857636-40-9Relevant academic research and scientific papers
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
Sibi, Mukund P.,Stanley, Levi M.,Soeta, Takahiro
, p. 2371 - 2375 (2006)
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 l-benzyl-5,5-dimethylpyrazolidin-3-one auxiliary in conjunction with MgI2 and a bisoxazoline ligand derived from (1R,2S)-(+)-cis-1-amino-2-indanol 6 proved optimal to obtain chiral dihydropyrazoles with high enantio-selectivity (up to 99% ee).
Enantioselective 1,3-dipolar cycloadditions of diazoacetates with electron-deficient olefins
Sibi, Mukund P.,Stanley, Levi M.,Soeta, Takahiro
, p. 1553 - 1556 (2008/02/04)
Equation presented A general strategy for highly enantioselective 1,3-dipolar cycloaddition of diazoesters to β-substituted, α-substituted, and α,β-disubstituted α,β-unsaturated pyrazolidinone imides is described. Cycloadditions utilizing less reactive α,β-disubstituted dipolarophiles require elevated reaction temperatures, but still provide the corresponding pyrazolines with excellent enantioselectivities. Finally, an efficient synthesis of (-)-manzacidin A employing this cycloaddition methodology as a key step is illustrated.
