307310-77-6Relevant articles and documents
Solvent- and temperature-dependent functionalisation of enantioenriched aziridines
De Ceglie, Maria Carolina,Musio, Biagia,Affortunato, Francesco,Moliterni, Anna,Altomare, Angela,Florio, Saverio,Luisi, Renzo
scheme or table, p. 286 - 296 (2011/02/27)
A highly stereo- and regioselective functionalisation of chiral non-racemic aziridines is reported. By starting from a parent enantioenriched aziridine and finely tuning the reaction conditions, it is possible to address the regio- and stereoselectivity of the lithiation/electrophile trapping sequence, thereby allowing the preparation of highly enantioenriched functionalised aziridines. From chiral N-alkyl trans-2,3-diphenylaziridines (S,S)-1 a,b, two differently configured chiral aziridinyllithiums could be generated (trans-1 a,b-Li in toluene and cis-1 a,b-Li in THF), thus disclosing a solvent-dependent reactivity that is useful for the synthesis of chiral tri-substituted aziridines with different stereochemistry. In contrast, chiral aziridine (S,S)-1 c showed a temperature-dependent reactivity to give chiral ortho-lithiated aziridine 1 c-ortho-Li at -78 °C and α-lithiated aziridine 1 c-α-Li at 0 °C. Both lithiated intermediates react with electrophiles to give enantioenriched ortho- and α-functionalised aziridines. The reaction of all the lithiated aziridines with carbonyl compounds furnished useful chiral hydroxyalkylated derivatives, the stereochemistry of which was ascertained by X-ray and NMR spectroscopic analysis. The usefulness of chiral non-racemic functionalised aziridines has been demonstrated by reductive ring-opening reactions furnishing chiral amines that bear quaternary stereogenic centres and chiral 1,2-, 1,3- and 1,5-aminoalcohols. It is remarkable that the solvent-dependent reactivity observed with (S,S)-1 a,b permits the preparation of both the enantiomers of amines (11 and ent-11) and 1,2-aminoalcohols (13 and ent-13) starting from the same parent aziridine. Interestingly, for the first time, a configurationally stable chiral α-lithiated aziridine (1 c-α-Li) has been generated at 0 °C. In addition, ortho- hydroxyalkylated aziridines have been easily converted into chiral aminoalkyl phthalans, which are useful building blocks in medicinal chemistry.
α- vs ortho-lithiation of N-alkylarylaziridines: Probing the role of the nitrogen inversion process
Affortunato, Francesco,Florio, Saverio,Luisi, Renzo,Musio, Biagia
supporting information; experimental part, p. 9214 - 9220 (2009/04/06)
(Chemical Equation Presented) The lithiation reaction of monophenyl- and diphenylaziridines has been investigated in detail in an effort to understand why the former undergo exclusively or mainly ortho-lithiation while the latter are lithiated exclusively at the α-position. Evidence is reported that ruled out the possibility that the α-lithiation, observed for the diphenylaziridines, is the result of an ortho- to α-translocation phenomenon, thus substantiating a direct α-deprotonation process. The role of the aziridine nitrogen lone-pair has been considered: dynamics at the aziridine nitrogen as well as complex-induced proximity effects seem to be responsible for the observed regioselectivity in both monophenyl and diphenylaziridines. It turns out that, by tuning the reaction conditions for the lithiation of trans-1-alkyl-2-methyl-3-phenylaziridines, it is possible to generate with high regioselectivity α- and/or ortho-lithiated aziridines, which can be stereoselectively functionalized by electrophilic trapping. A regioselective ortho-functionalization of diphenylaziridines is made possible by halogen- or tin-lithium exchange and by deprotonation of bis-deuterated aziridines.
Dual reaction pathways in the magnesium-mediated synthesis of aziridines from benzal halides and imines
Biscoe, Mark R.,Fry, Albert J.
, p. 2759 - 2762 (2007/10/03)
Reaction between benzal dihalides, benzaldehyde imines, and magnesium in ether affords aziridines in modest yields. Two mechanistic pathways for aziridine formation are discerned. One path involves nucleophilic attack by an alpha-halo Grignard species on
