Details

Autor(en) / Beteiligte

• Dokli, Irena
• Matanović, Ivana
• Hameršak, Zdenko

Titel

Sulfur Ylide Promoted Synthesis of N-Protected Aziridines: A Combined Experimental and Computational Approach

Ist Teil von

• Chemistry : a European journal, 2010-10, Vol.16 (38), p.11744-11752

Ort / Verlag

Weinheim: WILEY-VCH Verlag

Erscheinungsjahr

2010

Link zum Volltext

Quelle

Wiley Online Library - AutoHoldings Journals

Beschreibungen/Notizen

• A range of N‐protected aziridines [N‐Tosyl (N‐Ts), N‐2‐trimethylsilylethanesulfonamide (N‐SES), N‐tert‐butoxycarbonylamido (N‐Boc), and N‐o‐nitrobenzenesulfonamide (oNs)] were prepared in moderate to good yield and with high enantiomeric excess of both isomers starting from N‐protected imines, using a sulfonium salt derived from Eliel’s oxathiane. The diastereoselectivities of the reactions are influenced by the imine N‐protecting group, the imine substituent, and the sulfide structure. An unusual cis selectivity was observed in the formation of N‐tosyl‐2‐phenyl‐3‐tert‐butylaziridine and N‐o‐trimethylsilylethanesulfonamide‐2‐phenyl‐3‐tert‐butylaziridine, which was explained by using computational models. The analysis suggests that betaine formation in the case of N‐tosyl‐tert‐butylaldimine aziridination using oxathiane benzyl sulfonium ylide 1′ is reversible and that the selectivity is determined at the rotation step, which is unusual for semistabilized ylide aziridination. We have shown herein that the steric bulk of an imine substituent, in combination with a sterically demanding sulfonium ylide, can also affect the reversibility of the reaction. This is the first example of this sort involving aziridinations using semistabilized ylides. Selectivity explained: A range of N‐protected aziridines were prepared in moderate to good yield and with high enantiomeric excess (ee) of both isomers from N‐protected imines by using an oxathiane benzyl sulfonium salt (see scheme; Tf=triflate). An unusual cis selectivity was observed in the formation of tert‐butyl‐substituted aziridines and was explained by using computational investigations.