Oxidation urea-hydrogen peroxide complex

Anhydrous peroxytrifluoroacetic acid is not easy to handle, but the procedure has recently been revised.121 Namely, reaction of urea-hydrogen peroxide complex (UHP) with tri-fluoroacetic anhydride in acetonitrile at 0 °C gives solutions of peroxytrifluoroacetic acid, which oxidize aldoximes to nitroalkanes in good yields (Eqs. 2.58 and 2.59). Ketoximes fail to react under these conditions, the parent ketone being recovered. 

Bentley et al.m recently improved upon Julia s epoxidation reaction. By using urea-hydrogen peroxide complex as the oxidant, l,8-diazabicyclo[5,4,0]undec-7-ene (DBU) as the base and the Itsuno s immobilized poly-D-leucine (Figure 4.2) as the catalyst, the epoxidation of a, (3-unsaturated ketones was carried out in tetrahydrofuran solution. This process greatly reduces the time required when compared to the original reaction using the triphasic conditions. 

Some recent advances have been reported in oxime oxidation, including the in situ generation of peroxytrifluoroacetic acid from the reaction of urea hydrogen peroxide complex with TFAA in acetonitrile at 0 °C This method gives good yields of nitroalkanes from aldoximes but fails with ketoximes. 

Varma and Naicker published a solid-state oxidative protocol for the transformation of nitriles to amides and of A-heterocycles to A-oxides employing the urea hydrogen peroxide complex (Scheme 156) . The A-oxides depicted in Scheme 156 were synthesized... 

The oxidation of picolinaldehydes to the corresponding Af-oxides with dimethyldioxirane proceeds in good yield without the need to protect the aldehyde function <99T12557>. The urea-hydrogen peroxide complex oxidizes pyridines to pyridine Af-oxides <990L189>. 

Use of the urea-hydrogen peroxide complex and /V,/V -bis(TMS) urea provides an improved method126 for the preparation of bis(TMS) peroxide, TMSOOTMS. In the presence of Fe(m)(picolinic acid)3, bis(TMS) peroxide carries out selective oxidation of alkanes to ketones by a non-radical mechanism. The Fe(III)-Fe(IV) manifold is believed to be responsible127. On the other hand, using FeCU in pyridine, alkyl chlorides are formed through a radical mechanism. Here, the Fe(n)-Fe(IV) manifold has been proposed128. 

Secondary amines 65 were easily oxidized [27] to the corresponding nitrones 66 by hydrogen peroxide or urea hydrogen peroxide complex in the presence of Se02 as a catalyst (Eq. 11). 

Varma, R. S., Naicker, K. P. The Urea-Hydrogen Peroxide Complex Solid-State Oxidative Protocols for Hydroxylated Aldehydes and Ketones (Dakin Reaction), Nitriles, Sulfides, and Nitrogen Heterocycles. Org. Lett. 1999,1, 189-191. 

Keywords 2-hydroxybenzaldehyde, sulfide, nitrile, pyridine, urea-hydrogen peroxide complex, catechol, sulfoxide, sulfinic ester, amide, pyridine-A-oxide... 

This reaction has been modified by using sodium percarbonate and urea-hydrogen peroxide complex as the oxidant. In addition, this reaction has been efficiently carried out in liquid ionic solvent. 

The effect of structural variation and the use of different caboxylate salts as cocatalysts was investigated by Pietikainen . The epoxidation reactions were performed with the chiral Mn(III)-salen complexes 173 depicted in Scheme 93 using H2O2 or urea hydrogen peroxide as oxidants and unfunctionalized alkenes as substrates. With several soluble carboxylate salts as additives, like ammonium acetate, ammonium formate, sodium acetate and sodium benzoate, good yields (62-73%) and moderate enantioselectivities (ee 61-69%) were obtained in the asymmetric epoxidation of 1,2-dihydronaphthalene. The results were better than with Ai-heterocycles like Ai-methylimidazole, ferf-butylpyridine. 

Highly enantioselective sulfoxidation was observed using the di-/t-oxo Ti(salen)/UHP (salen = A. A -bisisalicylal-dehydolethylenediamine UHP = urea hydrogen peroxide) catalyst complex in methanol (Equation 43). In oxidations of 1,3-dithiolane derivatives, enantioselectivity increased with the size of the 2-substituent <2002TL3259>. 

Furthermore, MTO catalyzes the 1,3-transposition of allylic alcohols (eq. (2)) [12 c]. This reaction does not require the presence of peroxides or peroxo complexes. Theoretical investigations on the allylic rearrangement have also been performed [12d]. Recently it has been reported that allylic alcohols as well as alkenes can be oxidized in an ambient-temperature ionic liquid using MTO and the urea hydrogen peroxide [12 e]. 

Alternative strategies to improve MTO-catalyzed oxidations have made use of host-guest inclusion chemistry [45-47]. It was found that a urea/hydrogen peroxide (UHP) complex is a very effective oxidant in heterogeneous alkene epoxida-... 

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