Computational investigations on the BPE-ligated Cu-catalysed enantioselective addition of enynes to ketones were performed with DFT method. Two BPE-CuMes catalysts, BPE-CuMes and (S,S)-Ph-BPE–CuMes, were employed to probe the reaction mechanism with the emphasis on stereoselectivity. The calculations on the BPE-CuMes system indicate that the actvie metallized enyne intermediate acts as the catalyst for the catalytic cycle. The catalytic cycle involves two steps: 1) the ketone addition to the alkene moiety of the metallized enyne; 2) the metallization of enyne followed by the release of product with the recovery of the active metallized enyne intermediate. The first step accounts for the distribution of the products, and therefore is the stereo-controlling step in chiral systems. In the chiral (S,S)-Ph-BPE–CuMes system, the steric hindrance is vital for the distribution of products and responsible for the stereoselectivity of this reaction. The steric hindrance between the phenyl ring of the two substrates and groups at the chiral centers in the ligand skeleton is identified as the original of the stereoselectivity for the titled reaction.
Catalytic cycle of lactone polymerization with anionic ureas: Computational investigation
