New pathway to pyrrolidinones and pyrrolizidinones using aryl aldehydes, 3-phenyl-5-isoxazolone and secondary amino acids

High diastereoselective amine-catalyzed Knoevenagel-Michael-cyclization-ring-opening cascade between aldehydes, 3-arylisoxazol-5(4H)-ones and 3-aminocyclohex-2-en-1-ones

A highly diastereoselective three-component cascade reaction among aromatic aldehydes, 3-arylisoxazol-5(4H)-ones and 3-aminocyclohex-2-en-1-ones takes place under the catalysis of triethylamine, providing (3SR,4SR)-4-aryl-3-[(E)-(hydroxyimino)(aryl)methyl]-4,6,7,8-tetrahydroquinoline-2,5(1H,3H)-diones in 45-85% yields. The transformation presumably proceeds through a sequential cascade of Knoevenagel/Michael-addition/cyclization/ring-opening reactions. This process was carried out in green media (EtOH/water, 1:1-1:3) at reflux. Products are crystallized directly from the reaction mixture and their isolation includes only filtration. The structure of (3SR,4SR)-3-[(E)-(hydroxyimino)(phenyl)methyl]-7,7-dimethyl-4-phenyl-4,6,7,8-tetrahydroquinoline-2,5(1H,3H)-dione was confirmed by X-ray diffraction analysis.

A synthetic route towards 3,4-disubstituted pyrrolidin-2-ones via a Michael addition and reductive ring closing strategy

2-Pyrrolidinone scaffolds with a wide range of substituents were synthesized with good yield and diastereoselectivity.

Asymmetric synthesis of functionalized pyrrolizidines by an organocatalytic and pot-economy strategy

An enantioselective synthesis of indolizidines was achieved with a one-step purification by sequential asymmetric Michael–oxidative esterification–Michael–reduction–reductive Mannich–amidation reactions.