Design of new organic superacids with fused and isolated pyrrole and cyclopentadiene rings and assessment of effect of –BX₂(X = H, F, Cl, CN) substituents on the acidity enhancement: A DFT analysis

Abstract

New classes of organic Brønsted acids were designed with pyrrole and cyclopentadiene scaffolds, and their acidity was assessed theoretically by the B3LYP/6‐311++G(d,p) method. The hydrogen atom of NH group in pyrrole was substituted by an –BX2 (X = H, F, Cl, CN, CF3). The boron atom stabilizes the conjugated bases by interaction with the center of negative charge after deprotonation. The acidity of the compounds was promoted by substitution of the hydrogen atoms of the rings with CN moiety as a strong electron withdrawing group. Also, after deprotonation, delocalization of the negative charge in both pyrrole and cyclopentadiene rings causes stability of the conjugated bases and consequently enhances the acidity. The charge delocalization in the neutral acids and their conjugated bases was compared using nucleus‐independent chemical shift index. Enthalpies and Gibbs free energies of deprotonation in gas phase, ∆Hacid and ∆Gacid, were used as a measure of acidity. Both compounds with isolated and fused pyrrole and cyclopentadiene rings were investigated and it was found that the formers are more acidic. Using these strategies, several acids and superacids with wide range of acidity with ∆Gacid values of 244 to 328 kcal mol−1 were obtained.

A deeper computational look at Mumm rearrangement: Evaluation of substituent, solvent, and temperature effects

“…The suitable knowledge about Mumm rearrangement will help us to find out how we can change the Ugi reaction pathway in its final step via prevention of Mumm rearrangement occurrence, and hence, the vast number of novel compounds can be synthesized. In continuing our previous studies [ 12–21 ] and by inspiring the published investigations about DFT‐based evaluation of various rearrangements, [ 22–27 ] I studied the Mumm rearrangement and its various affecting parameters from the computational viewpoint. The effect of electron‐donating and electron‐withdrawing substituents and also different solvents and temperatures on activation barrier in Mumm rearrangement have been well studied using computational simulation based on DFT.…”

Green Synthesis of Pyrrole Derivatives Catalyzed by Molecular Sieves: DFT, ADMT, and Molecular Docking Investigations

“…[15][16][17] The design and theoretical assessment of new classes of organic Brønsted acids incorporating pyrrole and cyclopentadiene scaffolds, leading to highly acidic compounds with enhanced stability and potential applications in various fields, is of significant importance in advancing catalysis and chemical research. [18] Molecular dynamics simulations and docking studies have also been instrumental in predicting and rationalizing the binding modes and affinities of pyrrole-based ligands in drug discovery. [19] In this regard, the pyrrole-2,3dicarboxylate-based compounds are explored in terms of the capability of using them as potential anti-cancer agents against hepatic carcinoma, employing computational drug design techniques and experimental analyses; the synthesized compounds demonstrated significant anti-hepatic carcinoma activ-ity, indicating their potential as novel therapeutic candidates for treating liver cancer.…”

“…High‐level quantum chemical calculations can accurately predict the reactivity, stability, and electronic properties of these molecules, providing valuable insights to guide synthetic chemists [15–17] . The design and theoretical assessment of new classes of organic Brønsted acids incorporating pyrrole and cyclopentadiene scaffolds, leading to highly acidic compounds with enhanced stability and potential applications in various fields, is of significant importance in advancing catalysis and chemical research [18] . Molecular dynamics simulations and docking studies have also been instrumental in predicting and rationalizing the binding modes and affinities of pyrrole‐based ligands in drug discovery [19] .…”