Copper-catalyzed [3 + 2 + 1] annulation for functionalized pyridines as potent and dynamic UV absorbers

A novel synthesis of functionalized pyridines via copper-catalyzed [3 + 2 + 1] annulation for the development of potent UV absorbers is described.

Brønsted acid-catalyzed formal [5+2+1] cycloaddition of ynamides and isoxazoles with water: access to oxygen-bridged tetrahydro-1,4-oxazepines

The unique property of the Brønsted acid, as well as introducing a small amount of water, shows distinct chemoselectivity from the corresponding gold-catalyzed cycloadditions.

Ring-opening and cyclization of aziridines with aryl azides: metal-free synthesis of 6-(triflyloxy)quinolines

A metal-free synthesis of 6-(triflyloxy)quinolines has been developed via the ring-opening and cyclization of 2-aryl-1-tosylaziridines with 2-azidobenzaldehydes in the presence of TfOH.

Cu-Catalyzed switchable synthesis of functionalized pyridines and pyrroles

A switchable synthesis of functionalized pyridines and pyrroles via Cu-catalyzed cascade reactions with N-sulfonyl azadienes and alkynes.

Copper-Catalyzed [2+2+2] Modular Synthesis of Multisubstituted Pyridines: Alkenylation of Nitriles with Vinyliodonium Salts

A [2+2+2] modular synthesis of multisubstituted pyridines, with excellent regioselectivity, has been realized by copper catalysisand involves three distinct components: vinyliodonium salts, nitriles, and alkynes. The reactions proceeded with the facile formation of an aza-butadienylium intermediate by alkenylation of the nitrile with a vinyliodonium salt. Moreover, the alkynes in the reaction were extended to alkenes, which are an advantage of expense and relative scarceness of alkynes.

A Straightforward Access to Stable, 16 Valence-electron Phosphine-Stabilized Fe0 Olefin Complexes and their Reactivity

The use of the dialkene divinyltetramethyldisiloxane (dvtms) allows easy access to the reactive 16 valence-electron complexes [Fe⁰(L-L)(dvtms)], (L-L) = dppe (1,2-bis(diphenylphosphino)ethane), (1), dppp (1,2-bis(diisopropylphosphino)propane), (2), pyNMeP(ⁱPr)₂ (N-(diisopropylphosphino)-N-methylpyridin-2-amine), (4), dipe (1,2-bis(diisopropylphosphino)ethane), (5), and [Fe⁰(L)₂(dvtms)], L = PMe₃, (3), by a mild reductive route using AlEt₂(OEt) as reducing agent. In contrast, by the same methodology, the 18 valence-electron complexes [Fe⁰(L-L)₂(ethylene)], (L-L) = dppm (1,2-bis(diphenylphosphino)methane), 6, (L-L) = dppa (1,2-bis(diphenylphosphino)amine) 7 or (L-L)=dppe, 8, were obtained, which do not contain dvtms. In addition, a combined DFT and solid-state paramagnetic NMR methodology is introduced for the structure determination of 5. A comparative study of the reactivity of 1,2,4-6 and 8 with 3-hexyne highlights emerging mechanistic implications for C-C coupling reactions using these complexes as catalysts.

Solvent-free ruthenium trichloride-mediated [2 + 2 + 2] cycloaddition of α,ω-diynes and cyanamides: a convenient access to 2-aminopyridines

A convenient access to functionalized 2-aminopyridinesviaa solventless Ru-catalyzed [2 + 2 + 2] cycloaddition reaction of α,ω-diynes and cyanamides is described.

Silver-catalyzed cyclization of nitrones with 2-azetine: a radical approach to 2,3-disubstituted quinolines

A silver-catalyzed intermolecular cyclization of nitrones with 2-azetine has been developed for the synthesis of 2,3-disubstituted quinolines under mild conditions.

