The role of hypervalent iodine(iii) reagents in promoting alkoxylation of unactivated C(sp³)–H bonds catalyzed by palladium(ii) complexes

Abstract

Although Pd(OAc)2-catalysed alkoxylation of the C(sp3)-H bonds mediated by hypervalent iodine(III) reagents (ArIX2) has been developed by several prominent researchers, there is no clear mechanism yet for such crucial transformations....

Oxidative Addition of a Hypervalent Iodine Compound to Cycloplatinated(II) Complexes for the C–O Bond Construction: Effect of Cyclometalated Ligands

“…It shows that the reaction comprises concurrent cleavage of the I–OAc bond and construction of a Pt–I bond, which is prolonged to the production of intermediate IM2-B . The resultant five-coordinate intermediate is properly an iodonium salt, and its empty orbital on the iodine­(III) interacts with d z 2 orbital on the Pt atom . Similar to IM1-A , the geometry of the platinum center in intermediate IM2-B is square-pyramidal, and the incoming iodonium [PhI­(OAc)] + group is located in the apical position of Pt atom.…”

“…In this intermediate, the carbonyl oxygen group of PhI­(OAc) 2 binds to the platinum center. Indeed, a similar OA mechanism is previously reported in the palladium­(II) and platinum­(II) compounds. , The stronger coordination ability of carbonyl oxygen atoms than the bonded oxygens to the iodine atom in PhI­(OAc) 2 may lead to this nucleophilic occurrence . In the next step, the acetate ligand transfers from the iodine to the platinum atom via transition state TS-B and gives five-coordinated intermediate IM2-B as an iodonium salt.…”

“…Indeed, a similar OA mechanism is previously reported in the palladium(II) and platinum(II) compounds. 41,42 The stronger coordination ability of carbonyl oxygen atoms than the bonded oxygens to the iodine atom in PhI(OAc) 2 may lead to this nucleophilic occurrence. 42 Figure 5 exhibits the free energy barriers for the OA reactions of 1b with PhI(OAc) 2 .…”

Two-Stage Catalysis in the Pd-Catalyzed Formation of 2,2,2-Trifluoroethyl-Substituted Acrylamides: Oxidative Alkylation of PdII by an IIII Reagent and Roles for Acetate, Triflate, and Triflic Acid

“…The reaction of substrate LH 2 (1) with Pd(OAc) 2 [Pd 3 (OAc) 6 model] to yield 4 is calculated to be almost thermoneutral (details in the Supporting Information), as found in a related system. 17 Exploration of NH-deprotonation and CH-activation led to the formation of Pd(L)(NCMe) (5), supportive of the proposal 6 that 5 is a likely candidate for the subsequent oxidation step (Scheme 1a). We then studied the oxidation process commencing from 5, as a feasible component reaction for both the initial and subsequent stages of the reaction.…”

Palladium-Catalyzed Organic Reactions Involving Hypervalent Iodine Reagents

“…Due to the coordination between the alkoxylated product and the Pd(II) center, the regeneration of the active catalyst is endergonic. Thus, the subsequent catalytic cycles proceed with a substantially greater activation barrier in comparison to the initial catalytic cycle [70].…”