Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

Abstract

Organocatalysis is widely recognized as a key synthetic methodology in organic chemistry. It allows chemists to avoid the use of precious and (or) toxic metals by taking advantage of the catalytic activity of small and synthetically available molecules. Today, the term organocatalysis is mainly associated with redox-neutral asymmetric catalysis of C–C bond-forming processes, such as aldol reactions, Michael reactions, cycloaddition reactions, etc. Organophotoredox catalysis has emerged recently as another important catalysis type which has gained much attention and has been quite well-reviewed. At the same time, there are a significant number of other processes, especially oxidative, catalyzed by redox-active organic molecules in the ground state (without light excitation). Unfortunately, many of such processes are not associated in the literature with the organocatalysis field and thus many achievements are not fully consolidated and systematized. The present article is aimed at overviewing the current state-of-art and perspectives of oxidative organocatalysis by redox-active molecules with the emphasis on challenging chemo-, regio- and stereoselective CH-functionalization processes. The catalytic systems based on N-oxyl radicals, amines, thiols, oxaziridines, ketone/peroxide, quinones, and iodine(I/III) compounds are the most developed catalyst types which are covered here.

A Mechanistic Investigation of the N-Hydroxyphthalimide Catalyzed Benzylic Oxidation Mediated by Sodium Chlorite

“…1 H NMR (400 MHz, CDCl 3 ) δ 7.93 (dd, J = 7.5, 1.0 Hz, 1H), 7.69 (td, J = 7.5, 1.0 Hz, 1H), 7.54 (td, J = 7.5, 1.0 Hz, 1H), 7.50 (dt, J = 7.5, 1.0 Hz, 1H), 5.33 (s, 2H). 13 69 Electronic Calculations. Calculations were conducted using the GAUSSIAN16 software package.…”

The versatility of DABCO as a reagent in organic synthesis: a review

“…The broad spectrum of these processes includes oxidative coupling reactions, functional group transformations, oxidative cyclizations and CH-functionalization. 126–130 Due to the selectivity issues along with the frequent requirement for hazardous transition metal salts and oxidants, such oxidation techniques are often considered as a hurdle in organic synthesis. 131,132 However, in the recent past, organophotoredox catalysis has emerged as another major type of catalysis that has garnered significant attention.…”

g-C3N4 catalysed sustainable synthesis of (hetero)aryl acids and regioselective α-bromo ketones in one pot under visible light catalysis

“…1 These are mainly produced through the oxidation of alcohols, 2–10 aldehydes 11–15 and methylarenes 16–20 as well as through the oxidative cleavage of unsaturated molecules like olefins and alkynes. 21 It is generally known that benzyl chlorides and bromides are converted to benzaldehydes and benzyl alcohols on an industrial scale employing heating with stoichiometric excess of aqueous solutions of metal oxides, hydroxides, or carbonates. Nevertheless, despite many reported procedures, direct oxidation of benzyl halides to benzoic acids employing environmentally benign methodologies turns out to be advantageous from the synthetic standpoint.…”