Versatile Oxidation Methods for Organic and Inorganic Substrates Catalyzed by Platinum-Group Metals on Carbons

Abstract

Platinum-group metals on activated carbon catalysts, represented by Pd/C, Ru/C, Rh/C, etc., are widely utilized to accomplish green and sustainable organic reactions due to their favorable features, such as easy handling, recoverability, and reusability. The efficient oxidation methods of various organic compounds using heterogeneous platinum-group metals on carbons with or without added oxidants are summarized in this Personal Account. The oxidation of internal alkynes into diketones was effectively catalyzed by Pd/C in the presence of dimethyl sulfoxide and molecular oxygen or pyridine N-oxide. The Pd/C-catalyzed mild combustion of gaseous hydrogen with molecular oxygen provided hydrogen peroxide, which could be directly utilized for the oxidation of sulfide derivatives into sulfoxides. Furthermore, the Ru/C-catalyzed aerobic oxidation of primary and secondary alcohols gave the corresponding aldehydes and ketones, respectively. On the other hand, the dehydrogenative oxidation of secondary alcohols into ketones was achieved using Rh/C in water, and primary alcohols were effectively dehydrogenated by Pd/C in water under mildly reduced pressure to produce carboxylic acids.

Acceptorless Dehydrogenative Synthesis of Pyrimidines from Alcohols and Amidines Catalyzed by Supported Platinum Nanoparticles

“…Heterogeneous catalysts that promote one-pot reactions leading to value-added chemicals have attracted much attention. , Among various types of organic transformations that fall in this category, H 2 evolving, acceptorless dehydrogenation (AD) reactions have been developed to synthesize various types of organic compounds . AD reactions have advantages not shared by traditional reactions employing stoichiometric amounts of inorganic substances or O 2 as oxidants, because they do not require the use of oxidants or sacrificial hydrogen acceptors. − As a result, AD reactions do not generate stoichiometric amounts of waste . Gaseous H 2 generated in these processes is also valuable and can potentially be utilized as an energy source.…”

Catalyst-Free and Transition-Metal-Free Approach to 1,2-Diketones via Aerobic Alkyne Oxidation

“…During the past decade, one of the main choices for oxidizing alkynes to 1,2-diketones was transition-metal catalysis (Scheme ). Generally, various transition-metal-based catalysts (especially noble metals), such as Pd, Ru, Au, Ag, and Cu in combination with an oxygen source like DMSO, were employed but limited to narrow substrate scopes or higher reaction temperature . In recent years, photocatalytic oxidation of alkynes to 1,2-diketones using organic photocatalysts has also attracted much attention, since they are run in mild conditions with dioxygen or air as the oxidant .…”

C-Methylation of Alcohols, Ketones, and Indoles with Methanol Using Heterogeneous Platinum Catalysts

“…The organometallic agents are often air- and moisture-sensitive and can thus be difficult to handle . From the viewpoint of green and sustainable chemistry, it is highly desirable to develop new processes that do not rely on these toxic and hazardous materials, with the aim to eventually realize ideal yet practical processes …”

“…7 From the viewpoint of green and sustainable chemistry, it is highly desirable to develop new processes that do not rely on these toxic and hazardous materials, with the aim to eventually realize ideal yet practical processes. 8 Toward this aim, borrowing-hydrogen reactions have attracted much attention in recent years. 9−17 These reactions enable the catalytic formation of not only C−C bonds but also of many other types of linkages, including C−N bonds, using alcohols as the alkylating reagents, and are thus regarded as an atom-economical manufacturing approach for bulk and fine chemicals.…”