Stereoselective 1,3-Cyclotelomerization of Butadiene with Dienophiles under Nickel Catalysis.

The discovery of new chemoselectivity with readily accessible chemicals is important to expand the reaction space for modern chemistry. For dienes and dienophiles, most people will naturally use them to carry out the classic Diels-Alder reaction to construct six-membered cyclic compounds. Here, we demonstrated a chemoselective coupling of butadiene with dienophiles through stereoselective 1,3-cyclotelomerization. By utilizing robust Ni/IPr catalysis, valuable bicyclic products were created with high regio- and chemoselectivities under mild conditions. Asymmetric cyclotelomerization enabled by the chiral NHC ligand was also performed, generating enantioenriched bicyclic compounds. The reaction mechanism was also investigated via experiments and density functional theory (DFT) calculations, which indicate that the reaction might start with oxidative cyclometalation between two molecules of 1,3-diene and Ni(0) species, followed by a [3 + 2]-cycloaddition between nickelacycle and dienophile. The products can undergo a variety of intricate transformations, which emphasizes the potential applications of this strategy. It is hoped that the discovery of this protocol will further inspire people to rethink classic organic reactions.