[56790-59-1] · C6H5NO4Se · o-Nitrobenzeneseleninic Acid · (MW 234.08)
(catalyst with hydrogen peroxide for the epoxidation of alkenes,1,2 the oxidation of sulfides,2 the Baeyer-Villiger oxidation of aromatic aldehydes and ketones,3 and the conversion of aldehydes to esters4 and nitriles5)
Physical Data: mp 184-186 °C (dec).
Solubility: slightly sol water; sol DMF.
Preparative Methods: obtained from the oxidation of bis(2-nitrophenyl) diselenide with 30% Hydrogen Peroxide6 or concd Nitric Acid.7 Bis(2-nitrophenyl) diselenide is prepared by reaction of Lithium Diselenide with 2-nitrochlorobenzene8 or from the base hydrolysis of 2-nitrophenyl selenocyanate.1
Handling, Storage, and Precautions: both 2-nitrobenzeneseleninic acid and bis(2-nitrophenyl) diselenide are stable indefinitely at room temperature. Selenium compounds are potentially toxic and should be handled in a fume hood.
2-Nitrobenzeneseleninic acid catalyzes the epoxidation of alkenes in CH2Cl2 under two-phase reaction conditions with 30% Hydrogen Peroxide (eq 1).1,2,9,10 Bis(2-nitrophenyl) diselenide is typically used as an in situ source for 2-nitrobenzeneseleninic acid, and anhydrous MgSO4 is added to facilitate epoxidation by scavenging excess water (see also 2,4-Dinitrobenzeneseleninic Acid).1
As a safe, convenient, and inexpensive alternative to peroxycarboxylic acids, 2-nitroperoxybenzeneseleninic acid (eq 2),11 catalytically generated, converts sulfides either to sulfoxides (>95%) or cleanly to sulfones depending on the amount of H2O2 used.2 The low solubility of catalyst in both CH2Cl2 and H2O allows acid-sensitive substituents to remain intact during the Baeyer-Villiger oxidation of aromatic aldehydes (eq 3).3 a,b-Unsaturated aldehydes give vinyl formates as the major products, but the oxidation of ketones is limited to polymethoxyacetophenones, with 90% H2O2 being recommended to obtain reasonable reaction rates.12
Aromatic and aliphatic aldehydes are converted into esters via their aldoximes or aldoxime O-methyl ethers by treatment with alcohol solutions of 30% H2O2 in the presence of a catalytic amount of 2-nitrobenzeneseleninic acid (eq 4).4 These oxidation conditions are also effective for converting aldehyde dimethylhydrazones to nitriles (eq 5).5 Selenium(IV) Oxide catalyzes both transformations, but the yields are generally lower.
James M. Renga
DowElanco, Indianapolis, IN, USA