Synthesis of 4-Aryl-2-pyrrolidones and β-Aryl-γ-amino-butyric Acid (GABA) Analogues by Heck Arylation of 3-Pyrrolines with Arenediazonium Tetrafluoroborates. Synthesis of (±)-Rolipram on a Multigram Scale and Chromatographic Resolution by Semipreparative Chiral Simulated Moving Bed Chromatography

Enantioselective synthesis of β-aryl-γ-lactam derivatives via Heck-Matsuda desymmetrization of N-protected 2,5-dihydro-1H-pyrroles

We report herein an enantioselective palladium-catalyzed Heck-Matsuda reaction for the desymmetrization of N-protected 2,5-dihydro-1H-pyrroles with aryldiazonium salts, using the chiral N,N-ligand (S)-PyraBox. This strategy has allowed straightforward access to a diversity of 4-aryl-γ-lactams via Heck arylation followed by a sequential Jones oxidation. The overall method displays a broad scope and good enantioselectivity, favoring the (R) enantiomer. The applicability of the protocol is highlighted by the efficient enantioselective syntheses of the selective phosphodiesterase-4-inhibitor rolipram and the commercial drug baclofen as hydrochloride.

[2+2] Cyclo-Addition Reactions for Efficient Polymerization on a HOPG Surface at Ambient Conditions

Polymers obtained by on-surface chemistry have emerged as a class of promising materials. Here, we propose a new strategy to obtain self-assembled 1D polymers by using photochemical [2+2] cyclo-addition or by using a mild thermal annealing. All nanostructures are fully characterized by using scanning tunneling microscopy at ambient conditions on a graphite surface. We demonstrated that nature of the stimulus strongly alters the overall quality of the resulting polymers in terms of length and number of defects. This new way is an efficient method to elaborate on-surface self-assembled 1D polymers.

Samarium(II)-Electrocatalyzed Chemoselective Reductive Alkoxylation of Phthalimides

The unprecedented samarium-eletrocatalyzed reductive alkoxylation of phthalimides in a single step is presented. Under mild conditions, using electrogenerated Sm(II) with TMSCl (trimethyl chlorosilane), N-substituted 3-alkoxyl isoindolin-1-ones are isolated in good...

Metal-mediated synthesis of pyrrolines

The five-membered, nitrogen-containing pyrroline ring is a privileged structure. This ring is present in many bioactive compounds from natural sources. Pyrrolines-the dihydro derivatives of pyrroles-have three structural isomer classes, depending on the location of the double bond: 1-pyrrolines (3,4-dihydro-2H-pyrroles), 2-pyrrolines (2,3-dihydro-1H-pyrroles) and 3-pyrrolines (2,5-dihydro-1H-pyrroles). This review aims to describe the latest advances for the synthesis of pyrrolines by transition metal-catalyzed cyclizations. Only reactions in which the pyrroline ring is formed by metal promotion are described. Transformations of the pyrroline ring in other heterocycles, and the structural manipulations of the pyrroline itself are not discussed. The review is organized into three parts, each covering the metal-mediated synthesis of the three pyrroline isomers. Each part is subdivided according to the metal involved, and concludes with a brief description of notable biological activities within the class.

Synthesis of 3-Substituted Pyrrolidines via Palladium-Catalyzed Hydroarylation

Metal-catalyzed reactions have revolutionized synthetic chemistry, allowing access to unprecedented molecular architectures with powerful properties and activities. Nonetheless, some transformations remain sparse in number, or out of reach, even with the diverse modern catalytic chemical arsenal, including bimolecular alkene hydroarylation reactions. We report here a broad-scope, palladium-catalyzed pyrroline hydroarylation process that gives 3-aryl pyrrolidines, a class of small molecules with potency in a diverse range of biological scenarios. Thus, whereas N-acyl pyrrolines usually undergo palladium-catalyzed arylation to give alkene products, the corresponding reactions of N-alkyl pyrrolines deliver products of hydroarylation, pyrrolidines. The process has broad substrate scope and can be used to directly deliver drug-like molecules in a single step from readily available precursors.

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Pyrrolines undergo hydroarylation in palladium-catalyzed processes

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The process allows facile catalytic entry to molecules with potent biological activity

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The reaction has broad scope in arylating agents

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Enables efficient manufacture of drug-like molecules from readily available precursors

Silver-catalysed tandem hydroamination and cyclization of 2-trifluoromethyl-1,3-enynes with primary amines: modular entry to 4-trifluoromethyl-3-pyrrolines

A highly efficient AgNO₃-catalyzed tandem intermolecular hydroamination and cyclization reaction of 2-trifluoromethyl-1,3-enynes with primary amines leading to 4-trifluoromethyl-3-pyrrolines under mild conditions was developed.

Acetaldehyde in asymmetric organocatalytic transformations

This review summarize both the recent developments in the organocatalysed use of acetaldehyde as a substrate in various organic transformations and its application in the synthesis of bioactive molecules.

Total syntheses of (±)-musellarins A–C

The first, diastereoselective total syntheses of musellarins A–C were achieved concisely with 7.8–9.8% yields in 15–16 steps, featuring (i) Achmatowicz rearrangement, Kishi reduction, and Friedel–Crafts cyclization to construct the tricyclic framework and (ii) Heck coupling of aryldiazonium salts to introduce the aryl group into the dihydropyran in a 2,6-trans fashion.

Synthesis of single-enantiomer bioactive molecules: a brief overview

Chiral-center enantiomers have been shown to differ significantly in biological activity, pharmacodynamics, pharmacokinetics and toxicity. New developments in the stereoselective organic synthesis have enriched the vast literature of synthetic methodologies applicable to access natural products as well as bioactive molecules. These compounds also include new drugs, drug candidates and reagents used to explore biological processes. The article reviews the synthesis of optically pure drugs, biologically active intermediates and amino alcohols by using different methods.

Pd-catalyzed arylation reactions with phenol diazonium salts: application in the synthesis of diarylheptanoids

The first total synthesis of the natural product (3S,7R)-5,6-dehydro-de-O-methyl centrolobine and various analogues is reported, using a highly regio- and diastereoselective Mizoroki-Heck reaction of phenol diazonium salts and enantiopure dihydropyrans. The assigned relative configuration was confirmed by single-crystal X-ray structure analysis, but a revision of the absolute configuration is proposed based on polarimetric measurement.

Room-temperature, ligand- and base-free Heck reactions of aryl diazonium salts at low palladium loading: sustainable preparation of substituted stilbene derivatives

The Pd(OAc)(2)-catalyzed Heck reaction of aryl diazonium salts with 2-arylacrylates led to cis-stilbenes with good to excellent stereoselectivity. The environmentally friendly protocol developed in this work features low palladium loading in technical-grade methanol at room temperature under base-, additive-, and ligand-free conditions. The same protocol applied to simple Heck coupling of aryl diazonium salts with methyl acrylate allows astonishingly low palladium loading, down to 0.005 mol%. The stereoselectivity experimentally observed for the synthesis of cis-stilbenes has been rationalized by DFT calculations. Moreover, the role of methanol in promoting the reaction has been clarified by a computational study.