Recent Advances in Visible Light Induced Palladium Catalysis

Abstract

Visible light-induced Pd catalysis has emerged as a promising subfield of photocatalysis. The hybrid nature of Pd radical species has enabled a wide array of radical-based transformations otherwise challenging or unknown via conventional Pd chemistry. In parallel to the ongoing pursuit of alternative, readily available radical precursors, notable discoveries have demonstrated that photoexcitation can alter not only oxidative addition but also other elementary steps. This Minireview highlights the recent progress in this area.

Keywords: Excited-State Reactivity; Olefins; Palladium; Photochemistry; Radical.

Figure 1.

General overview of visible light-induced Pd catalysis.

Scheme 1.

Desaturation of silyl ethers involving hybrid Pd aryl radical species.

Scheme 2.

Desaturation of aliphatic alcohols, amines, and carboxylic acids.

Scheme 3.

Desaturation of amides via aryl radical.

Scheme 4.

Remote desaturation of amides via N-centered radical.

Scheme 5.

Radical chain remote desaturation of N-alkoxypyridinium salts via O-centered radical.

Scheme 6.

Alkyl Heck reaction using α-functionalized alkyl halides.

Scheme 7.

Alkyl Heck reaction using unactivated alkyl bromides.

Scheme 8.

Alkyl Heck-type reaction of α-ester hydrazones.

Scheme 9.

Reductive alkylation of imines.

Scheme 10.

Radical relay alkyl Heck reaction using aliphatic alcohols.

Scheme 11.

Radical relay α-alkenylation of amides.

Scheme 12.

Radical relay Heck reaction using of o-methylbenzamides.

Scheme 13.

Radical relay Heck reaction involving intermolecular HAT.

Scheme 14.

Radical relay C-2 alkenylation of carbohydrates via SCS.

Scheme 15.

C-2 carbonylation of carbohydrates.

Scheme 16.

Difunctionalization via HAT/ATRC cascade involving hybrid Pd vinyl radical.

Scheme 17.

ATRC cascade via reversible XAT.

Scheme 18.

Difunctionalization via dearomatizative radical cyclization/alkenylation cascade.

Scheme 19.

Synthesis of polyarylfuran skeletons involving tandem difunctionalization.

Scheme 20.

Difunctionalization via intermolecular radical addition/cyclization cascade.

Scheme 21.

Cascade 1,1-difunctionalization of isocyanides.

Scheme 22.

Three-component difunctionalization via trapping of translocated radical with isocyanides.

Scheme 23.

Three-component difunctionalization via RPC of the translocated radical.

Scheme 24.

Cross-coupling via radical recombination.

Scheme 25.

Cross-coupling via Dowd-Beckwith ring expansion.

Scheme 26.

Defluorinative Suzuki–Miyaura cross-coupling of trifluoromethylarenes.

Scheme 27.

Suzuki–Miyaura cross-coupling of α-chloroacetyl compounds.

Scheme 28.

Carbonylative coupling of organic halides.

Scheme 29.

Carbonylative coupling of organic halides to acyl fluoride.

Scheme 30.

Remote carbonylative coupling via radical translocation by N-centered radical.

Scheme 31.

1,4-Carboamination of dienes via radical generation of π-allyl Pd species.

Scheme 32.

Three-component 1,2-carbofunctionalization of dienes.

Scheme 33.

Carbofunctionalization of 1,3-dienes.

Scheme 34.

Synergistic Pd/Cu-catalyzed enantioselective 1,4-bisalkylation of butadiene.

Scheme 35.

Allylic C–H amination of internal alkenes with aliphatic amines.

Scheme 36.

Brønsted acid-assisted hydroalkenylation of diazo compounds.

Scheme 37.

Pd^IIH-enabled hydroalkenylation of strained molecules.

Scheme 38.

Pd^IIH-enabled head-to-tail hydroalkenylation of alkenes.