Reactions of Quinoxalinecarboxylic Esters

Two reactions of quinoxalinecarboxylic esters have been covered already reduction to hydroxyalkylquinoxalines (Section 4.3.2) and hydrolysis to quinoxaline carboxylic acids (Section 7.1.1). Other reactions are illustrated in the following classified examples. 

Methyl 3-ethoxycarbonylamino-6.7-dmiethyl-2-quinoxalinecarboxylate (72, R = OMe) gave 3-ethoxycarbonylammo-6,7-dimethyl-2-quinoxalinecarboxamide (72, R = NH2) (MeOH, NHji, 24°C until no tic spot for substrate 65%).  

Ethyl 3-oxo-4-phenyl-3,4-dihydro-2-qumoxalinecarboxylate (73, R = OEt) gave Af-methyl-3-oxo-4-phenyl-3,4-dihydro-2-quinoxalinecarboxamide (73, R = 

Ethyl 3-methyl-2-quinoxalinecarboxylate gave 7/-(2-dimethylaminoethyl)-3-methyl-2-quinoxalinecarboxamide (74) (neat H2NCH2CH2NEt2, reflux, 1 h  

2-Azido-3-ethoxycarbonylmethylquinoxaline (75, R = OEt) gave 2-azido-3-[A(-(2-hydroxyethyl)carbamoylmethyl]quinoxaline (75, R = NHCH2CH2OH) (neat H2NCH2CH2OH, 130°C, 30 min 75%).  

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This section covers the preparation and reactions of quinoxalinecarboxylic esters, generally the most convenient derivatives of quinoxalinecarboxylic acids. 

This chapter covers not only nuclear and extranuclear quinoxahnecarboxylic acids (and anhydrides) but also the carboxylic esters, acyl halides, carboxamides, carbohydrazides, carbonitriles, carbaldehydes, and (ketonic) acyl derivatives of quinoxaline a few related speceis are also included. To avoid repetition, the interconversions of these quinoxaline derivatives are discussed only at the first opportunity thus the esterification of quinoxalinecarboxylic acids in covered as a reaction of carboxylic acids rather than as a preparative route to carboxylic esters, simply because the section on carboxylic acids precedes that on carboxylic esters. To minimize any confusion, appropriate cross-references have been inserted. 

Reactions. Quinoxalinecarbonyl chlorides are occasionally used to make the corresponding quinoxalinecarboxylic esters (see Section 7.2.1) but more often to make quinoxalinecarboxamides or the like. Typical examples of such reactions follow. 

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