Role of Configuration at C6 in Catalytic Activity of l-Proline-Derived Bifunctional Organocatalysts

Asymmetric synthesis of (R)-baclofen and (3S,4S)-tetflupyrolimet via "on water" organocatalytic addition reactions: a tip on catalyst screening

This work demonstrates asymmetric synthesis of the GABA derivative (R)-baclofen and a new herbicidal mode-of-action inhibitor (3S,4S)-tetflupyrolimet featuring low loading (0.5 mol%) organocatalytic addition reactions of dithiomalonates to nitrostyrenes under "on water" conditions. Importantly, we observed that increasing the hydrophobicity of the catalyst does not guarantee improved catalytic performance under "on water" conditions and the trends in the catalytic efficiency of different HBD catalysts under "on water" conditions (with hydrophobic additives) align more closely with those observed in pure hydrophobic organic solvents. These findings propose a valuable tip for screening organocatalysts in developing asymmetric hydrogen-bonding catalysis under "on water" conditions.

Access to 2-pyridinones comprising enaminonitriles via AgOAc promoted cascade reactions of thioesters with aminomethylene malononitriles

The facile synthesis of 2-pyridinones containing enaminonitriles from thioesters with aminomethylene malononitriles is achieved through an AgOAc-promoted acylation/cyclization/tautomerization cascade reaction. Control experiments reveal that AgOAc acts as a versatile promoter, activating both thioester and cyano groups while also serving as a Brønsted base in the cascade sequence. Moreover, 2-pyridinones were transformed into biologically significant 2-pyridinone-fused 2-pyrimidones with intriguing fluorescence emission properties.

Enantio- and Diastereoselective Michael Addition of Cyclic Ketones/Aldehydes to Nitroolefins in Water as Catalyzed by Proline-Derived Bifunctional Organocatalysts

New l-proline-derived bifunctional secondary amine organocatalysts were synthesized for enantioselective Michael reactions in water as a solvent. Application of these catalysts in Michael additions provided high yield (up to 97%) with high stereoselectivity (dr up to 99:1 and ee up to 99%). The effect of phenyl group at (R)-C₆ in the catalyst was investigated and played a key role in successful catalysis by density functional theory computational calculations. The synthetic utility of this reaction was demonstrated by the formal synthesis of Sch 50971, which is a novel histamine H₃ receptor agonist.

Highly enantioselective one-pot sequential synthesis of valerolactones and pyrazolones bearing all-carbon quaternary stereocentres

Highly enantiopure and bioactive δ-valerolactones and pyrazolones, bearing α-all-carbon quaternary stereocentres, were successfully and sequentially prepared via a one-pot procedure starting from readily available, inexpensive materials, catalysed by a new chiral squaramide under mild reaction conditions. An organocatalytic Michael reaction afforded the valerolactones, while a one-pot Michael-hydrazinolysis-imidization cascade yielded the pyrazolones. This procedure is economically efficient and environmentally benign.

Recent advances in reactions promoted by amino acids and oligopeptides

During the last 20 years, Organocatalysis has become one of the major fields of Catalysis. Herein, we provide a recent overview on reactions where the use of amino acids and peptides as the organocatalysts was employed. All aspects regarding aldol reactions, Michael reactions, epoxidation, Henry reactions and many others that are crucial for the reaction conditions and reaction mechanisms are discussed.

Catalytic 1,2-Rearrangements: Organocatalyzed Michael/Semi-Pinacol-like Rearrangement Cascade of 1,3-Diones and Nitroolefins

New types of organocatalytic 1,2-rearrangements, which resemble the Smiles-like or semi-pinacol-like rearrangement, of Michael adducts of 1,3-dicarbonyl-2-alkyl compounds and nitroalkenes have been realized. Unlike the well-known conjugate addition, the reaction affords the 1-phenyl-1-nitroalkanes via unprecedented rearrangement and cascade reactions. Structures of the appropriate products were unambiguously characterized by X-ray crystallography.

Catalytically Active Imine-based Covalent Organic Frameworks for Detoxification of Nerve Agent Simulants in Aqueous Media

A series of imine-based covalent organic frameworks decorated in their cavities with different alkynyl, pyrrolidine, and N-methylpyrrolidine functional groups have been synthetized. These materials exhibit catalytic activity in aqueous media for the hydrolytic detoxification of nerve agents, as exemplified with nerve gas simulant diisopropylfluorophosphate (DIFP). These preliminary results suggest imine-based covalent organic frameworks (COFs) as promising materials for detoxification of highly toxic molecules.