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 enantioselective 1,3-dipolar cycloaddition 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)-(+
通过将腈亚胺对映选择性地1,3-偶极环加成到α-取代的和α,β-二取代的α,β-不饱和羰基底物上,制备了在5-位具有手性季中心的二氢吡唑。α,β-不饱和羰基底物与1-苄基5,5-二甲基吡唑烷丁-3-酮助剂与MgI 2和衍生自(1 R,2 S)-(+)-顺式-的双恶唑啉配体一起使用事实证明,1-氨基-2-茚满醇6是获得高对映体选择性(至多99%ee)的手性二氢吡唑的最佳选择。