title: Conjugate addition to 1-phosphono-2-aza-1,3-butadienes: synthesis of phosphonylated gamma-lactams.
abstract: 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.
authors.affiliation: Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium.
authors.forename: Bart
authors.initials: B
authors.lastname: Vanderhoydonck
authors.forename: Christian V
authors.initials: CV
authors.lastname: Stevens
mesh_terms: D001372:Aza Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D002070:Butadienes / Q000737:chemistry*; D002384:Catalysis; D020650:Combinatorial Chemistry Techniques; D007769:Lactams / Q000138:chemical synthesis*; D015394:Molecular Structure; D063065:Organophosphonates / Q000138:chemical synthesis / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D001372:Aza Compounds; D002070:Butadienes; D007769:Lactams; D063065:Organophosphonates