Density functional theory study of the regio‐ and stereoselectivity of diels–alder reactions of 5‐Aryl‐2‐pyrones

Abstract

A theoretical study of the mechanism and regio-and stereoselectivity of Diels-Alder reactions of 5-aryl-2-pyrones (Ar ¼ Ph, 4-(MeS)-Ph) with substituted alkenes (CHZ ¼ CH 2 , Z ¼ COMe, OAc) is performed at the B3LYP/6-31G(d) level. The analysis of the relevant stationary points of the potential energy surface and intrinsic reaction coordinate calculations show that these cycloadditions are undergoing through asynchronous concerted mechanisms yielding to the formation of the 5-endo isomers as the major cycloadducts. The calculation of activation and reaction energies indicates that the 5-endo cycloadducts are favored both kinetically and thermodynamically. The obtained results are in good agreement with experimental outcomes.

Prediction of the Regioselectivity of 1,3-Dipolar Cycloaddition Reactions of Nitrile Oxides with 2(5H)-Furanones Using Recent Theoretical Reactivity Indices

“…The global electrophilicity index (w) and the global nucleophilicity (N) were calculated for both NOs 1-3 and 25HFs 4-12 (see Scheme 1) and they are collected in Table 2. We note the electrophilicity index (w) is a reliable tool for the prediction of the direction of the charge transfer between reagents and also for the analysis of the polarity of 13DCs [47][48][49][50] and Diels-Alder reactions [51,52]. According to the electrophilicity scale [31], the systems involved in cycloaddition reactions can be classified as follows:…”

DFT study on the mechanism of the Diels–Alder reactions leading to bicyclo[4.2.0]octenones

“…The electrophilicity indices of 1a and 1b have very low values, ω = 0.75 eV and ω = 0.89 eV, respectively, while they are increased in the 2-substituted cyclobut-2-enones from 2-methoxyto 2-cyano-, from ω= 1.43 eV to ω = 2.55 eV, respectively, with the latter being classified as a strong electrophile [18]. The polar character of a cycloaddition process can be predicted using the electrophilicity difference of the reaction pair, Δω [19]. In this sense, the electrophilicity difference between 2c and 1a is 1.79 eV, which indicates a larger polar character for this cycloaddition, while the small Δω between, 1a and 2d, 0.73eV, shows a low polar character of the cycloaddition reaction and is thus classified as a pericyclic process.…”

Theoretical analysis of the mechanism and regioselectivity of the 1, 3-dipolar cycloaddition of E-3-(dimethylamino)-1-(10H-phenothiazin-2-yl)prop-2-en-1-one with some nitrilimines using DFT and the distortion/interaction model

“…42 The small Δω between 1a and 2 (0.98 eV), and 0.82 eV for 1b + 2, shows a low-polar character for these 1,3-DC reactions, but the presence of CF 3 group (an electron-withdrawing group) on phenyl ring in dipole 1c, not only increases Δω (1.35) but also, in comparison to the dipoles 1a and 1b, enhances electerophilicity (ω) and reduces nucleophilicity (N).…”