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

Abstract

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.