Fundamental Aspects of Structure, Bonding, and the Reactivity of Hypervalent Iodine Compounds

Abstract

Even though their importance in organic synthesis has grown tremendously, it is not until recently that iodane compounds have been rediscovered by theory and computation. In this chapter, using quantum chemical computation, we will explore the origins of the planar T‐shape equilibrium structures as well as the features of the multicenter bond commonly expressed by λ 3 ‐iodanes. This 3‐center‐4‐electron bond, established by the coupling of the bonds between iodine and its two ligands in apical position, will be shown to govern much of the rich and often unusual reactivity of these compounds. Further, the focus will be on the key steps involved in the electrophilic transfer of ligands (reductive elimination), nucleophilic substitution, and radical mechanisms) using Togni‐type reagents as well as diaryliodonium species. This study will show that once the basic principles of their reactivity are known, control over the outcome of a reaction involving iodane reagents can systematically be achieved. Finally, based on ab initio molecular dynamics simulations of the trifluoromethylation of an S‐nucleophile (thiophenol) in different solvents, the full complexity of a reaction where close competition between polar and radical mechanisms occurs, all leading to the same product, will be shown.

Diaryl hypervalent bromines and chlorines: synthesis, structures and reactivities

“…19,20 Consequently, despite their possible increased and complemental reactivity with respect to the iodine congeners, their applications remain largely unexplored. 4,21…”

“…1). 4,5 Such a unique electronic structure of hypervalent compounds translates into unusual reactivity, as breaking of X-L bonds occurs particularly easily. Therefore, hypervalent elements may be considered as extremely powerful leaving groups for example.…”

“…19,20 Consequently, despite their possible increased and complemental reactivity with respect to the iodine congeners, their applications remain largely unexplored. 4,21 Pivotal contributions by Ochiai, Miyamoto, and Uchiyama have signicantly inuenced the development of these areas, thus revealing and advancing the synthesis 22,23 and the unique reactivity of hypervalent bromines and chlorines as oxidants, [24][25][26][27] arylating agents 28 and as metal-free aminating agents of aliphatic alkanes and alkenes. 29,30 Although numerous reviews have been published discussing various aspects of the chemistry of l 3 -and l 5 -iodanes, 6,10,21,31,32 articles summarizing other hypervalent compounds are rare.…”

Nitrenium Ions from Amine‐Iodine(III) Combinations

“…Nitrenium ions get the stabilization mostly by interaction of the vacant p orbital at the nitrogen center with the filled non‐bonding orbital of an adjacent heteroatom such as oxygen or nitrogen . On the other hand, N ‐acyl‐ N ‐alkoxynitrenium ions 5 are easily accessible, relatively more stable and singlet in nature .…”

Trikoordinált jódvegyületek előállításainak és alkalmazásainak fejlesztése

“…Később kvantitatív magyarázatot a legegyszerűbb polikoordinált jódvegyületek, a jód-trifluorid és a trihidrido-λ 3 -jodán pályanergiáinak vizsgálata szolgáltatta, síktrigonális (D3h), trigonális piramis (C3v) és T-alakú (C2v) térszerkezetek figyelembevételével. [21] Mind a jód-trifluorid, mind a trihidrido-λ 3 -jodán térszerkezetei közül a T-alakú szerkezet engedi meg, hogy kötő kölcsönhatás alakuljon ki az energiaszintben közel álló legmagasabb betöltött molekulapálya (highest occupied molecular orbital; HOMO) és a legalacsonyabb betöltetlen molekulapálya (lowest unoccupied molecular orbital; LUMO) között, mely jelenség pszeudo-Jahn-Teller effektusként ismert. [22] Stirling a polikoordinált jódvegyületek kötésrendszerét vizsgálta kvantum mechanikai/molekula mechanikai (Quantum Mechanics/Molecular Mechanics; QM/MM) modellel.…”