Asymmetric formation of CN bonds in chiral enol ethers
作者:Stefania Fioravanti、M.Antonietta Loreto、Lucio Pellacani、Paolo A. Tardella
DOI:10.1016/s0040-4020(01)86538-8
日期:1991.7
Attack of EtO2CN on an enol ether carrying (S,S)-hydrobenzoin as chiral auxiliary gives diastereoselective aziridination with diastereomeric excess > 95%. Easy subsequent hydrolysis gives partially racemised alpha-amino ketone 4. Other chiral auxiliaries does not allow isolation of intermediate aziridines and the alpha-amino ketone is isolated with a 75:25 enantiomeric ratio. The thermolysis of EtO2CN3 in most of the same enol ethers gives the acetals of the alpha-amino ketone with prevailing opposite configuration at the new formed chiral centre.
Asymmetric addition of ethyl azidoformate to optically active enamines. Reversal of facial selectivity compared with (ethoxycarbonyl)nitrene
作者:Stefania Fioravanti、M. Antonietta Loreto、Lucio Pellacani、Paolo A. Tardella
DOI:10.1016/s0957-4166(00)82283-1
日期:1990.1
Thermalreaction of ethyl azidoformate with proline-derived optically active enamines of cyclohexanone, followed by photolysis, proceeds with opposite facial selectivity to that observed using (ethoxycarbonyl)nitrene. A tentative explanation is proposed. The absolute configuration of the main product, 2-(ethoxycarbonylamino)cyclohexanone (6), was deduced by chemical correlation.