DFT Study On The Mechanisms Of Several Reactions Catalyzed By Transition Metal

In present paper, the density functional method (B3LYP) is employed to study the reaction mechanism of direct amination ofβ-ketoesters catalyzed by copper(II)-bisoxazoline(BOX), and Pd-Catalyzed Intermolecular 1,2-Diamination of Conjugated Dienes, respectively. The main transition states of these reactions are found out. The mechanisms of these asymmetric cyclized reactions are discussed in detail.1. Theoretical Investigation of Direct Amination ofβ-Ketoesters Catalyzed by Copper(II)-Bisoxazoline(BOX)The mechanism of the direct amination ofβ-keto esters catalyzed by copper(II)-bisoxazoline has been studied by means of density functional theory of B3LYP method. The computational results support the present mechanism, which involves (i) the generation of the enol fromβ-keto esters, which coordinates to copper(II)-bisoxazoline. The coordination step appears to be fast, exothermic, and irreversible. (ii) The formation of theσ_N-C bond via a six-membered ring transition state after azo dicarboxylate coordination with the chiral catalyst. This step is chirality-control step. (iii) Intramolecular hydrogen migration generates a catalyst-product complex, which can finally yield product. The hydrogen shift is rate-determining step, which affords the experimentally observed (R)-product. The stereochemical predictions have been rationalized in terms of steric repulsions, showing a good agreement with experimental data.2. DFT Studies on the mechanism of Pd-Catalyzed Intermolecular 1,2-Diamination of Conjugated DienesThe reaction mechanism of the Pd(II)-catalyzed addition of ureas to dienes, resulting in the 1,2-diamine, was studied using density functional theory(DFT) calculations at the B3LYP level. The calculations indicate that the first C-Nσbond formation is therate-determining step, and that the bonds formatted by the terminal carbon atoms ofdienes and nitrogen atom are favorable. Pd(NCMe) as the active catalyst can decreasethe energy barrier than Pd. All of the theoretical results are consistent with theexperiment.