Oxidations manganese dioxide

Isoxazole-5-carbaldehyde was prepared by the manganese dioxide oxidation of 5-hydroxymethylisoxazole (67T4697), the latter being formed from sodium fulminate and propargyl alcohol in greater than 90% yield. 

Manganese(VI) complexes,4,109-111 Manganese(VII) complexes, 4,109-111 Manganese dioxide oxidation, 6, 356 Manganese gluconate... 

Ogawa and co-workers37 have reported the synthesis of 6,7-benzo-4,9-epoxy[ 11]-annulenone 60. Manganese dioxide oxidation of the bis(hydroxymethylene)benzo-xepin 57 gave the dialdehyde 58 which on condensation with dimethyl acetonedicarb-oxylate 23 in chloroform in presence of piperidinium acetate gave the diester 59. This on hydrolysis followed by decarboxylation gave the annulenone 60. The NMR spec-... 

Among the oxidative procedures for preparing azo compounds are oxidation of aromatic amines with activated manganese dioxide oxidation of fluorinated aromatic amines with sodium hypochlorite oxidation of aromatic amines with peracids in the presence of cupric ions oxidation of hindered aliphatic amines with iodine pentafluoride oxidation of both aromatic and aliphatic hydrazine derivatives with a variety of reagents such as hydrogen peroxide, halogens or hypochlorites, mercuric oxide, A-bromosuccinimide, nitric acid, and oxides of nitrogen. 

Using activated manganese dioxide oxidations, even 2-aminopyridine has been converted into 2-azopyridine (m.p. 85°C). When mixtures of two anilines are oxidized together, the products isolated are only the symmetrically substituted azobenzenes [69b]. 

Treatment of the 2-oxide (6) with acids, zinc(II), copper(I) ions, or methyl iodide affords the tetrazene (15). Oxidation of the same compound with hydrogen peroxide led to the bis(nitrosamine) (16) manganese dioxide oxidizes (6) to l,4-dimethyl-l,6-dihydro-l,2,3,4-tetrazin-5(4iT)-one 2-oxide (17), while on oxidation with potassium permanganate a compound was isolated which was formulated as l,4-dimethyltetrazol-5-one 2-oxide (18 Scheme 2) (78HCA1622). 

A convenient method for the specific introduction of 2H or 3h (or both) into a molecule is by ketone reduction with labeled metal hydride. Beale and MacMillan (10) have utilized this method for the preparation of GAs labeled at the 1, 2 or 3 positions from GA3 or GA7 (Figure 12). One point of interest is the lithium borohydride reduction of the enone formed by manganese dioxide oxidation of GA3 or GA7. When the reaction is carried out in anhydrous tetrahydrofuran it proceeds in two steps. Initially the lithium enolate is formed which incorporates a proton at carbon-2 from the acid used in the work-up, forming the 3 ketone. This ketone is reduced to the 3 -alcohol by the borohydride which is decomposed more slowly than is the lithium enolate. Thus it is possible to introduce two different labels in a single reaction. 

Neither of these systems has been prepared in the fully conjugated state. The tetrahydro-isoxazolo[4,3-e][l,2,4]triazine (145) is prepared by cyclization of the benzylidene triazinone (144) with hydroxylamine (Equation (18)) <82iJC(B)ii5>. Manganese dioxide oxidation of the isoxazole (146) forms the isoxazolo[4,5-e]triazine derivative (147) (Equation (19)) <86JHC1795>. 

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