Effect of the structure of N-hydroxyphthalimides on their catalytic activity in the oxidation of isopropylbenzene in the presence of cuprous salts

Theoretical Design of Multi‐Nitroxyl Organocatalysts with Enhanced Reactivity for Aerobic Oxidation

“…However, for NHNI (Figure 4), its gauche conformer is unstable in the gas phase and apolar benzene, and both conformers coexist in other solvents. These characteristics may explain its facile use at over 100 °C in the presence of sodium hydroxide23 or Co/Mn/Cu salts,24, 25 and also indicate its unsuitability for solvent‐free catalysis like NHPI 18. 26 Compound CL ‐ 5 is suggested to be facile to use under such harsh conditions owing to its structure, which is similar to that of NHNI.…”

“…Moreover, an analogous catalyst, namely N ‐hydroxynaphthalimide (NHNI), was employed in the aerobic oxidation of ethylbenzene23 and p ‐xylene24 and established higher conversion rates than NHPI over 100 °C. However, its oxidation of isopropylbenzene hardly occurred at 40 °C 25. These features drive us to gain a mature understanding of these differences in catalytic performance and possibly explore the limitations of this kind of catalysts.…”

An Efficient Method for the Catalytic Aerobic Oxidation of Cycloalkanes using 3,4,5,6-Tetrafluoro-N-Hydroxyphthalimide (F4-NHPI)

“…However, Lanzalunga et al has shown that the rate of oxidation of 1-(4methoxyphenyl)ethanol is possible to increase by introducing electron-withdrawing substituents in NHPI aryl ring, and therefore, the reactivity order parallels the increase of OH BDE in the substituted NHPIs [19]. The effect of the electron-withdrawing substituents on the aromatic ring of NHPI and the stability of the transition state after hydrogen abstraction reaction by the PINO radical was also discussed by others [20][21][22]. After getting positive effects by using the fluorinated alkyl chain in NHPI, our next aim was to investigate the catalytic activity of another lipophilic NHPI derivative by introducing four electronegative fluorine atoms directly in the aryl ring of NHPI.…”

Selective aerobic oxidation promoted by highly efficient multi-nitroxy organocatalysts

“…These features have stimulated the development of a wide array of strategies for targeted improvements in the involved chemical processes through the design of tailored catalysts and catalytic systems. These strategies include decoration of NHPIs with lipophilic chains [43][44][45][46] to improve solubility, immobilization of NHPIs on solid metal-organic framework solids or silica [47][48][49] for solvent-free use, NHPI modification with ion-pair compounds [38,50,51] to give facile recovery and increased reactivity, use of NHPIs with electron-withdrawing substituents [34,46] and multi-nitroxy organocatalysts [52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69] for enhanced activity, combined use of NHPI and photoinitiators such as naphthalene imides [70] or carbon materials [71] to avoid the use of sacrificial initiators, use of N-alkoxyphthalimides [40,72] for thermal catalysis above 100 °C or light-induced catalysis at room temperature under initiator/metal-free conditions, and physical adsorption [73] and polymer-supported [74,75] methods to improve recovery and recycling. Despite the continuing and extensive improvements in catalysis, efficient catalytic methods that have negligible environmental impacts, are economical, and address issues connected with long-term sustainability of these industrial processes have not yet been d...…”

“…This review focuses on selective oxidation protocols with multi-nitroxy organocatalysts developed in the last 15 years. The catalytic oxidation efficiencies of multi-nitroxy organocatalysts such as N,N-dihydroxypyromellitimide (NDHPI) [53][54][55][56][57][58][59] and N,N',N''-trihydroxyisocyanuric acid (THICA) [52,[60][61][62][63][64][65][66][67][68][69] (Fig. 1) are higher than that of NHPI in most cases, even if smaller amounts of catalysts are used.…”