Oxazaborolidinium Ion-Catalyzed Cyclopropanation of α-Substituted Acroleins: Enantioselective Synthesis of Cyclopropanes Bearing Two Chiral Quaternary Centers
                                
                                    
                                        作者:Lizhu Gao、Geum-Sook Hwang、Do Hyun Ryu                                    
                                    
                                        DOI:10.1021/ja209270e
                                    
                                    
                                        日期:2011.12.28
                                    
                                    A catalytic synthetic route to highly functionalized chiral cyclopropane derivatives was developed by Michael-initiated cyclopropanation of alpha-substituted acroleins with aryl- and alkyl diazoacetates. In the presence of chiral (S)-oxazaborolidinium cation 1b as a catalyst, the reaction proceeded in high yield (up to 93%) with high to excellent diastereoselectivity (up to 98% de) and enantio-selectivity (up to 95% ee).