Synthesis of 3-(2-thiopyridyl)indoles via the ruthenium catalyzed [2 + 2 + 2] cycloaddition of diynes and 3-thiocyanatoindoles

A highly efficient protocol for the synthesis of 3-(2-thiopyridyl)indoles via the ruthenium(ii) catalyzed [2 + 2 + 2] cycloaddition reaction of α,ω-diynes with 3-thiocyanatoindoles under mild reaction conditions has been developed.

Transition metal-catalyzed [2 + 2 + 2] cycloaddition of nitrogen-linked 1,6-diynes: a straightforward route to fused pyrrolidine systems

Transition metal-catalyzed [2 + 2 + 2] cycloadditions of nitrogen-linked 1,6-diynes with unsaturated motifs have recently attracted more attention from synthetic organic chemists because of their high efficiency in the construction of numerous pyrrolidine based systems.

Tf2NH-catalyzed formal [3 + 2] cycloaddition of oxadiazolones with ynamides: a simple access to aminoimidazoles

We herein develop a formal [3 + 2] approach to access aminoimidazoles through the Tf₂NH-catalyzed cycloaddition of oxadiazolones with ynamides, in which oxadiazolones are first employed as the three-atom building units.

Facile synthesis of heavily-substituted alkynylpyridines via a Sonogashira approach

A robust synthesis of highly-substituted alkynylpyridines via a Sonogashira approach is described, providing a library of functionalized pyridines for biological studies.

Sulfonamide-directed gold-catalyzed [2+2+2]-cycloadditions of nitriles with two discrete ynamides to construct 2,4-diaminopyridine cores

Gold-catalyzed [2+2+2]-cycloadditions of two discrete ynamides and one nitrile afford 2,4-diaminopyridine derivatives; our mechanistic analysis reveals that the reaction chemoselectivity is affected by the types of sulfonamides.

Preparation of Pd/Fe3O4 nanoparticles by use of Euphorbia stracheyi Boiss root extract: A magnetically recoverable catalyst for one-pot reductive amination of aldehydes at room temperature

We describe a method for supporting palladium nanoparticles on magnetic nanoparticles using Euphorbia stracheyi Boiss root extract as the natural source of reducing and stabilizing agent. The progress of the reaction was monitored using UV-visible spectroscopy. The nanocatalyst was characterized by FE-SEM, TEM, XRD, EDS, FT-IR spectroscopy and ICP. The nanocatalyst was applied as an efficient, magnetically recoverable, highly reusable and heterogeneous catalyst for one-pot reductive amination of aldehydes at room temperature. The nanocatalyst was easily recovered by applying an external magnet and reused several times without considerable loss of activity.

Copper(I)-Y Zeolite-Catalyzed Regio- and Stereoselective [2 + 2 + 2] Cyclotrimerization Cascade: An Atom- and Step-Economical Synthesis of Pyrimido[1,6-a]quinoline

An elegant copper(I)-Y zeolite-catalyzed tandem process, involving ketenimine-based termolecular [2 + 2 + 2]/[NC + CC + NC] cycloaddition, using sulfonyl azide, alkyne, and quinoline, to prepare pyrimido[1,6-a]quinolines is reported. In this straightforward, highly atom- and step-economical protocol, copper(I) promotes for azide-alkyne [3 + 2] cycloaddition which is followed by ring-rearrangement/ketenimine formation/regio- and stereoselective [2 + 2 + 2] termolecular cycloaddition and dehydrogenation cascade to yield selectively the E-isomer of pyrimido[1,6-a]quinoline.

Base-Promoted N-Pyridylation of Heteroarenes Using N-Propargyl Enaminones as Equivalents of Pyridine Scaffolds

N-Pyridylation of various N-heteroarenes, including N-heteroarene-containing peptides, was achieved using N-propargyl enaminones (isolated or generated in situ from propargyl amine and propynones) as masked polysubstituted pyridine cores. This metal-free procedure proceeds under mild reaction conditions and generates 1 equiv of H2O as the sole byproduct.