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Double Stereodifferentiation in the Catalytic Asymmetric Aziridination of Imines Prepared from α‐Chiral Amines
Author(s) -
Huang Li,
Zhang Yu,
Staples Richard J.,
Huang Rui H.,
Wulff William D.
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201102520
Subject(s) - diazo , chemistry , amine gas treating , ligand (biochemistry) , catalysis , imine , enantiomer , diastereomer , enantioselective synthesis , organic chemistry , medicinal chemistry , biochemistry , receptor
The catalytic asymmetric aziridination of imines and diazo compounds (AZ reaction) mediated by boroxinate catalysts derived from the VANOL and VAPOL ligands was investigated with chiral imines derived from five different chiral, disubstituted, methyl amines. The strongest matched and mismatched reactions with the two enantiomers of the catalyst were noted with disubstituted methyl amines that had one aromatic and one aliphatic substituent. The synthetic scope for the AZ reaction was examined in detail for α‐methylbenzyl amine for cis ‐aziridines from α‐diazo esters and for trans ‐aziridines from α‐diazo acetamides. Optically pure aziridines could be routinely obtained in good yields and with high diastereoselectivity and the minor diastereomer (if any) could be easily separated. The matched case for cis ‐aziridines involved the ( R )‐amine with the ( S )‐ligand, but curiously, for trans ‐aziridines the matched case involved the ( R )‐amine with the ( R )‐ligand for imines derived from benzaldehyde and n ‐butanal, and the ( R )‐amine with the ( S )‐ligand for imines derived from the bulkier aliphatic aldehydes pivaldehyde and cyclohexane carboxaldehyde.