期刊
JOURNAL OF ORGANIC CHEMISTRY
卷 71, 期 24, 页码 9144-9152出版社
AMER CHEMICAL SOC
DOI: 10.1021/jo061537j
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资金
- NHLBI NIH HHS [R01 HL025854-25, R01 HL025854, HL25854] Funding Source: Medline
- NIGMS NIH HHS [F32 GM073312, GM073312] Funding Source: Medline
The reaction of alkene-tethered R-ketocarboxylic acid derivatives with monosubstituted hydrazines allows highly substituted cis-cyclopentapyrazolidine ring systems 4 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 reflect not only the reactivity and equilibrium concentration of the azomethine imine intermediate, but, also in some cases, the rate at which hydrazone stereoisomers interconvert under the reaction conditions.
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