Imidazo quinoxaline-6,7-diones

The reaction of l-(o-methylaminophenyl)imidazole-2,5-dione 101 with ethyl formate under the action of sodium yields 1,3-dioxoimidazoquinoxaline 102, which is reduced by tin in a mixture of acetic and hydrochloric acids to give imidazo-quinoxaline 103 (Scheme 4.46) (King and Clark-Lewis 1951). 

Amino-3-phenyl-3,4-dihydro-2(177)-quinoxalinone (181) and triphosgene gave 4-phenyl-47/-imidazo[l,5,4-< e]quinoxaline-2,5(l//, 6//)-dione (182) (EtsN, THF, 20°C, N2, until substrate gone by tic 65%) analogs Ukewise. ... 

Imidazol 1,2-0Ipyridine, 879, 13.39 Imidazol I..5-a pyridine, 874. 13.39 Imidazol 1,5-a Ipyridine, 1.321 lmidazo 4,5-6jpyridine, 741 Imidazol 1,2-a ipyridin-3-one. 1000 Imidazol 1,2-a pyridin-5-one. 917 Imidazol 1,2-ajpyridin-7-one. 918 Imidazo 4,5-6 pyridin-2-one. 1129 Imidazo 4.5-b)pyridin-2-one, 948 Imidazo 4,5-( pyridin-2-one, 1139 Imidazol 1,2-a]pyrimidine, 874 Imidazoll,2-( pyrimidine, 998, 1237 Imidazol 1,2-a pyrimidin-4-one, 1009 Imidazol 1,2-a pyrimidin-5-one, 1300 Imidazoj 1,2-a jpyrimidin-7-one, 1300 Imidazol 1.2-ajpyridin-7-one. 1106 Imidazoll,2-r quinazolin-5-one, 886 lmidazo 4,5-/ quina/olin-7-one, 684 lmidazo 4.5-/> quinazoiin-8-one, 1161 Imidazol 1,5-a Iquinoiine, 998 Imidazoj4.5-( quinoline, 1313 Imidazo 4..5-/Iquinoiine, 981. 989 Imidazo 4,5-/ quinolin-7-one. 684 Imidazol 1,2-a Iquinoxaline, 975 Imidazol 1.5.4-de quinoxaline, 776 Imidazol I 3,4-de quinoxaline-2.5-dione, 1000... 

Scheme 4.46 l-(o-Methylaminophenyl)imidazole-2,5-dione as precursor for the synthesis of imidazo[ 1,5-a]quinoxalines... 

Heating l,4-bis(aroylmethyl)quinoxalin-2,3-diones 135a-j in acetic acid in the presence of ammonium acetate leads to 2-aryl-5-aroylmethylimidazo[l,2-a] quinoxaline-4-ones 136a-j (B3Q-type cyclization, see Fig. 4.6), whereas expected l,5-diarylbis(imidazo[l,2-a 2, r-c])quinoxalines 137 are not identified in the reaction mixture. Starting compounds 135 have been obtained by alkylation of quinoxalinediones 138a, b with aroylmethyl bromides (Scheme 4.61) (Hariharakrishnan et al. 2008). 

---