2 -Quinoxalinone ring-contraction

Novel l,2-diazepino[3,4-h]quinoxalines of type 98 have been reported to result from 1,3-dipolar cycloaddition of the quinoxaline 4-oxides 97 (R = Ph, CsH -p-Me, and Cfjii-p-OMe) with 2-chloroacrylonitriIe compounds of type 97 could also be converted to 99. Reaction of compounds 98 with selenium dioxide resulted in ring contraction to the pyridazino[3,4-h]quinoxalinones 100 <00MI03>. 

Quinoxaline-2,3-dione is converted into 2,3-dichloroquinoxaline by phosphoryl chloride142 or phosphorus pentachloride.143 2,3-Dibromo-quinoxaline is similarly obtained using phosphoryl bromide in dimethyl-aniline.144 Quinoxalin-2-one undergoes ring contraction to 2-methyl-benzimidazole (134) with hydrazine145 however, quinoxaline-2,3-dione gives 3-hydrazino-2-quinoxalinone.145 Quinoxalin-2-one yields a 3-p-dimethylaminophenyl derivative with 7V,N-dimethylaniline (in AcOH, with NH4N03), and a 3-(indol-3-yl) derivative with indole.146... 

X = SMe) and the oxadiazocine 30 (X = SMe). " Other benzodiazepine to quinoxaline ring contractions have been reported. The quinoxalinone 32 is unexpectedly formed on hydrogenation of the benzotriazepinone 31. ... 

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