Search

Pd‐catalyzed spiroannulation of bromophenylnaphthalenols with acetylenes to achieve asymmetric dearomatization is a powerful way to construct chiral spiro‐compounds. DFT calculations with the M06 functional have been performed to reveal the mechanism and enantioselectivity of this reaction. After reversible oxidative addition of aryl bromide to Pd(0), acetylene insertion into the Pd−C(aryl) bond is considered to be the rate‐ and enantioselectivity determining step. Subsequent deprotonation and reductive elimination then give the spiroannulation product. The overlay and noncovalent interaction analysis of the critical transition states were used to reveal the origin of the enantioselectivity for this reaction. We found that the axial chirality of the naphthol moiety affects the relative free energies of the corresponding transition states, whereas the enantioselectivity is controlled by the steric repulsion between the naphthol moiety and the ligand. [ABSTRACT FROM AUTHOR]

A theoretical study of the mechanism and regioselectivity of 1,3‐dipolar cycloaddition of nitrile oxides to 3‐methylene indolone has been performed by density functional theory at the M06‐2X/6‐311++G(d,p) level of theory. The results indicate that the concerted pathway is more favorable than the stepwise pathway. Investigation of the regioselectivity of this reaction shows that the main product is predicted to be 3,5‐substituted isoxazoline derivatives, which is consistent with experimental observations. The substituent effect of nitrile oxides on the reactivity and regioselectivity were also investigated. The opposite regioselectivity was observed for nitrile oxides with electron‐donating groups (methyl and phenyl) compared with electron‐withdrawing groups (CN and CO2Me). Distortion–interaction energy analysis shows that the reactivity of 1,3‐dipolar cycloaddition of nitrile oxides to 3‐methylene indolone is controlled by both the distortion and interaction energies. Natural population analysis indicates that the carbon atom of the 1,3‐dipole prefers to bond to the terminal carbon atom of the exocyclic double bond of 3‐methylene indolone, forming the 3,5‐substituted isoxazoline product. Frontier molecular orbital analysis shows that the regioselectivity is controlled by the orbital interaction between the lowest unoccupied molecular orbital of the nitrile oxide and the highest occupied molecular orbital of 3‐methylene indolone. [ABSTRACT FROM AUTHOR]

The possible hydrolysis mechanisms of dinotefuran with OH, HO, and HO in the gas phase were systematically simulated by applying the M06-2X/6-311++G(d,p) and MP2/6-311+G(d,p) methods. With regard to the hydrolysis with OH, path A which implies the proton transfer to the N2 atom of C1=N2 double bond is obviously preferable to other mechanisms. Our calculation clearly revealed that the hydrolysis with HO proceeds through path A with significantly lower energy than other channels. Due to its remarkable low energy barrier, path C, the protonation of the N2 atom, may be more prone to take place than other pathways for the hydrolysis in acidic media. It is shown that the most preferred pathway is the hydrolysis with OH which has obviously lower energy than other channels. In addition, the hydrolysis in solution is more favorable than that in the gas phase. [ABSTRACT FROM AUTHOR]

Density functional theory calculations were performed to study the counterion effect and directing group effect in rhodium mediated concerted metalation deprotonation type C H bond activation of arenes. The use of different carboxylates as counterions results in changes to the activation energies over a narrow range. These changes are mainly attributed to the opposing effects of alkalinity and nucleophilicity of the substituted groups. The effects of directing groups were also considered. By introducing directing groups, the C H bond activation energy is greatly reduced. Our results show that different directing groups have similar effects and activation energies. [ABSTRACT FROM AUTHOR]