Organocatalytic asymmetric double Michael reaction of Nazarov reagents with alkylidene azlactones for the construction of spiro-fused cyclohexanone/5-oxazolone system
                                
                                    
                                        作者:Ming-Qiang Zhou、Jian Zuo、Bao-Dong Cui、Jian-Qiang Zhao、Yong You、Mei Bai、Yong-Zheng Chen、Xiao-Mei Zhang、Wei-Cheng Yuan                                    
                                    
                                        DOI:10.1016/j.tet.2014.06.042
                                    
                                    
                                        日期:2014.9
                                    
                                    A bifunctional thiourea-tertiary amine-catalyzed enantioselective double Michael reaction of Nazarov reagents and alkylidene azlactones was realized. Using this protocol, a series of optically active spiro-fused cyclohexanone/5-oxazolone derivatives, bearing three consecutive chiral centers including one Spiro quaternary chiral center, were obtained in good yields with good stereoselectivities (up to 93% yield, 99:1 dr, and 91% ee). The synthetic utility of the products for the formation of chiral cyclic quaternary amino-acid derivatives was also demonstrated. (C) 2014 Elsevier Ltd. All rights reserved.