Highly stereoselective aziridine ring-opening with phenylselenide anion and selective intramolecular aldol closure for the enantiopure synthesis of γ-aminocyclopentene derivatives

Synthesis of β-Fluoroamines by Lewis Base Catalyzed Hydrofluorination of Aziridines

“…These diastereomers could be separated by standard column chromatography on SiO 2 , providing the major diastereomer (1 S, 2 S ,1′ S )- 16 in 60% isolated yield and >30:1 dr, as judged by 19 F NMR . The observed sense of diastereoinduction is consistent with literature precedent . Furthermore, the chiral auxiliary was readily cleaved by hydrogenolysis in the presence of Boc 2 O to provide ( S , S )- 2a in 98% yield and 99% ee.…”

“…We selected aziridine 15 , derived from inexpensive ( S )-1-phenylethylamine in two steps, as a model substrate for diastereoselective hydrofluorination (Scheme ). This aziridine has been used for the synthesis of chiral ligands and organocatalysts and provides modest diastereoselectivity in ring-opening reactions with a variety of heteroatomic nucleophiles . Under our standard catalytic conditions, the ring opening of 15 proceeded smoothly to provide a mixture of fluoroamine (1 S ,2 S ) and (1 R ,2 R ) diastereomers with modest selectivity (2.4:1 dr; for additional chiral auxiliaries and reaction conditions, see the Supporting Information).…”

Ring opening reactions of heterocycles with selenium and tellurium nucleophiles

“…Interestingly, this route was also extended to azirizidines, enabling the synthesis of pyrrolidin-3-ones (Scheme 22). 43 An interesting example of the application of selenolates in NRORs is represented by the stereoselective formation of chiral βphenylseleno amine, which was used as starting material to prepare enantiopure γ-aminocyclopentene derivatives (Scheme 23). These compounds represent important intermediates for the synthesis of carbocyclic nucleosides and γ-amino acid analogues.…”

Unexpected Ethyltellurenylation of Epoxides with Elemental Tellurium under Lithium Triethylborohydride Conditions

“…A number of ring-opening-based procedures for the synthesis of hydroxy-and amino-substituted selenides and tellurides have been developed over the last decade [37][38][39][40][41][42]. Such functionalised chalcogenides have also been employed as intermediates for the synthesis of valuable compounds [35,43,44] and as organocatalysts for the asymmetric addition of diethylzinc to aldehydes [45].…”