Desymmetrization ofmeso-N-Sulfonylaziridines with Chiral Nonracemic Nucleophiles and Bases

The cyclohexene-derived aziridine 7-tosyl-7-azabicyclo[4.1.0]heptane (1) reacts with Grignard reagents in the presence of chiral nonracemic Cu-catalysts to afford sulfonamides 3a – e (Scheme 3) in up to 91% ee under optimized conditions (Table 2). No activation of the aziridine by Lewis acids is required. The reaction may be extended to other bicyclic N-sulfonylated aziridines, but aziridines derived from acyclic olefins, cyclooctene, and trinorbornene are unreactive under standard conditions (Scheme 5). Exposure of 1 to s-BuLi in the presence of (−)-sparteine (2.8 equiv.) affords the allylic sulfonamide 31 in 35% yield and 39% ee (Scheme 6). Under the same conditions, the aziridines 33 and 35 yield products 34 and 36 derived from intramolecular carbenoid insertion with 75 and 43% ee, respectively.