Quinolone Analogues 4. Synthesis of 1-Methyl-3-Trifluo-Romethylpyridazino[3,4-b]Quinoxalin-4(1H)-Ones

摘要

The reaction of the quinoxaline N-oxides (7a,b) with 4,4,4-tri-fluoroacetoacetate gave the 1,5-dihydro-3-trifluoromethylyridazino[3,4-b]quinoxaline -4-carboxylates (15a,b), whose oxidation with nitrous acid afforded the 1,4-dihydro-4-hydroxy-3-trifluoromethylpyridazino[3,4-b]quinoxaline-4-carboxylates (16a,b), respectively. The reaction of compounds (16a,b) with 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) provided the 1,5-dihyro-3-trifluoromethylpyridazino[3,4-b]quinoxalin-4-ols (17,b), whose oxidation with sodium bromate produced the 1-methyl-3-trifluoromethylpyridazino[3,4-b]quinoxalin-4(1H)-ones (16a,b), respectively.