Computational Insights Into The Regioselectivities For Nickel-Catalyzed Dicarbofunctionalization Of Allyl Moiety Of N-allyl-2-aminopyrimidine

The transition-metal catalyzed functionalization of unsaturated C-C bonds has attracted wide and increasing interest as a powerful strategy for building up molecular complexity and diversity.Regardless of substantial progress in the past two decades,regioselective functionalization still remains a challenge.Insight into the cause of the different selectivity can help us to design and develop new alkenes' or alkynes'functionalization reactions.In this thesis,the mechanisms of divergent regioselectivities functionalization were studied by Density Functional Theory(DFT).Main content includes the following two parts:1.The mechanism of Ni-catalyzed difunctionalization of allyl moieties of N-allyl-2-aminopyrimidine with three kinds of organohalides and phenylboronic acid were studied by Density Functional Theory(DFT),respectively.When iodobenzene is used for the dicarbofunctionalization,the detailed reaction mechanistic pathway follows the sequential oxidative addition(OA)of iodobenzene,migratory insertion(MI)of phenyl group,?-H elimination followed by finished 1,3-H-migration,transmetalation is assisted by base,and reductive elimination(RE)to regenerate Ni(0)-catalyst.Due to the presence of chelation of the pyridinyl moiety of substrate with the Ni center,the competitive(3-H elimination leading to the product of Heck reaction is less favourable.Thus,we can afforded the 1,3-dicarbofunctionalization products.When bromostyrene is used,the proposed mechanistic pathway proceeds sequentially via oxidative addition of bromostyrene,migratory insertion,transmetalation assisted by base,and reductive elimination to obtain 1,2-dicarbofunctionalization products.The factors accounting for the constraint of ?-H elimination are revealed.In addition,the reversed 2,1-regioselectivity achieved by using alkynyl halides in the Ni-catalyzed dicarbofunctionalization is via sequential steps of oxidative addition,transmetalation.migratory insertion,and reductive elimination to obtain 2,1-dicarbofunctionalization products.The key intermediate formed by OA of alkynyl halides onto Ni(0)prefers the trans structural conformer,in which the alkynyl and the alkene moiety are in trans position.Thus,the migratory insertion step is unlikely to occur.Instead,the subsequent transmetalation occurs.Finally,we can afforded the product with 2,1-regioselectivity.2.We studied the mechanism of divergent regioselectivities of Pd-catalyzed hydroallylation of alkynes with two different ligands.The calculation results showed that when PCy3 is used as a ligand,the detailed reaction mechanistic pathway follows the sequential oxidative addition of n-butanol.H-migratory insertion.?-H elimination to form terminal methyl and further result in H-migration.transmetalation.and reductive elimination to obtain 2.1-dicarbofunctionalization products.When dppe ligand is used,the possible mechanism paths are oxidative addition.H-migratory insertion,transmetalation with Cu-catalyst,and reductive elimination to afford the 1.4-diene products.