Peroxydisulfate as an Oxidant in the Site‐Selective Functionalization of sp³ C–H Bonds

Abstract

The development of methodology for the site-selective functionalization of sp 3 C-H bonds has irrevocably altered the state of organic synthesis. These methods often rely on the use of strong oxidants in conjunction with transition-metal catalysis. Peroxydisulfate (S 2 O 8 2-) salts are some of the strongest inorganic oxidants known. They are low-cost crystalline solids that are stable at room temperature. Harmless sulfate salts are produced as a byproduct of their reactions, allowing S 2 O 8 2to serve as a 'green' alternative to other commonly employed oxidants. Despite these attractive properties, it has only been in the last ten years that the majority of sp 3 C-H functionalization reactions utilizing S 2 O 8 2for the diversification of complex molecules have been reported. The objective of this review is to provide a useful reference regarding the recent advancement of sp 3 C-H functionalization using S 2 O 8 2and to inspire the invention of new protocols utilizing this remarkable oxidant.

Palladium-Catalyzed Dehydrogenative Fluoroalkoxylation of Benzaldehydes

“…On the basis of the above results and related literature, ,, a possible mechanism for the palladium-catalyzed C–H oxidative fluoroalkoxylation of benzaldehydes was proposed (Figure ). First, benzaldehyde and amino acid A6 reversibly form imine intermediate A . Meanwhile, the active Pd­(II) species is generated in situ from Pd­(OAc) 2 with TFA .…”

“…To gain insight into the reaction mechanism, we independently synthesized the putative palladacycle intermediate (eq ). Pleasingly, the cyclopalladium intermediate 6 was isolated from the reaction system of benzaldehyde with stoichiometric Pd­(OAc) 2 , pyridine, and A6 . , Then, the cyclopalladium intermediate 6 was treated with TFE, K 2 S 2 O 8 , and TFA to give 3a in 55% yield (eq ). Subsequently, kinetic isotope effect (KIE) experiments were performed (eqs and ).…”

Selective Oxidation of Cyclohexane to Cyclohexanol/Cyclohexanone by Surface Peroxo Species on Cu-Mesoporous TiO2

“…The economical and safe persulfate salts (PSs) have also been extensively used for hydroxylation, fluorination, cyclization, and coupling reactions. − In general, SO 4 •– produced during PS activation is an important oxidizing species in the oxidation of various substrates. , For instance, SO 4 •– not only hydroxylates fluorobenzene and toluene to the corresponding p -fluorophenol and cresol but also decarboxylates 2-biphenyl acetic acid to the benzyl radical, which then undergoes intramolecular cyclization to yield fluorene . Ma et al also suggested that SO 4 •– activated the benzylic C–H and facilitated its further fluorination to benzylic C–F by Selectfluor.…”

Nitroxide‐Catalyzed Oxidative Amidation of Aldehydes to Yield N‐Acyl Azoles Using Sodium Persulfate

“…Persulfate salts are inexpensive, widely available crystalline solids that are very soluble in water and reasonably soluble in aqueous acetonitrile, small chain alcohols, and acetone and are beginning to attract interest in organic synthesis [34–38] . The peroxydisulfate ion (S 2 O 8 2− ) is a strong oxidant with an estimated standard redox potential of 2.01 V, this being higher than that of other peroxygen‐containing compounds such as hydrogen peroxide or sodium bisulfite.…”