Nickel-mediated carboxylative cyclization of enynes

Nickel-mediated carboxylative cyclization of α,ω-enyne using carbon dioxide was investigated. Oxidative cycloaddition of enynes having an electron withdrawing group on alkene to a zero-valent nickel complex smoothly proceeded to provide nickelacyclopentene intermediates, which regioselectively reacted with CO2 at the Csp3-nickel bond, giving cyclized carboxylation products in good yields.