Silver complexes aziridines

Silver has three synthetically useful oxidation states Ag(I), Ag(II), and Ag(III).16 Free Ag(III) is very unstable, and most currently known Ag(III) complexes are stablized with electron-donating and/or sterically demanding ligands.17 It is known that Ag(I) can be oxidized to Ag(II) with strong oxidants such as persulfates. Nitrogen-based ligands such as pyridines are commonly used to stabilize high-valence metal ions.18 In 2003, He and coworkers utilized a pyridine-supported silver catalyst and reported the first silver-catalyzed aziridination of olefins.19... 

After successful application of the silver catalyst shown in olefin aziridination (Section 6.1.1), He and coworkers showed that intramolecular amidation was possible with both hydrocarbon-tethered carbamates and sulfamate esters.24 They found that only the Bu3tpy silver complex could catalyze efficient intramolecular amidation, while other pyridine ligands gave either dramatically lower yields or complicated product mixtures. In an interesting control study, both copper and gold were also tested in this reaction. Both the copper and gold Bu tpy complexes can mediate olefin aziridination, but only silver can catalyze intramolecular C-H amidation, indicating that the silver catalyst forms a more reactive metal nitrene intermediate. 

Addition of an excess of anhydrous aziridine to silver chloride resulted in dissolution and the formation of a colourless solution. Attempts to isolate a complex were unsuccessful and addition of water, ethanol or ether caused reprecipitation of silver chloride. 

In the presence of a range of metal ions, including Ag1, aziridine was found to dimerize to l-(2-aminoethyl)aziridine (equation 4). A bis complex of this ligand was isolated as the silver nitrate salt. Characteristic JHNMR spectral data are given in Table 10.55... 

Table 10 HNMR Spectral Data for l-(2-Aininoethyl)aziridine and its Silver(I) Complex (p.p.m.)ss...

Synthesis of chiral SES aziridines was also performed by using a chiral nitridomanganese complex activated by silver salt and SES-Cl (3) (eq 26 and Table 6). Like that for the sulfonyl-iminoiodinane process, this reaction proceeds via nitrogen atom... 

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