title: An unexpected double Diels-Alder reaction of (E)-2-bromo-4-aryl-1,3-pentadiene involving [1,5]-hydrogen migration and HBr elimination: synthesis of bicyclo[2.2.2]octene derivatives.
abstract: An unexpected double Diels-Alder (DDA) reaction of (E)-2-bromo-4-aryl-1,3-pentadiene was developed and resulted in a series of "butterfly-like" bicyclo[2.2.2]octene derivatives in moderate to good yields without the need for a metal catalyst. The proposed mechanism involves a [1,5]-sigmatropic hydrogen migration and HBr elimination. Through this decisive [1,5]-hydrogen shift step, the electronic properties and steric hindrance of the conjugated diene substrate are completely altered and the DDA reaction of this potential diene synthon is successfully achieved.
authors.affiliation: State Key Laboratory of Elemento-Organic Chemistry, The Department of Chemistry, Nankai University, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Weijin Road 94#, Nankai District, Tianjin 300071 (P.R. China).
authors.forename: Pingping
authors.initials: P
authors.lastname: Huang
authors.forename: Lingyan
authors.initials: L
authors.lastname: Liu
authors.forename: Weixing
authors.initials: W
authors.lastname: Chang
authors.forename: Jing
authors.initials: J
authors.lastname: Li
keywords: conjugated dienes; cycloaddition; hydrogen migration; maleimides; synthesis design