Air-tolerant, ligand-free nickel-catalyzed, manganese-assisted reductive Heck reaction of alkyl/aryl halides with electron-deficient olefins

An air-tolerant reductive Heck reaction of alkyl/aryl halides with α, β-unsaturated esters, nitriles and amides catalyzed by simple nickel bromide has been developed by using manganese as reductant in refluxing acetonitrile. Water plays a double-face role in the catalytic process, hydrolysis of the enolate and/or C-tautomer intermediates to afford the conjugate adducts while suppressing the catalysis at high concentration. The scope and limitations of the nickel-catalyzed manganese-mediated process have been demonstrated by more than 40 examples, showing large steric effects and good functional group compatibility except for reduction-sensitive ones.