Enantioselective Ag(I)-catalyzed [3+2] cycloaddition of azomethine ylides using a chiral ferrocene-based phosphine–phosphoramidite ligand having a stereogenic P-center
摘要:
A series of chiral ferrocene-based phosphine-phosphoramidite ligands (PPFAPhos) have been employed in the Ag(I)-catalyzed asymmetric [3+2] cycloaddition of azomethine ylides with dimethyl maleate. The results showed that the ligand with a stereogenic P-center in the phosphino moiety displayed the best diastereo- and enantioselectivities, in which LIP to 99% enantiomeric excesses and 99/1 endo/exo selectivities have been achieved. (C) 2009 Elsevier Ltd. All rights reserved.
Asymmetric Construction of Pyrrolidines Bearing a Trifluoromethylated Quaternary Stereogenic Center via Cu<sup>I</sup>
-Catalyzed 1,3-Dipolar Cycloaddition of Azomethine Ylides with β-CF<sub>3</sub>
-β,β-Disubstituted Nitroalkenes
convenient method has been developed for the synthesis of opticallyactivepyrrolidines bearing a quaternary stereogenic center containing a CF3 group at the C‐3 position of the pyrrolidine ring. The synthesis system, CuI/Si‐FOXAP‐catalyzed exo‐selective 1,3‐dipolar cycloaddition of azomethine ylides with β‐CF3‐β,β‐disubstituted nitroalkenes, provides pyrrolidines with high diastereoselectivities (up to
Tetrasubstituted N−H pyrroles were accessed through the tandem copper(II)-catalyzed 1,3-dipolarcycloaddition of α,β-ynones and glycine iminoesters, followed by a copper(II)-promoted oxidative dehydrogenative aromatization reaction in air. Fully substituted pyrroles could then be obtained by N-alkylation.