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(4 H )-ones and 3-aminocyclohex-2-en-1-ones takes place under the catalysis of triethylamine, providing (3 SR ,4 SR )-4-aryl-3-[( E )-(hydroxyimino)(aryl)methyl]-4,6,7,8-tetrahydroquinoline-2,5(1 H ,3 H )-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 (3 SR ,4 SR )-3-[( E )-(hydroxyimino)(phenyl)methyl]-7,7-dimethyl-4-phenyl-4,6,7,8-tetrahydroquinoline-2,5(1 H ,3 H )-dione was confirmed by X-ray diffraction analysis. Graphical Abstract