Stereocontrolled synthesis of functionalized cis-cyclopentapyrazolidines by 1,3-dipolar cycloaddition reactions of azomethine imines.

ABSTRACT: The reaction of alkene-tethered alpha-ketocarboxylic acid derivatives with monosubstituted hydrazines allows highly substituted cis-cyclopentapyrazolidine ring systems to be constructed rapidly. Successful cyclocondensations are realized under thermal reaction conditions; in some cases, protic or Lewis acids accelerate these reactions. alpha-Methoxy-alpha,beta-unsaturated esters are suitable alkene components, as are alkenes having either electron-withdrawing or electron-donating substituents at the terminal alkene carbon. alpha-Ketoesters, alpha-ketoamides, and alpha-ketothioesters can be employed. Various hydrazines substituted with N-acyl, N-carboalkoxy, or N-carbamothioyl protecting groups are tolerated in these transformations. The rate of intramolecular cycloaddition is found to refl

SUBMITTER: Gergely J 

PROVIDER: S-EPMC2516743 | biostudies-literature | 2006 Nov

REPOSITORIES: biostudies-literature