Hypervalent Iodine Reagents in Palladium-Catalyzed Oxidative Cross-Coupling Reactions

Abstract

Hypervalent iodine compounds are valuable and versatile reagents in synthetic organic chemistry, generating a diverse array of useful organic molecules. Owing to their non-toxic and environmentally friendly features, these reagents find potential applications in various oxidative functionalization reactions. In recent years, the use of hypervalent iodine reagents in palladium-catalyzed transformations has been widely studied as they are strong electrophiles and powerful oxidizing agents. For instance, extensive work has been carried out in the field of C-H bond functionalization via Pd-catalysis using hypervalent iodine reagents as oxidants. In addition, nowadays, iodine(III) reagents have been frequently employed as arylating agents in Pd-catalyzed C-H arylation or Heck-type cross-coupling reactions. In this review, recent advancements in the area of palladium-catalyzed oxidative cross-coupling reactions using hypervalent iodine reagents are summarized in detail.

Keywords: bond formation; catalyst; hypervalent iodine reagents; oxidant; palladium.

Graphical Abstract

Figure 1

Examples of hypervalent iodine(III)/(V) reagents 1–16.

Scheme 1

(A) Pd(II)-catalyzed synthesis of substituted catechols 19 using PhI(OAc)₂ 1 as an oxidant and (B) Pd(II)-catalyzed synthesis of cyclic ethers 27 using PhI(OAc)₂ 1 as an oxidant.

Scheme 2

(A) Pd(II)-catalyzed α,α-disubstituted benzofuran-2-ones 31 using PhI(OAc)₂ 1 and (B) Pd(II)-catalyzed synthesis of γ-lactones 34 using oxidant PhI(OAc)₂ 1.

Scheme 3

Pd(II)-catalyzed ortho C–H benzoxylation of 2-arylpyridines 38 using substituted iodobenzene dibenzoates derivatives 39 as oxidant and source of benzoxyl group.

Scheme 4

Pd(II)-catalyzed C3-acetoxylation of substituted indoles 43 to afford C3-acetoxylated indoles 44 using PhI(OAc)₂ 1.

Scheme 5

(A) Pd-catalyzed PIDA-mediated C(sp³)–H acetoxylation of substrates 47 and (B) Pd-catalyzed C(sp³)–H acetoxylation of alkylamines 50 using oxidant PIDA 1.

Scheme 6

Pd-catalyzed C(sp³)–H bond alkoxylation of aminoquinoline-derived substrates 53 to provide β-alkoxylated products 55 using cyclic hypervalent iodine(III) reagent 12.

Scheme 7

(A) Pd(II)-catalyzed C–H oxidation of terminal alkenes 61 using DMP 8 as an oxidant and (B) Pd(II)-catalyzed C–H phosphorylation/sulfonation of methylquinolines 63 using hypervalent iodine reagent 64.

Scheme 8

(A) Pd(II)-catalyzed synthesis of 3-(1-arylmethylene)oxindoles 69 using iodine(III) reagent 68 and (B) Pd(II)-catalyzed enantioselective synthesis of bicyclic lactones 76 by employing terminal oxidant PhI(OAc)₂ 1.

Scheme 9

Pd(II)-catalyzed synthesis of bicyclic heterocycles 78 from 1,6-enynes 77 using oxidant PhI(OAc)₂ 1.

Scheme 10

Pd(II)-catalyzed Hseck-type coupling reactions using hypervalent iodine(III) reagents 84.

Scheme 11

(A) Pd(OAc)₂-catalyzed synthesis of azetidines 92 using oxidant PhI(OAc)₂ 1 and (B) Pd(OAc)₂-catalyzed synthesis of indolines 94 using oxidant PhI(OAc)₂ 1.

Scheme 12

(A) Palladium-catalyzed C–H borylation of olefins 97 mediated by PhI(TFA)₂ 2 and (B) Palladium-catalyzed C–H silylation of terminal olefins 102 using PhI(OCO(4-NO₂C₆H₄))₂ 105 as an oxidant.

Scheme 13

(A) Pd(II)-catalyzed C–H fluorination of 8-methylquinoline analogs 108 using oxidant PhI(OPiv)₂ 3 and (B) Pd(II)-catalyzed C–H iodination of phenol carbamates 111 by employing Togni's reagent 12b.

Scheme 14

Plausible mechanism for the Pd(II)-catalyzed difunctionalization of alkenes 61.

Scheme 15

(A) Pd(II)-catalyzed 1,1-difuntionalization of acrylate derivatives 119 using iodine(III) reagent 121 and (B) Pd(II)-catalyzed 1,1-difuntionalization of terminal olefins 61 using iodine(III) reagent 130 as oxidant.

Scheme 16

Pd-catalyzed intramolecular oxyalkynylation of phenols 132 and aminoalkynylation of activated amides 135 by using TIPS-EBX 15 as acetylene transfer reagent.

Scheme 17

(A) Intermolecular diamination of internal alkenes 137 using Pd/PhI(OPiv)₂-catalytic system and (B) Palladium-phthalimidato complex-catalyzed diamination of alkenes 61 using PhI(OPiv)₂ 3 as oxidant.

Scheme 18

(A) Pd(II)-catalyzed PIDA-mediated aminoacetoxylation of alkenes 137 and (B) Pd(II)-catalyzed aminocarbonylation of alkenes 61 induced by iodine(III) reagent 130.

Scheme 19

Pd(II)-catalyzed oxycarbonylation of alkenes 154 and 156 using PhI(OAc)₂ 1 as an oxidant.

Scheme 20

(A) Pd(II)-catalyzed asymmetric 1,2-dioxygenation chiral oxime allyl ether 107 using PhI(OBz)₂ 160 and (B) Pd(II)-catalyzed iodofluorination of alkenes 110 employing fluoroiodane reagent 166.