Computational exploration of the copper(I)-catalyzed conversion of hydrazones to dihalogenated vinyldiazene derivatives.

This computational study explores the copper (I) chloride catalyzed synthesis of (E)-1-(2,2-dichloro-1-phenylvinyl)-2-phenyldiazene (2Cl-VD) from readily available hydrazone derivative and carbon tetrachloride (CCl4). 2Cl-VD has been extensively utilized to synthesize variety of heterocyclic organic compounds in mild conditions. The present computational investigations primarily focus on understanding the role of copper (I) and N1,N1,N2,N2-tetramethylethane-1,2-diamine (TMEDA) in this reaction, TMEDA often being considered a proton scavenger by experimentalists. Considering TMEDA as a ligand significantly alters the energy barrier. In fact, it is only 8.3 kcal/mol higher compared to the ligand-free (LF) route for the removal of a chlorine atom to form the radical ·CCl3 but the following steps are almost barrierless. This intermediate then participates in attacking the electrophilic carbon in the hydrazone. Crucially, the study reveals that the overall potential energy surface is thermodynamically favorable, and the theoretical turnover frequency (TOF) value is higher in the case of Cu(I)-TMEDA complex catalyzed pathway.

Computational predictions on Brønsted acidic ionic liquid-catalyzed carbon dioxide conversion to five-membered heterocyclic carbonyl derivatives.

Experimentally conducted reactions between CO2 and various substrates (i.e., ethylenediamine (EDA), ethanolamine (ETA), ethylene glycol (EG), mercaptoethanol (ME), and ethylene dithiol (EDT)) are considered in a computational study. The reactions were previously conducted under harsh conditions utilizing toxic metal catalysts. We computationally utilize Brønsted acidic ionic liquid (IL) [Et2NH2]HSO4 as a catalyst aiming to investigate and propose 'greener' pathways for future experimental studies. Computations show that EDA is the best to fixate CO2 among the tested substrates: the nucleophilic EDA attack on CO2 is calculated to have a very small energy barrier to overcome (TS1EDA, ΔG‡ = 1.4 kcal mol-1) and form I1EDA (carbamic acid adduct). The formed intermediate is converted to cyclic urea (PEDA, imidazolidin-2-one) via ring closure and dehydration of the concerted transition state (TS2EDA, ΔG‡ = 32.8 kcal mol-1). Solvation model analysis demonstrates that nonpolar solvents (hexane, THF) are better for fixing CO2 with EDA. Attaching electron-donating and -withdrawing groups to EDA does not reduce the energy barriers. Modifying the IL via changing the anion part (HSO4-) central S atom with 6 A and 5 A group elements (Se, P, and As) shows that a Se-based IL can be utilized for the same purpose. Molecular dynamics (MD) simulations reveal that the IL ion pairs can hold substrates and CO2 molecules via noncovalent interactions to ease nucleophilic attack on CO2.

Crystal structure and Hirshfeld surface analysis of 2-(4-amino-6-phenyl-1,2,5,6-tetra-hydro-1,3,5-triazin-2-yl-idene)malono-nitrile di-methyl-formamide hemisolvate.

The title compound, 2C12H10N6·C3H7NO, crystallizes as a racemate in the monoclinic P21/c space group with two independent mol-ecules (I and II) and one di-methyl-formamide solvent mol-ecule in the asymmetric unit. Both mol-ecules (I and II) have chiral centers at the carbon atoms where the triazine rings of mol-ecules I and II are attached to the phenyl ring. In the crystal, mol-ecules I and II are linked by inter-molecular N-H⋯N, N-H⋯O and C-H⋯N hydrogen bonds through the solvent di-methyl-formamide mol-ecule into layers parallel to (001). In addition, C-H⋯π inter-actions also connect adjacent mol-ecules into layers parallel to (001). The stability of the mol-ecular packing is ensured by van der Waals inter-actions between the layers. The Hirshfeld surface analysis indicates that N⋯H/H⋯N (38.3% for I; 35.0% for II), H⋯H (28.2% for I; 27.0% for II) and C⋯H/H⋯C (23.4% for I; 26.3% for II) inter-actions are the most significant contributors to the crystal packing.

