Investigating the Mechanism of Palladium‐Catalyzed Radical Oxidative C(sp³)−H Carbonylation: A DFT Study

Abstract

Palladium (Pd)-catalyzedr adical oxidativeC ÀHc arbonylation of alkanes is au seful methodf or functionalizing hydrocarbons, but there is still al ack of understanding of the mechanism, which restricts the application of this reaction. In this work, density functional theory (DFT) calculations were carried out to studythe mechanism for aPd-catalyzed radical esterification reaction. Twop lausible reaction pathways have been proposed and validated by DFT calculations. The computational results revealt hat the generated alkyl radicalp refers to add to the carbon monoxide (CO) molecule to form ac arbonyl radical beforeb onding with the Pd species. Radicala ddition ontoP df ollowed by CO migratory insertion wasu nfavorable owing to the high energy barrieroft he migratory insertion step. The regioselectivity of the C(sp 3 )ÀHc arbonylationw as also investigated by DFT. The results show that the regioselectivity is controlled by both the bond dissociation energy of the reactingC ÀH bond andt he stabilityo ft he corresponding generated carbon radical.C ompetitives ide reactions also affected the yield and regioselectivity owing to the rapid consumption of the stable radical intermediate.[a] Q.

Direct C–H Arylation of Aldehydes by Merging Photocatalyzed Hydrogen Atom Transfer with Palladium Catalysis

“…Density functional theory (DFT) calculations enabled insight into the mechanisms for the generation of ketone products and for the coupling of the palladium catalytic cycle and the photocatalytic cycle. As shown in Figure , abstraction of hydrogen from an aldehyde by the excited AQ reagent (*­[AQ]) was the proposed origin of the acyl radical and therefore accompanied the generation of an AQ-H radical. ,− Calculations indicated two plausible pathways for the generation of the aromatic ketone products − (Figures and ). In path A, oxidative addition of the Pd 0 catalyst precursor with aryl halide leads to a Pd II intermediate INT1A , which is then oxidized by the acyl radical to form a Pd III intermediate INT2 (i.e., Pd 0 –Pd II –Pd III path).…”

Palladium-catalyzed radical arylation of N-hydroxyphthalimides with triphenyl phosphites as an unusual arylating agent via C(sp2)–O bond cleavage

“…24,26 The resulting complex 5a could readily be reduced to the active catalytic species 6a in the presence of an excess amount of TPP and water. 24,26,27 Next, the radical PINO derived from NHPI could react with complex 6a 28 to form intermediate II . Then, intermediate II could be converted into intermediate III via intramolecular electron transfer.…”

Mechanistic Insights into the Palladium-Catalyzed Perfluoroalkylative Carbonylation of Unactivated Alkenes to β-Perfluoroalkyl Esters: A DFT Study

“…Thus, it further rationalizes the Path II extrusion. On the basis of the previous experimental results, , in the presence of K 2 CO 3 , PhOH could be transformed into PhO – due to the minus Gibbs reaction free energy (eq S2). Thus, F can be generated from D by the exchange between I – and PhO – , as well as the following reduction–elimination reaction.…”