Combined Directed <i>ortho</i> Metalation−Halogen Dance (HD) Synthetic Strategies. HD−Anionic <i>ortho</i> Fries Rearrangement and Double HD Sequences
                                
                                    
                                        作者:Ricarda E. Miller、Toni Rantanen、Kevin A. Ogilvie、Ulrich Groth、Victor Snieckus                                    
                                    
                                        DOI:10.1021/ol100493v
                                    
                                    
                                        日期:2010.5.21
                                    
                                    A general and efficient directed ortho metalation (DoM)-halogen dance (HD)-electrophile quench sequence for the synthesis of trisubstituted pyridyl O-carbamates is described. A second HD sequence furnishes highly functionalized tetrasubstituted pyridines. Furthermore, a hitherto unobserved double HD rearrangement is reported. Under similar LDA conditions, aromatic O-carbamates with OMe, Cl, and F substituents (4a-c) undergo either a HD-electrophile quench sequence, 4a-c -> 18-20, or a HD-anionic ortho Fries rearrangement, 4a-c -> 6a-c, respectively.