Nitrile TV-oxides

Table 11 Stability of Some Nitrile TV-Oxides, R—C=N—O, towards Dimerization to Furoxans <70EU69>...

Both 4,5-dimethylisoxazole and 3,4-dimethylisoxazole are formed on treatment of the sodium derivative of a-methylacetaldehyde with hydroxylamine hydrochloride. The two isomers can be separated by fractional distillation (62HC(17)1, p. 54). 4,5-Dialkylisoxazole or 3,4-dialkylisoxazole can be obtained as the sole reaction product from an appropriate nitrile TV-oxide and an appropriate vinyl acetate. 

Dibenz[c,/][1,2]oxazcpine-ll-carbonitrile isomerizes to the TV-oxide acridine-9-carbonitrile 10-oxide on heating in aprotic solvents. Attempted chromatography on silica gel or alumina columns gave a mixture of the oxepino[2,3-6]quinolinecarbonitrile 2, the oxoazepinoindolecarbo-nitrile 3 and the benzo[c]-2-aza-l,6-oxa[10]annulenecarbonitrile 4. Only these types of compounds were isolated when 2,7-dimethylacridine 10-oxide was irradiated.6... 

The formation of iminium ions of 20-epipandoline occurred only under Polo-novski-Potier conditions. Thus on treatment of the TV-oxide of 165 with tri-fluoroacetic anhydride followed by an aqueous solution of KCN, the iminium ion 329 was obtained, readily isolated as the corresponding a-amino nitrile 331 (Scheme 17). The reaction was completely regioselective and no traces of the enamine 332 could be obtained. This made the synthesis of spiroketone 333... 

A quite different approach to the 1,5-benzodiazodne system begins with 1,3-dipolar cycloaddition of a nitrile oxide and an indolenine (78MI51900). The spiroisoxazoline (303) is converted by irradiation in good yield to the 1,5-benzodiazocinone (304). By using TV,TV - alkylenediindoles and bifunctional nitrile oxides, the diazocine ring is incorporated as a repeating unit into a photoconducting polymer. 

Racemic pipecolic acid (6) is obtained by ring closure of TV-alkylglycines by ionic 203 or radical 204 mechanisms. It also may be obtained by conversion of suitable substituents at the C2 of piperidine into the 2-carboxy group, e.g. hydrolysis of a nitrile group 205 or oxidation of a 1,2-dihydroxyethyl group. 206 Resolution of the racemic mixture can be carried out by fractional crystallization. 207-209 Enzymatic resolution of racemic pipecolic acid 210-213 or of synthetic intermediates 214 has been reported. 

Functional group transformations. Dimethyldioxirane effects conversion of isothiocyanates to isocyanates," TV, Al-dimethylhydrazones of aldehydes to nitriles, and the oxidative cleavage of nitronate ions (Nef reaction) with relative ease. Regioselective oxidation of diols and triols is also achieved. " ... 

The useful complex (MeCN)2PdCl2 has palladium in the +2 oxidation state because of its tv chlorine atoms and the number of electrons is 8 for the Pd(II) oxidation state and another two ea< from the four ligands making 16 in all. This complex does not fulfil the IS-electron rule and reactive. You would have got the same answer if you had counted ten for the palladium, two each f the nitriles, and one each for the chlorines, but this is not so realistic. 

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