Sigmatropic rearrangements of 2,4-dinitrophenyl oximes

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)-1,3,6-trimethylpyrrolo[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-(2-methyl-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 2,4-dinitrophenyl oxime (19) of chloroacetone in presence of potassium iodide. Mechanisms are suggested for these unusual reactions.