RESUMO
The Zn(II)/UCD-Imphanol-catalyzed highly endo-selective [3 + 2] asymmetric cycloaddition of acyclic enones and azomethine ylides has been developed. Moderate to high yields (up to 94%) with excellent endo/exo selectivities (99 : 1) and enantioselectivities up to 96.5 : 3.5 er were obtained.
RESUMO
Asymmetric [3+2] cycloaddition reactions are fascinating and powerful methods for the synthesis of enantioenriched pyrrolidines up to four stereocentres. Pyrrolidines are important compounds for both biology and organocatalytic applications. This review summarizes the most recent advances in the enantioselective synthesis of pyrrolidines by [3+2] cycloadditions of azomethine ylides using metal catalysis. It has been organized by the type of metal catalysis used and further arranged by the complexity nature of dipolarophile. The presentation of each reaction type highlights their advantages and limitations.
RESUMO
We present a facile synthetic route toward a novel series of imidazolinyl-[2.2]paracyclophanol (UCD-Imphanol) ligands possessing central and planar chirality. Both sets of diastereomeric ligands were successfully purified by column chromatography. The preliminary application of this family of ligands showed excellent activities in the asymmetric Zn-catalyzed azomethine ylide cycloaddition. Enantioenriched pyrrolidines, in a substrate scope of 20 examples, were accessed in high levels of endo/exo ratios (up to >99/1) and enantioselectivities (up to >99 % ee) with excellent yields (up to 99 %) by using (S,S,SP )-UCD-Imphanol/(S,S,RP )-UCD-Imphanol, respectively.
RESUMO
Expedient synthesis of benzosuberone-tethered spirooxindoles was accomplished by a three-component 1,3-dipolar cycloaddition reaction between azomethine ylide (generated in situ) and arylidene benzosuberone. This protocol offers good yield and wide functional group tolerance under mild reaction condition with high regio- and stereoselectivities.
Assuntos
Compostos Azo/química , Cumarínicos/química , Oxindóis/química , Oxindóis/síntese química , Compostos de Espiro/química , Tiossemicarbazonas/química , Reação de Cicloadição , EstereoisomerismoRESUMO
Sustainable assembly of imidazolidines is accomplished via a sequential stereospecific ring opening and C-H amination using aziridines with secondary cyclic amines under visible light mediated indazoloquinoline photoredox catalysis at ambient conditions. Optically active aziridines are coupled with high enantiomeric purities. The computational studies provide insights on the redox properties of the catalysts as well as a profile of the reaction.
RESUMO
Copper(II)-catalyzed cross-coupling of anilines, methyl arenes, and TMSN3 in the presence of tert-butylhydroperoxide at moderate temperature produced 2-aryl benzimidazoles via a tandem C(sp3/sp2)-H functionalization and C-N bond formations. The selectivity and multiple C-H functionalization of the simple substrates are significant practical features.