Reactions of Quinoxaline Ketones

Reactions already covered comprise reduction of acyl- to alkylquinoxalines (Section 2.2.1.3), conversion of acylmethyl- into halogenoalkenylquinoxalines (Section 3.3), and reduction of extranuclear acylquinoxalines to hydroxyalkylquinoxalines (Section 4.3.1). Other reactions that have been used recently are illustrated by the following examples. 

C-Deacylation appears to be quite facile, at least when the acyl group is adjacent to an A -oxide entity. 

3-Acetyl-2-quinoxalinecarboxylic acid 1,4-dioxide (203) gave 2-quinoxaline-carboxylic acid 1,4-dioxide (204) (2.5M NaOH, 20°C, briefly ethyl 

3-benzoyl-2-quinoxalinecarboxylate 1,4-dioxide (205) gave the same product (204) (KOH, EtOH, 20°C, briefly 58% note concomitant saponihcation). ° 

2-Acetyl-3-methylquinoxaline 1-oxide (206) gave 2-methylquinoxaline 4-oxide (207) [HN(CH2CH2)20, MeCN, reflux, 24 h 30%].  

3-Acetyl-2-quinoxalinecarboxylic acid 1,4-dioxide (203) gave 2-quinoxaline-carboxylic acid 1,4-dioxide (204) (2.5M NaOH, 20°C, briefly %) 249 ethyl 3-benzoyl-2-quinoxalinecarboxylate 1,4-dioxide (205) gave the same product (204) (KOH, EtOH, 20°C, briefly 58% note concomitant saponification).540 

2-Phenacyl-3-phenyl-l,2-dihydroquinoxaline (208) gave 2-phenylquinoxaline (HC1, MeOH, H20, reflux, 15 min 53% acetophenone also isolated as its dinitrophenylhydrazone. Note that this is a passenger deacylation in the course of a dealkylation).782 

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