Reactivity and mechanism of nucleophilic addition reaction of amine with alkene: A systematic DFT study

The reactivity and mechanism of the nucleophilic addition reaction of diethylamine 1 and 1-cyano-2-phenylvinyl methane sulfonate 2 have been studied for systematic understanding of this relevant organic transformation, using DFT calculations method at the B3LYP/6-311G(d,p) computational levels. Analysis of the conceptual DFT reactivity indices allows explaining the reactivity, and the calculated nucleophilic and electrophilic Parr functions at the reactive sites of reagents 1 and 2, respectively, allows explaining correctly the regioselectivity observed experimentally. The study has also been applied to predict the mechanism of amine with alkene. Interestingly, the study predicts a switch to a two-step mechanism due to the higher polar character of this zw-type nucleophilic addition reaction.

Synthesis of Some Pyrimidine, Pyrazole, and Pyridine Derivatives and Their Reactivity Descriptors

A series of novel pyrimidine (2, 3), pyrazole (4, 5), and pyridine (6) derivatives were synthesized using a chalcone-bearing thiophene nucleus (1). The target compounds were synthesized by reaction of compound (1) with urea, thiourea, malononitrile, hydrazine hydrate, and 2,4-dinitrophenyl hydrazine, respectively. Molecular electronic structures have been modeled within density functional theory framework (DFT). Reactivity indices and electrostatic surface potential maps (ESP maps) allow us to establish trends that enable making predictions about chemical characteristics of the newly synthesized molecules and their proton transfer tautomers. Proton transfer is generally more favored in solution than in the gas phase. In acetonitrile, keto-form tautomers and thione-form tautomers become more energetically stable than the corresponding enol or thiol tautomers due to solvent-induced enhancement in the molecular polarity identified by computed dipole moment.

A Molecular Electron Density Theory Study of the Reactivity of Azomethine Imine in [3+2] Cycloaddition Reactions

The electronic structure and the participation of the simplest azomethine imine (AI) in [3+2] cycloaddition (32CA) reactions have been analysed within the Molecular Electron Density Theory (MEDT) using DFT calculations at the MPWB1K/6-311G(d) level. Electron localisation function (ELF) topological analysis reveals that AI has a pseudoradical structure, while the conceptual DFT reactivity indices characterise this TAC as a moderate electrophile and a good nucleophile. The non-polar 32CA reaction of AI with ethylene takes place through a one-step mechanism with low activation energy, 5.3 kcal/mol-1. A bonding evolution theory (BET) study indicates that this reaction takes place through a non-concerted [2n+2τ] mechanism in which the C–C bond formation is clearly anticipated prior to the C–N one. On the other hand, the polar 32CA reaction of AI with dicyanoethylene takes place through a two-stage one-step mechanism. Now, the more favourable regioisomeric transition state structure (TS) is located 8.5 kcal•mol−1 below the reagents, in complete agreement with the high polar character of the TS. The current MEDT study makes it possible to extend Domingo’s classification of 32CA reactions to a new pra-type of reactivity.