جستجوی مقالات مرتبط با کلیدواژه « diels-alder reaction » در نشریات گروه « شیمی »

A mild procedure for the diastereoselective Diels-Alder reaction of methyl acrylate and cyclopentadiene was performed using modified silica with different concentrations of metal ions as Lewis acid support. According to the results, among the tested metal ions, cadmium ion supported on the silica was the best diastereoselective catalyst in this reaction.

In this study, the application of the Diels-Alder cycloaddition reactions between methyl acrylate and cyclopentadiene has been studied using a silica-supported catalyst with various concentrations of Zn2+ ion (Silica@Zn+2) as Lewis acid catalyst without using the solvent. The effective role of silanol groups in increasing stereoselectivities of products was also studied.

In this work, density functional theory (DFT) method was employed at the M062X/6–311G (d,p) level of theory to investigate the Diels-Alder reaction of isobenzofuran and ethylene in the gas and solution phases theoretically. To perform the computations in the solution phase, the polarizable continuum model (PCM) was applied. It was evaluated how the solvent affects the barrier height (DE‡) and thermodynamic parameters (DG‡ and DH‡) in this reaction. The dependency of these parameters on the Onsager function was discussed. The polar character of the reaction was measured through the global electron density transfer (GEDT). The Wiberg bond indices were used to assess the progress of the reactions, and the synchronicity values of the reactions were determined. Results revealed that, the barrier energy values of the reaction increased in solution phase compared to gas phase. GEDT values were lower than 0.15 e and activation barrier higher than 18 kcal/mol in the gas and solution phases. Therefore, this reaction was considered as a non-polar DA reaction.

As the basis and preliminary work of future experimental study on PAHs formation under high temperature, theoretical computations on the intramolecular rearrangement reactions of sylvestrene (1-methyl-3-vinylcyclohexene) and 1,4-dimethyl-4-vinylcyclohexene are conducted and reveal that they may be transformed to themselves. The conversion between Dipentene and 2,4-dimethyl-4-vinylcyclohexene is also predicted. All the reactions proceed along concerted paths through a single cis-endo transition state with relatively high energy barrier (~200 kJ/mol) and presumably occur when alkenes burn. These possible Cope rearrangement reactions have some characters of stepwise Diels-Alder cycloadditions during which diene and dienophile are replaced by each other and may suggest the complexity of cyclic hydrocarbons formation.

In the present work, the regioselectivity for a series of Diels–Alder reactions (4 reactions) has beenstudied using hardness, electrophilicity and polarizability of products.Furthermore,thermodynamicand kinetic calculations have been done. In all results predicted pararegioisomer is more favorableregioisomerinthese investigated reactions.All calculations have been done at the DFT-B3LYP/6-31G(d) level of theory.