Diastereofacial selectivity of the cycloaddition of diazo compounds to enones
作者:G Galley、M Pätzel、P.G Jones
DOI:10.1016/0040-4020(94)01049-6
日期:1995.2
Chiral α,β-unsaturated γ-alkoxy- or γ-amino-ketones (enones) 1 react with diazocompounds in a stereoselective manner affording conjugated Δ2-pyrazolines 5 and 6. In all cases syn-selectivity for the cycloaddition was observed. The diastereomeric ratio is improved at lower temperatures, but no significant influence of high pressure is observed. Carrying out this reaction with (E) and (Z) derivatives
Polyfunctionalized Pyrrolidines by Stereoselective 1,3-Dipolar Cycloaddition of Azomethine Ylides to Chiral Enones
作者:Guido Galley、Juergen Liebscher、Michael Paetzel
DOI:10.1021/jo00121a019
日期:1995.8
The cycloaddition reactions of chiral alpha,beta-unsaturated ketones substituted by alkoxy or amino groups in the gamma-position to azomethine ylides (obtained from glycine imines) were investigated in the presence of a base, LiBr and AgOAc. High regioselectivities were observed in most cases, resulting in the formation of a single diastereomer, particularly if a DBU/AgOAc catalyst system was employed. The influence of reaction conditions and olefin structure on the stereoselectivity of the reaction was investigated, and models rationalizing stereocontrol are proposed. In addition, an interesting deconjugation reaction of acetals derived from gamma,delta-dihydroxy alpha,beta-unsaturated enones or esters is described.