Diverse Reactions of Thiophenes, Selenophenes, and Tellurophenes with Strongly Oxidizing I(III) PhI(L)₂ Reagents

Abstract

We report the outcomes of the reactions of aromatic group 16 thiophene, selenophene, and tellurophene rings with the I(III) oxidants PhI(OAc)(OTf) and [PhI(Pyr)][OTf] (Pyr = pyridine). In all reactions, oxidative processes take place, with generation of PhI as the reduction product. However, with the exception of tellurophene with PhI(OAc)(OTf), +4 oxidation state complexes are not observed, but rather a variety of other processes occur. In general, where a C-H unit is available on the 5-membered ring, an electrophilic aromatic substitution reaction of either -IPh or pyridine onto the ring occurs. When all positions are blocked, reactions with PhI(OAc)(OTf) give acetic and triflic anhydride as the identifiable oxidative byproducts, while [PhI(Pyr)][OTf] gives pyridine electrophilic aromatic substitution onto the peripheral rings. Qualitative mechanistic studies indicate that the presence of the oxidizable heteroatom is required for pyridine to act as an electrophile in a substantial manner.

[Ag]2[B12Cl12] as a Catalyst in PhICl2 Mediated Chlorination

“…A 1 H-NMR spectrum of an aliquot of the reaction mixture revealed the presence of several species. Notably, similar reactivity was observed in the presence of catalytic (10 mol%) We have previously observed electrophilic aromatic substitution processes in reactions with electron poor λ 3 -iodane species, [12] and therefore surmised that residual PhI generated from the decomposition of PhICl2 was undergoing electrophilic aromatic chlorination. [Ag]2[B12Cl12] was essential for the reaction to proceed, suggestive of an "iodonium" type mechanism, in which Ag(I) abstracts a chloride from PhICl2 resulting in a in an active [PhICl] + species, which is presumably stabilised by the weakly coordinating [B12Cl12] 2anion (Scheme 3).…”

Heterocyclic group transfer reactions with I(iii) N-HVI reagents: access to N-alkyl(heteroaryl)onium salts via olefin aminolactonization

“… 24–32 Considering the versatile group transfer reactivity of I( iii ) reagents 33,34 we wondered if N -HVIs could serve as “heterocyclic group transfer” (HGT) reagents to access diverse N -alkyl(heteroaryl)onium salts through incorporation of the heterocyclic ligand into a substrate of interest. 35 Given the appealing features of I( iii ) reagents, and the modular synthesis of N -HVIs, we envisioned that this could serve as a convenient, general platform for the synthesis of diverse (heteroaryl)onium salts from alkenes, providing a novel means of accessing these valuable functional handles.…”

Reactions of PhIX2 I(iii) oxidants with heavy triphenyl pnictines

“…[12][13][14] In the main group we have explored the chemistry of these dicationic I(III) oxidants with aromatic group 16 rings, which largely resulted in electrophilic aromatic substitution type reactions on the ring or ring substitutents. 15,16 We also reported one reaction in group 15, the reaction of Ph3P with [PhI(4-DMAP)2] 2+ , which resulted in oxidation of phosphorus to P(V) and ligation of a 4-DMAP giving dicationic complex 6 (Scheme 4), 17 previously reported by Burford using the oxidation/halide abstraction method from the phosphine. 18 No reaction is observed between PPh3 and PhI(OAc)2.…”