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Density functional theory calculations have been performed to explore the Ru‐catalyzed decarbonylative annulation reaction of 3‐hydroxy‐2‐phenyl‐chromone with an alkyne to synthesize spiroindenebenzofuranones. A Ru(II)−Ru(0)−Ru(II) rather than a Ru(II)−Ru(IV)−Ru(II) transformation was found involved in the decarbonylation process, which is responsible for the sequence of alkyne insertion/decarbonylation. Oxidative addition of C(carbonyl)−C(carbonyl) bond to Ru(0) and the Ru(II)−C(sp2) bond formation were confirmed to be favorable for the decarbonylation, meanwhile oxidative addition of C(carbonyl)−C(carbonyl) bond to Ru(0) is likely to be the rate‐determining step for the entire catalytic cycle. It is predicted that the regeneration of the catalyst was achieved by the oxidation of air oxygen in the absence of other oxidants. The current theoretical study provides new insights into the decarbonylative annulation. [ABSTRACT FROM AUTHOR]

By carrying out density functional theoretical calculations, we have performed a detailed mechanistic study of the Au(i)-catalyzed cycloisomerization of 1,6-enylnyl ester in a dry and wet dichloromethane solvent corresponding to hydrogenation and hydrolysis processes, respectively. The hydrogenation and hydrolysis mechanisms proposed in the previous literature starting from an enol ketal intermediate without the involvement of an Au(i) catalyst are found to involve high barriers and thus contradict the observed experimental findings. Alternatively, based on the theoretical calculations, a novel hydrogenation mechanism (i.e., Au-induced H-shift followed by enol intermediate self-promoted H-shift) and a hydrolysis mechanism (i.e., Au-stabilized H-shift/C–O binding with subsequent H2O-assisted H-shift) from an Au–enol ketal adduct corroborate the experimental observations. The calculated results indicate that under unchanged wet conditions, the formation of a hydrolysis product is not involved in the intermediacy of the hydrogenation product. However, if the initial dry environment is provided, a hydrogenation product will be afforded. And then it will relentlessly evolve into a hydrolysis product in the subsequent wet conditions. The present theoretical results not only rationalize the experimental observations well but provide new insight into the mechanisms of the significant water-mediated cycloisomerization reaction. [ABSTRACT FROM AUTHOR]

With the help of density functional theory (DFT) calculations, we theoretically investigated and rationalized the controlled metathesis reactions of methylruthenium complex trans-[Ru(CH3)2(dmpe)2] [dmpe = 1,2-bis(dimethylphosphanyl)ethane] ( A) with terminal acetylenes. On the basis of the mechanistic study, two important issues related to the generation of mono- and bis-acetylido Ru complexes have been addressed. One issue is why the formation of bis-acetylido complex C, trans-[Ru(C≡CPh)2] (dmpe)2, is more difficult than the formation of mono-acetylido complex B, trans-[Ru(C≡CPh)(CH3)(dmpe)2]. A strong d→π*(C≡C) interaction between Ru and the alkynyl in B is believed to weaken π back-donation of Ru to the phenylacetylene C-H σ* bond, and then makes the phenylacetylene C-H bond difficult to break. The second issue is what role methanol plays in promoting the ligand metathesis between the methyl group in B and one alkynyl moiety in 1,4-diethynylbenzene to give bis-acetylido species D, trans-[(PhC≡C)Ru(dmpe)2(C≡CC6H4C≡CH)]. The relatively strong proton-donating ability of methanol was found to be the major reason. The present study is indicative of the controllable synthesis of mono- and bis-acetylido, and even di- and trinuclear acetylide-bridged ruthenium(II) complexes. [ABSTRACT FROM AUTHOR]

Abstract: Reaction mechanisms of the Ni(COD)2-catalyzed [2 + 2 + 2] cycloaddition of unsymmetric diynes and CO2 have been theoretically studied by using the density functional theory calculations. Three major steps are included, oxidative coupling of CO2 with Et-substituted C C bond, the second C C bond insertion and reductive elimination of the product from the Ni center, in which the C C bond insertion was found to be rate-determinant. The steric arrangement of the N,P-bidentate ligand was demonstrated to be influential on reaction barriers. Based on the mechanistic study, the regioselectivity of the catalytic reaction was elucidated. In addition, we also explained why the mechanisms involving oxidative coupling of both the C C bonds are unavailable. [Copyright &y& Elsevier]

Abstract: The hydrocarboxylation and hydrosilylation processes proposed in the copper-catalyzed reaction among carbon dioxide, diphenylacetylene and HSi(OEt)3 were comparatively studied with the aid of density functional theory calculations. Our study is to explore why the reaction preferred a hydrocarboxylation rather than a hydrosilylation process. It was found that the σ bond metathesis between Cu–C and H–Si involved in the hydrosilylation process had a significantly high reaction barrier in the presence of CO2 (47.4 kcal/mol). Instead, CO2 insertion and the subsequent σ bond metathesis between Cu–O and H–Si involved in the hydrocarboxylation process were confirmed kinetically feasible, consistent with the experimental facts. [Copyright &y& Elsevier]

