Ni/photoredox-catalyzed coupling of aryl bromides and methylenecyclopropanes via selective distal bond cleavage†

Abstract

C(sp³) hybridized fragments have been widely explored for the formation of crucial Ni-alkyl intermediates in the field of nickel-catalyzed C(sp²)–C(sp³) coupling reactions. Traditional alkyl metal reagents and diverse C(sp³) radical precursors developed with the renascence of photocatalysis are effective coupling partners. However, though Ni-alkyl intermediates can be readily obtained to activate carbon–carbon bonds, cyclopropane derivatives have rarely been employed as partners to couple with aryl halides. Herein, we disclose a Ni/photoredox protocol for coupling methylenecyclopropanes with aryl bromides via selective distal bond cleavage. A range of 1,1-dibenzylethylene derivatives has been obtained in moderate-to-good yields under mild conditions with excellent functional group tolerance. Mechanistic studies demonstrate the unique ratio of the nickel catalyst to bidentate ligand (Ni/Ligand = 2/1) utilized in this reaction, which was derived from two distinct roles of nickel played in the oxidative addition step with MCP substrates and aryl bromides. This context presents an unusual catalytic mode in transition-metal-catalyzed transformations of methylenecyclopropanes.