The three-component reaction of lithiated methoxyallene, nitriles and trichloroacetic acid gave three model β-keto enamides that were starting materials for the synthesis of trichloromethyl-substituted pyridine and pyrimidine N-oxide derivatives. Upon treatment with acetic anhydride, the methyl group of the prepared pyrimidine N-oxides was converted into an acetoxymethyl group by a Boekelheide rearrangement. A few typical experiments also revealed that the trichloromethyl group of the prepared pyrimidine N-oxides can be replaced by an alkoxy or a hydroxy group, or transformed into an arylthiomethyl group. An alternative approach to β-keto enamides via the corresponding β-keto enamines was also examined and provided the expected 4-hydroxy-6-(trichloromethyl)pyridine derivative in good yield.
Key words
allenes - cyclocondensation - pyridines - pyrimidines - Boekelheide rearrangement
