The chiral monoaza-15-crown-5 lariat ethers annellated to methyl-4,6-O-benzylidene-α-d-glucopyranoside-1 or mannopyranoside 2 have been applied as phase-transfercatalysts in the epoxidation of substituted chalcones and chalcone analogues with tert-butylhydroperoxide resulting in significant asymmetricinduction. It was found that the position of the substituents in the aromatic ring of the chalcone
Diaryl-2-pyrrolidinemethanols catalyzed enantioselective epoxidation of α,β-enones: new insight into the effect of structural modification of the catalyst on reaction efficiency
作者:Alessandra Lattanzi、Alessio Russo
DOI:10.1016/j.tet.2006.10.005
日期:2006.12
Catalytic enantioselectiveepoxidation of α,β-unsaturated ketones promoted by diaryl-2-pyrrolidinemethanols and tert-butyl hydroperoxide (TBHP) is described. Investigation on structural modifications of the diaryl-2-pyrrolidinemethanols showed that fine tuning of the stereoelectronics of the substituents on the aryl moiety is important to achieve high efficiency. By employing a structurally optimized
We present the first synthesis of air/moisture-stable λ3-bromanes (9 and 10) by using a cyclic 1,2-benzbromoxol-3-one (BBX) strategy. X-ray crystallography and NMR and IR spectroscopy of N-triflylimino-λ3-bromane (12) revealed that the bromine(III) center is effectively stabilized by intramolecular R–Br–O hypervalent bonding. This strategy enables the synthesis of a variety of air-, moisture-, and
Unprecedented Direct Oxygen Atom Transfer from Hypervalent Oxido-λ<sup>3</sup>-iodanes to α,β-Unsaturated Carbonyl Compounds: Synthesis of α,β-Epoxy Carbonyl Compounds
Tetra-n-butylammonium oxido-lambda(3)-iodane, prepared from 1-hydroxy-1,2-benziodoxol-3(1H)-one by reaction with tetra-n-butylammonium fluoride, directly undergoes oxygenatom transfer to alpha,beta-unsaturated carbonylcompounds, yielding epoxides.
Chiral cyclic α-amino acid containing oligopeptide catalyzed highly enantioselective epoxidation of α,β-unsaturatedketones and the α-helical secondary structure of the peptide catalyst were revealed by X-ray crystallographic analysis.