Novel bifunctional thiourea–ammonium salt catalysts derived from amino acids: application to highly enantio- and diastereoselective aza-Henry reaction
作者:Hong-Yu Wang、Zhuo Chai、Gang Zhao
DOI:10.1016/j.tet.2013.04.079
日期:2013.6
development of new efficient and easily accessible catalysts has been one of the focuses in asymmetric phase-transfer catalysis. In this paper, a novel class of chiral bifunctional thiourea–ammonium phase-transfercatalysts were synthesized from commercially available α-amino acids. The structural modularity of these catalysts permits facile tunings to achieve optimum results, which was demonstrated
Asymmetric Hydroazidation of Nitroalkenes Promoted by a Secondary Amine-Thiourea Catalyst
作者:Tiziana Bellavista、Sara Meninno、Alessandra Lattanzi、Giorgio Della Sala
DOI:10.1002/adsc.201500403
日期:2015.10.12
Chiral β-nitro azides are obtained by asymmetric addition of azides to nitroalkenes, with an enantioselectivity of up to 82% ee. The reaction, promoted by an easily accessible secondaryamine-thioureacatalyst, is performed with azidotrimethylsilane in the presence of benzoic acid. Products with different aliphatic β-substituents are obtained in good yields and with the highest enantioselectivity reported
New chiral bifunctional thiourea-phosphonium salts have been developed based on natural amino acids as highly efficient phase-transfer catalysts in the enantioselectiveaza-Henryreaction.
ammonium chlorides to provide the corresponding aza-Henry adducts in good yields and very high selectivities. It represents the first general enantioselectiveaza-Henry method for azomethines derived from enolizable aldehydes, giving rise to enantiomeric excesses above 94%. In addition, the reactions with nitroethane afforded high diastereo- and enantioselectivities (syn:anti up to 95:5; up to 98% ee for syn)