Copper complexes with N-alkylated NS ₂-macrocyclic ligands: Synthesis, characterization, and capabilities as aziridination precatalysts

The syntheses of two new ligands containing macrocyclic [10]-aneNS ₂ (1-aza-4,8-dithiacyclodecane) units are reported, including the N-methylated analogue (L ^Me) and a dinucleating version that separates two [10]-aneNS ₂ groups with a m-xylyl spacer (L ²). Copper complexes with these new ligands as well as previously reported related complexes have been found to mediate the aziridination of olefins. Thus, isolated copper complexes containing the ethylnaphthyl-appended [10]-aneNS ₂ macrocyclic ligand (L ^nap), including [L ^napCu]PF ₆ (1) and [L ^napCu(CH ₃CN)]PF ₆ (2), the Cu(I) complex [L ^MaCu(CH ₃CN)]PF ₆ (3), and the Cu(II) complex L ^MeCuBr ₂ (4), were compared in their ability to function as aziridination precatalysts. In addition, the aziridination capabilities were probed for complexes generated in situ from copper(I) ion sources and L ², 1,4,7-triazacyclononane, 1,4,7-trithiacyclononane, or 1,4,7-trimethyl-1,4,7-triazacyclononane. The synthesis and characterization of the new complexes 3 and 4 are reported, including X-ray crystal structures. The aziridination reaction using precatalyst 3 was examined for its tolerance to different functional groups near the olefin as well as to the use of other nitrogen group sources and reaction conditions.