Catalytic Wacker‐type Oxidations Using Visible Light Photoredox Catalysis

Abstract

A combined palladium/photoredox catalytic system for the efficient oxidation of terminal olefins to the corresponding methyl ketones is presented. The interplay of air, water, and light leads to a protocol in which the stoichiometric oxidants required for oxidative palladium catalysis are substituted with catalytic, single‐electron transfer processes. Detailed mechanistic investigations revealed the role of the key components, in situ generated species, and catalysts. A broad range of substrates was examined in homogeneous as well as heterogeneous photoredox protocols, delivering the desired products in good yields.

Markovnikov Wacker‐Tsuji Oxidation of Allyl(hetero)arenes and Application in a One‐Pot Photo‐Metal‐Biocatalytic Approach to Enantioenriched Amines and Alcohols

“…With the exception of the isomerization reaction, these transformations reduce catalytically active Pd(II) into Pd(0), which obviously needs to get reoxidized. In our particular case, it was envisaged that [Acr‐Mes]ClO 4 under blue light, in a similar approach than the one described by Fabry et al ., [25] could catalyze the recovery of the Pd(II) species. However, it was noticed that the photosensitizer was not strictly necessary, as the Wacker‐Tsuji oxidation also proceeded, just affecting to the product selectivity.…”

“…developed the Wacker‐Tsuji oxidation of various terminal alkenes to produce the corresponding methyl ketones, by mixing a palladium(II) salt and [Ir(ppy) 2 (bpy)]PF 6 as SET photocatalyst under white light in a DMF:H 2 O (6:1 v/v ) mixture at 120 °C. In this particular case, the photosensitizer reoxidized the palladium center transferring the electrons to the oxygen and closing the oxidative cycle [25] . It must be emphasized that the addition of the photocatalyst was strictly necessary.…”

“…In this particular case, the photosensitizer reoxidized the palladium center transferring the electrons to the oxygen and closing the oxidative cycle. [25] It must be emphasized that the addition of the photocatalyst was strictly necessary.…”

Selective oxidation of styrene by H2O2 over novel supported palladium(ii)-based catalysts

“…Wacker oxidation is also employed for the preparation of agrochemicals, fine chemicals and organic intermediates under mild conditions. [3][4][5][6][7] It can also be an intermediate process for other one-step reactions, and provides a possible mechanism for the design of some complex steps. 8,9 In addition, the distinguished Tsuji-Wacker oxidation may effectively convert more substrates to the corresponding target products in DMF-H 2 O medium.…”

Palladium/Iron-Catalyzed Wacker-Type Oxidation of Aliphatic Terminal and Internal Alkenes Using O2

“…These reactions require high temperatures (60–100 °C) and/or high O 2 pressures (2–10 atm) to smoothly promote the oxidation step. Polyoxometalates, − alkyl nitrites and nitrite salts, − and Ir or BiVO 4 photocatalysts have been reported as cocatalyst alternatives to Cu salts. The nonredox metal ion Sc­(III) can also operate as an efficient cocatalyst in the Pd­(OAc) 2 /Sc­(OTf) 3 /O 2 system …”