Nickel-catalyzed direct stereoselective α-allylation of ketones with non-conjugated dienes

The development of efficient and sustainable methods for the construction of carbon-carbon bonds with the simultaneous stereoselective generation of vicinal stereogenic centers is a longstanding goal in organic chemistry. Low-valent nickel(0) complexes which promote alpha-functionalization of carbonyls leveraging its pro-nucleophilic character in conjunction with suitable olefin acceptors are scarce. We report a Ni(0)NHC catalyst which selectively converts ketones and non-conjugated dienes to synthetically highly valuable alpha-allylated products. The catalyst directly activates the alpha-hydrogen atom of the carbonyl substrate transferring it to the olefin acceptor. The transformation creates adjacent quaternary and tertiary stereogenic centers in a highly diastereoselective and enantioselective manner. Computational studies indicate the ability of the Ni(0)NHC catalyst to trigger a ligand-to-ligand hydrogen transfer process from the ketone alpha-hydrogen atom to the olefin substrate, setting the selectivity of the process. The shown selective functionalization of the alpha-C-H bond of carbonyl groups by the Ni(0)NHC catalyst opens up new opportunities to exploit sustainable 3d-metal catalysis for a stereoselective access to valuable chiral building blocks. Low-valent nickel(0) complexes that promote alpha-functionalization of carbonyls leveraging its pro-nucleophilic character in conjunction with olefin acceptors are very scarce despite their attractivity. Here, the authors report a Ni(0)NHC catalyst which converts ketones and non-conjugated dienes to synthetically highly valuable alpha-allylated products.