Quinone‐Catalyzed Selective Oxidation of Organic Molecules

Abstract

Lead In Quinones are common stoichiometric reagents in organic chemistry. High potential para-quinones, such as DDQ and chloranil, are widely used and typically promote hydride abstraction. In recent years, many catalytic applications of these methods have been achieved by using transition metals, electrochemistry or O2 to regenerate the oxidized quinone in situ. Complementary studies have led to the development of a different class of quinones that resemble the ortho-quinone cofactors in Copper Amine Oxidases and mediate efficient and selective aerobic and/or electrochemical dehydrogenation of amines. The latter reactions typically proceed via electrophilic transamination and/or addition-elimination reaction mechanisms, rather than hydride abstraction pathways. The collective observations show that the quinone structure has a significant influence on the reaction mechanism and have important implications for the development of new quinone reagents and quinone-catalyzed transformations.

Palladium(II) Catalyzed Cyclization-Carbonylation-Cyclization Coupling Reaction of (ortho-Alkynyl Phenyl) (Methoxymethyl) Sulfides Using Molecular Oxygen as the Terminal Oxidant

“…Free hydroxyl groups were also tolerated. The scope of the substrate for the CCC-coupling reaction was expanded further by investigating the reactions of substrates bearing R 2 substituents (Table 2, Entries [13][14]. The reactions of 1m-o bearing a Cl substituent, methyl group, and methoxy group in an aromatic moiety proceeded well.…”

“…The initial steps of the CCC-coupling reaction are mediated by Pd II [5] and p-benzoquinone acts as a co-oxidant (ETM) to transfer protons and electrons from palladium to CuCl 2 . Finally, CuCl is re-oxidized by molecular oxygen, the terminal oxidant [13,14].…”

“…When the solvent was DMSO-d 6 , solvent peak was used as a reference (2.50 ppm for 1 H, and 39.5 ppm for 13 C). 13 C-NMR spectra were recorded at 100 MHz. All reagents were purchased from commercial sources and used without purification.…”

Quinone 1 e– and 2 e–/2 H+ Reduction Potentials: Identification and Analysis of Deviations from Systematic Scaling Relationships

“…2 Quinones are also the focus of increased attention in energy storage and conversion applications, including redox flow batteries, dye-sensitized solar cells, and water-splitting devices. 3 Studies in our labs have focused on the use of quinones as electron-proton transfer mediators for O2 reduction 4 and as aerobic oxidation catalysts that resemble oxidase enzymes with quinone active sites.…”

Stereodynamic Quinone–Hydroquinone Molecules That Enantiomerize at sp3-Carbon via Redox-Interconversion

“…12 In synthetic applications, quinones are often employed as electron shuttles in reactions that are either reductive or oxidative in nature. 13,14 Furthermore, the redox-properties of these molecules have been used in applications ranging from in vivo imaging, and biomimetic studies to clinical diagnostics. 15–21 Importantly, the 1:1 mixture of quinone and hydroquinone, often called “quinhydrone,” has been described as a charge transfer complex.…”