An Entry to a Chiral Dihydropyrazole Scaffold: Enantioselective [3 + 2] Cycloaddition of Nitrile Imines
摘要:
We have developed a versatile strategy to access dihydropyrazoles in highly enantioenriched form. Dipolar cycloaddition of electron-deficient acceptors and in situ-generated nitrile imines proceeds with high regio- and enantioselectivity using 10 mol % chiral Lewis acid catalyst. A variety of dihydropyrazoles that incorporate functionality for further manipulation have been prepared.
An Entry to a Chiral Dihydropyrazole Scaffold: Enantioselective [3 + 2] Cycloaddition of Nitrile Imines
摘要:
We have developed a versatile strategy to access dihydropyrazoles in highly enantioenriched form. Dipolar cycloaddition of electron-deficient acceptors and in situ-generated nitrile imines proceeds with high regio- and enantioselectivity using 10 mol % chiral Lewis acid catalyst. A variety of dihydropyrazoles that incorporate functionality for further manipulation have been prepared.
Enantioselective 1,3-Dipolar Cycloaddition of Nitrile Imines to α-Substituted and α,β-Disubstituted α,β-Unsaturated Carbonyl Substrates: A Method for Synthesizing Dihydropyrazoles Bearing a Chiral Quaternary Center
作者:Mukund P. Sibi、Levi M. Stanley、Takahiro Soeta
DOI:10.1002/adsc.200600307
日期:2006.11
Dihydropyrazoles bearing a chiral quaternary center at the 5-position have been prepared by enantioselective1,3-dipolarcycloaddition of nitrile imines to α-substituted- and α,β-disubstituted-α,β-unsaturated carbonyl substrates. Use of α,β-unsaturated carbonyl substrates with a 1-benzyl-5,5-dimethylpyrazolidin-3-one auxiliary in conjunction with MgI2 and a bisoxazoline ligand derived from (1R,2S)-(+