作者:Robert R. Knowles、Song Lin、Eric N. Jacobsen                                    
                                    
                                        DOI:10.1021/ja101256v
                                    
                                    
                                        日期:2010.4.14
                                    
                                    A new thiourea catalyst is reported for the enantioselective cationic polycyclization of hydroxylactams. Both the yield and enantioselectivity of this transformation were found to vary strongly with the identity of a single aromatic residue on a common catalyst framework, with more expansive and polarizable arenes proving optimal. Evidence is presented for a mechanism in which stabilizing cation-Pi interactions are a principal determinant of enantioselectivity.