Conjugate Addition to 1-Phosphono-2-aza-1,3-butadienes:  Synthesis of Phosphonylated γ-Lactams
                                
                                    
                                        作者:Bart Vanderhoydonck、Christian V. Stevens                                    
                                    
                                        DOI:10.1021/jo0488661
                                    
                                    
                                        日期:2005.1.1
                                    
                                    Several 1-phosphono-2-aza-1,3-butadienes, 1 and 13-20, were evaluated in the reaction with different enolate-type nucleophiles to induce addition at the 1- or the 4-position of the azadiene. 1-Phosphono-2-azadienes 1 react with sodium malonate at the 1-position, leading to the formation of bisenamines 12 after elimination of the phosphonate moiety. On the contrary, sodium malonate adds at the 4-position of 1-aryl-1-phosphono-2-azadienes 14-19 when the azadienes bear a halogenated phenyl substituent, and the resulting addition products 21-26 are easily transformed into the corresponding phosphonylated gamma-lactams 35-40. The regioselectivity of the addition is explained by reversal of polarization of the azadiene due to the electron-withdrawing character of the halogenated phenyl substituents.