title: Phosphine-catalyzed annulations of 4,4-dicyano-2-methylenebut-3-enoates with maleimides and maleic anhydride.
abstract: A novel phosphine-catalyzed [4+1] annulation of maleimides with 4,4-dicyano-2-methylenebut-3-enoates has been developed to afford spirocyclic products, and the maleimides serves as C1  synthons. Moreover, a phosphine-catalyzed formal [3+2] annulation between 4,4-dicyano-2-methylenebut-3-enoates and maleic anhydride has been also achieved, and maleic anhydride behaved as a C3  synthon in the reaction, thus efficiently affording the functionalized cyclopentenones. A stable phosphinium-containing zwitterionic compound is the key reactive intermediate in both annulations and was successfully isolated. Plausible mechanisms have been proposed on the basis of control experiments and deuterium-labeling experiments.
authors.affiliation: State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Linglin Lu, Shanghai 200032 (China).
authors.forename: Xiao-Nan
authors.initials: XN
authors.lastname: Zhang
authors.forename: Gen-Qiang
authors.initials: GQ
authors.lastname: Chen
authors.forename: Xiang-Ying
authors.initials: XY
authors.lastname: Tang
authors.forename: Yin
authors.initials: Y
authors.lastname: Wei
authors.forename: Min
authors.initials: M
authors.lastname: Shi
mesh_terms: D002087:Butyrates / Q000737:chemistry*; D002384:Catalysis; D008299:Maleic Anhydrides / Q000737:chemistry*; D008301:Maleimides / Q000737:chemistry*; D010720:Phosphines / Q000737:chemistry*
chemical_list: D002087:Butyrates; D008299:Maleic Anhydrides; D008301:Maleimides; D010720:Phosphines; C044646:phosphine
keywords: anhydrides; cyclization; organocatalysis; phosphorus; zwitterions