An asymmetric Ugi three-component reaction induced by chiral cyclic imines: synthesis of morpholin- or piperazine-keto-carboxamide derivatives.
A 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.
Key Laboratory of Green Chemistry & Technology of Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, PR China.
Deguang
D
Zhu
Liang
L
Xia
Li
L
Pan
Sheng
S
Li
Ruijiao
R
Chen
Yongren
Y
Mou
Xiaochuan
X
Chen