183184-04-5Relevant 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.
Nucleophilic ring opening of cyclic 1,2-sulfites with nitrogen nucleophiles. A route to enantiopure benzylic amino alcohols
Nymann, Kirsten,Mylvaganam, Saravanapavan,Svendsen, John S.
, p. 1060 - 1063 (2007/10/03)
The reaction between cyclic 1,2-sulfites and two imide and two sulfonamide nucleophiles has been investigated in order to develop a procedure for the enantioselective preparation of N-protected vicinal amino alcohols. The results show that both imide and sulfonamide anions react with cyclic sulfites, yielding the desired products. In some cases the regioselectivities are low, and for the sulfonamides products originating from nucleophilic addition to the sulfite sulfur are observed. Acta Chemica Scandinavica 1998.
Nucleophilic reactions between cyclic 1,2-sulfites and chloride ions
Nymann, Kirsten,Jensen, Linda,Svendsen, John S.
, p. 832 - 841 (2007/10/03)
When cyclic 1,2-sulfites are ring opened by chloride ion, the chlorohydrins are formed with low regio- and stereo-selectivity. The mechanisms involved in the process were investigated by measuring the stereochemical outcome of the reactions. The results showed that reversible inversion pathways (SN2 reactions) and a retention pathway (SN2i reaction) gave rise to the loss in ee in both the chlorohydrins and in the cyclic 1,2-sulfites. Acta Chemica Scandinavica 1996.
