Unveiling the Origin of the Selectivity and the Molecular Mechanism in the [3+2] Cycloaddition Reaction of N-aryl-C-carbamoylnitrone with N-arylitaconimide

The [3+2] cycloaddition reaction of N-aryl-C-carbamoylnitrone (nitrone 1) with N-arylitaconimide (ethylene 2) was computationally studied using the B3LYP/6-31G(d) level of theory. An analysis of the different energetic profiles and the transition states’ optimized structures clearly indicated that this 32CA occurred through a non-polar, asynchronous, one-step mechanism, favoring the formation of the ortho–endo cycloadduct, as observed experimentally. The analysis of the reactivity indices derived from the conceptual DFT explains well the low polarity of this 32CA reaction. Parr functions and a dual reactivity descriptors analysis correctly explained the regioselectivity ortho of this 32CA reaction. Solvent effects did not modify the obtained selectivity but it increased the activation energies and decreased the exothermic character of this 32CA reaction. A thermodynamic parameters analysis indicated that this 32CA wascharacterized by an ortho regioselectivity and endostereoselectivity and exothermic and exergonic characters

Synthesis of tetrahydroquinolines and quinoline derivatives through the Lewis acid catalysed Povarov reaction: A comparative study between multi step and multi-component methods

In this work, we have synthesised a new disubstituted tetrahydroquinolines by the Povarov [4+2] cycloaddition reaction between imines derivatives and an electron-rich olefin such as vinyl ethers. These reactions were carried out in the presence of different acid catalysts in its two versions, multi-step reaction starting with imine synthesis and multi-component reaction in which the imine is formed in situ. The reactivity of the cycloaddition reaction is directly attributed to the nature of the reagents, the used synthetic strategy, in which the obtained yield is found in the case of multi-step reactions lower than that in the multi-component reaction one. Additionally, the multi-step reactions are faster kinetically in comparison with that of the multi-component one. The nature of the catalyst directly increases the rate and enhances the yield of the reactions

Regio- and stereoselective synthesis of novel isoxazolidine heterocycles by 1,3-dipolar cycloaddition between C-phenyl-N-methylnitrone and substituted alkenes. Experimental and DFT investigation of selectivity and mechanism

International audienceA series of isoxazolidine heterocycles was synthesized through the 1,3-dipolar cycloaddition (13DC) reaction of C-phenyl-N-methylnitrone with different substituted alkenes. The structures and stereochemistry of the cycloadducts were determined by spectroscopic methods. These 13DC reactions are characterized by complete regioselectivity and high stereoselectivity. The molecular mechanism, reactivity and selectivity of these 13DC reactions have been investigated by means of transition state theory and reactivity indices derived from conceptual DFT using DFT methods at the B3LYP/6-31G(d,p) level of theory. The obtained results indicate that these cycloaddition reactions take place through a one-step synchronous mechanism with a non-polar mechanism and high activation energies. The theoretical results are in agreement with the experimental findings

A theoretical study of the regio- and stereoselectivities of non-polar 1,3-dipolar cycloaddition reaction between <i>C</i>-diethoxyphosphoryl-<i>N</i>-methylnitrone and <i>N</i>-(2-fluorophenyl)acrylamide

<p>The 1,3-dipolar cycloadditions (13DC) of <i>C</i>-diethoxyphosphoryl-<i>N</i>-methylnitrone and N-(2-fluorophenyl) acrylamide have been studied using density functional theory (DFT) calculations at B3LYP/6-31G(d) level of theory. Our calculations show that this 13DC reaction takes place with complete <i>ortho</i> regioselectivity with <i>endo</i> stereoselectivity, which favours kinetically the formation of the <i>ortho</i>–<i>endo</i> cycloadduct, in agreement with the experimental observations. The inclusion of solvent effects does not modify the gas-phase selectivities but slightly decreases the reactivity of the reagents. Analysis of the bond order and charge transfer at the transition states indicates that this 13DC reaction takes place <i>via</i> a one-step asynchronous mechanism. Analysis of the DFT global reactivity indices and the Parr functions of the reagents allow us to provide an explanation of the regioselectivity of this 13DC reaction.</p> <p></p