Facile Synthesis and Ring Transformations of a Spiro-[cyclobutene-1, 2'(1H)-quinoxaline]

Abstract

The reaction of 3-(N, N-dimethylcarbamoyl) furo [2, 3-b] quinoxaline (2) with ethyl cyanoacetate in sodium ethoxide-ethanol occurred with ring transformation to give 4-cyano-2-ethoxy-carbonyl-3-hydroxy-3'-oxo-3', 4'-dihydrospiro [2-cyclobutene-1, 2'(1H)-quinoxaline] (5). When 5 was refluxed in acetic acid and in N, N-dimethylformamide, it afforded 2-cyano-3-hydroxy-3'-oxo-3', 4'-dihydrospiro [2-cyclobutene-1, 2'(1H)-quinoxaline] (6) and 7-cyano-5, 6-dihydro-6, 10-dioxo-8-hydroxy-10H-pyrido [1, 2-a] quinoxaline (9), respectively. Refluxing of 5 with hydrazine dihydrochloride and with o-phenylenediamine dihydrochloride in acetic acid also induced ring transformation to produce 6-(3-oxo-3, 4-dihydroquinoxalin-2-yl)-3-amino-5-hydroxy-7-oxo-1, 2-dihydro-1, 2-diazepine hydrochloride (12a) and 16-amino-1, 8-dioxo-1, 2, 8, 10-tetrahydro-quinoxalino [1', 2' : 1, 2] pyrido [4, 3-b] [1, 5] benzodiazepine hydrochloride (13a), respectively.