Nickel-catalyze D Asymmetric Coupling Reaction Of ?-benzyl Bromides And Alkynyl Aluminum Reagents

Chiral propargyl compounds are important intermediates in organic synthesis,because its carbon-carbon triple bond can be converted to other functional groups.Both the asymmetric substitution reactions and the asymmetric coupling reaction are the most common methods of s ynthesis of chiral propargyl compounds.In this thes is,we focus on synthesis of chiral propargyl compounds through the nickel-catalyzed asymmetric cross-coupling reaction of benzyl bromide with alkynyl aluminum.After the screening of catalyst and chiral ligand,we found the 10 % mol NiBr2(diglyme)and 12 % mol(R)-iPr-Pybox ligand could highly catalyze the cross-coupling reaction of benzyl bromide with phenylethynyl aluminum to afford the corresponding product in 89% yield with 82 % ee.Next,different substrates were explored in our reaction system,and the reaction result was influenced by different electronics groups and steric hindrance.For the electron-donating groups of aromatic bromides or alkynyl aluminum reagents,the asymmetric cross-coupling reaction afforded the corresponding products in high yield with good stereoselectivity.Steric effects show little impact on yield both in alkynylaluminum reagents and aromatic bromides.However,the steric effects of the substrates slightly decreased the stereoselectivity of the products.In summary,the asymmetric coupling reaction of ?-benzyl bromides and alkynyl aluminum reagents catalyzed by NiBr2/(R)-iPr-Pybox can be reacted quickly,and it has showed a wide scalability.