Acetone oxime, reaction with ethyl

Acetone oxime, reaction with ethyl m-bromopropionalc, 48, U1... 

S.5.2.3 Synthesis from i-xylose L-Xylose has been used as a starting material for the synthesis of euglenapterin (3) (Scheme 3). Its oxidation to L-xylosone (19) followed by reaction with acetone oxime in aqueous solution produced 20. Condensation of 20 with ethyl... 

Unsubstituted quinazoline 3-oxide was prepared in an attempt to react quinazoline with hydroxylamine. This reaction gave a product of variable composition, but when an acetone solution was heated in a sealed tube it gave quinazoline 3-oxide. The oxide is more conveniently prepared, in excellent yield, from o-aminobenzaldehyde oxime and ethyl orthoformate. This method appears to be of general use and has been used for the preparation of 4-methylquinazoline... 

The Knorr pyrrole synthesis was also employed for the synthesis of 3-trifluoropyrroles [91]. Treatment of ethyl trifluoroacetoacetate 267 with sodium nitrite in acetic acid led to the oxime 268. Refluxing with zinc dust and addition of 1,3-dicarbonyl compounds 269 afforded the 3-trifluoromethylpyrroles 270 in moderate yields. Using more acidic trifluoroacetic acid allowed to lower the reaction temperature to 70 °C [92]. Using a similar approach, the tricarboxylic acid ester 273 was prepared starting from the acetone dicarboxylic acid ester 271 and the fluorinated keto ester 272 [93]. 

The reaction is generally carried out using 1.1 equiv of Boc-ON and 1.5 equiv of Triethylamine in either 50% aqueous dioxane or 50% aqueous acetone. Boc derivatives are obtained in high yields after 4-5 h at 20 °C or 1 h at 45 °C. The oxime byproduct (eq 1) can be easily and completely removed from the reaction mixture by extraction with ether, ethyl acetate, or benzene. To secure high purity and high yield, distillation of the dioxane or acetone prior to extraction of the oxime byproduct is recommended, though direct extraction may be feasible in most cases. Yields... 

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