The mechanisms and origins of substituent-induced Z − E chemoselectivity for gold(I)-catalyzed [4+1]-annulations of 1,4-diyn-3-ols with isoxazoles are explored theoretically. [Display omitted] Density functional theory (DFT) calculations were used to explore the Au(I)-catalyzed selective [4 + 1] annulations of cyclopropyl- and H-substituted 1,4-diyn-3-ols with isoxazole. The results indicated that after the N-nucleophilic attack of isoxazole, instead of obtaining the α–hydroxy gold carbene intermediate proposed experimentally, a concerted three-step forward product by isoxazole O N cleavage, 1,2-phenylalkyne shift and the hydroxyl H shift was identified as the key intermediate, for the reaction proceeding either via an Au-assisted C C double-bond rotation to produce the Z -isomeric enone or via two different Au-assisted C C rotations to furnish the E -configured enone depending on the substituents used. Further theoretical investigations indicated that the chemoselective step is the nucleophilic cyclization but not the C C double-bond rotation. The chemoselective preference for the Z -configured product using the cyclopropyl substitutent was attributed to two factors: i) the additional O H N hydrogen bonding interaction stabilizes the rate-determining cyclization TS leading to the Z -product, and ii) further Z - E product-isomerization is blocked due to significant structural deformation being involved. In contrast, using the H substituent results in a reversed chemoselectivity with exclusive formation of the E -configured enone, which is closely related to the smaller entropy effects involved. [ABSTRACT FROM AUTHOR]

With the aid of density functional theory (DFT) calculations, the Pd-catalyzed reactions of aryl iodide with unsymmetrical alkyne leading to two products containing C(sp 3 )−I bond ( P3 and P4 ) and one product containing a three-membered carbocyclic unit ( P5 ), have been studied theoretically. It is found that both the alkyne insertion and the subsequent C C bond insertion involved in the reaction are the major thermodynamic driving forces. The alkyne insertion instead of the C(sp 3 )−I reductive elimination is predicted to be rate-determinant. Similar barrier heights calculated for the two insertion modes of unsymmetrical internal alkyne ( TS 3-4 and TS 3′-4′ ) lead to the products P3 (47.2%) and P4 + P5 (48.8%) having similar product yields. The intriguing formation of the product containing a three-membered carbocyclic unit ( P5 ) was investigated in details. The second alkene insertion is found to be kinetically more favored than the C(sp 3 )−I reductive elimination, leading to product P5 (39.0%) more productive than P4 (9.8%). The remarkably thermodynamically favored β−H elimination is the key factor enabling formation of P5 . Why significant bulky phosphine ligand such as P(t-Bu) 3 instead of small one such as P(Me) 3 was employed experimentally have also been rationalized based on our calculation results. [ABSTRACT FROM AUTHOR]

Thereaction mechanism for the palladium(II)-catalyzed cross-couplingof N-tosyl hydrazone S1with alkene S2has been studied with the help of density functional calculations.The acetate present in the catalyst was found to directly participatein the reaction. The tBuO–group that was addedin excess into the reaction system plays an important role in formingthe new CC double bond. In addition, we clarified how waterplays an assisting role to promote the catalytic reaction studied. [ABSTRACT FROM AUTHOR]

The Pd-catalyzed reactions of α-diazocarbonylcompounds withallylic esters have been comprehensively studied with the aid of DFTcalculations. The reaction can be divided into two catalytic processes.The first process is Pd-catalyzed allylic ester decarboxylation leadingto formation of the intermediate product 1,4-enyne (P1). In this process, the ester oxidative addition proceeds via anion-pair mechanism rather than a concerted mechanism. The decarboxylativestep from the oxidative addition product (4) proceedsvia an (η2-CC)→Pd-coordinated ion-pairintermediate (9). The rate-determining step for thiscatalytic process is found to be the 1,4-enyne reductive eliminationstep. The second process is the Pd-catalyzed reaction between 1,4-enyne(P1) and the diazo substrate, leading to the final product.In this process, the coupling between 1,4-enyne (P1)and the metal carbene generated from the reaction of PdL2with the diazo substrate forms a four-membered metallacyclic intermediate,from which β-phenylethynyl elimination and subsequent reductiveelimination step are followed to produce the final product, a quaternarycarbon compound. Our study revealed that the terminal allylic carbonatom instead of the internal atom is linked to the carbon center ofthe diazo substrate. [ABSTRACT FROM AUTHOR]

The reaction mechanism of gold(I)-catalyzed cascade reaction of aminaloalkynes involving Petasis-Ferrier arrangement was studied with the aid of density functional theory calculations. Our study showed that two mechanisms proposed by the Patil group and by us are possible. With the substrate bearing a -C≡C-H component the mechanism by us is preferred in which the reaction undergoes first a Petasis-Ferrier rearrangement. With the substrate bearing a -C≡C-Ar component the mechanism by the Patil group is preferred in which the reaction undergoes first a protodeauration step. In summary, both reaction mechanisms are related and reaction substrate governs which pathway is followed. [ABSTRACT FROM AUTHOR]

• The mechanism and Selectivity on amidation of terminal alkenes with the nitrene precursors was explored with the aid of DFT calculations. Additionally, influence of the catalyst Ir(III) vs Rh(III) on the selectivity of above reactions was also elucidated. The Cp*IrIII-catalyzed coupling of terminal alkenes with dioxazolones to achieve C H amidation was studied theoretically with the aid of the density functional calculations. Employing the Ir=nitrenoid intermediate species involved in the reaction mechanism, the Ir N R bonding nature was analyzed based on LUMO/HOMO interactions. Especially, the branch-selectivity with Cp*Ir(III) as the catalyst, the influence of Ir(III) vs Rh(III) on branch/linear selectivity, and the impossibility of aziridination were elucidated. This work provided further understanding and beneficial information for designing novel related selective reactions. [Display omitted] [ABSTRACT FROM AUTHOR]