Iron‐Enabled Utilization of Air as the Terminal Oxidant Leading to Aerobic Oxidative Deoximation by Organoselenium Catalysis

Abstract

In contrast to conventional organoselenium-catalyzed oxidation reactions that require peroxide oxidants such as hydrogen peroxide, in this work we found that, addition of a low loading of iron (II) could enable the successful utilization of air as the terminal oxidant in organoseleniumcatalyzed oxidative deoximation reaction of ketoximes. This led to a new mild and relatively green aerobic oxidative deoximation method. Control reactions and X-ray photoelectron spectroscopy (XPS) analysis suggest that iron is crucial in the catalytic cycle, working to prohibit the deactivation of selenium catalyst through an iron-catalyzed aerobic oxidation of low valent selenium species by air to the active high valent selenium species. Since air can be utilized as the terminal oxidant, this work may contribute to the advance of organoselenium catalysis.

Organotellurium catalysis-enabled utilization of molecular oxygen as oxidant for oxidative deoximation reactions under solvent-free conditions

“…Thus, in this work, commercially available (PhTe) 2 was tested to catalyze the oxidative deoximation reaction, which, at present stage, usually requires chemical reagents generating a lot of solid waste [33], explosive oxidants [34,35], halogen-or nitro-contained solvents or additives [36], or precious metal catalysts [37]. By using organoselenium catalysts, the reaction occurred under relatively green conditions, but strong oxidants such as H 2 O 2 or transition metal co-catalysts were used to avoid the Se catalyst deactivation [21,34].…”

“…Because diselenides are stable compounds difficult to be directly re-oxidized by molecular oxygen under the general reaction conditions, strong chemical oxidants are excessively employed to restrain their generation so that the catalyst deactivation can be avoided [18][19][20]. Addition of iron salt as co-catalyst could promote the aerobic oxidation of diselenides into hypervalent organoselenium species, so that the Se/Fe-cocatalyzed oxidation reactions could utilize molecular oxygen as the terminal oxidant [21], but introducing transition metal components into the catalyst systems might bring new issues, such as the increased catalyst cost, waste generation and the transition metal residues that might limit the application scope of the products. In comparison with the recently booming progresses of organoselenium catalysis [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], organotellurium-catalyzed reaction was not well-documented yet [22][23][24][25].…”

“…Addition of iron salt as co-catalyst could promote the aerobic oxidation of diselenides into hypervalent organoselenium species, so that the Se/Fe-cocatalyzed oxidation reactions could utilize molecular oxygen as the terminal oxidant [21], but introducing transition metal components into the catalyst systems might bring new issues, such as the increased catalyst cost, waste generation and the transition metal residues that might limit the application scope of the products. In comparison with the recently booming progresses of organoselenium catalysis [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], organotellurium-catalyzed reaction was not well-documented yet [22][23][24][25]. Recently, we found that, owing to the lower Te-Te bond energy (149 kJ/mol vs. 192 kJ/mol of Se-Se) [26], ditellurides are even more active than diselenides, so that the (PhTe) 2 -catalyzed oxidation reactions could utilize molecular oxygen (O 2 ) as the mild, cheap and safe oxidant.…”

Metal Catalyzed Oxidation Reactions of Alkenes Using Eco-Friendly Oxidants

“…It efficiently catalyzed the oxidative of alkenes in dimethyl carbonate (DMC) under mild reaction conditions (Figure 18). The synergistic effect of Se with Fe in the material, Se/Fe 2 O 3 enhanced its catalytic activity [52].…”

AIBN‐Initiated Oxidative Deoximation Reaction: A Metal‐Free and Environmentally‐Friendly Protocol

“…Catalyzed by (PhSe) 2 , the reaction could occur under mild conditions using H 2 O 2 /air as oxidant [19a] . Introducing iron salt into the system could facilitate the re‐oxidation of low‐valent selenium species by air, so that the explosive H 2 O 2 could be avoided and air was utilized as the only oxidant for the process [19b] . In the last year, tellurium, the same axis element of selenium, was successfully applied in the catalytic oxidative deoximation reactions [20] .…”