Expedient Organocatalytic Syntheses of 4-Substituted Pyrazolidines and Isoxazolidines.

The efficient organocatalytic synthesis of heterocyclic systems of biological relevance is a subject of growing interest. We have found that the pyrrolidine/benzoic acid-catalyzed reaction of α-substituted propenals such as methacrolein, 2-benzylpropenal and 2-(-hexyl)propenal with activated hydrazines takes place in very good yields (83%-99.6%) under very mild conditions to afford 4-substituted pyrazolidin-3-ols (as diastereomer mixtures); subsequent oxidation with PCC affords the corresponding-4-substituted-3-pyrazolidinones in essentially quantitative yields.

(2E,2'E)-1,1'-Bis(6-chloro-2-methyl-4-phenyl-quinolin-3-yl)-3,3'-(1,4-phenyl-ene)diprop-2-en-1-one ethyl acetate disolvate.

In the title solvate, C44H30Cl2N2O2·2C4H8O2, the complete polycyclic mol-ecule is generated by inversion symmetry. The dihedral angle between the quinolyl ring system (Q; r.m.