Computational investigation on the mechanism and the stereoselectivity of Morita-Baylis-Hillman reaction and the effect of the bifunctional catalyst N-methylprolinol

Morita-Baylis-Hillman Reaction: How Do Optimal Enzyme Active Sites Compare with Organocatalysts

Morita-Baylis-Hillman reaction attracts significant attention for the synthesis of highly functionalized compounds. It requires multiple catalytic elements for efficient catalysis, making it an appealing target for the design of a...

Investigation of catalytic effect on carbon-carbon bond formation by Baylis-Hillman (BH) reaction between (2/3/4)-nitro-arylaldehyde and alkylacrylates and computational approaches through DFT functional

The 4-diazabicyclo[2. 2. 2] octane, DABCO, had widely established with gigantic and celestial applications on catalysis for carbon-carbon bond formation reactions. Thus, it has been employed to synthesize the alkyl 2-(hydroxyl (nitrophenyl) methyl)acrylate by the reaction of arylaldehydes and alkylacrylates under a mild condition with good yields. First of all, reaction was examined effect of various solvents, such as water, MeOH, Dioxane, DMSO, t-Butanol, DMF, Toluene, and THF and THF was the best solvent in term of yield. Next, the room temperature (R.T) was the optimized condition than 60 °C and 80 °C. The overall reaction progress was monitored in presence of DABCO, Et₃N, C₂H₅ONa, C₄H₉OK, (CH₃)₃COK and pyridine catalysts with THF solvents at room temperatures, and calculated the amount for superior of catalyst. There was no product obtained in presence of catalysts, such as Et₃N, C₂H₅ONa, C₄H₉OK, (CH₃)₃COK and pyridine. But in present of DABCO, this reaction has proceeded and monitored the concentration of catalyst and various temperature effects on reaction progress. In addition, the computational approaches for speculative investigation of solvents effect has employed for predicating and comparatively verified with the proposed reaction mechanism in presence of DABCO catalyst through the Density Functional Theory (DFT). The most acceptable tools for the thermodynamic had been illustrated to get the reaction kinetics by formation energy, entropy, enthalpy for reactant, product and transition state. Finally, the Gibbs free energy for reactions from the reactants and product has calculated to predict the occurring spontaneously possibility with and without solvents, and it is said that the reaction is spontaneously occurred through the water, DMSO, THF solvent although it is opposed fact without solvent even other solvents. It might be concluded that the optimization conditions of reaction are the THF solvent in presence of 20% DABCO catalyst at room temperature with high (about 90%) throughout 6–8 h where the 4- position of nitro group in arylaldehyde is the most preferable in case of time and yield.

Towards a converged strategy for including microsolvation in reaction mechanism calculations

A major part of chemical conversions is carried out in the fluid phase, where an accurate modeling of the involved reactions requires to also take into account solvation effects. Implicit solvation models often cover these effects with sufficient accuracy but can fail drastically when specific solvent-solute interactions are important. In those cases, microsolvation, i.e., the explicit inclusion of one or more solvent molecules, is a commonly used strategy. Nevertheless, microsolvation also introduces new challenges-a consistent workflow as well as strategies how to systematically improve prediction performance are not evident. For the COSMO and COSMO-RS solvation models, this work proposes a simple protocol to decide if microsolvation is needed and how the corresponding molecular model has to look like. To demonstrate the improved accuracy of the approach, specific application examples are presented and discussed, i.e., the computation of aqueous pK_a values and a mechanistic study of the methanol mediated Morita-Baylis-Hillman reaction.

Phosphine-catalyzed intramolecular Rauhut–Currier reaction: enantioselective synthesis of hydro-2H-indole derivatives

A highly enantioselective intramolecular Rauhut–Currier reaction catalyzed by a multifunctional chiral aminophosphine catalyst was reported.

A mechanistic study on guanidine-catalyzed chemical fixation of CO2 with 2-aminobenzonitrile to quinazoline-2,4(1H,3H)-dione

Both basicity of TMG and acidity of the [TMGH]⁺ guanidinium are crucial for a reaction.

A case study of the mechanism of alcohol-mediated Morita Baylis-Hillman reactions. The importance of experimental observations

The mechanism of the Morita Baylis-Hillman reaction has been heavily studied in the literature, and a long series of computational studies have defined complete theoretical energy profiles in these reactions. We employ here a combination of mechanistic probes, including the observation of intermediates, the independent generation and partitioning of intermediates, thermodynamic and kinetic measurements on the main reaction and side reactions, isotopic incorporation from solvent, and kinetic isotope effects, to define the mechanism and an experimental mechanistic free-energy profile for a prototypical Morita Baylis-Hillman reaction in methanol. The results are then used to critically evaluate the ability of computations to predict the mechanism. The most notable prediction of the many computational studies, that of a proton-shuttle pathway, is refuted in favor of a simple but computationally intractable acid-base mechanism. Computational predictions vary vastly, and it is not clear that any significant accurate information that was not already apparent from experiment could have been garnered from computations. With care, entropy calculations are only a minor contributor to the larger computational error, while literature entropy-correction processes lead to absurd free-energy predictions. The computations aid in interpreting observations but fail utterly as a replacement for experiment.

Insights into the Morita–Baylis–Hillman reaction of isomeric dibenzofuran carbaldehydes: a theoretical and mass spectral study

Systematic theoretical and mass spectral investigations on the faster Morita–Baylis–Hillman (MBH) reaction of dibenzofuran-4-carbaldehyde (2) compared to its isomer, dibenzofuran-2-carbaldehyde (1) are described.

A unified mechanistic view on the Morita-Baylis-Hillman reaction: computational and experimental investigations

The thermodynamic properties and reaction mechanism of the Morita-Baylis-Hillman (MBH) reaction have been investigated through experimental and computational techniques. The impossibility to accelerate this synthetically valuable transformation by increasing the reaction temperature has been rationalized by variable-temperature experiments and MP2 theoretical calculations of the reaction thermodynamics. An increase in temperature results in a switching of the equilibrium to the reactants occurring at even moderate temperature levels. The complex reaction mechanism for the MBH reaction has been investigated through an in-depth analysis of the suggested alternative pathways, using the M06-2X computational method. The results provided by this theoretical approach are in agreement with all the experimental/kinetic evidence such as reaction order, acceleration by protic species (methanol, phenol), and autocatalysis. In particular, the existing controversy about the character of the key proton transfer in the MBH reaction (Aggarwal versus McQuade pathways) has been resolved. Depending on the specific reaction conditions both suggested pathways are competing mechanisms, and depending on the amount of protic species and the reaction progress (early or late stage) either of the two mechanisms will be favored.