Quinine Synthesis Studies:  A Radical−Ionic Annulation via Mn-Mediated Addition to Chiral <i>N</i>-Acylhydrazones
                                
                                    
                                        作者:Chandra Sekhar Korapala、Jun Qin、Gregory K. Friestad                                    
                                    
                                        DOI:10.1021/ol7017938
                                    
                                    
                                        日期:2007.10.1
                                    
                                    A radical-ionic annulation approach to functionalized perhydroisoquinolines involving Mn-mediated coupling of alkyl iodides and chiral N-acylhydrazones was achieved using only 1.25 equiv of the alkyl iodide. Application of this reaction to alkene-containing substrates en route to quinine offered modest yields, decreasing on scaleup. Control experiments revealed that the alkene interfered with the coupling reaction. A revised approach involving prior oxidation of the alkene offered 93% yield in the Mn-mediated coupling, with the adduct obtained as a single diastereomer.