Computational investigation of cyclic substituted iodine(III) halogen bond donors

Abstract

Several novel substituted iodine(III)-based halogen bond donors have been computationally investigated using density functional theory (DFT). Their properties of interest related to their Lewis acidity and stability were evaluated. These results constitute a theorical background for the rational design of new active iodine(III)-based organocatalysts. Notably, cyclic diaryliodonium salts with a central six-membered ring (iodininium salts) have been identified as a promising new class of halogen bond donors, although highly Lewis acidic variants have not been synthetized yet.

A quantum-chemical analysis on the Lewis acidity of diaryl-halonium ions

“…[19] We however recently explained that the difference is linked to the distortion required to bring the nucleophile in the correct position for reductive elimination to occur. [23] NBO analysis is producing a correct description of the electronic situation on iodine (Figure 3): one lone pair is of pure p character and is orientated perpendicular to the C-I-C plane. The second lone pair is predominantly an s orbital (75% s character).…”

“…Furthermore, a recent computational study reported a link between cycle size and Lewis acidity of several cyclic diaryliodonium analogs, which hints at an underlying electronic cause of this effect. [23] Furthermore, recently the related bromolium and chlorolium analogs have been introduced in catalysis. [13], [14] As bromolium catalysts sometimes outperformed iodolium ones, X the order in Lewis acidity remained unclearuntil very recently, when Stuart and co-workers reported insights on the nature of bonding and behavior of these diarylhalonium ions.…”

A quantum-chemical analysis on the Lewis acidity of diaryl-halonium ions

“…[19] We however recently explained that the difference is linked to the distortion required to bring the nucleophile in the correct position for reductive elimination to occur. [23] Figure 3. Common yet incorrect representation of the iodine(III) lone pairs compared to a electronically sound representation.…”

“…Furthermore, a recent computational study reported a link between cycle size and Lewis acidity of several cyclic diaryliodonium analogs, which hints at an underlying electronic cause of this effect. [23] Next to pure activation, asymmetric induction was recently also achieved by bifunctional hydrogen and halogen bonding organocatalysts, which featured iodolium and related bromonium moieties as Lewis acids (Figure 2). While in one case the latter produced markedly higher yield and somewhat improved enantioselectivity, [13] the iodolium catalyst clearly outperformed bromolium (and chlorolium) alternatives in a second study.…”

Introduction to hypervalent iodine chemistry. Part 3

“…Part 1 (2020) and Part 2 (2021) contain total 20 papers covering a broad range of topics of the HI chemistry. Specific topics of these papers include the following: theoretical and computational studies of HI compounds, [2][3][4] structural studies, 5 development of new synthetic approaches to HI reagents, [6][7][8][9] photochemical reactions involving HI chemistry, 10,11 industrial applications of hypervalent polyiodides, 12 and numerous synthetic applications of HI reagents. [13][14][15][16][17][18][19][20] Part 3 of the HI series will be published in 2022 covering all topics of iodine chemistry involving hypervalent species and halogen bonding.…”