Recent advancements in iodide/phosphine-mediated photoredox radical reactions

Abstract

Photoredox catalysis plays a crucial role in contemporary synthetic organic chemistry. Since the groundbreaking work of Shang and Fu on photocatalytic decarboxylative alkylations in 2019, a wide range of organic transformations, such as alkylation, alkenylation, cyclization, amination, iodination, and monofluoromethylation, have been progressively achieved using a combination of iodide and PPh₃. In this review, we primarily focus on summarizing the recent advancements in inexpensive and readily available iodide/phosphine-mediated photoredox radical transformations.

Keywords: annulation; decarboxylative; iodide/phosphine; photocatalytic; radical reaction.

Scheme 1

Photocatalytic decarboxylative transformations mediated by the NaI/PPh₃ catalyst system.

Scheme 2

Proposed catalytic cycle of NaI/PPh₃ photoredox catalysis.

Scheme 3

Decarboxylative alkenylation of redox-active esters by NaI/PPh₃ catalysis.

Scheme 4

Decarboxylative alkenylation mediated by NaI/PPh₃ catalysis.

Scheme 5

NaI-mediated photoinduced α-alkenylation of Katritzky salts 7.

Scheme 6

n-Bu₄NI-mediated photoinduced decarboxylative olefination.

Scheme 7

Proposed mechanism of the n-Bu₄NI-mediated photoinduced decarboxylative olefination.

Scheme 8

Photodecarboxylative alkylation of redox-active esters with diazirines.

Scheme 9

Photoinduced iodine-anion-catalyzed decarboxylative/deaminative C–H alkylation of enamides.

Scheme 10

Photocatalytic C–H alkylation of coumarins mediated by NaI/PPh₃ catalysis.

Scheme 11

Photoredox alkylation of aldimines by NaI/PPh₃ catalysis.

Scheme 12

Photoredox C–H alkylation employing ammonium iodide.

Scheme 13

NaI/PPh₃/CuBr cooperative catalysis for photocatalytic C(sp³)–O/N cross-coupling reactions.

Scheme 14

Proposed mechanism of NaI/PPh₃/CuBr cooperative catalysis for photocatalytic C(sp³)–O/N cross-couplings.

Scheme 15

Photocatalytic decarboxylative [3 + 2]/[4 + 2] annulation between enynals and γ,σ-unsaturated N-(acyloxy)phthalimides.

Scheme 16

Proposed mechanism for the decarboxylative [3 + 2]/[4 + 2] annulation.

Scheme 17

Decarboxylative cascade annulation of alkenes/1,6-enynes with N-hydroxyphthalimide esters.

Scheme 18

Decarboxylative radical cascade cyclization of N-arylacrylamides.

Scheme 19

NaI/PPh₃-driven photocatalytic decarboxylative radical cascade alkylarylation.

Scheme 20

Proposed mechanism of the NaI/PPh₃-driven photocatalytic decarboxylative radical cascade cyclization.

Scheme 21

Visible-light-promoted decarboxylative cyclization of vinylcycloalkanes.

Scheme 22

NaI/PPh₃-mediated photochemical reduction and amination of nitroarenes.

Scheme 23

PPh₃-catalyzed alkylative iododecarboxylation with LiI.

Scheme 24

Visible-light-triggered iodination facilitated by N-heterocyclic carbenes.

Scheme 25

Visible-light-induced photolysis of phosphonium iodide salts for monofluoromethylation.