Abstract
Reaction of 6-amino-1,3-dimethyluracil (14) with the 2,4-dinitrophenyl oxime (21) of iodoacetone led to initial condensation followed by an unexpected [3,3] sigmatropic rearrangement, followed in turn by ring closure to give 5-(2-hydroxy-3,5-dinitrophenyl)-1,3,6trimethylpyrrolo[2,3-d]pyrimidine-2,4(1H,3H)-dione (22). 6-Methylamino-1,3-dimethyluracil under the same conditions underwent a similar sigmatropic rearrangement, but the product cyclised instead to give 1,3-dimethyl-6-methylamino-5-(2methyl-5,7-dinitro-3-benzo[b]furanyl)pyrimidine-2,4(1H,3H)-dione (32). A third type of product, 4-amino-6-(2-hydroxy-3,5-dinitrophenyl)-5-methyl-2-phenylfuro [2,3-d]pyrimidine (35), was obtained when 6-amino-2-phenyl-4(3H)-pyrimidinone (33) reacted with the 2,4dinitrophenyl oxime (19) of chloroacetone in presence of potassium iodide. Mechanisms are suggested for these unusual reactions.
Highlights
It was shown recently by Narasaka[1,2,3,4] and co-workers that 2,4-dinitrophenyl oximes can serve as a source of electrophilic nitrogen, and that in suitable cases intramolecular electrophilic cyclisation of nitrogen on to a benzene ring may lead to the formation of quinolines
It was of interest to see if 2,4-dinitrophenyl oximes such as (3) or (4) could undergo intramolecular cyclisation on to the pyrimidine 5-position to give 7,8dihydropteridines (5) or (6) respectively, which could be readily oxidised to the corresponding fully aromatic pteridines
In agreement with the above, the 13C NMR spectrum for (22) showed only two aromatic CH signals at δ 123.41 and 128.83. These results suggested the presence of a 2-hydroxy-3,5-dinitrophenyl moiety in the new molecule
Summary
It was shown recently by Narasaka[1,2,3,4] and co-workers that 2,4-dinitrophenyl oximes can serve as a source of electrophilic nitrogen, and that in suitable cases intramolecular electrophilic cyclisation of nitrogen on to a benzene ring may lead to the formation of quinolines. The same product was obtained by reaction of the iodooxime (21) with 6-amino-1,3-dimethyluracil (14) in methanolic solution at 120 °C in a pressure tube.
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