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

Pingping Huang; Lingyan Liu; Weixing Chang; Jing Li

doi:10.1002/asia.201403092

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

Chem Asian J. 2015 Mar;10(3):548-52. doi: 10.1002/asia.201403092. Epub 2015 Jan 23.

Authors

Pingping Huang¹, Lingyan Liu, Weixing Chang, Jing Li

Affiliation

¹ 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).

PMID: 25620015
DOI: 10.1002/asia.201403092

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.

Keywords: conjugated dienes; cycloaddition; hydrogen migration; maleimides; synthesis design.