Using an Aldehydo Ester or Related Synthon

These synthons behave much as do the foregoing aldehydo acids but they are usually more convenient and reactive, as indicated by the following examples. 

5-Dimethyl-1,2-benzenediamine (143) gave 6,7-dimethyl-2(l //)-quinoxali-none (144) [0HCC02Me, EtOH, reflux, 2 h 72% 718 or 0HCC02Bu, similarly 69%].697 

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