| Abstract: | Ring transformation of the 3-quinoxalinyl-l,5-benzodiazepine ( 2 ) gave 3-(benzimidazol-2-ylmethylene)-2-oxo-l,2,3,4-tetrahydroquinoxaline hydrochloride ( 4a ), whose treatment with 5% sodium hydroxide provided the free base 5a , while refluxing of the 3′-chloro-l-formyl derivative 3 in acetic acid and in 10% hydrochloric acid/acetic acid afforded 3-(3-oxo-3,4-dihydroquinoxalin-2-yl)-1,2-dihydro-1-formyl-2-oxo-3H-1,5-benzodiazepine hydrochloride ( 7 ) and 3-methyl-2-oxo-l,2-dihydroquinoxaline ( 6 ), respectively. Compounds 4a and 5a were converted into 3-(α-hydroxyiminobenzimidazol-2-ylmethyl)-2-oxo-l,2-dihydroquinoxaline ( 8 ) and 3-(benzimidazol-2-ylcarbonyl)-2-oxo-l,2-dihydroquinoxaline ( 10 ), respectively, which were further transformed into 3-(benzimidazol-2-yl)isoxazolo[4,5-b]quinoxaline ( 9 ) and 12 -(benzimidazol-2-yl)-6H-quinoxalino[2,3-b I 1,5]benzodiazepine ( 11 ), respectively. |