Computational mechanistic studies on persulfate assisted p-phenylenediamine polymerization.

p-Phenylenediamine (p-PDA) is a monomer of many important polymers such as kevlar, twaron, poly-p-PDA. Most of the noticed polymers formation is initiated by a free-radical, but their polymerization mechanism is not elucidated computationally. The proposed study helps to fully understand the frequently utilized initiator/oxidant, potassium persulfate (K2 S2 O8 ) role in the aromatic diamines polymerization, which support experimental protocols, and a polymer scope. The formation of the poly-p-PDA is studied with the density functional theory (DFT) B3LYP-D3 functional using experimental polymerization parameters (0°C and aqueous media). K2 S2 O8 initiated free-radical polymerization of p-PDA is studied in detail, taking into account sulfate free-radical (SO4 - )· , SFR, persulfate anion (S2 O8 )2- , PA and K2 S2 O8 cluster, PP. The reaction mechanism is calculated as the conversion of p-PDA to free-radical, the p-PDA free-radical attack to the next p-PDA (dimerization), ammonia extrusion from the dimer adduct, the dimer adduct conversion to the free-radical (completion of p-PDA polymerization cycle) for the polymer chain elongation. Calculations show that the dimerization step is the rate-limiting step with a 29.2 kcal/mol energy barrier when SFR initiates polymerization. In contrast, the PA-assisted dimerization energy barrier is only 12.7 kcal/mol. PP supported polymerization is calculated to have very shallow energy barriers completing the polymerization cycle, i.e., dimerization (TS2K, ∆G‡  = 11.6 kcal/mol) and ammonia extrusion (TS3K, ∆G‡  = 6.7 kcal/mol).

Computational investigation of catalytic effects of CX3COOH (X = F,Cl,H) on the three-component cyclocondensation reaction.

The mechanism of acetic acid (AA), trifluoroacetic acid (TFA), and trichloroacetic acid (TCA) catalyzed three-component cyclocondensation reaction to (4S,6S)-4,6-diphenyl-1,3,5-triazinane-2-thione was determined via density functional calculations. Based on the potential energy surface diagram, TCA was found to be a reasonable catalyst [energy span (δG) is 2 kcal mol-1 less than TFA and AA] for the reaction. An energetic span model implies that TFA and AA show the same catalytic performance. The impact of the presence of halogen atoms in TFA and TCA catalysts is quantified via energy barriers. Graphical Abstract Ranking catalytic efficiency of OTC triazinane-2-thione formation Graphical Abstract contains poor quality and small text inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf.It is attached as tiff format.

Ionic Liquid Solvation versus Catalysis: Computational Insight from a Multisubstituted Imidazole Synthesis in [Et2NH2][HSO4].

The mechanisms of a tetrasubstituted imidazole [2-(2,4,5-triphenyl-1 H-imidazol-1-yl)ethan-1-ol] synthesis from benzil, benzaldehyde, ammonium acetate, and ethanolamine in [Et2NH2][HSO4] ionic liquid (IL) are studied computationally. The effects of the presence of the cationic and anionic components of the IL on transition states and intermediate structures, acting as a solvent versus as a catalyst, are determined. In IL-free medium, carbonyl hydroxylation when using a nucleophile (ammonia) proceeds with a Gibbs free energy (ΔG≠) barrier of 49.4 kcal mol-1. Cationic and anionic hydrogen-bond solute-solvent interactions with the IL decrease the barrier to 35.8 kcal mol-1. [Et2NH2][HSO4] incorporation in the reaction changes the nature of the transition states and decreases the energy barriers dramatically, creating a catalytic effect. For example, carbonyl hydroxylation proceeds via two transition states, first proton donation to the carbonyl (ΔG≠=9.2 kcal mol-1) from [Et2NH2]+, and then deprotonation of ammonia (ΔG≠=14.3) via Et2NH. Likewise, incorporation of the anion component [HSO4]- of the IL gives comparable activation energies along the same reaction route and the lowest transition state for the product formation step. We propose a dual catalytic IL effect for the mechanism of imidazole formation. The computations demonstrate a clear distinction between IL solvent effects on the reaction and IL catalysis.

Design and synthesis of pyrrolotriazepine derivatives: an experimental and computational study.

The pyrrole derivatives having carbonyl groups at the C-2 position were converted to N-propargyl pyrroles. The reaction of those compounds with hydrazine monohydrate resulted in the formation of 5H-pyrrolo[2,1-d][1,2,5]triazepine derivatives. The synthesis of these compounds was accomplished in three steps starting from pyrrole. On the other hand, attempted cyclization of a pyrrole ester substituted with a propargyl group at the nitrogen atom gave, unexpectedly, the six-membered cyclization product, 2-amino-3-methylpyrrolo[1,2-a]pyrazin-1(2H)-one as the major product. The expected cyclization product with a seven-membered ring, 4-methyl-2,3-dihydro-1H-pyrrolo[2,1-d][1,2,5]triazepin-1-one was formed as the minor product and was converted quantitatively to the major product. The formation mechanism of the products was investigated, and the results obtained were also supported by theoretical calculations.