC@IL catalysts are selective for the cycloaddition of CO₂ to epoxides, giving rise to value-added products.

Benzotriazole as an Efficient Ligand in Cu-Catalyzed Glaser Reaction

Benzotriazole has been established as an efficient ligand in Cu-catalyzed cross-coupling of terminal alkynes to form 1,3-dialkynes using CuI as the catalyst and K2CO3 as the base at room temperature in an open round-bottom flask. The established protocol has the following notable advantages: simple to handle, easy work-up, mild reaction condition, high substrate scope, requirement of less quantity of ligand and also Cu-catalyst, less expensive, and high reaction yield.

General Immobilization of Ultrafine Alloyed Nanoparticles within Metal-Organic Frameworks with High Loadings for Advanced Synergetic Catalysis

The development of a general synthesis approach for creating fine alloyed nanoparticles (NPs) in the pores of metal-organic frameworks (MOFs) shows great promise for advanced synergetic catalysis but has not been realized so far. Herein, for the first time we proposed a facile and general strategy to immobilize ultrafine alloyed NPs within the pores of an MOF by the galvanic replacement of transition-metal NPs (e.g., Cu, Co, and Ni) with noble-metal ions (e.g., Pd, Ru, and Pt) under high-intensity ultrasound irradiation. Nine types of bimetallic alloyed NPs of base and noble metals were successfully prepared and immobilized in the pores of MIL-101 as a model host, which showed highly dispersed and well-alloyed properties with average particle sizes ranging from 1.1 to 2.2 nm and high loadings of up to 10.4 wt %. Benefiting from the ultrafine particle size and high dispersity of Cu-Pd NPs and especially the positive synergy between Cu and Pd metals, the optimized Cu-Pd@MIL-101 exhibited an extremely high activity for the homocoupling reaction of phenylacetylene under unprecedented base- and additive-free conditions and room temperature, affording at least 19 times higher yield (98%) of 1,4-diphenylbuta-1,3-diyne than its monometallic counterparts. This general strategy for preparing various MOF-immobilized alloyed NPs potentially paves the way for the development of highly active metal catalysts for a variety of reactions.

A walk around the application of nanocatalysts for cross-dehydrogenative coupling of C–H bonds

Cross-dehydrogenative coupling reactions between two unmodified C–H bonds are one of the most attractive and fundamental strategies for the construction of C–C bonds. As these reactions avoid pre-functionalization and de-functionalization of the substrates, they are cleaner, safer, and faster than traditional cross-coupling reactions. After the introduction of the modern area of cross-dehydrogenative coupling in 2003, many efforts have been devoted to the development of more efficient and selective catalytic systems for these appealing reactions. Among the different types of catalytic systems that have been investigated, nanostructured metal catalysts are highly attractive in view of their high catalytic performance, easy separability and good reusability. The purpose of this review is to focus on the application of nanocatalysts for cross-dehydrogenative coupling of C–H bonds with particular emphasis on the mechanistic aspects of the reactions. Specifically, we have structured this review based on the type of C–C bonds. Thus, the review is divided into six major sections: (i) C(sp³)–C(sp³) coupling; (ii) C(sp³)–C(sp²) coupling; (iii) C(sp³)–C(sp) coupling; (iv) C(sp²)–C(sp²) coupling; (v) C(sp²)–C(sp) coupling; and (vi) C(sp)–C(sp) coupling.

Cross-dehydrogenative coupling reactions between two unmodified C–H bonds are one of the most attractive and fundamental strategies for the construction of C–C bonds.

Rise of Conjugated Poly-ynes and Poly(Metalla-ynes): From Design Through Synthesis to Structure-Property Relationships and Applications

Conjugated poly-ynes and poly(metalla-ynes) constitute an important class of new materials with potential application in various domains of science. The key factors responsible for the diverse usage of these materials is their intriguing and tunable chemical and photophysical properties. This review highlights fascinating advances made in the field of conjugated organic poly-ynes and poly(metalla-ynes) incorporating group 4-11 metals. This includes several important aspects of conjugated poly-ynes viz. synthetic protocols, bonding, electronic structure, nature of luminescence, structure-property relationships, diverse applications, and concluding remarks. Furthermore, we delineated the future directions and challenges in this particular area of research.