Methyltrioxorhenium-Catalyzed Oxidation of Aromatic Aldoximes

Abstract

The first catalytic oxidation of aryl oximes to nitro compounds by means of methyltrioxorhenium and urea hydroperoxide is reported. The formation of carbamates, probably occurring through formation of nitrile oxide intermediates, has been observed from 2,6-disubstituted aryl oximes.

Sustainable routes to polyurethane precursors

“…Cardona et al developed the first catalytic oxidation procedure to convert aromatic aldoximes in the presence of alcohols to the corresponding carbamates (Scheme 21). 153 The oxidation is performed with catalytic quantities of methyl trioxorhenium (MTO) and an excess of urea hydrogen peroxide as the oxidant. Long reaction times (4-8 days) at room temperature are required to obtain the carbamates in moderate yields ranging from 35 to 72%.…”

Selective Oxidation of Aromatic Amines to Nitro Derivatives using Potassium Iodide‐tert‐Butyl Hydroperoxide Catalytic System

“…Several stoichiometric oxidants such as peracetic acid, [5] MnO 2 , [6] PbA C H T U N G T R E N N U N G (OAc) 4 , [7] HgA C H T U N G T R E N N U N G (OAc) 2 [8] and dioxirane. [9] or with peroxides in combination with metal catalysts like Mo, [10] W, [11] Zr, [12] Re, [13] Ti silicates or Cr silicates, [14] Fe(3+) and Mn(3+) tetraarylporphyrins [15] etc., are reported for the oxidation of aromatic amines. The nature of the oxidation products formed depends on the type of the oxidant, catalyst and reaction conditions.…”

“…In the cases of 2,6-diethyl-, 2-benzyl and 2-methoxy-6-methylaniline derivatives, the lower yields may be due to steric factors ( Table 2, entries 7-9). Aromatic amines with electron-withdrawing groups have shown lower conversions ( Table 2, entries [11][12][13][14][15][16][17]. The reaction with 4-nitroaniline resulted in the formation of 2,4-dinitrobenzene in 67% yield.…”

Recent Development of Rhenium-Catalyzed Organic Synthesis

“…On the other hand, Cardona and co-workers employed the catalytic oxidation system MTO/UHP (UHP = urea hydroperoxide) to further oxidize benzaldehyde oximes in methanol to nitro compounds in moderate yields [95] (Scheme 63).…”