Experimental and theoretical study of the [3 + 2] cycloaddition of carbonyl ylides with alkynes

Abstract

The [3 + 2] cycloaddition reaction between carbonyl ylides generated from epoxides and alkynes ( phenylacetylene, methyl propiolate, methyl but-2-ynoate and methyl 3-phenylpropiolate) to give substituted 2,5-dihydrofurans was investigated. The effect of indium(III) chloride on the outcome of the reaction was studied in the case of phenylacetylene and methyl propiolate. The thermal reaction between the carbonyl ylide coming from 2,2-dicyano-3-phenyloxirane and both methyl propiolate and methyl but-2-ynoate was theoretically investigated using DFT methods in order to explain the reactivity and regioselectivity observed.

Selectivities of Multicomponent [4 + 2]/[3 + 2] Cycloadditions of 3-Nitroindole with Substituted Alkenes: A DFT Analysis

“…In this situation, the dipolarophile thus played the role of the electron donor, in contrast with the electron demand expected from the MO energies, but consistently with the potential competition between the two processes, as explained above. The fact that steps b and c were not initiated at the TS was fully in line with the absence of charge transfer at that point, as proposed from the geometry and the literature. , We note that a similar description was obtained in the case of model nitronate 8 (Table , channel 8, and Figure FS5, Supporting Information) and for the reaction involving vinylether 2 (Table , channel 3, and Figure FS6, Supporting Information), except that for the reaction coordinate values and for the details of step b, as in these two cases, no enrichment of the LP (N2) was observed. These results can also be compared to the description of the 1,3-dipolar cycloaddition between fulminic acid and acetylene published by Polo et al for which similar LP (N), B (C–C), and B (C–O) formations were also observed, but for which the B (C–N) and B (C–C) bond breaking were found to be monotonous during the reaction course, with no abrupt B (C–C) formation step.…”

“…The reaction was found to proceed through a concerted mechanism, and the TS were slightly asynchronous (Figure ). These structural features were proposed to be associated with a small charge transfer at the TS and with nonpolar mechanisms …”

“…These structural features were proposed to be associated with a small charge transfer at the TS and with nonpolar mechanisms. 19 The electronic rearrangements occurring during [3 + 2] cycloadditions were previously studied in depth. 20 A detailed scheme for the electronic reorganization during the reaction course 20a and a study of the role played by the pseudoradical character of the starting materials in the decrease of the reaction barrier were proposed.…”

Control of Chemoselectivity by Coordinated Water and Relative Size of Ligands to Metal Cations of Lewis Acid Catalysts for Cycloaddition of an Oxirane Derivative to an Aldehyde: Theoretical and Experimental Study

“…However, these calculations will show that the sole indicator of the HOMO–LUMO gap cannot account for the difference in chemoselectivities caused by different Lewis acid catalysts, especially for C–O selectivity. For those complicated reactions beyond the control of a simple FMO picture, density functional theory (DFT) was widely used to gain a more quantitative picture of reaction paths and corresponding activation energy barriers . The catalytic effects of noble metals (for instance, the complexes of Rh, Pt, et al) and Lewis acids (such as the metallic salts and BF 3 ) have been addressed theoretically.…”

Regioselective combination of 1,3-dinucleophiles such as 2-mercaptobenzimidazole, 5-mercapto-3-phenyltriazole and potassium thiocyanate with 2,2-dicyanooxiranes

“…7 The synthesis of such compounds has been the subject of several reviews which demonstrate the high importance of this class of compounds. [8][9][10][11][12][13] Considering the importance of these compounds, many methods for the synthesis of these derivatives have been reported successively. The conventional synthesis imidazoles, 17 1,3-oxathioles 18 and condensed imidazolo and thiazolo derivatives, 19 because of their multifunctional structure.…”