Bromine-Radical-Mediated Bromoallylation of C–C Unsaturated Bonds: A Facile Access to 1,4-, 1,5-, 1,6-, and 1,7-Dienes and Related Compounds

Abstract

AbstractThe radical bromoallylation of alkynes, allenes, and vinylidene cyclopropanes proceeds efficiently in the presence of a radical initiator to give 2-bromo-substituted 1,4-, 1,5-, and 1,6-diene derivatives, respectively. Three-component reactions comprised of allenes, electron-deficient alkenes, and allyl bromides give 1,7-dienes in good yields. The bromoallylation of an arylalkene can override β-scission of the bromine radical from β-bromoalkyl radicals to give 5-bromoalkenes, whilst the bromoallylation of vinylcyclopropanes is accompanied by 5-exo ring closure to give 1-(bromomethyl)-2-vinylcyclopentane derivatives in good yields. All of the products contain a reactive vinyl bromide moiety, which can be readily functionalized by Pd-catalyzed cross-coupling and radical cascade reactions.1 Introduction2 Synthesis of 1,4-Dienes by Bromoallylation of Acetylenes3 Synthesis of 1,5-Dienes by Bromoallylation of Allenes4 Synthesis of 1,6-Dienes by Bromoallylation of Methylenecyclopropanes5 Synthesis of 1,7-Dienes by Bromoallylation of Allenes and Electron-Deficient Alkenes6 Bromoallylation of Arylalkenes and Vinylcyclopropanes7 Conclusion