Scope and limitation of propylene carbonate as a sustainable solvent in the Suzuki–Miyaura reaction

The Suzuki–Miyaura reaction is one of the most used transformations in drug research. Thus making this reaction more sustainable is of considerable current interest. Here we show that propylene carbonate (PC) can be used as a solvent for the Suzuki–Miyaura reaction. PC is one of the greenest solvents since it is synthesized under green conditions by the use of carbon dioxide in the air. All reactions proceeded well and good or excellent yields were observed for the biaryl products. Nonetheless in the case of pyridazinones, 2-hydroxypropyl- chain containing side-products were observed. Importantly, this fact allowed the isolation of several novel compounds which were generated under prominently green conditions.

The Suzuki–Miyaura reaction was carried out in propylene carbonate yielding an interesting side-product besides the biphenyl derivative.

Copper(I)-USY as a Ligand-Free and Recyclable Catalyst for Ullmann-Type O-, N-, S-, and C-Arylation Reactions: Scope and Application to Total Synthesis

The copper(I)-doped zeolite Cu^I-USY proved to be a versatile, efficient, and recyclable catalyst for various Ullmann-type coupling reactions. Easy to prepare and cheap, this catalytic material enables the arylation and heteroarylation of diverse O-, N-, S-, and C-nucleophiles under ligand-free conditions while exhibiting large functional group compatibility. The facility of this catalyst to promote C-O bond formation was further demonstrated with the total synthesis of 3-methylobovatol, a naturally occurring diaryl ether of biological relevance. From a mechanistic viewpoint, two competitive pathways depending on the nature of the nucleophile and consistent with the obtained results have been proposed.

Diaryl ethers synthesis: nano-catalysts in carbon-oxygen cross-coupling reactions

The diaryl ether moiety is not only prevalent in a significant number of natural products and synthetic pharmaceuticals but also widely found in many pesticides, polymers, and ligands. Ullmann-type cross-coupling reactions between phenols and aryl halides are regarded as one of the most important methods for the synthesis of this important and versatile structural motif. In recent years, the use of nano-sized metal catalysts in this coupling reaction has attracted a lot of attention because of these catalysts with their high surface-to-volume ratio, high surface energy, and reactive morphology allows for rapid C-O bond formation under mild and ligand-free conditions. In this review we will highlight the power of these catalysts in Ullmann-type C-O cross-coupling reactions.

New routes to Cu(I)/Cu nanocatalysts for the multicomponent click synthesis of 1,2,3-triazoles

An array of copper and copper-zinc based nanoparticles (NPs) have been fabricated employing a variety of polymeric capping agents. Analysis by TEM, XRPD and XPS suggests that by manipulating reagent, reductant and solvent conditions it is possible to achieve materials that are mono-/narrow disperse with mean particle sizes in the ≤10 nm regime. Oxidative stability in air is achieved for monometallic NPs using poly(methyl methacrylate) (PMMA) anti-agglomerant in conjunction with a variety of reducing conditions. In contrast, those encapsulated by either poly(1-vinylpyrrolidin-2-one) (PVP) or poly(4-vinylpyridine) (PVPy) rapidly show Cu(2)O formation, with all data suggesting progressive oxidation from Cu to Cu@Cu(2)O core-shell structure and finally Cu(2)O. Bimetallic copper-zinc systems, reveal metal segregation and the formation of Cu(2)O and ZnO. Catalysts have been screened in the synthesis of 1,2,3-triazoles through multicomponent azide-alkyne 1,3-dipolar cycloaddition. Whereas PMMA- and PVPy-coating results in reduced catalytic activity, those protected by PVP are highly active, with quantitative triazole syntheses achieved at room temperature and with catalyst loadings of 0.03 mol% metal for Cu and CuZn systems prepared using NaH(2)PO(2), N(2)H(4) or NaBH(4) reductants.