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2,5‐disubstituted N,N'‐alkylpiperazines represent an interesting target in organic synthesis both for pharmaceutical or agrochemical applications and as a promising class of ligands in coordination chemistry. We report here a microwave‐enhanced synthesis of these compounds starting from non‐activated N‐alkyl aziridines in the presence of catalytic amounts of simple ammonium metallates. A remarkable TOF of 2787.9 h−1 has been observed in the case of [TBA]2[ZnI4] as the catalyst (catalyst loading 0.1 mol %) and with an almost complete selectivity (up to 97 %) in favor of both diastereoisomers (meso and chiral form) of the target 2,5‐disubstituted piperazines, obtained in 1 : 1 ratio. The two isomers are easily separated, because the meso form precipitates in pure from the reaction crude. A stereochemical investigation and the unprecedented isolation of 2,6‐disubstituted N,N'‐alkylpiperazines allowed us to shed light on the reaction mechanism. [ABSTRACT FROM AUTHOR]

An enantioselective phosphine‐catalyzed [3+2] cycloaddition between aza‐aurones and allenoates is here described. The reaction proceeded under mild reaction conditions to afford 2‐spirocyclopentyl indolin‐3‐one derivatives as single γ‐isomer and with high levels of stereocontrol. [ABSTRACT FROM AUTHOR]

The development of alternative benign reaction conditions to perform multicomponent reactions is an interesting and desirable strategy to increase the sustainability of organic synthesis. In this paper, we report a new version of A3‐coupling MCR for the preparation of differently substituted propargylamines starting from aldehydes, alkynes and amines in an acidic DES as reaction media, under dielectric heating, and in the presence of a tetraaza‐macrocyclic silver complex as catalyst. The reaction scope is broad in terms of aldehyde partners. Electron‐rich phenylacetylenes are the more reactive alkynes partners, whereas the nature of the amine is the more serious limitation as only secondary cyclic amines are tolerated. [ABSTRACT FROM AUTHOR]

Research has been conducted on the 2-amino-3-hydroxynorbornene-2-carboxylic acid derivatives. The results of the enantioselective synthesis of these derivatives carried out via the Diels-Alder reaction between cyclopentadiene and various dienophiles are discussed.

The Cover Feature shows the synthesis of substituted indolo[1,2‐a]quinoline‐5(6H)‐ones starting from 1‐(2‐ethynylphenyl)‐1H‐indoles and N‐oxides by a gold‐catalyzed oxidation of the triple bond, followed by an acid‐promoted intramolecular cyclization at the indole C‐2 position. More information can be found in the Research Article by E. Brambilla, V. Pirovano and co‐workers (DOI: 10.1002/ejoc.202400083). Cover design by Dominica Del Grosso...By Elisa Brambilla; Mariaclara Gugiatti; Silvia Rizzato; Giorgio Abbiati and Valentina PirovanoReported by Author; Author; Author; Author; Author [Extracted from the article]

The reaction between epoxides and CO2 to yield cyclic carbonates is efficiently promoted under solvent‐free and relatively mild reaction conditions (0.5 mol % catalyst loading, 0.8 MPa, 125 °C) by zinc(II) complexes of pyridine containing macrocyclic ligands (Pc−L pyridinophanes). The zinc complexes have been fully characterized, including X‐ray structural determination. The [Zn(II)X(Pc−L)]X complexes showed good solubility in several polar solvents, including cyclic carbonates. The scope of the reaction under solvent‐free conditions has been studied and good to quantitative conversions with excellent selectivities have been obtained, starting from terminal epoxides. When solvent‐free conditions were not possible (solid epoxides or low solubility of the catalyst in the oxirane) the use of cyclic carbonates as solvents has been successfully investigated. The remarkable stability of the catalytic system has been demonstrated by a series of consecutive runs. [ABSTRACT FROM AUTHOR]

Spiroindolenines were employed as cyclic imine substrates in formal aza-Diels--Alder reactions with Danishefsky's diene or silyloxy-substituted electron-rich dienes for the synthesis of the corresponding tetrahydropyrido[1,2-α]spiroindolinones. The reactions occur under mild conditions in the presence of ytterbium triflate as Lewis acidic catalyst delivering the desired compounds in good yield. The reaction results in the preparation of a small library of a new class of conformational constrained heterocyclic derivatives that easily undergo selective and efficient manipulations. [ABSTRACT FROM AUTHOR]

The reactivity of vinyl‐/furoindole derivatives with gold‐activated π‐systems is the subject of extensive investigation. In the presence of these electrophilic partners, the realized transformations allow for the construction of different and fascinating architectures via cycloaddition and cyclization reactions often included in cascade processes. The reactions realized involving in these processes an external substituent at the indole moiety are the subject of the present minireview. [ABSTRACT FROM AUTHOR]

A palladium-mediated multicomponent domino reaction leading to 2-aryl-4-amino-quinolines and 2-aryl-4-amino[1,8]naphthyridines is reported. The scope of the reaction was examined using carbon monoxide, two 2-ethynyl-arylamines, four aryl iodides, and 10 primary amines as substrates.

The synthesis of the pyrazinol[1,2-a]indole nucleus was achieved by intramolecular cyclization of several 2-carbonyl-1-propargylindoles in the presence of ammonia. It is indicated that cyclization of 1-alkynylindole-2-carbaldehydes was easily accomplished under standard heating conditions, whereas microwave heating contributed to reduced reaction times and improved overall yields.