Quinoxaline-2-carboxaldehyde reactions

Quinoxaline-2-carboxaldehyde has been converted into the 2-carboxylic acid by oxidation with potassium permanganate in acetone and reduced to the 2-hydroxymethyl compound by treatment with formalin and potassium hydroxide. It also undergoes other typical reactions of aromatic aldehydes such as benzoin formation on reaction with potassium cyanide - and condensation reactions with malonic acid and its diethyl ester and Schiff base formation. Acid-catalyzed reaction of quinoxaline-2-carboxaldehyde with ethylene glycol gives the cyclic acetal the diethylacetal has been prepared by reaction of 2-dibromomethylquinoxaline with sodium ethoxide. " An indirect preparation of the oxime 11 is achieved by treatment of 2-nitromethyl-quinoxaline (10) with diazomethane followed by thermolysis of the resulting nitronic ester. 

Diazomethane methylation of quinoxaline-2-carboxaldehyde yields 2-acetylquinoxaline in excellent yield,and a number of 2-benzoyl-quinoxalines have been prepared by chromium trioxide oxidation of the corresponding 2-benzylquinoxalines Reaction of the quinoxaline ester 2 with acetone and sodium hydride yields the acetoacetylquinoxaline 3 in excellent yield. ... 

Selenium dioxide oxidation of 2-methylquinoxaline yields quinoxaline-2-carboxaldehyde, and 3-methylquinoxaline-2-carboxaldehyde has been similarly prepared from 2,3-dimethylquinoxaline. Dimethylsulfoxide oxidation of 2,3-bis(bromomethyl)quinoxaline yields the furoquinoxaline 45, and this on sublimation gives quinoxaline-2,3-dicarboxaldehyde. 3-Dibromomethylquinoxaline-2-carboxaldehyde (46) is a by-product of the oxidation reaction. Direct selenium dioxide oxidation of 2,3-dimethylquinoxaline appears to be a less satisfactory method of preparing the dialdehyde. ... 

Methods for the synthesis of these hetarylquinoxalines are limited. An option involves the reaction of the 1,2-DAB 5a with 3-hydroxyimino-2-butanone 54 and bromine in a one-pot reaction (Scheme 6.17, Eq. 1) (Sarodnick and Kempter 1983). Another possibility is to react 1,2-DABs 5a-g with quinoxalin-2-carboxylic acid 56, but this synthetic route needs to be performed in a polyphosphoric acid media at 200 °C (Scheme 6.17, Eq. 2) (Mizutani et al. 1994 NoveUino et al. 2005). A third route is to react the 1,2-DAB 5a with quinoxalin-2-carboxaldehyde 58 in benzene at reflux temperamre (Scheme 6.17, Eq. 3) (Lippmann and Shilov 1984). In all three cases, the yield of the target product remains very low. 

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