Chiral Thiophosphoramidate-Catalyzed Asymmetric Michael Addition of Ketones to Nitro Olefins

One-pot synthesis of 1,5-diketones from 3-acetyl-4-hydroxycoumarin and effective cyclization to unexpected 3,4-dihydropyridines

A facile synthesis of 1,5-diketones from 3-acetyl-4-hydroxycoumarin, aldehydes and cyclic-ketones via a one-pot aldol condensation and subsequent Michael addition reaction in the presence of a single catalyst of l-proline under mild reaction conditions has been developed. Novel 1,5-diketones were further cyclized to unexpected 3,4-dihydropyridines rather than generally formed pyridine analogues with ammonium acetate in acetic acid. One pot, high yields (72-92%) for novel 1,5-diketones and (70-90%) for the 3,4-dihydropyridine adducts, easy work-up and purification of products are the key advantages of this method.

4-Fluoro and 4-Hydroxy Pyrrolidine-thioxotetrahydropyrimidinones: Organocatalysts for Green Asymmetric Transformations in Brine

The synthesis of both trans- and cis-diastereomers of pyrrolidinine-thioxotetrahydropyrimidinone bearing either a fluorine or a hydroxyl group was accomplished. The new compounds were tested for their catalytic properties in a variety of asymmetric organic transformations and compared with the first generation catalyst. It was found that the new catalysts could efficiently catalyze the reactions in brine, without the use of organic solvent, and by employing an almost stoichiometric amount of reagents. Thus, the products were isolated by simple extractions, avoiding the use of chromatography in excellent yields, diastereoselectivities, and enantioselectivities.

Organocatalytic asymmetric Michael addition of aldehydes and ketones to nitroalkenes catalyzed by adamantoyl l-prolinamide

A series of adamantoyl l-prolinamides have been synthesized.

Peptidomimetic organocatalysts: efficient Michael addition of ketones onto nitroolefins with very low catalyst loading

The syntheses and applications of peptidomimetic triazole-based catalysts are described as efficient organocatalysts in Michael reaction with low loading.

Hydrogen-bonding in aminocatalysis: from proline and beyond

This Concept article summarizes recent progress in the field of hydrogen-bonding aminocatalysis using proline-derived systems. The aminocatalysts available in the literature are categorized by the incorporated hydrogen-bonding scaffold and its mode of recognition. Both mono- and double-hydrogen-bonding motifs are discussed and examples of their application in asymmetric synthesis are given.

(2S,4S)-2-[(S,E)-2-Bromo-1-nitromethyl-3-phenylallyl]-4-methylcyclohexanone

The crystal structure of the title compoud, C₁₇H₂₀BrNO₃, contains three chiral centers, which all exhibit an S configuration. The C=C double bond has an E conformation. The cyclo­hexane ring is in a chair conformation. In the crystal, mol­ecules are linked by weak N—O⋯Br inter­actions [O⋯Br = 3.136 (4) Å].