jo2021967_si_001.pdf (1.83 MB)
An Asymmetric Ugi Three-Component Reaction Induced by Chiral Cyclic Imines: Synthesis of Morpholin– or Piperazine–Keto-carboxamide Derivatives
journal contribution
posted on 2012-02-03, 00:00 authored by Deguang Zhu, Liang Xia, Li Pan, Sheng Li, Ruijiao Chen, Yongren Mou, Xiaochuan ChenA series of chiral 5,6-dihydro-1,4-oxazin-2-one substrates,
as
preformed cyclic aldimines and ketoimines, were employed to develop
a new asymmetric Ugi three-component reaction for the first time.
The Ugi reaction of the imines, isocyanides, and carboxylic acids
opens an efficient access to novel morpholin-2-one-3-carboxamide compounds.
The chiral imines showed promising stereoinduction for the new chiral
center of the Ugi products, and predominant trans-isomers were obtained
in the most cases. Addition of some Lewis acids or proton acids could
improve the diastereoselectivity further but usually led to a drop
in total yield. The Ugi-3CR could be extended to the stereoselective
synthesis of ketopiperazine-2-carboxamide derivatives.